HEAVY METAL CONTAMINATION OF SURFICIAL TIDAL FLAT

SEDIMENTS IN THE YANGTZE RIVER ESTUARY, CHINA

A thesis

Presented to

The Faculty of Graduate Studies

of

The University of Guelph

by

SHELLEY ANNE GORENC

In partial fulfillment of requirements

for the degree of

Master of Science

May, 200 1

O Shelley Anne Gorenc, 200 1

National Library I*I of Canada Bibliothèque nationale du Canada

Acquisitions and Acquisitions et Bibliographie Services setvices bibliographiques

395 Wellington Street 395, rue Wellington Ottawa ON K I A ON4 Ottawa ON K I A ON4 Canada Canada

Ycur iye Voue réterence

The author has granted a non- exclusive licence allowing the National Library of Canada to reproduce, loan, distribute or seil copies of this thesis in microform, paper or electronic formats.

The author retains ownership of the copyright in this thesis. Neither the thesis nor substantial extracts f?om it may be printed or otherwise reproduced without the author's pemiission.

L'auteur a accordé une licence non exclusive permettant a la Bibliothèque nationale du Canada de reproduire, prêter, distribuer ou vendre des copies de cette thèse sous la fome de microfiche/nlm, de reproduction sur papier ou sur format électronique .

L'auteur conserve la propriété du droit d'auteur qui protège cette thèse. Ni Ia thése ni des extraits substantiels de celle-ci ne doivent être imprimés ou autrement reproduits sans son autorisation.

HEAVY METAL CONTAMINATION OF SURFICLAI, TIDAL FLAT SEDIMENTS IN T a YANGTZE RIVIER ESTUARY, CHINA

Shelley Anne Gorenc University of Guelph

Advisor: Professor R.A. Kostaschuk

The purpose of this research was to determine controls of onshore-offshore

variations in heaw metal concentrations within surficial sediments of the Yangtze

Estuary tidal flats. In order to accomplish this, two sampling transects were

established dong the eastern shores of Chongming and Hengsha Islands. Results

showed that, while raw metals increased with distance seaward, no significant

relations exist between normdized rnetals and distance within transects and that

proximity to the turbidity maximum is not a significant control on metal distributions.

Statisticd analysis using Spearman's Rank, Mann-Whitney and PCA al1

established grain-size as the primary control on the spatial distribution of rnetals

within the Estuary. Furthemore, metal concentrations are consistent with Grade A

soils and represent a reiatively pristhe environment. This lack of evidence in support

of sediment contamination fiom dornestic and industrial discharge is likely the result

of dilution by high fluvial sediment loads.

Acknowledgernents

This thesis could not have been completed without the support and

contributions of many people. Firstly, this research opportunity would not have been

possible without the funding provided by C D A in assistance to the China Project

overseen by Dr. K.C. Tan. I would like to thank by advisor, Ray Kostaschuk for his

insight. editing and support of rny efforts. 1 also thank Dr. Chen and Yang Meng for

being such gracious hosts during my stay In their country and Dr. Les Evans for being

associated with this project. Lastly, 1 would like to thank Jen and Vicky for putting

up wiih their crazy ofice mate and my parents for al1 of their love and

encouragement. This thesis is dedicated to my husband.

TABLE OF CONTENTS

............................................................................ Acknowledgements .. i Table of Contents ............................................................................ 11

List of Figures .............................................................................. iv List of Tables ................................................................................... iv

Chapter One: Introduction ............................................................... 1

......................... ............................. 1.1 Problem Statement ... 1 ............................................. 1.2 Smdy Purpose and Hypothesis 4

..................................................................... 1 -3 Objectives 4 ............................................................. 1.4 Research Context 5

.......................................................... 1.4.1 Introduction 5 ................................... 1 .4.2 The Chemistry of Heavy Metals 6

...................................... 1.4.3 Sediment/Metal Associations 8 ................................................... 1.4.4 Sorption Processes 8

1 .4.5 Metal Associations with Organic Matter .......................... 9 1.4.6 TheGrah-SizeEffect ............................................. IO 1.4.7 Sediment Transport in the Estuarine Environment ............. 13

........................................... 1 .4.8 The Turbidity Maximum 14 ............................ 1.4.9 Tidal Flats and Tidal Wetlands ... .. 15

1 .4.10 Sediment-bound Meîais in the Estuarine Environment ....... 16 1.4.1 1 The Role of the Turbidity Maximum as a Metals Sink ....... 17 1 -4.12 Global Approaches to Estuarine Metal

............................................. Contamination Studies 18 1.4.13 Research on MetA Contamination in the Yangtze River

....................................................... Estuary, China 21 ............................................................... 1.5 Thesis Format 25

Chapter Two: Study Area ............................................................... 26

.......................................... 2.1 The Yangtze (Changjiang) River 26 ............................................... 2.2 The Yantgtze River Eshiary 29

................................................. 2.3 Yangtze Estuarine Islands 32 ............................................................ 2.4 Island Tidal Fiats 32

................................................... 2.5 The Turbidity Maximum 34 2.6 Chongming and Hengsha Island Economies ............................ 35

............................................................ Chapter Three: Metbodology 37

3.1 Objective #1: Transect Selection and Sediment Sampling ........... 37 3.2 Objective #2: Determination of Sediment Parameters and

........................... Heavy Metal Concentrations 38 3.2.1 Dx-ying ............................................................... 38

3.2.2 Grain-SizeAnaIysis ................................................ 42 ....................................................... 3.2.3 TOC Analysis 42

.................................................... 3.2.4 Percent Moisture 43 ...................................................... 3.2.5 Acid Digestion 44

3.2.6 Metal Concentrations ............................................... 45 Objective #3 : Anal yze Relations Between Metal Concentration .

Sediment Parameters and Sites AlongJBetween ..................................................... Transects 46

................................................ 3.3.1 Statistical Approach 46 Objective #4: Comparison of Heavy Metal Concentrations with

National Standards for Sediment Quality- and Global Estuaries ........................................... 50

Chapter Four: Results ...................................................................... 51

4.1 Variations in Sediment Parameters and Heavy Metal Concentrations Along Tidal Flats ............................................................ 51

4.2 Relations Between Heavy Metal Concentrations and Sediment Characteristics. Position on the Tidal Flat and Proximity to the Turbidity Maxhum ......................................................... 58 4.2.1 Scatterplots and Spearmans Rank Correlations ................ 58 4.2.2 Mann-Whitney U-Test Analyses ................................. 62 4.2.3 Principal Components Analyses (PCA) .......................... 63 Comparison of Heavy Metal Concentrations wi th National Standards For Sediment Quality and wirh Global Estuaries ....................... 66

Chapter Five: Discussion ................................................................. 69

5.1 Relations Between Heavy Metal Concsntrations and Sediment Parameters. Position on the Tidal Flat and Proximity to the Turbidity Maximum ......................................................... 69

5.2 Comparison of Heavy Metai Concentrations with National Standards for Sediment Quality and with Global Estuaries ........... 72

Chapter Six: Summary and Conclusions .......................~...........~........... 76

Appendix A: Sediment Parameters for Transects 1 and 2 ........................... 85

Appendix B: Heavy Meta1 Concentrations for Transects 1 and 2 .................. 87

Appendix C: Raw and Normalized Scatterplots for Transect 1 .................... 89

Appendix D: Raw and Normaiized Scatterplots for Transect 2 .................. 103

List of Fipures

Figure 1: Complexation and chelation by organic carboxylic acid functional groups ................................................................. 10

.................................................. Figure 2: Tidal flat classification system 15 Figure 3: Prîmary variables controlling heavy metai behaviour in the esniarine

........................................................................ environment 18 Figure 4: District of Shanghai .............................................................. 27

.......................................................... Figure 5: Yangtze Estuary? China 31 Figure 6: Plant progression along the tidal flats on Chongming and

Hengsha Islands .................................................................. 33 ........ Figure 7: Grain-size progression dong Chongming and Hengsha tidal flats 34

Figure 8: Location of the turbidity maximum n the Yangtze River E s t u q .... .. ... 35 Figure 9: View of Chongming Island tidal flats looking seaward fiom the

.......... ..................................................... retaining wall .. 39 Figure 10: View of Hengsha Island tidal flats looking towards the retaining

wall ............................................................................... 39 Figure 11: Sample collection on Chongming Island tidal flats ......................... 40 Figure 12: Kelway soi1 pH meter .......................................................... 40 Figure 13: UTM transects for Chongming and Hengsha Islands .................. .... . 41 Figure 14: Oven-dried sample fiom Chongming Island ................................. 43 Figure 15: Graphs comparing sediment characteristics between Transect 1

(Chongming Island) and Transect 2 (Hengsha Island) ..................... 52 Figure 16: Raw heavy metal concentrations on Transect 1 ........................ .... 54 Figure 17: Raw heavy metal concentrations on Transect 2 ........................... 56 Figure 18: Plot of component loadings for Transect 1 ................................... 65 Figure 19: Plot of component loadings for Transect 2 .......................... .. .... 66

List of Tables

Table 1: National standards @pm) for soi1 environmental qudity ..................... 22 Table 2: Spearrnan's Rank data for distance dong Transect 1 .......................... 60 Table 3: Spearman's Rank data for distance dong Transect 2 .......................... 60 Table 4: Spearman's Rank data for %TOC dong Transect 1 ........................... 61 Table 5: Speannan's Rank data for %TOC dong Transect 2 ........................... 61 Table 6: Mann-Whitney U-Test results for Transect 1 and 2 sediment

parameters ........................................................................... 62 Table 7: Mann-Whitney U-Test results for Transect 1 and 2 heavy metal

concentrations ...................................................................... 62 Table 8: Principal components analysis loadings ...................................... ... 64 Table 9: Principal Components Analysis summary for Transects 1 and 2 ............ 65 Table 10: Heavy metal concentrations in various global estuaries ..................... 68

Chapter One: Introduction

1.1 Paoblem Statement

Human kind is becoming aware of the complexity of nature and the delicate

baiance that exists in the global ecosystem. Every action taken towards modi*ng

the environment has countless repercussions. Geographers seek to understand these

complex interactions so that an assessrnent of the present condition of the ambient

environment rnay be known and measures may be taken in the hopes of preventing or

minlmizing future degradation. One important element of this dynamic system is the

estuarine environment and, according to Schubel(l97 1, p. XV-5):

"It is in the estuary that man has his most intimate contact with the marine environment. He makes many uses of estuaries; for shipping and transportation, for their biologicd and mineraiogical resources, and for the many varied recreational opportunities which they afford the inhabitants of the surrounding areas."

Estuaries are so vitd that many of the World's major cities have developed on

their bariks and the shores of their respective rivers. As the population and level of

industriakation of these cities increased, so did the pressure to produce a wealth of

resources, yield good land for fùrther urbanization, agricultural and industrial

development through land rectamation efforts, and accommodate waste products

(Stewart, 1972). One group of waste products associated with these pursuits is heavy

Heavy metals are produced fiom a variety of natural and anthropogenic

sources. In fluvial environments, however, metal pollution can result fiom direct

atmosphenc deposition, geologic weathering or through the discharge of agricultural,

municipal, residential and industrial waste products (Dawson and Macklin, 1998).

These metals are transporteci in solution or on suspended sediments downstream and

may reach coastal environments such as estuaries. Upon entering estuanes, complex

interactions amongst river discharge, saltwater intrusions, local currents. effluent

point sources. pH, temperature, oxygen content and sediment re-suspension processes

can effect the accumulation of rnetals in surficid sediments (Forstner and Wittman.

1979).

The distribution of metals in marine sediments adjacent to metropditan areas

c m provide researchers with endence of anthropogenic impacts on cov td

ecosystems and, therefore, aid in assessing the risks associated with discharged

hurnan waste (Buckley and Winters. 1992; Dauvalter, 1998; Karuppiah and Gupta,

1998). The build-up of metals in estuarine sediments holds significant environmental

implications for local communities as well as for mariRe water quality. For example,

many estuarine invertebrates process sediment as a food source and are susceptible to

the bioaccumulation of toxic metals. This bioaccumulation c m potentially threaten

the health of many species at the top of the food chain, especially birds, fish and

humans (Fang and Hong, 1999; Wright and Mason, 1999). Additionally, the

reclamation of metal-contaminated estuarine sediments poses a significant risk to

local consumers through the remobilization of metals from agrîcultural lands into

crops (De Jong and Stortelder, 1993; Ross and Kaye, 1994).

Most research on sediment contamination in estuaries has focussed on mid-to-

small-sized rivers in North America and Europe (Buckley and Winters, 1992; Zhang,

1999). Despite the fact that they play host to a significant portion of the global

population, there have been few studies of metals within large, high turbidity

estuaries. The watershed of the Yangtze (Changjiang) River. China, is one of the

most densely populated regions in the World (Zhang, et al, 1999b) and would be

expected to suffer fkom anthropogenic perturbations such as heavy metal pollution.

The issue of solving metal contamination has, thmefore, become a pressing task in

many Chinese cities (Zhang, et al., 1999a). Due to its abundant water and sediment

ioads, the Changjiang River provides an excellent Iaboratory for studying the

behavior of metals in hi& turbidity estuaries.

While considerable research has been performed on the Yangtze Estuary,

sampling sites tend to be very spradic in distribution and ciearly defined sampling

transects that focus on the onshore-offshore distribution of metals are lacking. There

are also few studies concerning the role of the turbidity maximum in effecting the

behavior of met& in estuaries. In their study, Chen, et al. (1996) provided a

cornparison between metal concentrations in suspended and submerged surficial

sediments in the turbidity maximum of the Yangtze Estuary. This work, however,

was performed around the JiuDuansha sand bar, the most seaward portion of land in

the Estuary and no transects, statisticd, or grain-size distribution analyses were

performed. Consequently, a stnictured study on the effects of proximity to the

turbidity maximum on heavy metal concentrations is unavailable. This observation

can be applied more generally to studies in other areas of the World as well.

Most sediment-contaminant studies in the Yangtze have focussed on

subaqueous samples, rather than studies of exposed tidal flat sediments in order to

establish the possible effects of land reciamation on metals. Of the studies that have

focussed on tidal flats within the Estuary, oniy a couple of studies have looked at

metal distributions on Chongming Island. Consequently, the question must be asked:

what is the relative statisticd significance of the various controls on heavy rnetal

concentrations within surficial tidal flat sediments of the Yangtze River Estuary.

China?

1.2 Study Purpose and Hypothesis

The purpose of this research was to determine the patterns and controls of

onshore-offshore variations in heavy metal concentrations within surficiai sediments

of the Yangtze River Estuary tidal flats. From this purpose, a research hypothesis

developed as follows:

Hvpothesis: The spatial distribution of heavy metals in surficial tidal flat sediments of the Yangtze River Estuary is affected by position on the tidal flat, sediment characteristics and proximity to the turbidity

1.3 Objectives

In order to test the research hypothesis, the following objectives have been

identified:

Obiective #1: Select two tidal flat transects (one near the turbidity maximum and one far fiom it).

Objective #2: Detennine heavy rnetal concentrations and sediment parameters for sarnples fiom each transect.

Obiective #3: Analyze relations between heaty metal concentrations and sediment characteristics, position on the tidal flat and proximity to the turbidity maximum in the Yangîze River Estuary.

Obiective #4: Compare metal concentrations on the Yangtze Estuary tidd flats with national standards for sediment quality and Ievels recorded in other estuaries around the globe.

1.4 Research Context

1.4.1 Introduction

Throughout history, it has been recognized that certain metals should be

considered toxic (Thorriton, 1995). As far back as the 19207s, research focussed on

metals within the context of agicultural production and metal deficiencies in soils-

While the postwar penod saw an increased concern in elevaîed metal concenh-ations

due to human impact, widespread interest in metal contamination of the environment

has reaily only emerged over the past 25-30 years @avies, 1992). By 1979, the field

of metal analysis in natural waters was still in a stage of developrnent, stalled by a

Iack of accurate and fiordable technoiogy. As this equipment becarne available,

however, the measurement of met& increased in popularïty within the scientific

comrnunity (Forstner and Wittman, 1979).

Mthough heavy metals are produced fkom numerous sources, both naturai and

anthropogenic in origul large-scale discharge into the environment requires human

activities (Dawson and Macklin, 1998). Natural sources of metals include the

weathering of rocks, gaseous emissions such as volcanic activity, natural methylation

and c d degassing, and airborne particulates such as windblown dust, seaspray and

volcanic emissions (Rasmussen, 1996). In fluvial environments~ anthropogenic metal

inputs resdt fiom the direct discharge of various treated and untr-ated agrïculturai.

W n g , residential or industrial effluents in addition to atmosphenc deposition and

stom water runoff (Dauvalter, 1998; Dawson and Macklin, 1998; Wright and Mason,

1999).

The significance of metals in the natural environment lies in the recognition

that heavy metals play an important role in ecotoxicology since they c m be highly

persistent and toxic in trace quantities (Fang and Hong, 1999). The ingestion or

absorption of metals by living organisms, especidly benthic invertebrates, c m lead to

bioaccurnulation within these organisms. This process can potentially Iead to the bio-

magnification of metals dong the food chain, threatening many species (Wright and

Mason, 1999). Coastal features such as estuaries are, in general, most affected by

local inputs fYom domestic and industrial wastes (Thornton. 1995; Saiz-Salinas. et al..

1996). As metals enter estuanes. complex interactions among river discharge,

saltwater intrusion, effluent point sources, pH, oxygen concentration and sediment re-

suspension processes can e ffect the concentration of heavy metals in sedirnents

(Forstner and Wittman, 1979; Williams. et al., 1994). This section discusses the

transport and deposition of sediment-bound heavy metats in the estuarine system and

reviews the current status of research regarding controis on heavy metals in estuaries,

with emphasis on metal behavior within the Yangtze Estuary, China.

1.4.2 The Chemistry of Heavy Metals

'Heavy metal' is a terni that generally includes any element with an atomic

density greater than 6 g/cm3 and may involve some 39 elernents (Jennett, et al.. 1980;

Davies, 1992). W i t b the context of this broad category, major metals such as Na,

K, Ca, and Mg are not u d l y considered to be heavy metals due to their lighter

weight and prevalence within the natural environment. Metals such as Ai, As, Cr,

Co, Cu, Fe, Mn, Mo, Ni, Sc, Sn, Va and Zn may be required by some organisrns in

small quantities and are sometirnes referred to as trace metals or trace elements

(Thomton, 1995). There is some debate over the inclusion of Al, As, Fe and Mn

under the heading of heavy metal.

AIurninum fdls outside of most definitions of heavy metals due to its light

density (3 &cm3) but is often included in contamination studies because can serve as

an indicator of clay content (Daskalakis and O'Connor, 1995). It also has a high

natural concentration that causes Al to exhibit conservative behavior in estuarine

systems (de Groot, 1995). Consequently, it tends to have relatively constant

concentrations over space and time purton and Statham, 1990). This property makes

AI usefid in normdizing totai metal results according to n a d ievels of enrichment

(Menon, et al., 1998). Arsenic is technically considered a metalloid but is often

regarded as a heavy metal due to its similar chernical properties and behavior to other

heavy metals. Lastly, Fe and Mn are not usually thought of as contaminants because

of their high, naturally occurrîng concentrations. Under certain soi1 conditions,

however? such as strong reducing, anoxic conditions, the toxicity of these elements is

a concem (Williams, et al., 1994; Chen, et al., 1999). A group of non-essential

elements hcluding Ag, Au, Cd. Hg and Pb dso qualifi as heavy metals (Furness and

Rainbow, 1990).

The most usehl definition for the purposes of this study is Thomton's (1995)

definition of heavy metal. This involves any metal or metalloid that is associated

with contamination and potentid toxicity. Heavy metds most commonly associated

wiîh human-induced contamination of the aquatic environment include As, Cd, Cr,

Cu Pb, Hg, Ni, and Zn (Jennett, et al., 1980).

1.4.3 SedimentIMetal Associations

In aquatic systems, metals are nansported either in solution or on the surface of

suspended sediments (Dawson and Maclclin, 1998). Due to their strong affinity for

particles (Luorna, 1990), metds tend to be accumulated by suspended matter or

trapped immediately by bottom sediments (Dauvalter, 1998). In estuaries, these

metals enter though direct discharge or atmospheric deposition from various sources

as well as through discharge from tributary rivers (Williams, et al., 1994; Wright and

Mason. 1999). Sediments then act as a storage cornparmient for metd contaminants

and may act as a source if changing environmental conditions cause a remobilization

of these rnetals (Salomons and Forstner, 1984). Sediment-metal associations occur

primarily through two dinerent phenomena: sorption processes and complexation by

organic matter.

1.4.4 Sorption Processes

Sorption processes are a broad group of fixation mechanisms that include

physical adsorptiodco-precipitation, chernical adsorption and ion exchange. While

some literature differentiates between adsorption and CO-precipitation (Sparks, 1999,

the distinction between the two processes is insignificant for most purposes.

Adsorption involves the precipitation of the fixating surface before the metal ion is

added and CO-precipitation involves the addition of a metai pnor to precipitation

(Salomons and Forstner, 1984). For the purposes of this discussion, the two

processes are both considered as adsorption.

Physical adsorption on the surface of a material is govemed by Van der Waals

forces (electrostatic forces of attraction produced by ions of opposing charge)

(Sparks, 1 995) and chemical adsorption requires the formation of chemical bonds

between ions or molecdes in solution with the solid surface (Salomons and Forstner,

1984). Ion exchange involves the substitution of an ion in solution with an ion on the

solid surface (Sparks, 1995). The solid phase for adsorption c m be made up of a

variety of components including clay minerals and metal oxides (iron and manganese

oxides in particular) that often form an outside layer on clay minerals. This coating

works effectively in combination with the clay as a sorbing surface for metals

(Forstner and Wittrnan? 1 979; Feltz, 1980; Salornons and Forstner, 1984; Sparks,

1995).

1.4.5 Metal Associations with Organiç Maîter

Organic matter has the ability to cornplex metais on its own but it is usually

found in association with clay minerals that are coated with Fe and Mn oxides (Feltz,

1980, Sparks, 1995). The metal sorption ability of humic organic matter lies

somewhere between those of clay mherals and metal oxides and is generally a result

of three main chemical binding groups: salicylic acid, carboxylic acid and phenolic

acid functional groups (Salomons and Forstner, f 984). As illustrated in Figure 1,

these groups c m form affiliations with met& involving one or more bonding sites on

the functional groups. If complexation involves the formation of two chemical bonds

with the metal, the process is called chelation (Sparks, 1995).

Figure 1: Complexation (A) and chelation (B) by organic

CiPTboxylic acid hctional groups (based on Sparks, 1995).

1.4.6 The Grain-Size Effect

It is possible to sub-divide estuarine sediments into two groups based upon

their respective diameters: a fine hc t ion composed of silt and clay-sized particles

(average grain diameter of less than 60 pm) and a coarser fiaction cornposed of sands

and grave1 (average grain diameter greater than 60 pm). Within the silt-clay fiaction,

the shape of particles is relatively diverse due to its various components including

clay minerals, organic matter, fine quartz and feldspars. The coarser fraction contains

sub-rounded particles of quartz and feldspars. Due to their larger size, sand and

grave1 travel relatively srnall distances in rivers and estuaries, moving close to the

bed. The silt-clay fraction may travel over large distances, suspended within the flow

and accumulate in areas of calm water such as flood plains or tidd flats (Salomons

and Forstner, 1984).

In general, the surface area and the sorption area of sediment increases

logarithmically with decreasuig grain-size (Luorna 1990). This results in a pattern of

increasing metal concentration with decreasing grain-size that has been well

establisbed within the literature (Forstner and Wittman, 1979; Buckley and Winter,

1992; Palanques, er al., 1998; Lrabien and Velasco, 1999). Within the silt-clay

fraction. two types of metal sorption can occur: pH-dependent and pH-independent

sorption. Clay rninerds are unique in that they can support both sorption processes.

W l e pH-dependent sorption occurs across the many broken bonds on the surface of

the particle, their net negative structural charge supports pH-independent sorption.

This latter phenornenon can be generated in two ways: isomorphous substitution in

one of the phylosiIicate layers or non-ideai occupancy of the octahedrai sheet. The

former involves the replacement of Si by Ai in the tetrahedral or octahedral layers of

a clay mineral while the latter occurs where the concentration of Al is slightly lower

than that required to produce a neutral charge in the mineral. The remaining silt

fiaction can attract metal ions only through pH-dependent sorption to the broken

bonds scattered across their surface (Sparks, 1995).

This strong dependency of metai concentration on the composition of

sedirnents (de Groot, 1995) is referred to as the grain-size effect. According to

Ackemann, et al. (1983, p. 3 17),

"The greatest influence on the final results in the course of the sampling processing is exerted by the grain-size effect, i.e. coarse components of the sediment (sand) with normdly very low heaw metal contents produce a random shifting of the heavy metai contents of the total sediment sample by 'diluting' it."

Most heavy metal contaminatisn studies, therefore, involve some method to correct

for this effect. This can involve the comparison of the total metals content with

reference to a conservative element such as AI, Fe or Sc (Daskalakis and O'Connor,

1995: Chen et al., in press; Shang, 1999) or separation and analysis of o d y the < 60

pm (Palanques, et al, 1998; Irabien and Velasco, 1999) or the < 20 pm (Ackermann,

1980) fraction. The analysis of total metals in sediment samples followed by a

correlation with the percentage silt-clay present has also been applied to heavy metal

research (Ackermann, et al., 1983; Palanques, et al., 1998). In some cases, however,

metals with very low sediment concentrations (typically Ag, Cd, Hg and Sb) do not

show good correlations with grain-size or Al in comparison with rnetals whose

occurrence is more prevalent in the natural environrnent (Daskalakis and O'Connor,

While metal mzdysis of the entire silt-clay fraction or correlation to its relative

abundance in a sedirnent sample rernains the dominant method of grain-size

correction, some researchers question the suitabiiity of this technique. Ackermann, et

al. (1983) studied 22 similarly polluted sediment samples fi-om the Elbe Estuary,

Germany and f o n d that the correlation of metals with the < 20 pm fraction is 2-3

times betrer than in the < 60 p fiaction. Furthemore, the 20-60 prn fraction

contains oniy 10-20% of the metals present in the < 20 jun fraction. They concluded

that the rationale behind using the eritire silt-clay hct ion seems to be based primarily

on the traditional break between silt and smd-sized sediment, Although metals have

been found within this hction. the research presented by Ackermann, et al.,

illustrates that the majority of those metals are contributed by the < 20 p m fraction.

This work is particularly relevant for estuaries, where the primax-y size of sediment

travelling in suspension lies in this segment. These findings were supported by

Forstner (1 985) who found a good correlation between conservative elements and the

< 20 pm fiaction and de Groot (1995) who confirmed a linear relationship between

metal concentrations and the c 20 pm hction.

1.4.7 Sediment Transport in the Estuarine Environment

According to Forstuer and Wittrnan (1979), an estuary c m be deficed as a

semi-enclosed body of water that has a fkee connection to the open sea and within

which seawater experiences dilution by fkesh water fiom land drainage. Simply put,

an estuary represents a mixing zone between river and sea- Estuarine sediment

transport is complex and often varies fkom case to case. In general, however.

estuaries are areas of accretion where sediment deposition and movernent is driven by

circulation patterns within the water body (Salomons and Forstner, 1984).

The primary characteristics responsible for sediment distribution are tidal

action, river inflow, waves and wind. As a result of the complex relations between

these factors, sediment distributions tend to be extremely variable on both a spatial

and temporal scale (Perillo, 1995; Williams, et al., 1994), although tides arguably

exert the most significant control over an estuary's ability to transport sediment

(Dyer, 1995). Estuaries can be classified according to their tidal range as: microtidal

(< 2 m), mesotidal (2-4 m) and rnacrotidal (> 4 rn) (Dyer, 1994). With increasing

tidal range, the whole of the esniarine water mass can move in response to tidai

periodicity @yer, 1995).

1.4.8 The Turbidity Manimum

The turbidity maximum is a feature common to mesotidal and macrotidal

estuaries and is defmed as the area within an estuary that contains higher suspended

sediment concentrations than those in the river or m e r seawards in the estuary

(Dyer, 1994). The position of the turbidity maximum responds dynamkally to

changes in river flow and tidal currents but is generally located at, or (due to diffision

processes) slightly landward of, the tip of the salt-wedge intrusion (Dyer, 1995). The

semi-enclosed residual circulation that occurs in the system sustains the high

concentration of sediment in the turbidity maximum (Dyer, 1 972).

This circulation pattern, resulting fiom a salt water intrusion and river flow of

differing densities, creates residual landward bottom flow and seaward surface flow

(Dyer, 1995). Sediment being discharged within the river flow- travels dong the

surface in a mean seaward direction until velocities are no Ionger sufficient to support

transport. The sediment then settles into the bottom layer of saline flow and is carried

dong with particles entering fiom the sea back to the upper estuary (Dyer, 1972).

This process is termed vertical gravitation circulation and is an effective sorting

mechanism for depositing coarser particles dong the bed while sweeping a narrow

range of particles through the estuary (Dyer, 1995).

1.4.9 Tidal FIlats and Tidal Wetlands

Most classification systems for tidd flat areas involve separation of the flats

into several sub-units (Figure 2). The hîghest or most landward portion of the flats is

usudly termed the supratidal or supralittord zone. Sitting above the mean hi& water

spring tide (MHWST) level, it expenences inundation only during large storm events.

The intertidal or littoral zone is comprised of three sub-units. The most landward

sub-unit falls between MHWST and mean high water neap tide (MI-IWNT) levels and

is occasiondly covered by water. The middle intertidal flats sit between MHWNT

levels and mid low water neap tide (h4LWNT) and experience inundation with every

tide. The most seaward sub-section sits below MLWNT and is occasionally exposed.

Finally, the subtidal or sublittoral zone lies seaward of the lower intertidal flats and is

very rarely fkee of water (Amos, 1995).

Supratidai Intertidal Zone Subtidal Zone

A Zone * I I I

- - I I

I 1 I rn 9

1 Upper : Middle i I Lower 1

9

Figure 2: Tidal flat classification system (based on Amos , 1995).

Tidal flats are ofien linked with the occurrence of vegetated salt marsh areas.

Salt marshes thrive in the sheltered coastal environrnents of estuaries that experience

medium to large tidal ranges (ranges > 3 m). According to Williams, et al. (2994).

colonking species establish themselves dong the flats according to their relative

tolerance to inundation and salinity. This progression of plant species can be utilized

to m e r sub-divide the tidal fiats into three distinct areas. The lowest portion of the

marsh occurs between MHWN tides and mean high water levels and displays

little v&ety in plant species due to the extremely saline conditions of the inundating

water. As a result, this area usuaiIy displays a very patchy plant distribution,

separated by areas of mud flat. The middle rnarsh lies between MHW and MHSW

tides. This area contains a greater diversity of plants because of the decrease in

sdinity. Finally, the upper marsh zone sits above MHWS tide, thus receiving tidal

inundation only 5- IO times per year. Ln general, tidal flats display an increase in grain

size with distance fiom shore. This is in due in part to the slack water produced by

tidal advancement and retraction as well as the energy attenuation ability of the native

plant species. The vegetation effectively slows currents over the flats, decreasing the

sediment load of advancing waters (Yang, 1998; Yang, 1999a).

1.4-10 Sediment-bound Metals in the Estuarine Environment

Two opposing mechanisms control the behavior of metals in the estuarine

environment. The first process involves the removal of metals from arnbient waters

by sorption, organic matter complexation and adsorption by FeMn oxides. The

second involves remobilization by desorption processes (L'Her Roux, et al. ,1998).

Re-mobilization of sediment-associated metds can occur for a variety of reasons. An

increase in salinity produces elevated concentrations of Na ions that compete with

metals for sorption sites on the sediment (Forstner and Wittman, 1979). An increase

in complexing agents, such as chioride, that form stable, soluble metal compounds

wiIl also act to release rnetals. According to de Groot (1995): significant

solubilization of metals occurs between salinities of 1-6 %.

A decrease in oxygen content results in anoxic. reducing conditions that

promotes the disassociation of Fe/= oxide coatings by altering the valencies of

manganese and iron, releasing sorbed and CO-precipitated metals to the surrounding

water (Williams, et al, 1994). Lastly, a decrease in pH effectively increases the

concentration of protons that c m compte for sorption sites (Forstner and Witmian.

1979). Forstner (1985) reported that metal adsorption increases from nearly zero to

approxirnateiy 100% over a pH elevation of one to two units. Low pH levels also act

to dissolve carbonate and hydroxide-metal compIexes (Forstner and Wittrnan, 1979).

1.4.11 Role of the Turbidity Maximum and Estuaries as a Metals Sink

While ion exchange and pH are the most significant controls on metal

mobilization, the re-suspension of bottom sediments and subsequent increase in

sorption surfaces c m act to interfere with metal solubilization (L'Her Roux, et al..

1998) and constitutes a significant loop in the cycling of metals within estuaries.

Depending on the mechanisms involved in creating a turbidity maximum, fine

sediments can either accumulate or be removed dong witt their associated metals

(Menon, et al., 1 998).

The question remains, however, whether estuaries are truly an effective sink

for heavy metids. While many studies have shown that estuaries are efficient in

trapping sediments (Palanques, et al, 1998; Fang and Hong, 1999), this may not

necessarily hold true for metals. In fact, few detailed mass balance studies have been

perfonned on estuaries. This is most likeiy due to the complex nature of the

environment and the numeruus, inter-related contro lling variables. A particular

estuary c m be considered a rnobilizing or retaining system depending on the balance

between sorption and solubilization processes within the system (Salomons and

Forstner, 1984). Figure 3 provides a summary of the prirnary variables controlling

heavy metai behaviour in an estuarine environment.

Tributary + Discharge

Atrnospheric Deposition +

Grain Size u H - -

f Remobilization from Bottorn Sediments

+ Direct Discharge

Figure 3: Primary variables controlling heavy metal ôehaviour in the estuarine environment (Based on Forstner and Wittman, 1979).

1.4.12 Global Approaches to Estuarine Metal Contamination Studies

In their 1999 study, Wright and Mason compared the distribution of metals in

the top 30 cm of sedirnent fiom two adjacent estuaries dong the East Coast of

England. Samples were collected at three sites for both the Stour and Orwell

eshiaries in order to represent the, upper rniddle and Iower estuarine sections.

Analysis of the <500 pm hct ion indicated a peak in metal concentrations at the head

and mouth of both estuaries. In the saltmarsh sediments of the Orwell Estuary.

meanwhile, metal levels were generdly higher Phan those at other sites. Spearman's

Rank Correlation coefficients identified reiationships between pairs of metals (Cd/Cu,

Cu/Hg, Zn/Hg and Pb/Zn in the Orwell and Cu/Pb in the Stour). The authors

concluded that patterns in heavy metal concentrations were most likely the result of

local point sources. The trapping of sediment by saltmarsh vegetation and the

dilution of contaminated river sediments by relatively pristine marine sediments were

also considered to effect metal distributions.

Palanques, et al. (1998) studied the distribution of heavy met& in the densely

populated and highly industrialized Besos Prodelta in the Mediterranean. Sediment

cores were taken to a depth of 30 cm to 3 m in order to determine spatial and

temporal patterns in contamination. Once normalized to percent silt-clay, results

indicated a decrease in metal concentrations and depth of contamination wiih distance

seaward. Histoncal analysis revealed present metal levels to be 5-20 times of those at

the beginning of the century and peaks in metal concentrations matched increases in

population and industrialization in the area Palanques, et al. (1998) concluded that

the vertical increase in contamination was the result of anthropogenic activities.

Physical processes such as sediment settling and fkesh and salt water scavenging

controlled the spatial distribution of rnetals within the estuary.

h b i a n and Velasco (1999) surveyed the Oka River estuarine basin in Northem

Spain to determine the distribution of heavy metals in surficial sediments and identi@

possible metal sources. Due to the relatively pnstine conditions of the ecosystem,

only the top few miHimeters of sediment were analyzed for local enrichment. The <

63p.m hction was selected for acid digestion and findings revealed a decrease in

metal concentration towards the mouth of the estuary. While point sources were

identified as the main inputs for metals, the seaward decrease in concentrations was

attributed to a variety of factors including an increase in chlorinity, decrease in point

sources and dilution by marine sediments.

Zwolsman, et al. (1996) perfomed a study of the spatial and temporal

variations in sediment-associated metals of the Schefdt Estuary, southwest

Netherlands. The authors utilized analysis of variance (ANOVA) on the < 16 p m

fraction of 13 1 1 samples that had been collected fiom the site between 1959-1 990.

Resuits isolated two groups: a group of sediments with low metals and high organic

matter content representing pristine conditions and a group of fine-grained, high

organic rnatter, high metals sediments representing polluted harbor conditions.

Principal Component Analysis identified three components that accounted for 90-

95% of the total variance. The first, and rnost significant, component explained 80-

90% of this variation and was comprised of grain-size effects, organic matter content

and al1 metals. The authors subsequently concluded that the spatial distribution of

metais in the Scheldt Estuary is primarily controlled by the dilution of polluted fluvial

sediments by relatively cIean marine particles.

BucMey and Winters (1992) utilized Principal Axis Factor Analysis with

varimax rotation to determine relationships between metal concentrations, point

sources, grain size and organic matter content for 274 samples of contarninated

surface sediments f?om Halifax Harbor. They isolated five factors that accounted for

64% of the total variance. The primary contamination factor (comprising 4 I % of the

variance) found that metal concentrations correlated with areas of fine-grained or

organic matter-rich sediment and proximity to sewage outfalls and treatment plants.

Factors 2-5 accounted for only 8%, 6%, 5% and 4% of the total variance and were

associated with the influences of land drainage, pH, reducing/anoxic conditions and

calcium carbonate on metal concentrations, respectively.

1.4.13 Research on Metal Contamination in the Yangtze River Estuary, China

The Yangtze River watershed is one of the most densely populated areas in the

World and is, therefore, expected to experience detrimental ef3ects fiom

anthropogenic activities (Zhang, et al., 1999b). As of 1996, o d y 5% of the municipal

and 17% of industrial wastewater received treatment prior to entering aquatic systems

in China (Wu, er al., 1999). While this pattern could be attributed to the high cost of

treatrnent and a lack of equipment, it resulted in an average sewage to runoff ratio of

0.014 (Chen, et al., 1999). By the 198O's, industrial and dornestic waste discharges

into the river had reached a rate of 3 5 . 7 ~ 1 0 ~ t/d. Since that tirne. the govemment of

China has made efforts to control pollution and establish national standards for

environmental quality. In July of 1995, the govemment published the first National

Standard for Soi1 Environmental Quality (Chen. et al., 1999) and in 1998, China

spent 150 million Yuan on the construction of pollution control plants for theYangtze

River (Beijing Review, 1998). Table 1 illustrates the national soi1 standards for

heavy metals established in 1995.

A variety of studies have examined heavy metals in the Yangtze River Estuary.

Meng and Liu (1996) studied 32 submerged

metds and R-mode Factor Analysis revealed

surficial sediment samples for total

that a significant relationship exists

between mean rnetal concentrations and percent clay in the sediment. Chen, et al.

(1 996) studied heavy rnetal concentrations in suspended and bed sedirnents in the area

of the turbidity maximum around the Jiuduansha sandbar in the Yangtze Estuary.

Total metal analysis for Cd, Cu, Pb and Zn indicated that higher concentrations

generally occurred in suspended sedirnents. Wu. et al. (1996) performed an

assessment of heavy metal concentrations in the tidal beach sedirnents near the

Bailonggan wastewater outlet in the Pudong New Are% China Five sampling pits

along the beach displayed unacceptable levels of Cu. Zn, Pb and Hg according to

governrnent standards. Results suggested that tidal currents tend to cany metals

against the flow of the river and deposit them on local tidal flats.

Table 1: National standards (ppm) for soil environmental quality. (8ased on Chen, et a&, 1999)

Metal

1 As: 1 1

Cd

Grade A Soi1

I Cu: I 1

(Natural Background)

1 0.20

1 farmland 1 1 3 5 1 50 1 1 00 1 100 1 400 1

Grade B Soi1

paddy soi1 ' S 15

Grade C Soi1

pH < 6.5

0.30

30 40 dryland

1 Cr: I I

I l 5

orchard

Pb

pH 6.5-7.5

0.30

25 30

paddy soi1

dryland

pH > 7.5

0.60

20 25

I

pH > 6.5

1 .O

30 40

200 300

--..- 1 3 5

_< 90

150 250

200 350

250

400 1 500

300 5 90 200 150

350 400 250 300

Xu, et al. (1997) conducted a study of the dynamic accumulation of heavy

metals along the tidai flats that connect Shanghai to Hangzhou Bay. Forty-five

surface sediment samples were collected to a depth of 5-10 cm along stable.

accumulating and eroding banks of the flats. Total metal results indicated that the

spatial distribution of Cu, Zn. Pb. Cr, and Cd was dependent on local sedimentary

dynamic conditions. with peak concentrations occurrhg in accumulating banks.

Further, while municipal sewage and hdustrial wastes were f o n d to have produced a

serious impact on the environmental quality of sediments, point source metal inputs

were not found to be a significant variable in the distribution of metals in the area

In their investigation of heavy rnetal concentrations in the intertidal zone of the

Yangtze Estuary, Zhang, et al. (in press) sarnpled 5 sites dong the southern ban. of

the Estuary and the tidal flats of Chongming Island and the Jiuduansha Shoal. Short

transects, m i n g parallel to retaining walls, were composed of 3-5 sampling sites

each. These samples were then subjected to metal and gain size analysis. Results of

the study indicated higher concentrations of metals in the marsh zones (especially the

Phragmitis zones) of the islands due to their abiiity to trap fine sediments. In general.

metal concentrations from the islands were lower compared to those on the southern

shore, with metal levels increasing hdward. These patterns were explained by

proximity to sewage discharge sources along with the strong influence of grain size

effects.

In an attempt to describe the distribution of sediment-bound metals in the

Changjiang River, Zhang, et al. (1994) anaiyzed metal concentrations in suspended

sediments dong the lower reaches of the river. Field data indicated relatively low

rnetal concentrations compared to those in the Amazon, Zaire and Orinoco Rivers as

well as those h m most Euopean rives. The authors conciuded that the enormous

discharge and tremendous sediment Ioad of the Changjiang River causes

contaminants to be rapidly diluted. Identification of heavy rnetd pollution in the

Yangtze is. therefore, extremely difficult. In an extension of this research, Zhang

(1 999) iooked at the behavior of sediment-associated metals within the Changjiang

Estuary and along the East China Sea shelf region. Suspended sediment samples

were collected in these areas during the period of 1986-1988 over three surveys.

Results of organic matter quantification showed very low, hi@y variable

concentrations lying in the range of 0.5-1 -5%. Nomalization of metd concentrations

to AI levels indicated only minimal variations in metal concentrations between

sampling sites, indicating that metal variations are rnost likely due to changes in

sediment composition across the Estuary. The author went further to compare

normalized metal levels from the Yangtze Estuary with metal concentrations fiorn

other estuaries around the WorId. The comparison indicated that metzUaluminum

ratios for Cd, C u Ni, Mn and Pb are lower than those fiom polluted European and

Asian systems such as the Sheldt, Rhine, Cauvery and Gironde by as much as a factor

of five. In fact, the ratios were comparable to those fiom the Lena Estuary, a system

that is generally considered to be one of the most pristine aquatic systems in the

WorId.

Chen, et al. (in press) used five short cores to distinguish temporal and spatial

patterns in heavy metal contamination of tidal flats in the Yangtze River Estuary.

Four sampling sites were chosen along the coast of Chongming Island in addition to

one site on the southern bank of the Estuary. AU locations were placed in the vicinity

of sewage discharge outiets. Heavy metal levels in the < 150 pm fraction were

normalized by aluminum content to account for grain-size effects and the spatial

distribution of the metals correlated with proximity to sewage outfails and local

industry. Overall, however, concentrations were lower than in other estuaries around

the globe. n i e authors suggested that this is most likely due to the dilution of

sediment-associated heavy metals by river sediment. Lead-210 dating resdts

performed on each core lacked an exponential profile that confirmed high

sedimentation rates on the tidal flats.

1.5 Thesis Format

The following thesis contains 6 Chapters. Chapter 1 has given a brief

overview of the research topic and objectives as well as a review of the Iiterature

pertaining to the fate and transport of sediment-bound merals in estuarine systems.

Chapter 2 provides a description of the study area while the Chapter 3 illustrates the

methodology utilized to achieve the objectives outlined in Chapter 1. The fourth

Chapter presents the field resdts and statistical data that are then discussed in Chapter

5. Finally, Chapter 6 provides a summary of the research findings and presents some

conclusions on relatiom of heavy metal concentrations with sediment characteristics

and the turbidity maximum in the Yangtze River Estmry.

Chapter Two: Study Area

2.1 The Yangbe (Changjiang) River

Of the estimated 7x10~ tons of fluvial sediment discharged each year by the

World's nvers, Chinese rivers contribute approximately 28% of the total (Dyer,

1994). Furthemore, the dissolved solutes associated with this discharge contribute

between 15 and 20% of the World's fluvial solute inputs. Studies of significant

Chinese river/estuary systems, therefore, should provide a positive contribution to the

global oceanographical database (Zhang, 1995; Zhang, et al., 1 999).

Stretching a distance of 6300 km and draining a total area of 1,809,000 km2 of

land, the Yangtze River is the iargest river in China and the third largest river in the

World (Yang, 1999). The mean m u a l flow of the river is 29,400 m3/s with peak

flows reaching 96,600 m3/s during the rainy season. Lasting frorn May to October,

the rainy season accounts for 71.7% of annual river flows and 87% of total annual

sediment inputs to the Yangtze Estuary (Shen, et al., 1993a). Total sediment outputs

from the river average 4 . 8 6 ~ 1 0 ~ tonnes per year. This comprises the second largest

contribution in China and the f o u l i largest in the World (Shen, et al., 1993 b).

The Yangtze River Delta covers an area of 30,000 km2 (exclusive of the

subaqueous part) and supports a population of over 60 million inhabitants (Chen, et

al., in press). The extensive tidal flat system of the D e b provides nch land resources

for the District of Shanghai (Figure 4) and some 1000 km2 of tidal flats have been

reclaimed in the Iast 50 years in order to accommodate the expanding

Figure 4: District of Shanghai (Based on Shanghai Municipal Institute of Surveying and Mapping, 2000).

population. Presently, an additional 90 km2 of flats are being targeted for

reclamation. In generaf, these efforts are seen as an opportunity to increase land

resources in the area while reducing blockages in the indispensable Yangtze shipping

channel that are produced by the immense sediment loads being carried by the river

(Li and Zhang, 1996).

While the Delta's rapid expansion into the East China Sea has provided

opportunities for agicultural production and housing, concerns have arisen regarding

the potential impact of metal contamuiated sediments on food quality and human

health. Years of unsuccessful waste management resulted in excessive pollution of

tributaries to the Changjiang River, including the Huangpu River (Zhang, 1999). In

an attempt to rninimize impacts on local land, the Chinese govemment installed a

systern of sewage pipelines in the Shanghai region in the 1980's. The purpose of this

system was to discharge urban and industrial wastes deep into the estuarine channel

where it was more likely to be flushed away and dihted by littoral hydrodynamic

circulation of the Yangtze Estuary. These municipal and industrial discharges

represent the main source of metals within the Estuary, although inputs along the

entire drainage basin contribute as well (Chen, et al., in press). Figure 5 shows the

locations of these sewage outfalls and their relative contribution of urban and

industrial waste. Three major sewage water outlets occur along the southem coast of

the Estuary near Bailonggan, Zhuyuan, and Baoshan. Chongrning Island, meanwhile,

has six sewage discharge locations. Three minor outlets are located dong the less

industrialized northem shore while the remaining three lie dong the southem shore of

the IsIand. Of the 8.4 million tons of sewage being discharged annually into the

estuary fiom Chongmhg Island, Chengqaio outfidl contributes 76% of the total

(Chen, et al., in press).

2.2 The Yangtze River Estuary

The Yangtze Es- is the outlet of the Yangtze River Valley and the

navigation channel for Shanghai Port, the Iargest shipping port in China (Shen, et al.,

1992). it supports aquaculture, fishenes and domestic waterfowl production for the

surrounding population and Zs also used as a source of water for agricultural imgation

and domestic consmption (Chen, et al., in press). The mouth of the Estuary is

approximately 90 kilometers wide and requires an annual dredging volume of 18x 1 o6

m3 to maintain river depths suficient for navigation (Shen, et al., 1 992). This is due

to the fact that, whiIe typical accretion rates in North Arnencan and European

intertidai zones are in the range of a few millimeters per year and in some cases are

retreating, deposition in the Yangtze Estuary is greater than 2 mrn/yr on average

(Yang, 1999). This rate surpasses the estimated annual global rise in sea level (Chen,

et al., 2000).

The Estuary is a coastal plain, mesotidal, partially rnixed estuary with four

mouths connecting it to the open sea (Figure 5). Each mouth is the product of river

flow diversion around islands within the Estuary. Chongming Island is the largest

island in the Yangtze Estuary and creates the barrier between the North and South

Branches. Changxing and Hengsha Islands then further divide the South Branch into

the North and South Channels. The South Channel is spIit into the North and South

Passages by the Jiuduan sandbar formation at the mouth of the Estuary.

Ninel-eight percent of the sediment that the Estuary receives from the

Yangtze River is suspended load with grain sizes ranging from fine sand to clayey

silts (Shen, et al., 1993a). Bed sediments consist of fine sands in the South Branch.

sandy silts in the South Channel and clayey silts in the North and South Passages.

Tides may effect a distance as great as 350 km into the lower reaches of the river

(Zhang, 1999). creating mean tidal ranges of 2.66 m in the Southern Branch. with

hi& tides of 3 . 3 4 2 m and low tides of 0.28-0.18 m (Li and Zhang, 1996). Marine

inputs of sediment do exist but sediment inputs fiom the River make the most

significant contribution by far to the Estuary (Li, et al, 1993). More than one half of

the sediment that enters the estuary becomes deposited on the broad deltaic area,

helping to create the well-developed tidal wetiands that prograge seaward at a rate of

100-300 m/yr (Zhang, et al., in press). The remaining sediment travels southward

and eastward and settles on the continental shelf zone of this area (Zhang, 1999).

b Sewage water outlet

Scale of arrow relative to the * amount of m a g e discharge

Lake ,, Sample transect (not to sale)

15 h O-

I rn

1 21° 122'

Figure 5: Yangtze Estuary, China (Based on Chen, et al, in press).

2.3 Yangtze Estuarine Islands

The formation of Chongming, Changxhg, Hengsha Islands and the Jiuduan

sand bar began in the 7", 17', 19', and 1950's respectively. The ùiree islands are

constantly being reclaimed using a system of continuous ring-like retaining walls or

dykes (Yang, 1999~). In total, they share approximately 301 retaining walls, each an

average of 145 m in length. These walls are used to improve shore stability and

prevent erosion or migration. As of 1999, Chongming, Chongxing and Hengsha

Islands had shorelines that were approximately 210 km, 59 km and 30 km in length,

respectively (Yang, 1999d). Alluvial grain size dong the shores of Chongming Island

lies in the range of clayey-silt whiIe sediment dong Hengsha Island ranges fiom

clayey-silt to sandy-siIt with increasing distance offshore. Benthic fauna on al1 three

Islands is dominated by the presence of two types of bottorn-feeding crabs: Sesarma

debaani and 27yoplmc deschampsi (Yang, 1 999c).

2.4 Island Tidal Flats

RecIamation efforts have significantly altered the tidal flat areas on each

island (Yang 19994. The resultant intertidai areas are 2093 km2, 44 km2 and 16 km2

for Chongming, Changxing and Hengsha Islands, respectively (Yang, 1999d). In a

seaward direction, the intertidal zone contains several distinct units that can be

identified by their colonizing pIant species: the Phragmitis ustralis zone, Scirpus

marqueter zone, and Scirpus triqueter zone followed by bare rnud flats (Figure 6).

This entire progression of plants, however, does not necessarily occur at each island

due to land reclarnation (Zhang, et al., in press). As a result, the uppermost

vegetated region of the intertidal zone is usually non-existent (Yang, 1999b). In

general, the division between continuous plant colonization and mud flat occurs at

about 50 cm above mean water Ievel (Yang, 1998).

Figure 6: Plant progression along the tidal flats on Chongming

and Hengsha Islands (Based on Zhang, et al., in press).

According to Li and Zhang (1996), the high intertidal flats in the area are

submerged a total of 3-5 h o m during a tidal period with a sediment size of clayey-

silt. The middle intertidal flats are exposed at tidal heights between mean neap hi&

tides and neap low tides and are composed mainly of silt. Lastly, the lower intertidal

flats are o d y exposed during low tide and are comprised of sandy silt, silt sand and

fine sand. This landward decrease in grain size with distance c m be affected by the

local vegetation as well as the 4-5 storm events that occur annually in the Estuary

(Yang, 1998). Grain size distributions for the upper, middle and lower tidal flats are

illustrated in Figure 7.

Figure 7: Grain-size progression dong Chongming and Hengsha tidal Bats (Based on Li and Zhang, 1996).

2.5 The Tinrbidity Maximum

The turbidity maximum is 25-46 km in length with sediment concentrations

ranging from 0.1-0.7 kg/m3 at the surface to 1-8 kg/rn3 near the bed. It is generally

located in the Southem Branch of the Estuary (Figure 8) but the ultimate position of

the turbidity maximum depends upon the season, tidal action, waves and curent

velocity. During the rainy season and at ebb tide, the turbidity maximum is forced

seaward (Shen, ef a l , 1993a). Cornposed of sediment prirnarily in the range of silts

and clays, this turbid region may experience seasonal variations due to changes in

sediment input fiom upstrearn sources (Li and Zhang, 1998). Tidal effects c m reach

as far as 300-350 km into the lower reaches of the river while brackish waters have

been recorded as much as 100 km idand fkorn the rnouth of fhe river (Zhang, 1999).

Furthemore, with approximately half of the fluvial-supplied sediment being trapped

in the mouth of the river. the turbidity maximum acts as a filter for materials such as

heaw metals, preventing their escape h t o the open sea-

. . - -_ . *. -.. .-- . .::, .. . . , Island '.,-aanfi

Figure 8: Location of the turbidity maximum in the Yangtze River Estuary.

2.6 Chongming and Hengsha Island Economies

Chongming Island is the third largest island in China and the largest alluvial

island in the World. Covering an area of 1,160 km2, the Island stretches 79 km in

length and supports a population of 733,000 people. Twenty-six villages, eight state

farrns and seven municipal state-owned enterprises exist on the land (Govemment of

China 2000a). Although it falls within the District of Shanghai, far less Uidustry has

established on the Island and it currently maintains a predominantly agricultural

economy. In 1996,448 industrial plants and factories were in existence on the Island.

the majority of which are located on the Island's south-central coast (Chen, et al., in

press). Industrial sectors include textiles, metallurgy, machinery, brick making and

electricity. More than 40 hovercraft car-passenger ships and other ferryboats provide

transportation between Shanghai and Chongming Island daily (Govemment of China

2000b).

Hengsha Island is the smailest and most seaward island in the Estuary. The

Island was founded in 1909 and also falls within the District of Shanghai. Hengsha

boasts a thriving a g r i c u l t d economy with grain, Cotton, orange, vegetable, pig and

fishery production. The 109 factories on the island focus mainly on calcination.

metal machining. fumiture, embroidery and brick making. The island is also

attempting to foster a tourism industry, encouraging visitors fkom mainland China to

stay at their national vacation site, constmcted in 1992. As with Chongming I s h d ,

ferry service allows travel to the isIand several times per day (Land Planning and

Management Authority of Baoshan, 1995).

Chapter Three: Methodology

3.1 Objective #1: Transect Selection and Sediment Sampling

The eastern shores of Chongming and Hengsha Islands were chosen as field

sites firstly because they are the shores that experience the highest degree of sediment

deposition and, thus, offer the most developed tidal flat regions for study. Secondly,

the eastern tidal flats are those ciosest to the rnouth of the Estuary and are most

intluenced by the turbidity maximum. Transect locations were selected on the basis

of accessibility and by the extent of exposed tidal flat available for sampling. Since

the islands remain relatively undeveloped and reclamation is constantly extending

their outer boundaries, very few roads extend to the edge of the tidal flats.

Furthemore, travel along the retaining walls to a particular portion of flat was

dificult and sornetimes restncted by construction activities.

Sediment samples from Chongming Island were collected on May 5, 2000

along a survey transect on the most seaward portion of the Island. The initial

sampling site was located at the retaining wall, with subsequent sites located along

the tidal flats. progressing towards the sea in an eastward direction (Figure 9).

Sampling sites were located at 100 m intervals to a total distance of 1800 m. Samples

from Hengsha Island were taken on May 6, 2000 along a survey line that progressed

offshore from the most seaward retaining wall. A more compact sampling interval of

25 m was chosen due to the limited expanse of exposed tidal flat at this location

(Figure 10). The total distance covered by the Hengsha transect was 550 m.

Horizontal distance was measured using a tape measure and a compass was

utitized to maintain a relatively straight path between points. For Chongming Island,

the compas direction was 90° and for Hengsha Island it was 150". Sampling site co-

ordinates were recorded using a hand-held Garmin GPS- 12 Personal ?%avigatorQ'.

These CO-ordinates were subsequently converted to UTM grid CO-ordinates and

plotted on a spreadsheet to c o d m the actual transect path. Figure 13 indicates that

both the Chongming and Hengsha Island transects ran very close to the estimated

lines of site at average angles of 93S0and 149S0, respectively. Samples were

collected to a maximum depth of 5cm using a stainless steel trowel and placed in

ia'oeied, sterile plastic bags for storage (Figure 11). Weather conditions, vegetation

height and relative density were recorded at each site. pH Ievels of the sedirnent were

also measured in the field using a Kelway Soi1 pH ~ e t e r @ (Figure 12). Al1 samples

were placed in cold storage to presewe them for later analysis.

Objective #2: Determination of Sedirnent Parameters and Heavy Metal Concentrations

3.2.1 Drying

Samples were allowed to dry in batches of six at 40°C in an electric oven for a

minimum of 48 hours in coated metal pans to sirnulate air-drying (Figure 14). Once

dry, the sedirnent was ground into a fine powder using a ceramic rnortar and pestle

and sieved using a 2mm plastic sieve to remove any large organic matter such as

reeds or gras. The sieved material was then placed in sterilized plastic bags and

labeled for storage at room temperature.

Figure 9: View of Chongming Island tidal flats Iooking seaward fiom the retaining wall.

Figure 10: View of Hengsha Island tidal flats looking landward towards the retaining wall.

Figure 11: Sample collection on Chongrning Island tidal flats.

Figure 12: KeIway soi1 pH meter?

UTM Co-ordinate Transect for Chongming Island

UTM Co-ordinate Transect for Hengsha island 3465300

392450 392500 392550 392600 392650 392700 392750 392800

Easting Coordinates

Figure 13: UTM co-ordinates for Transects 1 (Chongming 1s.) and 2 (Hengsha 1s.).

3.2.2 Grain Size Anaiysis

Five miIligram sub-sarnpies from each site were sent to the State Key

Laboratory of Estuarine and Coastal Sediment Dynamics and Morphodynamics at

East China Norrnal University (ECNU) for grain size analysis using a Coulter Laser

~ranulometer@ (Coulter Counter). With the exception of C h o n m g samples 1-6, al1

of the samples were sent for analysis before being dned in the electric oven due to

project time constraints. Dilute solutions of each sub-sample were treated with an

anti-flocculent (sodium metaphosphate) and fed into the Coulter Counter by a lab

technicim. Al1 results were obtained and recorded for data analysis.

3.2.3 TOC Analysis

Five gram sub-samples fiom each site were delivered to the Academy of Soi1

Science at Nanjing University for totai organic carbon (TOC) quantification. Prior to

delivery, each sub-sample was air-dried and sieved using a 0.1 mm plastic sieve to

remove any large fragments of extraneous organic matter that could contaminate

results.

Figure 14: Oven-dried sarnple fiom Chongming Island.

3.2.4 Percent Moisture

Ln preparation for heavy metals analysis, percent moisture was calculated for

each oven-dried, sieved sample. Approximately 5 g of sedirnent from each sampling

site was pfaced in clean, dry, pre-weighed cmcibles. The combined weight of the

sedirnent and the crucible was then recorded Crucibles were placed in an eleciric

oven and heated to 10S°C until they had rcached constant weight. The crucible and

sediment were then re-weighed and the difference in weight recorded. Percent

moisture for each sample was subsequently calculated as follows:

3.2.5 Acid Digestion

In order to investigate the role of grain-size in heavy metal concentntions.

sediment samples were not pre-sieved to isolate the fine fiaction prior to analysis.

Instead, two sub-samples of approximately 0.5 g in rnass were removed fkom each

original sample and placed in acid-rinsed glass. Two sub-samples were required from

each site to ensure precision and replicability. Sub-samples were then prepared for

metal extraction in batches of ten by adding 5 mL of 70% Perchloric Acid standard

solution and 15 mL of 70% Nitric Acid standard solution to each beaker. Beakers

were covered with petri dishes and placed on a large heating plate under a fume hood

and brought to a boil. Once a boil had been reached, the heat was removed and the

beakers were allowed to stand overnight. A blank sample containing the standard

solutions but no sediment was also prepared for each batch to account for any

background Ievels of heavy metals that could affect results.

After cooling overnight, heat was once again applied to the beakers in order to

produce a light boil. The samples remained in this state until al1 of the liquid had

been removed. Sub-samples turned fkom an orangehrown color (representing the

Nitric Acid) to a lime green solution. This green solution emitted a white gas that

was caused by the removal of the remaining Perchlonc Acid. Once al1 of the liquid

had been removed, the beakers were allowed to cool. A solution of 10%

Hydrochloric Acid (HCI) was then used to transfer the digested paste fkom each

beaker into a 25 mL volumetric flask that had been rinsed with dilute acid. Srnall

aliquots of the acid were used to rime each beaker and the resulting mixture was

poured into the flasks. Once the transfer was complete, the rernaining volume in each

flask was filled with 10% HCI. The material in the flasks was then mixed. allowed to

settle and delivered to the Key Lab at ECNU for metals analysis.

3.2.6 Metal Concentrations

The quantification of sediment-bond heavy metais requires reliable and

sensitive analytical tools. Criteria upon which analytical rnethods are chosen include:

sensitivity and accuracy, speed and ease of operation, degree of automation. cost of

equiprnent, and reliability of results. Analysis of heavy met& in sediment requires

sensitivity liniits in the range of parts per billion and lower (Savory and Herman,

1999).

Historically, flame Atomic Absorption Spectroscopy ( U S ) has been the

method of choice for the measurement of trace met& in sedirnent for most

researchers (Savory and Herman, 1999). For many elements, detection limits for this

device lie within the range of 0.001 to 0.020 ppm and precision is in the range of one

to two percent. Cold-vapor analysis is also available with th is technique for rnercury

quantification. Mercury represents a special case as it is the only metallic element

that has a significant vapor pressure at arnbient temperatures (Skoog et al., 1998).

With the development of Inductively Coupled Plasma Atomic Emission

Spectroscopy (ICP-AES), however, analytical results gained a sensitivity of up to

1000 times better than flarne AAS (Savory and Herman, 1999). Furthemore, while

flame AAS ody ailows for the analysis of one metal at a time, ICP-AES offers the

opportunity for muiti-element analysis (Skoog et al., 1998). Both methods are

currently wideiy used in trace rnetd research.

For this study, heavy metal concentrations were detennined using an

Inductively Coupled Plasma Atomic Emission Spectrometer. Each sample was fed

into the ICP-AES directly fiom its volumetric flask by a laboratory technician at the

Key Lab. Sarnples are carried through the instnunent to a chernically inert argon

torch that constiiutes the plasma. Upon entering the plasma, beavy metal atoms enter

an excited state and emit a charactenstic wavelength of light. A photomultiplier

detects these wavelengths and their relative intensity is coiiverted into a concentration

by entering the dry weights of each sub-sarnple into the device (Skoog, et al., 1998).

thus eliminating the need for metal concentration calculations. Percent moisture

values are ofien used to adjust heavy metal concentrations according to the oven-

dried weight of the sub-sample but moisture values fiom the study samples were so

low that they were negligible in cornparison to the error associated with ICP-AES

metal quantification. As a result, there was no need to account for the percent

moisture of the sediment sub-samples.

3 3 Objective #3: Analyze Relations Between Metal Concentrations, Sediment Parameters and Sites AlongBetween Transects

The purpose of Objective 3 was to test the hypothesis that the spatial

distribution of heaw met& in surficiai tidal flat sediments is af5ected by position on

the tidal flat, sediment characteristics and proximity to the turbidity maximum.

3.3-1 StatisticaI Approach

The initial step in the interpietaion of the data was to prepare the database for

statistical analyses. The data sets for both Chongming and Hengsha Island sites were

composed of 16 variables including individual heavy metals, distance dong the tidai

f l a ~ average grain size, percent < 20 p, %TOC and pH. Since Al, Fe, and Mn

concentrations were large relative to the other metAs, their values were converted

fiom ppm to percentage for convenience. Metal concentrations were normalized to

the < 20 pm fkacticn in order to remove the grain-size effect (Acke rmw 1983). The

percent clay fraction was also considered for normalization but clay fractions

accounted for a maximum of 18% of any sample while the < 20 p fiaction

accounted for as much as 75% of the sediment and had a larger range.

Scatterplots were constnicted for raw and normalized metal concentrations.

Raw values were plotted against average grain-size, % TOC and pH while distance

measurements were plotted against average grain-size, pH, TOC and normdized

metais. The scatterplots allow for visual analysis of relations between variables.

Simple bivariate correlations were determined using Spearman's Rank Correlation.

Spearman's correlation coefficient (Spearman's rho) was chosen over other

correlation rneihods because it is a non-parametric test that does not assume normally

distributed data with equal variances (MendenhaII and Beaver. 1994). Rasmussen

(1 996) noted that metals cannot be assumed to follow a normal distribution over even

relatively short distances. In this study, Spearman's rho was caiculated to establish

the strength of correlation between raw metal levels and the < 20 pn fraction and

%TOC, and between normalized metals and distance dong each transect and %TOC.

C o n s i d e ~ g that the turbidity maximum is an area concentrated with fine-

grained sediment, an important aspect of this study was to assess the role of this

feature with respect to metal accumulation. While Spearman's Rank Correlation

analysis dlowed for the detection of significant changes in metal concentration within

each transect, the Mann-Whitney U-Test was used to identie significant differences

in metals between the two transects. The Mann-Whitney U-Test is a non-parametric

alternative to the t-test for comp,aring differences in population means (Mendenhall

and Beaver, 1994). This technique was applied to nonnalized metal concentrations as

well as average gain size, % < 20 pm fiaction and %TOC results. A significant

difference between variables fiom the Chongming and Hengsha Island data sets

would indicate that the two population relative frequency distributions were shifted

with respect to their relative locations. This would, in turn, isolate proximity to the

turbidity maximum as a significant control on the distribution of heavy metals within

surficial sediments of the Yangtze River Es- tidal flats.

Principal Components Analysis (PCA) was applied to the original data set.

PCA is a method of data reduction that takes a large set of interrelated variabIes and

uses them to construct a srnall number of independent components or surrogate

variables. These components are ordered such that the first few components identifi

the rnajority of the variance present in al1 of the original variables (Joliffe, 1986).

While some Iiterature considers PCA as a special method of Factor Analysis (Carey,

1969), the two methods are distinct techniques (Joliffe, 1986). While PCA assumes a

closed system in which al1 variance is accounted for by the variables themselves,

Factor Analysis d!ows for sorne degree of external error. In rnost cases, however, the

two methods usually yield similar results (Shaw and Wheeler, 1985). For the

purposes of this research, PCA was chosen to detect relations between heavy metal

concentrations and sediment characteristics. This method was chosen because it

provides uncorrelated and statistically independent variables that are ranked in

descendhg order of ability to interpret variance (Carey, 1969). It was also employed

by Zwolsman. et al. (1996) to study cootrols on sediment-associated metals in the

estuarine environment.

The output values of PCA are referred to as eigenvaiues or component

loadings. These values represent the correlation between each original variable and

the new component. A perfect correlation between a variable and a component is

represented by an eigenvalue of +/- 1. The ultimate goal of PCA is to maximize the

loading value on one component while minimizing loadings on the remaining

components for each variable. In situations where this is not possible, component

rotation can be used to better isolate ctusters of variables. Two methods of data

rotation are avaiiable to the researcher. Orthogonal rotation rotates the cornponent

axes around the origin while maintaining a 90' angle between each a i s . Oblique

rotation rotates the component axes around the origin but does not preserve a 90'

angie between each axis. Both methods have the advantage of isolating groups of

variables without altering the pattern or structure of the data set. The ideal rotation

has been attained when most eigenvalues lie close to an axis and a minimal number of

eigenvaiues lie at some distance from the axes (Shaw and Wheeler, 1985).

For this study, both sets of raw data were subjected to PCA. A decision was

made to elirninate the pH data from the statistical analysis because it was uncertain

whether the instrument readings could be considered accurate. Data was analyzed

using SPSS@ software and results were plotted in component space to visualize

component loadings. Although an orthogonal rotation technique (varimax rotation)

was applied to the da- no improvement in the final results was noticeable. Rotation

was, therefore, not utilized in the statistical analysis of results.

3.2 Objective #4: Cornparison of Heavy Meta) Concentrations with National Standards for Sediment Quality and Global Estuaries

In order to establish the degree of sedirnent contamination within the two

sampbg transects, raw heavy metal concentrations were compared to national

standards for soi1 environmental quality (Table 1) and graded accordingly. When

comparing levels of As, Cu and Cr with the categories in Table 1, paddy soi1 and

familand were chosen to best represent the tidal flat environment since the study axa

is often inundated and, once reclaimed, will most likely be used for f m i n g purposes.

Results fiom this study were then compared to metal levels observed in other studies

performed in the Yangtze Estuary dong with other estuaries around the World (Table

12). A cornparison of this nature would place the research findings within a local and

global context, thus detennining the relative degree of pollution of the Yangtze River

Delta.

Chapter Four: Results

This chapter presents data on sediment charactenstics and heavy metal

concentrations recorded along each transect in the Yangtze River Estuary. Rau- data

from both the field and laboratory portions of the study have been compiied into

tabular and graphicd form. In the course of storing the Hengsha samples for

laboratory analysis, seven labels were lost (HS-1, HS-2, HS-8.5, HS-9, HS-10, HS-

I I , HS-11.5) and these unknown specimens could not be used in the study. This

chapter provides a description of the ravi data followed by a discussion of the

statistical trends present in the data.

4.1 Variations in Sediment Parameters and Heavy Metal Concentrations Along Tidal mats

Figure 15 presents grain size. TOC and pH data for surficial sediments along

the Chongming and Hengsha Island sarnpling transects, respectively (Appendix A).

Transect 1 on Chongming Island was positioned on a tidal flat that graded seaward

from a relatively dense Scirpus marsh, to a sparse marsh and finally to bare mud flat.

This area was lacking in a Phragmitis zone due to constant reclamation in the area.

Ln fact, the most recent set of retaining walls at this site was constructed only two

years ago. Transect 2, on Hengsha Island, was situated on a tidal flat that graded

seaward h m mature, dense reeds (Phragmi~is) to Scirpus marsh to relatively bare

flat. This last segment, however, was compnsed of a noticably Iarger sedirnent size

and had a definite sandy texture. Both sites had well-developed tidal creek systems

across their expanse.

Average grain size data for Transect 1 indicates a slight increase in sedirnent

diameter with distance seaward dong the flat. In general, grain size is relatively

Distance versus %TOC along Transects 1 and 2. 4.0

0.0 ! -

3

O 250 50 7M 1000 1250 1500 1750 2ûûû

Distana along trameçt (m)

Distance versais average grain diameter along Transectr 1 and 2

O 4 O 250 SM 750 Io00 lm 1500 1T50 Mo0

Distance along transeci (m)

Distance versus pH along Trans- 1 and 2.

75 1

4.0 1 0 250 MO 750 1000 1250 1MO 1750 2000

Distance almg transect (m)

Disiance versus percent QO mlcromden along Transects 1 and 2

O 4 1

O 250 500 750 Io00 1250 1500 1750 2000

Distance along b a n d (m)

I 1

Figure 15: Graphs cornparhg sediment characteristics between Transects 1 (Chongming Island) and 2 (Hengsha Island).

constant and covers a m o w range of 18 to 35 p. In contrast. the Hengsha transect

shows greater variability and range in grain diameter. Sediment size is, for the most

part, larger than in Transect 1 (ranging fiom 1 7 to 1 60 pm) and experiences a rnarked

increase at a distance of 475 meters. The < 20 pm fraction mirrors the mean grain

size results. T-tansect 1 shows an overall decrease in the fiaction with increasing

distance. Transect 2 also portrays this pattern, but with a greater degree of variability

and a significant decline at 475 meters.

Total organic carbon content for d l of the tidal flat specimens was minimal,

with a maximum value of approximately 3.5%. This peak was found at the beginning

of Transect 2, which had higher TOC values than Transect 1 up to around 150 meters.

Subsequent to this point. Transect 2 TOC levels were lower than those found on

Chongming Island. Lasdy. pH values for sampling sites along Chongming Island did

not show a significant increase or decrease with distance, although a slight dip did

occur at 100 meters. Hengsha pH vaiues showed greater variability but no visible

pattern besides a marked decrease at the end of the transect

Figure 16 presents raw heavy metal concentrations for Transect 1 and Figure

17 contains concentrations for Transect 2 (Appendix B). Concentrations for Al, Fe,

and Mg were converted fiom parts-per-million to percent for ease of use but represent

the same information. Ln general, al1 of the metals display a decrease in concentration

with distance seaward along the tidal flats. On Chongming Island, the Fe profile

exhibits a sharp peak at 1200 meters that is distinct fiom the rest of the

concentrations. Zinc, Cu, Cdr Al, As, Pb and, to a lesser extent, Mg and Ni

Chromlum rr. ~ t s a n c e Along ndjl Flat (Chongmlng I r )

Znc v s Dlstance Along Tldal Fla! (Chongmlng I r )

Copper rs. Dlstanca Along TM& nR (Chongmlng I r )

500 lm lm 2000

D l ~ . m c Along F l d (m)

4a O 500 la00 lm zoo0

Ohancc Along Fld (m)

Magneslum v s Dl8tanct Along Tldol Ra (Chongmlng 16.)

O 5(r] tooo 1500 ZOO

Distance Along Fla (m)

Nlckcl rs. Dlstance Along Tldal Flat (Chongmlng . l a ) - .

500 lm 15al MOa Distance Along FIat (m)

Figure 16: Raw heavy metal concentrations on Transect 1 (Chongming Island).

Alurninum vs. Distance Along Tldal Flmt (Chongming h)

r

O rac tra, sa, 12a: l s o iarr D i n o m Along Fht (m)

Lmid vs. Distince Along TÏdd FI.1 (Chongming h)

28 ,

Arsenic K Distance Along Yidal FIat (Chongrning k)

11 -,

--- O 5w lm 1 9 0 tOOO

Distance Alang Flat (m)

Cadmium vs. D i S i n a Along Tidil R i t (Chongming k)

Dntincc Along Flat (m)

Chmmium *r Oistance Along TiiI Fht (Herqsha k)

Pnc m. Dl- Along Tldal Rd (Hengsha 1%)

lron ~ 5 . Disîanca Along T i a l Fht ( H e w h a k)

040;

0.10 1 O 1 0 0 2 0 0 3 0 0 4 m 500m

Di- AIong Fia! (m)

Copper vz Distance Along lïdal Flat (Hengsha h)

50 ;

Y agrœsiun K Didincs Aiong Tidal Fid (Hengsha k)

006 4

O 100 200 300 400 500 600

Distance Along Flat (m)

Nlckel vs. Mdance Abng Tldal Flat (Hcngsha !S.)

10 j O 1 0 0 2 0 0 3 0 0 4 0 0 5 0 0 m

Distance Aimg Flat (ml

Figure 17: Raw heavy metal concentrations on Transect 2 (Hengsha Island).

Aîurnlnum vr Dlstancs Along ndal FI* (Hengsha 1%)

0.71 - 1

D i m n c s Along Rit (m)

Lead vs. Dtstance Along Tidal Fiat (Henpsha 1s)

50 -

O

O f O O X K ) J 0 0 4 m S 0 6 0 0 0 1 i ~ a c c long mat (m)

Cadmium vs. Distance Along Tidal Flat (Hergsha 1s.)

Manganse e. OIsgnce A l ~ n q Tidal Flat (Hengsha is.)

- I / Y

mit vs. Distana Nang Ttdal Flat (Herigsha 1s.)

4 '

O 1 0 0 2 M J 0 0 a O O m 6 0 0

Oistance Along Flat (ml

al1 show slight dips in concentration at the second sampling site and Zn, Cu, NiT As.

Mn and Al d l dispIay a visible decrease at the 700' 1500 and 1800 meter marks.

With respect to Transect 2, metals generally showed a minimum concentration at the

475 meter mark? with the steepest decline in concentration usually occurring over the

initial 100 meters for most of the contarninants. While the majority of metals display

a decrease in concentration with increasing distance, the Pb, As and Cd data sets are

extremely variable, making it difficult to distinguish pattern.

4.2 Relations Between Heavy Meta1 Concentrations and Sediment Characteristics, Position on the Tidal Flat and Proximity to the Turbidity Maximum

Results of the statistical analyses are presented in three sections. The first

section presents the results of scatterplot (Figures 15-17) and Spearman's Rank

Correlation analyses (Tables 2-5) for Transects 1 and 2. The second section contains

results from the Mann-Whitney U-Test (Tables 6 and 7) for difference of means. The

third section presents the output fiom the Principal Component Andysis conducted

on Yangtze River Estuary data.

4.2.1 Scatterplots and Spearmans Rank Correlations

Appendix C provides scatterplois for the raw and normalized data from

Transect 1 and Appendix D provides scatterplots for the raw and normaiized data

from Transect 2. On Chongming Island, al1 metals dispIay a decrease in

concentration with distance and average grain size. When pIotted against TOC

content, metal levels increase with increasing %TOC. In contrast. the scatterplots of

pH levels versus heavy metal concentrations did not dispIay any clear relationships.

On Chongming Island, normaiized metal concentrations are variable and do

not exhibit a trend in rnetal concentration with distance dong the transect. Metals,

however, do display a slight increase in concentration with average grain dimeter.

Of these increases. Cd, Pb, As and Cu show the weakest relationships. Upon pfotting

the organic carbon content of the sediment against normalized metal levels, the

previously noted increase with increasing TOC is no longer apparent. The graphs

also indicate a higher degree of variance within the data. Lastly. scatterplots of pH

versus the normaiized data did not show any visible trends.

On Hengsha Island, the normalized metal concentrations d l indicate an

increase over the 1 s t two sarnpling sites. Prior to this section of the transect, no

visible increase or decrease in concentration is evident. Similar to the results fiom

Transect 1, this data set also displays an increase in met& with average grain size

dthough the large increase in sediment diameter over the last several sampling

locations causes a gap in the plot. Scatterplots of metais versus %TOC are highly

variable with the highest rnetal levels occurring at the lowest organic matter contents.

pH data. meanwhile, do not show any obvious relationships.

Tables 2 and 3 provide Spearman's Rank correlation values for raw and

nomdized (by % < 20 prn) heavy metd concentrations fiom Chongrning and

Hengsha Islands. Before performing correlation analyses on the Fe data, the outlying

point on Chongming Island identified in the previous section was removed and

replaced with a new value by taking the mean of the two surrounding points.

Significant correlation coefficients with the < 20 p fiaction confirm the grain-size

effect for al1 of the metals except Cr and Mg in Transect 1 and Mg, As and Cd in

Transect 2- Upon normalization (by % < 20 pn), correlation analyses do not exhï'bit

statistically significant relationships between any of the metals and distance along

either transect.

Table 2: Spearrnan's correlation coefficient for raw and normalized heavy metal concentrations almg Transect 1.

Table 3: Spearman's correlation coefficient for raw and normalized heavy metal concentrations along Transect 2.

r . - . . - , . . 7 .: z - . - . - - . . - , . . . . . . . .

Spearman's Rho (metal vs. -= 20pm)

r . b w D m . ', - , - . . - . .

In order to isolate whether heavy metals were correlated to the amount of

Al

.756

*

organic matter present in the sediment, independent of grain-size, Spearman's rho was

Cr

-228

- - .: . r . . N o i m d k & ï D ~ ~ . . - . . - . - , . - . - . . - - ,. . . , - .L . . . -

Speaman's Rho (metal vs.

-=mm

Z n

;.$$O ., - 1 . , .-

<. .. 1

" la..

, - . r - . - - 3 ,. A

' . - -- .. . - . ' l

''<sig~fi&& &;OS. hl (2-taiied)

Cd

.j96

Fe

.:568'. ". . - -

. &

. . L, . .. -

Mn

,484

Cr

.661

NormilizedDlitn . . . . "

- . _

* * Signifhni a* the .OZ level(2-tuilen)

Spearman's Rho (metal vs. distance)

Fe

' -577 . . . . .. ,

f - - . . Ir

Pb

.6O.f

Z n

.354

Mn

.261

Mg

-472

Ni

.742

As

7

Z n

,641

As

.O30

Cr

-35 I

Pb

-.ZOO

Ni

.630

C u

.752

Mn

-215 Spearman's Rho (metal vs. distance)

Cd

.O42

Fe

-153

Mg

.352

C r

.O87

M g

-35 1

Fe

,087

C u

-681

C u

-.O30

AI

.675

Cd

--- Mg

,467

Zn

-386

Pb

-380

As

-493

As

-473

Ni

-339

Cd

.O57

Mn

- . -583 -

. , O --- " .

Cu

-.391

Al

-.334

Pb

- 508

- .

Ni

-410

Al

-.200

calculated for raw and noraalized metais versus %TOC. As Tables 4 and 5 indicate,

almost all of the metals correlate with %TOC at the 0.01 significance level prior to

normalizat ion. M e r norrnalization, however, only the Transect 1 Al data exhibits a

statistically signiftcant relationship with TOC.

Table 4: Speamian' s correlation coefficient for raw and normdized heavy metal concentrations versus %TOC for Transect 1.

* 4 S~W& at ,th& -05: 1&@(2-tail@) 1 ** Signijkznt at the -02 level(2-tuiled)

. . . ". . Dm.. . - _ A - ..- , , , . - * . " . I . - .. - . . r 2,

- . ' _

Table 5: Spearman's correlation coefficient for raw and n o d i z e d heavy metal concentrations versus %TOC for Transect 2,

As

.883

Spearman's Rh0 (metal vs. OhTOC)

-O*. :- . . ,. . . . . . . : . . . - - . . - - .

M g

.878

Cd

512

~~h-- D*': :. ' - . . . .,. . 5 . .

. - . - , - . . . . . . . - . - - - . : - " - . - - . .-

7 - . ' 1 .

Spearman's Rh0 (metal vs. %TOC)

C u

-920

Z n

.9S8

Cr

-706

Cr

- -832-

Fe

.763

As

-105

Spearman's Rh0 (metalvs.

Fe

: -847 , - -

. " . . , , - . . % Norm.iPiaDif.,;,. - b - ..A . . . u . - ' ,.- ; . . ? . - . - :.. . . _? . . . . . - - > . - ' , . -

Cd

.O44 %TOC)

Cr

-.227

Ni

-933

1

Fe

-001

Z n

=635 - - . . ..

Ni

: .80q -

Spearrnan's Rh0 (metalvs. Yo TOC)

Mn

-956

Al

-901

Mg

-.135

Z n

-.la3

Mn

-815 -

Ai

:. 871

Cr

-.O99

Pb

.826

Mg

-705 . . + - j

Cd

- Fe

-.O44

Cu

-.391

Pb

-200

Cu

... 835 .

Z n

-.324

As

-509

Ni

-.193

Cd

.419

M g

-,458

Mn

.158

Al

-464

Pb

.246

Cu

.463

Ni

-.410

Pb

-.315

As

-.470

Ai

.147

Mn

-.228

4.2.2 Mann-Whitney IJ-Test Analyses

Tables 6 and 7 summarize the results of the Mann-Whitney U-Test comparing

the sediment parameter and normalized metal population means fiom the Chongming

and Hengsha I s h d data sets. Tables 8 and 9 indicate that average grain size, Al, Cr

and Cd values fiom the Hengsha Island data set are signiticantly different and higher

than those on Chongming Island at the 95% level. If the confidence levei for the

analysis was expanded fiom 95% to 90%, %TOC and Fe would also be considered

significant ly different between the two transect S.

Table 6: Mann- Whitney U-Test comparing sediment parameters between Transects 1 and 2.

Table 7: Mann- Whit ney U-Test comparing heavy metal concentrations fi0 m Transects 1 and 2.

4.2.3 Principal Component Analyses (PCA)

The pH data was excluded from the PCA due to the uncertain reliability of the

field results. Furthemore, the outlying Fe data point in the Transect I data set was

also repIaced with the mean of the two closest neighboring points to ensure that this

anomaly did not affect the output fiam the test. Raw data generated fiom PCA

calculations are provided in Table 8. Table 9 provides the component loadings

calculated fkom Principal Component Anaiysis using SPSS" software. Statistical

variables for both transects consisted of raw heavy metal concentrations. distance

dong the transect, %TOC and average grain size. Figures 18 and 19 are plots of the

eigenvalues against the principal axes (components 1 and 2).

As indicated by Table 9 and Figure 18, the first component groups al1 of the

variables except Cr and Cd in Transect 1 and Cd in Transect 2. Within this grouping,

however. distance and grain size variables hold negative eigenvalues while the

remaining variables have positive eigenvaiues. Component 1 accounts for more than

70% of the variance arnong metal concentrations and sedirnent parameters for the

Chongming and Hengsha Island data sets while cornponent 2 accounts for

approximately 10% of the variance. Transect 1 shows relatively weaker relationships

between grain size with Component 1 and, Cr and Cd with Component 2, as indicated

by the similar eigenvalues for both axes. Transect 2 (Figure 19) has weaker

component loadings for Pb and As with Component 1 but these metals still show

good differentiation in eigenvalues between each a i s .

Table 8: Principal Components Analysis loadings.

Transect 1 : Chongming Island I

Variable Cornpanent

Transect 2: Hengsha Island I

TOC AS Mn Fe Pb

Distance Mg

Grain Size Cd Cr

Variable 1 Component

0.952 0.950 0-935 0.89 1 0.853 -0.792 0.784 -0.640 0.583 0.565

O. 188 -0.037 0.294

O. 1 O0 -0.158 0.0 13 0.35 1 0.618 -0.642 0.67 1

Zn TOC

Distance AI

Grain Size

0.899 0.898 -0.895 0.874 -0.785

0.058 -0.151 O. 168 -0.182 0.33 1

Component 1 1

Table 9: Principal Components Analysis summary for Transects 1 and 2.

Component 2 1 Component 1

Transect 1 Transect 2

Distance TOC

Grain Size Al Fe Mg Zn Cu Ni Mn Pb As Cr

Distance TOC

Grain Size Ai Fe Mg Zn Cu Ni Mn Pb

As % of total variance:

73.68 % of total variance: - L I

Component Plot

grain

% of total variance: 11.02

Cornponent 1

% of total variance: 7135

Figure 18: Plot of component loadings for Transect 1.

Component Plot

' - O 0

-51

grain

istance

-1 .O -.5 1

Component 1

Figure 19: Plot of component loadings for Transect 2.

4.3 Cornparison of Heavy Metal Concentrations with National Standards for Sediment Quality and with Global Estuaries

According to the National Standards for Soi1 Environmental Quality (Table

l), the ievels of heavy met& within tidal flat sediments of the Yangtze Estuary

(Table 10) contain metal concentrations consistent with natural background levels,

that is Grade A quality. Along Transect 1, Cr, Zn, Cu,Ni, Pb and As level al1 fa11

within the Grade A category and Cd falls between Grades A and B. Along Transect

2, Cr, Zn, Cu, Ni, Pb and As are consistent with concentrations in Grade A soils.

Cadmium concentrations on Hengsha Island range between those found in Grades B

and C soil.

Table 10 compares the heavy metal concentrations fkom this study with those

recorded elsewhere in the Yangtze Estuary as -ive11 as various other estuaries

throughout the World. Results from this study are consistently lower than metal

concentrations measured by Zhang (1999) and Zhang, et al. (1994) in suspended

sediments of the Yangtze Estuary. Alurninum, Cr, Fe and Mg levels in this study al1

fa11 well below those reported in other estuaries and Mn concentrations only approach

those fiom the Orinoco River. Zinc concentrations are comparable to concentrations

noted by Wright and Mason (1999). Copper and Pb ranges are similar to levels

documented in the Scheldt (intertidal flat) and Lena Estuaries and, to a lesser extent,

the Mississippi. Nickel levels approximate concentrations in Orinoco, Scheldt

(intertidal flat) and Lena Estuaries. With the exception of Cd, al1 metal

concentrations measured in this snidy are lower than those from other estuaries.

Chapter Five: Discussion

This chapter presents a discussion of the data trends and statistical results

provided in Chapter 4. The arguments are organized according to research objectives

three and four. The first section. therefore. focuses on analyzing the scatterplot and

statisticai results for both the raw and nomalized heaw metal concentrations and

interpreting the implications of these results with respect to controls on heavy metal

behavior in the Yangtze River Estuary, China. This is followed by a cornparison

between the metal Ievels recorded in this study with national standards for soi1

environmental quality as well as those documented in other studies of the Yan,atze

Estuary and estuaries around the globe.

5.1 Relations Between Heavy Metal Concentrations and Sediment Parameters, Position on the Tidal Flat and Proximity to the Turbidity Maximum

In general. the Hengsha Island tidal flats display a larger average grain size

than Chongming Island, peaking at a value of 160.2 p m compared to 37.3 p m on

Transect 1. This confirms Yang's (1 999c) observation of a progression from clayey-

silt to sandy-silt along the Hengsha flats while Chongming is primely clayey-silt.

The peak in %TOC and fine sedirnent along the initial 100 m of Transect 2 is most

likely due to die dense Phragmitis u s ~ l i s marsh situated along the Hengsha Island

seawalls. It is also possible that the rising tides wash organic matter frorn the lower

flats and deposit them in this upper marsh section. The subsequent decrease in TOC

and increase in average gain diameter beyond this point contribute to the decline in

metal concentration over the remaiMg stretch of flats. This initial peak near shore is

also seen, to a lesser extent, in the % < 20 pm fraction data. Similar fmdings were

noted by Zhang (in press) and are a testament to the current-attenuation and sedirnent-

trapping ability of the reeds during their sporadic inundation. OveralI, however. the

organic content of the sediment dong both transects is very low. This observation is

supported by the findings of Zhang (1999). In fact, the range in %TOC recorded on

the Chongming Island transect matches aimost exactly the results of Zhang (1999) of

051 .5% total organic carbon. Finally, decreases in Zn, Cu. Ni, As, Mn and Al at

700 m, 1200 m and 1700 m dong Transect 1 do not correspond to increases in grain

size but are the result of lower organic content.

The interdependent nature of grain size with TOC and raw metal

concentrations makes it difficult to interpret whether or not trends actually exist with

distance along each transect. Consequently, the nomalized scatterplots should

eliminate the possibility of these interdependencies and allow for a bivariate analysis

of results that reveal relationships between independent variables. Normdization of

the Transect 1 data resulted in no obvious trends in heavy metals with distance along

either transect while the Hengsha Island normdized metal concentrations peaked

sornewhat within the last 150 rn of the transect. While it is tempting to interpret these

results as an indication of the turbidity maximum's abiIity to trap metals, Daskalakis

and O'Connor (1995) note that high nomalized metal concentration should not be

accepted as evidence of contamination before carefid examination of the values that

comprise the ratio. This is due to the sensitivity of the normaiized value to the

denominator of the ratio. However. metal concentrations at the Iast two sarnpling

sites are much lower than concentrations over the remainder of the transect. This

would suggest that the elevated concentrations being witnessed in the scatterplots are

hkely a function of the extreme increase in average grah diameter. not an extreme

increase in heaw rnetd concentrations.

Spearman's Rank Correlation results confinned the lack of any significant

increase in sedirnent-associated heavy metal concentrations with distance seaward

along the tidai flats and, consequently, proxirnity to the turbidity maximum within

each transect for both data sets. The same was true for sediment-associated total

organic carbon levels since no significant relationships could be established once

normalization of the raw data had been performed. Furthemore, for the most part.

the Mann-Wtney U-Test result did not identifi a significant correlation between

proxirnity to the turbidity maximum and elevated metal levels between transects.

This irnplies that correlation in the raw data was merely the product of a strong

dependency between metals and organic matter content with the fine sediment

fraction.

The Principal Cornponents Analysis (PCA) results, in turn. echoed the

findings of the Spearrnan's Correlation analysis. in both transects. the primary

component, which refiects the grain-size effect. contains distance. grain diarneter,

TOC and the majority of the heavy metais. This component accounts for more than

70% of the overall variance. The second component contains the rernaining rnetals.

including Cd. This confirms the weak Spearman's correlation between Cd and grain-

size and suggests that cadmium's chemical properties are distinct fiorn other heavy

xnetals. Zwolsman, el al. (1996) reported similar fmdings in their study of the Sheldt

E s t u q . While PCA isolated Cr under Component 2 for C h o n m g Island, the

strength of the relationship is not strong enough to necessarily be considered

significant. The PCA results for both transects? therefore, are essentially identical and

lead to the conclusion that grain-size is the prirnary controIling factor in the

distribution and behavior of heavy metals in the Yangtze Estuary. China,

Magnesium was the o d y raw metal that did not indicate a significant

relationship with the < 20 pm fraction along both transects under the Spearman's

correlation technique. Furthemore. the element did not exhibit a change in

correlation afier normalization. This conse~ative behavior indicates that Mg levels

are primarily lithogenic in origin and that any anthropogenic inputs of this element

are insignificant in comparison to nanirally occurring concentrations. The Mann-

Whitney U-Test did identifi statistically significant differences in the frequencies of

average grain diameter, Al, Cr and Cd. The larger average grain-size of Transect 2

simply adds fiirther support to Yang's (1999~) observations. Aluminum

concentrations are of lithogenic origin and most likely reflect the difference in

sediment size distribution between the two islands. Finally. the elevated levels of Cr

and Cd on Hengsha Island could have resulted fkom a strong affinity for aluminurn,

which may explain cadmium's anomalous behavior with repect to other metals and

norrnalization. The possibility remains, however, that these findings are simply due

to the relatively low concentrations of Cd and Cr in the estuary.

5.2 Cornparison of Heavy Metal Concentrations with National Standards for Sediment Quality and with Global Estuaries

With the exception of Cd, the levels of heavy metals within tidal flat

sediments of the Yangtze Estuary are prharily Grade A in character. This apparent

high quality of sediment along the tidal flats does not correspond to the large arnount

of contaminating effluent that is known to be entering the study site. Two possible

explanations exist for this discrepancy between pollution inputs and level of

contamination: dilution of heaw metals by riverine suspended sedirnents or the

mobilization and subsequent transport of metals farther seaward along the continental

shelf. Whïle approximately 50% of estuarine sedirnent does escape and become

deposited on the continental shelf (Zhang, et al., in press), the lack of rnetal

contamination along the Yangtze Estuary tidal flats is likely a function of "self-

purification" by the tremendous water and sediment load of the Yangtze River. This

finding cofirms the research performed by Zhang, et ai. (1990), Zhang (1 999) and

Chen. et al. fin press) and supports their conclusion that heavy rnetal contamination in

the Yangtze E s t u q is dificuit to detect due to the dilution of metals by riverine

sediment.

When results fiorn this study were compared to metal leveis observed in two

other studies of the Yangtze Estuary, heavy metal concentrations in the tidal flat

sediments were found to be lower than those recorded in previous work. This

discrepancy can be explained by a number of factors. Firstly. the metal levels

recorded by Zhang, et al. (1994) and Zhang (1 999) were attained from suspended

sediments that are finer than those of the tidal flats and are likely to adsorb more

contaminants. They are also subject to a variety of different environmental

conditions than tidal flat sediments. Where tidd flats are intermittentiy exposed to

the atxnosphere and are effected by colonizing salt marsh species, suspended

sediments are completely inundated and experience the various adsorption and

depositional processes associated with estuarine mixing. Furthemore, the temporal

variability in riverine and tidal flow conditions as well as the spatial and temporal

variability inherent to sediment-associated metal distributions within this dynamic

system are Iikely to produce inconsistencies between studies.

Yangtze Es* tidal flat sediments have Al, Cr, Fe and Mg levels below

those reported in other estuaries. The lower Al. Fe and Mg concentrations primarily

reflect differences in the Iithogenic composition between the source materials of

sediment in the different locations, rather than lower contamination Zevels. Zinc

concentrations fa11 near those recorded in the Orwell Estuary which is considered by

Wright and Mason (1999) tc be of poor water quality due to industrial and sewage

inputs. While Cu. Ni and Pb levels match closely those of Lena Estuary, a relatively

pristine river system, they also approach rneasurements fiom Scheldt (intertidal flat)

Estuary, a highly industriaiized and populated environment. It is important to note.

however, that the Scheldt intertidal flat metal concentrations are substantially lower

than those found in submerged samples. Thus, the distinction between tidal flat

versus submerged bottom sediment is a meaningful one.

While concentrations of Cd were minimal relative to the presence of other

heavy metals detected in the Yangtze Estuary, îhey approxirnate those recorded in

heaviiy polluted estuaries h m North America, Europe and the rest of the World.

The high toxicity of Cd and its ability to accumulate aIong the food chah (Thornton,

1995), poses a significant threat to the people of Shanghai District. Concentrations

should, therefore, be closely monitored, not only in the estuarine sediment but also in

the vegetation and fish yields that are being harvested fiom the area. Finaily, Cr

levels are considerably lower in the Yangtze intertidal sediment than in other study

locations. This occurrence is most likely the result of a difference in industriai

practices between the sites. As China continues to grow and develop. however. it can

be expected that these concentrations will also increase.

Chapter Six: Summary and Conclusions

Heavy metals are produced boom a variety of natural and anthropogenic

sources. These metals enter estuaries fiom points dong the entire drainage basin and

within the estuary itself. Once ioside an estuarine system, complex interactions

amongst river discharge, saltwater intrusions. local currents, effiuent point sources.

pH. temperature, oxygen content and sediment re-suspension processes c m affect the

degree of contamination of surficial sediments. The accumulation of metals in

estuarine sediments holds significant environmental implications for local

cornmunities as well as for marine water quaiity.

The watershed of the Yangtze (Changjiang) River, China is one of the most

densely populated regions in the World. Rapid reclarnation of tidal flat zones for

agricultural and housing purposes within the District of Shanghai have raised

concems regarding the impact of contaminated sediments on the local population.

Understanding the behavior of heavy metals and establishing patterns of

contamination would allow for the prediction of areas within the Estuary that are at

high nsk to pollution. The purpose of this research was to determine the patterns and

controls of onshore-offshore variations in heavy metal concentrations within surfrcial

sediments of the Yangtze River Estuary tidal flats.

While raw heavy metal concentrations were shown to increase with distance

seaward. Spearman's Rank correlation analysis did not exhibit statistically significant

reiations between normalized metal concentrations and distance or organic matter

content within transects. With the exception of average grain diameter, Al, Cr and

Cd, the Mann-Whitney U-Test results found no significant difference between

Chongming and Hengsha tidal flats. This irnplies that proximity to the turbidity

maximum does not play an important role in controlling the occurrence of heavy

met& within surficial tidal flat sediments of the Yangtze River Estuaq.

The Spearman's Rank, Mainn-Wtney and Principal Component analyses dl

established grain-size as the dominant control on the spatial distribution of metals and

organic rnatter in the study site. Cadmium was the only heavy metd that did not

exhibit a strong relûtion with grain-size, most likely because of the its unique

chernical attributes and anomalous behaviour during normalization. Consequently.

any increase in heavy metal concentrations with distance landward on the tidal flats is

a product of the depositional pattern of nsing tidal waters, where advancing waters

experience attenuation and a decrease in sediment load with thek advance to shore.

This conclusion is supported by a variety of studies in the study area (Zhang et al.. in

press; Zhang, ei al.. 1 990; Zhang, 1 999 and Chen, ei al., in press).

While it is clear that a tremendous arnount of heavy metals, and pollutants in

general, are constantly being discharged into the Estuary. there is no evidence of

contamination on the Yangtze tidal flats. In fact, with the omission of Cd. al1 heavy

metals display concentrations that are consistent with natural background Ievels

according to China's national standards for environmental soi1 quality. Cornparison of

these results with other estuarine studies likens the sediment quality of the Yangtze

Estuary with relatively pnstine environments. The lack of evidence in support of

sediment contamination fiom ciomestic and industrial discharge is most likely the

product of dilution by high fluvial sediment loads fiom the Yangtze River. This

discrepancy, along with that between metal concentrations in intertidai sediment

versus suspended or bonom sedirnent is an ineiguing area of focus for future

research. Eventually, the "self-purification" dilution phenomena wili not be abIe to

compensate for the tremendous level of development that is, no doubt. fated for

China. While it is taking steps towards regulating pollution in the Yangtze

watershed. the govenunent of China should continue studies such as this to help

monitor. preserve and irnprove sediment and water quality in the Yangtze Estuary.

References

Ackermann. F. 1980. A procedure for correcting the grain size effect in heavy metal analyses of estuarine and coastal sediments. Environmental te ch no log^?

Letters, 1 : 5 18-527.

Ackexmann. F.. G. Bergmann and U. Schieichert. 1983. Monitoring of heavy metals in coastal and estuarine sediments - a question of grain size:

prn versus <60 prn. Environmental Technology Letters, 4: 3 17-328.

Amos. C.L. 1995. Siliciclastic tidal flats. In Geomorphology and SedimentoZogy of Estuaries, ed. G.M.E. Penllo, 273-306. New York: Elsevier Science Publishers.

Buckley, D.E. and G.V. Winters. 1992. Geochemical characteristics of contaminated surficial sediments in Halifax Harbour: impact of waste discharge. Canadian Journal of Earth Sciences, 29: 26 1 7-263 9.

Burton, J.D. and P.J. Statham. 1990. Trace met& in seawater. In H e q Metals in the Marine Environment, ed. R.W. Furness and P.S. Rainbow. 5-25. Flonda: CRC Press. Inc.

Carey, G. W. 1969. Principle component factor analysis and its application to geography. In Quantitative Merhods in Geography. ed. Arnerican Statistical Association? 6-20. New York: Ainericm Geographical Society.

Chen, M., B.L. Chen and F.X. Xia. 1996. Heavy metals in suspended and bed sediments in turbidity maximum of the Yangtze Estuary. Journal of Easr China Normal University, 1 : 3 8-43.

Chen. H.M., C.R. Zheng, C. Tu. Y.G. Zhu. 1999. Heavy metal pollution in soils in China: status and countermeasures. Ambio. 28: 13 0- 134.

Chen, Z., R. Kostaschuk and M. Yeng. Spatial and temporal distribution of heavy metals on the tidal flats on the Yangtze Estuary, China. Environmental Geology, 40: 743-747.

Daskalakis. K.D. and T.P. O'Connor. 1995. NormaIization and elemental sediment contamination in the coastal United States. Environmental Science and Technology, 29: 470-477.

Dawson. E.J. and M.G. Macklin. 1998. Speciation of heavy metals in floodplain and flood sediments: a reconnaissance s w e y of the Aire Valley, West Yorkshire, Great Britain. Environmental Geochernistry and Health, 20: 67- 76.

Dauvalter. V.A. 1998. Heavy metals in the bottom sediments of the Inari-Pasvik lake-river system. H'ater Resources. 25: 45 1-457.

Davies- B.E. 1992. Trace metals in the environment: retrospect and ~rospect. In Biogeochemistry of Trace Metals, ed. D.C. Adriano, 1 - 1 7. Florida: Lewis Publishers.

de Groot, A.J. 1995. Metals and sediments: a gIobd perspective. Ln Metal Contaminated Aquatic Sedirnents, ed. H.E. Allen, 1-20. Michigan: Am Arbour Press. Inc.

De Jong, D. and Stortelder? P.B.M. 1993. River basin.: sediments as a key factor in policies and research programs. In ïntegrated Soil and Sediment Research. ed. P. Eijsackers and T. Harnes. 23-36. Massachusetts: Kluwer Academic Publishers.

Dyer. KR. 1972. Sedimentation in estuanes. In 73e Estuarine Environment. ed. R.S.K. Barnes and J. Green. 10-32. London: Applied Science Publishers. Ltd.

Dyer, KR. 1994. Estuarine sedirnent transport and deposition. In Sedimsnt Transport and Depositional Processes, ed. K. Pye, 193-2 18. England: Blackwell Scientific Publications.

Dyer, K.R. 1995. Sediment transport processes in estuaries. In Geornorphology and Sedimentology of Estuaries? ed. G.M.E. Pedlo, 423-449. New York: Elsevier Science Publishers.

Fang, S. and E. Hong. 1999. Mechanisms influencing the spatial distribution of metds in surficial sedirnents of the south-western Taiwan. Marine Pollution Bulletin.38: 1026-1037.

Feltz. H.R. 1980. Significmce of bottom material data in evaluating water qudity. 1 n Contmninants and Sediments Volume I : Fate and Trunsport, Case Studies, Modeling, Toxicity, ed. R.A. Baker, 27 1-287. Michigan: Ann Arbor Science Publishers- Inc.

Forstner. U. 1985. Chemicai forms and reactivities of metals in sediments. In Chernical Methods for Assessing Bio-availab le Metals in SZudges and Soils, ed. R. Leschber, R.D. Davis and P.L. Hermite, 1-30. New York: Elesevier Applied Science Publishers.

Forsîner, U. and G.T. Wittman. 1979. Metul Pollution in the Aquatic Environment. New York: Springer-Verlag.

Funiess, R. W. and P.S. Rainbow. 1990. Heaw metals in the marine environment. In Heavy Metals in the Marine Environment. ed. R.W. Fumess and P.S. Rainbow. 1-3. Florida: CRC f ress, Inc.

Govenunent of China. 2000a. Chongming Island: investment and development. <h~:!!w~w.sh.comidistnctf~h~n~min~~chonhtm Accessed on February 24. 2000.

Governent of China. 2000b. China: land and resources. chrtp:i:'ww~v.China~or~~~n~En~Ii~h~chinaiZand~html Accessed on February 24. 2000.

Irabien. M.J. and F. Velasco. 1999. Heavy metals in Oka River sediments (UrdaibaiNational Biosphere Reserve, northern Spain): lithogenic and anthropogenic effects. Environmental Geolom, 3 7: 54-63.

Jemett, J.C., S.W. Effler and B.G- Wixon. 1980. Mobilisation and toxicological aspects of sedimentary contarninants. In Contumimnts and Sedimenrs Vol. 1: Fate and Transport, Case Studies, Modelling, Toxicify, ed. R.A. Baker, 429- 444. Michigan: Ann Arbor Science Publishers, Inc.

Joliffe, I.T. 1986. Principal Component Analysis, New York: Springer-Verlag. Inc.

Karuppia, M. and G. Gupta. 1998. Chronological changes in toxicity of and heavy metals in sediments of two Chesapeake Bay tributaries. Journal of Hazardous Waste? 59: 159-166.

Land Planning and Management A~thOrity of Baoshan. 1995. Toponomy of Baoshan. Shanghai, Shanghai Scientific and Technical Literature Pubiisher. 217.

L'Her Roux, L., S. LeRoux and P. Appriou. 1998. Behaviour and speciation of metallic species Cu, Cd, Mn and Fe during estuarine mixing. Marine Pollution Bulletin. 36: 56-64.

Li. J.F. and C . Zhang. 1996. The tidal flats morphological development and the coastal Iand reclamation in Shanghai. The Journal of Chinese Geography, 6: 84-9 1.

Li, J.F., W.R. Shi, H.T. Shen, H.G. Xu and D. Eisma. 1993- The bedload movement in the Changjiang Estuary . China Ocean Engineering, 7: 44 1 -450.

Luoma, S.N. 1990. Processes affecting metal concentrations in estuarine and coastal marine sediments. In Heavy Metals in the Marine Environment, ed. R.W. Furness and P.S. Rainbow, 5 1-66. Florida: CRC Press, inc-

Mendenhall, W. and RJ. Beaver. 1994. Introduction to ProbabiZity and Statistics. California: Duxbury Press.

Meng, X. and C.Z. Liu. 1996. The quantitative research on sediment geochemical characteristics of the Yangtze Estuary. Journal of East China Normal University, 1 : 73-84.

Menon. M.G.. R.J. Gibbs and A. Phillips. 1998. Accumulation of muds and metals in the Hudson River estuary turbidity maximum. Environme ntal Geology, 3 4 : 2 1 4-232.

Palanques, A., J.A. Sanchez-Cabeza. P. Masque, and L. Leon. 1998. Histoncal record of heaw metals in a highly contamùiated Mediterranean deposit: the Besos Prodelta. Marine Chernistry, 6 1 : 209-2 1 7.

Perillo. G.M.E. 1995. Geomorphology and sedimentology of estuaries: an introduction. In GeornorphoZogv and Sedirnenrology of Estuaries. ed. G.M.E. Perîllo. 1 - 1 6. New York: Elsevier Science Publishers.

Pollution control on the Yangtze strengthened. 1998. Beijing Review. June 1-7: 6.

Rassrnussen, P.E. 1996. Heavy Metals in the Environment: A Geoscience Perspective. Ontario: The International Council on Metals and the Environment.

Ross, S.M. and K J . Kaye. 1994. The meaning of metal toxicity in soil-plant systems. in Toxic MetaZs in Soil-Plant Systems, ed. S.M. Ross. 27-6 1. Ontario: Wiley and Sons.

Saiz-Salinas, J.I., J.M. Ruiz and G. Frances-Zubillaga. 1996. Heavy metal levels in intertidai sediments and biota fiom the Bidasoa Estuary. Marine Pollzttion Bulletin. 32: 69-7 1 ,

Salomons. W. and U. Forstner. 1984. Metals in the Hydrocycle. New York: Springer-Verlag Publishing.

Savory, J. and M.H. Herman. 1990. Advances in instrumental methods for the rneasurement and speciation of trace rnetals. Annals of CZinical and Laboratoty Science, 20: 1 1 8-1 26.

Schubel. J. R. 1 97 1 . The Estuarine Environment: Estuaries and Estuarine Sedirnentation. Maryland: Amencan Geological Institute.

Shanghai Municipal Instinite of Surveyuig and Mapping. 2000. Shanghai Tourist Map, China Map Press.

Shaw. G. and D. Wheeler. 1985. Statisticai Techniques in Geographical Analysis. Ontario: John Wiley and sons.

Shen. H.T., S-L. He, D. Pan and J.F. Li. 1993a. Study on turbidity maximum in the south and north passages of the Changjiang Estuary. Proceedings of the Svmposium on the Physical and Chernicol Oceanopphy of the China Sens. 6: 23 7-243.

Shen. H.T.. J.F. Li. H.F. Zhu. M.B. Han and R.G., Zhou. 1993b. Transport of the suspended sedirnent in the Changjiang Estuary. Internarional Journal of Sediment Research, 7: 45-63.

Skoog. D.A.. F.J. Holler and T.A. Nieman. 1998. Principles of Inshwmental Analysis. Ontario: Saunders College Publishing.

Sparks. D.L. 1995. Environmental Soi1 Chemistry. Ontario: Academic Press. hc .

Stewart, W.D.P. 1972. Estuarine and brackish waters - an introduction. In The Estuarine Environment, ed, R.S.K. Barnes and J. Green, 1-9- London: AppIied Science Publishers, Ltd.

Thornton, 1. 1 995. Metals in the Global Environment: Facts and Misconceptions. Ontario: International Council on Metals and the Environment.

Williams. T.P.. J.M. Bubb and J.N. Lester. 1994. Metai accumulation within salt rnarsh environments: a review. M~rine Pollution Bulletin. 28: 277-290.

Wright, P. and C.F. Mason. 1999. Spatial and seasonal variation in heavy rnetals in the sediments and biota of two adjacent estuaries, the Orwell and the Stour, in eastern England. The Science of the Total Environment, 226: 139-1 56.

Wu. G.Y., W. Tu, C. Shi and D.L. Liu. 1996. Pollution and assessrnent of heavy metals in the substratum of the tidal beach near the Bailonggan outlet of waste water in Pudong New Area. Journal of East China Normal University, 1 : 52- 56.

Wu, CH., C. Maurer. Y. Wang, S.Z. Xue, and D.L. Davies. Water pollution and hurnan health in China. Environmental Health Perspectives, 4: 25 1 -256.

X- S.Y., J. Tao, X.L. Chen, Z.Y. Chen and Q.R. Lu. 1997. Dynarnic accumulation of heavy metals in tidal flat sediment of Shanghai. Oceanologia et Limnologia Sinica, 28: 509-5 15.

Yang, S.L. 1998. The role of scirpus marsh in attenuation of hydrodynarnics and retention of fine sedirnent in the Yangtze Estuary. Estuarine, Coastal and Shelf Science, 47: 227-233.

Yang, S.L. 1999a. A study of coastal morphodynarnics on the muddy islands in the Changjiang River Estuary . Journal of Coastal Research. 1 5 : 3 7-44.

Yang, S .L. 1 999b. Tidal wetland sedimentation in the Yangtze delta. Journal of Coastal Research. 1 5: 1090- 1 099-

Yang, S.L. 1999c. Sedirnentation on a growing intertidal island in the Yangtze River mouth. Estuarine, Coastal and ShelfScience, 49: 40 1-41 0.

Yang, S.L. 1999d. A study of coastal morphodynarnics on the muddy islands in the Changjiang Estuary. Journal of Coastal Research, 1 5 : 3 2-44.

Zhang. J., W.W. Huang and Q. Wang. 1990. Concentration and partitioning of particulate trace metals in the Changjiang (Yangtze River). Waler, Air and Soil Pollution. 52: 52-70.

Zhang, J.? W. W. Huang, M.G. Liu and J.Z. Cui. 1994. Eco-social impact and chernical regimes of large Chinese rivers - a short discussion. Water Resources, 28: 609-6 1 7.

Zhang, J. 1995. Geochemistry of trace metals from Chinese RiverEstuary systerns: an ovex-view. Estuarine, Coasral and ShevScience, 4 1 : 63 1 -658.

Zhang, J. 1999. Heavy metal compositions of suspended sediments in the Changjiang (Yangtze River) estuary: significance of riverine transport to the ocean. Continental ShelfResearch, 19: 1 52 1 - 1 543.

Zhang, H., D. Ma, Q. Xie and X. Chen. 1999a. An approach to studying heavy metal pollution caused by modem city development in Nanjing, China. Environmental Geology, 3 8: 223-228.

Zhang, J., Z.F. Zhang, S.M. Liu, Y. Wu, H. Xiong and H.T. Chen. 19996. Human impacts on the large world rivers: would the Changjiang (Yangtze River) be an illustration? Global Biogeochemical Cycles, 1 3 : 1 099- 1 1 05.

Zhang, W., L. Yu and S.M. Hutchinson. Geomorphic influences on heavy metal accumulation in intertidal sediments of the Yangtze Estuary, In Press, Shanghai, China: State Key Laboratory of Estuarine and Coastal Research, East China Normal University.

Zwolsman. J.J.G, G.T.M. van Eck and G. Burger. 1996. Spatial and temporal distribution of trace metals in sediments fiom the Scheldt Estuary, south-west Netherlands. Estuarine, Coastal and ShelfScience, 43: 55-79.

Appendix A

Table A-1: Sediment characteristics along the Chongming Island transect.

Sample Location

CH- 1 CH-2 CH-3 CH-4 CH-5 CH-6 CH-7 CH-8 CH-9

CH- 1 O CH-I 1 CH- 12 CH- 13 CH- 14 CH- 1 5 CH-16 CH- I 7 CM- 18 CH- 19

Percent 20 pm

Distance Along Flat (ml

O 1 O0 200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400 1500 1600 1 700 1800

Percent TOC

Average Grain

Diameter ( pm) 19.24 3 1 .O2 24.80 18.29 22.63 20.2 1 18.49 23.10 24.36 26.71 24.92 23.42 27.82 24.36 26.2 1 32.55 3 5 -47 21.36 37.3 1

Appendix A (cont'd)

Table A-2: Sediment characteristics along the Hengsha Island transect.

Sample Location

HS- 1.5 HS-2.5 HS-3 .O HS-3.5 HS-4.0 HS-4.5 HS-5.0 HS-5.5 HS-6.0 HS-6.5 HS-7.0 HS-7.5 HS-8.0 HS-9.5

HS- 10.5 HS- 12

Distance Along Flat (m) 25 75 t O0 125 f 50 175 200 225 250 275 300 325 350 425 475 550

Average Grain

Diameter (pm) 18-08 3 7.43 29.34 37.64 44.16 16.8 1 19.86 24.35 32.03 25.94 37.59 30.64 25 .O0 32.77 1 60.20 152.50

Percent < 20 pm

Percent TOC

O O CC) T

Sample Location

hs-1.5 hs-2.5 hs-3

hs-3.5 hs-4

hs-4.5 hs-5

hs-5.5 hs-6

hs-6.5 hs-7

hs-7.5 hs-8

hs-9.5 hs-10.5 hs-12

Distance an Tidal Flat (m)

25 75 1 O0 125 1 50 175 200 225 250 275 300 325 350 425 475 550

Appendix B Heavy Metal Concentrations Along Transect 2 (Hengsha Island)

Appendix C (cont'd)

%TOC vs. Alurninum (Chongrning Ir.)

%TOC vs. Manganese (Chongming 1%)

%TOC vs. Cadmium (Chongming 1s.) I

%TOC vs. Lcld (Chongming 1s.) 28

%TOC vs. Arsenic (Chongming 1s.)

%TOC vs. Chmmlum Concentration (Chongrning 1s.) l

a.

Chromiurn vs. Avermge Grain Size (Chongrning k) , . Zinc K Avemge Grain Size (Chongming k) . -. - - - - .- - - : !

. > . , 7 s 7 . .

O 5 10 15 M 25 30 35 40 Avmge Grain Size (mkroirmters)

lron va Average Grain She (Chongmlng 1%) 1- 7 - - . .

O 10 20 30 a 1 1

Average Grain Size (micmmctcrs)

I

Coppr vs. Average Graln Slze (Chongmlng l a )

10 1 O 5 10 15 20 25 30 35 401

! Average Grain Sire (mlcmmetera) ,

10 20 30 40

Average Grain Size (micrometers)

Magncrium vs. Avemge Grain Size (Chongming Ir.)

ocnoJ O 5 10 15 2û 25 M 35 4û

I Avernge Grain Stze (micrometers)

Nickel vs- Avetage Grain S i n (Chongming Ir.) L

- . . j 33 7

< O 1 O 20 30 i Average Grain Size (micrometers) I

Aluminum vs. Average Grain Size (Chongming k) I - - -. - - -. - - --

Average Gmin Size (micrm1en) I

Y angrnue rr Avemge Grain Sue (Chongming k) . - . _ . . l

tcad v s Average Griln Slrc (Chongrnlng 1s.)

0 10 1 1 O 10 20 Y) 40 '

! Average Grain Size ( m i c ~ e r s )

1 Arscnlc vn. Average GmIn Slze (Chongrnlng l a ) , 11 -- A -

3001 O I I

O 10 20 30 40 i O 10 20 30 40 Average Gmln Size (micromrters) 1 1 Average Grain Size (micrometerr)

I

I Cadmium vs. Average Gmin Size (Chongming h)

i 035,

, I

' 0.1 1

O 10 20 30 ag ' I I Average Grain Size (micrometers)

I

Chranium vs pH (Chongming k) i ( Zinc vs pH (Chongming ls.]

" T - - - - - - - - - - - - - - - - - -- - : ; "1 -- - - - - -- -

1 I

iron va pH (Chongmlng la) Magnalum va pH (Chongmlng 1%)

l PH ' f

I PH

i f

Copper n pH (Chongmlng 1%) Nickel K pH (Chongming k)

Cadmium vs. pH (Chongming k) . . -. - . - - . . -

Lead v r pH (Chongming k.)

- - - - -

Nonnalized lron vs. Disance Atong Flat (Chongrning 1s.)

Nonnallzed Alum~num vs. Distance Along Fkt 1

1 l Numalucd Magncuum vs. Dislance Along Flat (Chongmtng

(ChMigminp Is.) I

Nonnaluecl Chromtum vs. Distance Along Flat(Chongming is.]

0035

- O 015 - , 0 1 i

O 500 1000 1500 2oOo1

Dirtince Along FLat (m)

m

Nonnalized Z n c vs. Distance Along Flat (Chongmrng 1s.)

O 500 lm 1500 2000 i Distance Along Flat (m) I

1s.)

-

Normalized Copper vs. Distance Along Flat [Chongrntng 1s.)

O 25 I

1 0 2 . i I I O 500 :m 1500 2m j , Distance Along Flot (m)

O

- O O

+ O

O * + * O - O * O

00755 0 07 1 O M .

t O MO IO00 lm 2000 1 O 500 1OOa 1500 Mao

Distance Along Flat (m) 1

I Distance Along Flat (m)

f ""'

= o f f i . E f 0055..

! 5 - &

a - - j i 5 i o m . w X 8 o o s f - 1 ! g 0 0 2 . . - -

0 0 6 - O 2 O W -

0 0 3 5 .

O U -

O - O O

& 1 , ; O

O 0 0 : ' O = 0015 1) +

1 I

O 1 I

O 0 1 '

: ! i Nonnalkad Magnaslurn v% %TOC (Chongmlng Ir) * . ou, - - .

O 03 , 0011 O O 5 1 1 5 2 , O 0 5 1 1 5 2

% TOC x TOC

Nonalized Imn vs. % T m (Chongmlng 1%)

O4 f . -- - - -

o J G 0.5 1 1.5 2

X TOC

Normalned Chmnium vs. %TOC (Chongmlng 1s.) 0.55 - . . - . - -

O 0.5 1 15 2 i

R TOC

Nomalzed Zlnc vs. %TOC (Chongmlng lx.) Normalized Copper vs. %TOC (Chongming 1s.)

l 8 1 0 7 7 - - - - - I

1 7 A 1 065- * * . 1

1 6 , * 1 06 - *

I

O 0.5 1 15 2 X TOC

1

O O 5 1 1 5 2 .

% TOC

I

Nofmallzea Nickel vs. %TOC (Chongmlng I r ] 1

Namml id h d n %TOC (Chongming k) I

O 0 5 1 1.5 2 . X TOC

, d l O O. 5 1 1.5 2

1 X TOC

Uormallzed Caemlurn vr %TOC (Chongmlng I c ) l I - - - A - - -- -- . - - -

I I

O 0 5 1 15 2 X TOC

Nomdlted Amenlc vr %TOC (Chongmlng 1%) -- -

Oz2

O 1 O 0.5 1 1.5 2

X TOC

0003 1 O 0 5 1 ? 5 2

A TOC

I 003- '

O 5 10 15 n 25 30 35 40

Average Gmln Slze (mlcrumeter)

Hormallrtd iron vs. Average Graln Slze (Chongmlng ta) I

1

Average Grain Slze (mkmmcler)

Nonmlizcd Zinc vs. A v e q ~ e Grain Size (Chongming 1%)

1 8 7 - - - - -

Averîge Grain Size (rnicmrneter)

NormaJlxed Mqncllum vs. Average Grain Slze

: O O l J 1

O 5 1 0 1 5 2 0 2 5 j 0 3 5 4 0

Avetage Grain S i a [micromctrr]

0.1 J O 5 10 15 20 25 30 35 QO

Avemge Grain Size (micrometer)

Nonnalized Copplr vs. Aveme Grain Size (Chongming Ir.) . - -- - -- . -

- -

0.25

0.2 ! I O 10 M 30 40 j

Average Gmin S i n (micrometer) I

Normaîirrd Nickel vs. Avemgt Gnin Size (Chongming 1s.)

- -- - - ---- - &

O 10 20 30 40. Avenge Grain S i n (micrometer)

Normalizd Manganese vr. Avtrage Grain S i n (Chongming Ir.)

'6 1 . . - - . . - -- .- - - - - - - . . -

O 10 20 30 40 Average Gnin S i (micrometrr)

Nonnalizd Cadmium vs. Average Grain Sire (Chongming k)

' u - - - 5 5

1 E o m 3 O = 00035 *+

O 003 I

I O 10 20 30 40 8

Average Gmin Size (micrometer)

I Nonnalizrd hixi vr Average Grain S i n ! (Chongming k.) ! 0 6 î-- -. . . . .

I

0.25 1 O 10 20 30 40

I Average Grain Size (micromohr)

Normalizcd Arsenic vr. Average Grain Size (Chongming 1s.)

Avemge Gnin Size (micromeîcr)

Normalized Imn vs. pH (Chongming 1s.)

- - -. - -- --

Nomaiued Chmmium vr. pH (Chongming Ir.)

050- --a .- 6

045 - 6 0

Normalized Zinc vs. pH I . . 8 : . . Nomalizcd Copper vs. pH

(Chongming Ir.) 1 , I , . (Chongming Ir.)

1 8 . . , ; 070 a : -

I

Nom;alized Maganese vs. pH (Chongrnlng 1s.)

- -

Normallzed Cadmtum vs. pH (Chongm ing 1s.)

Normalized Lead vs. p H 1 (Chongming 1s.) 0 T'

Normalized Arsemic vs. pH , (Chongrn mg 1s.)

----- : 1- - --

Average Grain Sire vs. %TOC (Hengsha 1s.) / , i I %TOC vs. Zinc Concentration (Hengsha 1s.)

Average Grain Size (micrometers) %TOC

%TOC vs. lron Concentration (Hengsha 1s.) %TOC vs. Magnesium Concentration (Hengsha 1s.)

1

8 .

%TOC vs. Copper Concentration (Hengsha 1s.) / %TOC vs. Nickel Concentration (Hengsha 1s.) I

%TOC vs. Aluminum C o n c e m o n (Hengsha Is.]

7 m - . - - . - - - - - - - -- I %TOC vs. Manganese C o n c e m o n (Hengsha 1s.)

1 8 0 0 - - - -. - .

XTOC vs. Arrenlc C o n c e m o n (Hengsha 1s.)

- - - - - - -- -. -

O

%TOC vs. Lead Concerrmmon (Hengsha 1s.)

%TOC vs. Cadmium Concentmtion (Hengsha 1s.) . , 8 ,

, , %TOC vs. Chmmiurn Concentranon (Hengsha 1s.)

Appendix D (cont'd)

Chrornium Concentration vs. Average Grain Size 25 , (Hengsha 1s.) 1

t j Zinc Concentration vs. Average Grain Size

(Hengsha 1s.)

O O 50 100 150

Average Grain Size (micrometers) 200 1

I

20 1 + O 50 100 150 200

Average Gain Size (micrometers)

lron Concentration vs. Average Grain Size (Hengsha 1s.)

Magnesium Concentration vs. Average Grain Size (Hengsha 1s.)

1OOOO 0: O 50 100 150 MO

Average Grain Size (micrornctilrs) O 50 100 150 200 ,

Average Grain Size (micrometers) 1

Nickel Concentration vs. Average Grain Size (Hengsha 1s.)

Copper Concentration vs. Average Grain Size (Hengsha 1s.) I

10

O 50 100 150 200 Average Grain Size (micrometers)

1 O 50 100 150 200 1 Average Grain Size (micrometers)

Appndh D ( c d d )

Aluminum ConcenaaUon vs. Average Grain Sue Manganese Concenuanon vs. Average Grain Sue (Hengsha 1s.) (Hengsha 1s.)

70000 - - - - - - -- -

= 50000

C

E 2 m - - 5 loaoo O

ü I

O 50 1 0 0 150 O 50 100 150 200 j ; 1 ) Average Grain Site (micrometen) Average Grain Size (micrometers)

M o : I ! I

,

O ' I l

O 50 100 150 M O I ' O M 100 150 200 Average Gmin Sire (mmmhrs) Avenge Grain Size (micromebers)

Arsenic ConcemraOon VS. Average Grain Size . . ( ! Lead Concentzrbon vs. Average Grain Size

(Hengsha 1s.) 1 l

(Hengsha 1s.) - 1 l 4 5 - - - -

32 -

Cadmium Concentrabon vs. Average Grain Size (Hengsha 1s.)

Ci8 7

Ê 07 1 O

8 0 6 4 O 4

-g 11 - P = 1 0 O

O 50 100 150 2 0 0 ; I Average Gnin Size (micrometcrs)

= 9 * i 2 2 5 - ,

* - ' 1 C * C 6 7 *+ - *

' 2 . r 6 - ' ! 2 1 0 -

O j ! *+ .

5 -. O

I I

+ 4 ' 1 - ; , E 3 5 - 1 z30-

Appendix D (cont'd)

Chmmium Concentration vs. pH (biengrha 1%) ï inc Concentration us. pH (Hengsha 1%) -

- - - - - - - - - - - - .

Imn Concentration vs. pH (Hengsha 1s.) - -

Magnaium Concemon vs. pH (Hengsha Ir.)

-1 I

0 '- 1 -- - --

I

Copper Concc&aüon vs. pH (Hengsha 1s.) 45 7 -

Nickel Concentration vs. pH (Hengsha Ir.)

Aluminum Concentration vs. pH (Hengsha 1s.) . . Manganese Concentration vs. pH (Hengsha 1s.)

Arsenic Concentration us. pH (Hengsha 1s.) Lead Concentration vs. pH (Hengsha 1s.)

Cadmium Concentration vs. pH (Hengsha 1s.)

Normalized Aluminum vs. Distance Along Rat 1 , Homuluid Magnesium vs. Distance Along Flat I

(Hengsha 1s.) (Hengsha 1s.)

, ' 0.09 ,

a

Distance Along Flat (m) O l W 2 0 0 3 0 0 4 0 0 5 0 0 6 0 0

Distance Aiong Flat (m)

Normalized lron vs. Distance Along Flrt (Hengsha 1s.)

; : ! '

O 1 0 0 2 0 0 3 0 0 4 a l 5 0 0 6 0 0

Distance Along Flat (m)

Normalized Chromiurn vs. Distance Along Flat (Hengsha Is.)

1

O-' 1

0.1 1 O 100 200 300 400 500 600:

Distance Along Flat (m) ,

/ : Normalized Zinc vs. Cistrtnce Afong F l a

j : Normalized Copper vs. Distance Along Fiat (Hengsha 1s-) (Hengsha 1s.) I

Distance Along Flat (m)

1 025 -,

1 020 1

!

O 100 200 300 4M3 500 600 l

l Distance Along mat (m)

Uonnalized Nickel vs. Distance Afong Flat (Hengsha 1s.)

2.5

+

Distance Along Flat (m) ,

Nomalized Manganese vs. Distance Aiong Flat (Hengsha 1s.)

Distance Along Flat (ni)

Nomalized Cadmium us. Distance Aiong Flat (Hengsha 1s.)

I O 1 0 0 2 0 0 3 0 0 4 0 0 5 0 0 6 0 0 i

I Distance Along Flat (m)

Nomralized Lead vs. Distance Along Flat (Hengsha 1s.)

t 1.8 O

1.6 ,

02 + - - ' 0.0 I

O 1 0 0 2 0 0 3 0 0 4 M 3 5 0 0 6 0 0

Distance Along Flat (m) ,

i Nomalized Arsenic vs. Distance Along Flat (Hengsha 1s.)

Distance Along Flat (m)

Normalized Aluminum vs. %TOC , . Nomaltzed Chromicm vs. %TOC (Hangrha 1s.) (Hengsha 1s.)

- -. - - - - -- - - - -. - .

Nomalized lron vs. %TOC ' i Nonnalized Zinc vs. %TOC

(Hengsha 1s.)

1 2 3 XTOC

Nonalized Magnesium vs. *ATOC Norrnalized Copper vs. %TOC (Hengsha 1s.) (Hengsha 1s.)

08 - 1 !

07 - 1

1 XTOC

2

Normaltzed Cadmium vs. %TOC

: 008, (Hengsha 1s.)

Appendix 0 (cont'd)

Ncrmaltzed Ntckel vs. XTOC i g Normaltzed Lead vs. %TOC

250 7 (Hengsha 1s.) - - - 1 8 0 - --

(Hengsha 1s.)

I t s 160..

1 '

j lm 1 1 00

x 3 la- ZlM

O

- -

iq* * * G::-* Z " = 0 6 0 i

1

Osa - - i 1 000 * * O 2 0

000 -1 O 0 0 - O * -

\ * -. - *

O 1 2 3 4 O 1 7 4

'ATOC 3

1 %TOC

Normalaed Manganese vs. %TOC Nomalaed Arsentc vs. %TOC

-33 - (Hengsha 1s.) - - .- -- * - - 0 8 -y (Hengsha 1s.)

! O 0 7 - 1

25 -. Y: 1 : 0 6 . l - E c tu

z20- i l * E O S !

5 u I

g O4 - B - - - lu Tii 15 1 : g 0 3 - .

Z - 0

O

0 2 - - v*- + O v

8 e * 0" . O , : f - 0 1 -

Appendix D ( c M d )

Normalized Aiurninum vs. Average Grain Sim Normalized Magnaiurn us. Average Gtain Size ( b g s h a 1s.) (Hengsha 1s.) o is7 - - - - -- -- --- ' ""T---- - 6

002 1 i

O 02 - , O01 1 &Ge-

O 50 100 150 200 ! O M 100 150 MO Average G n i n S i n (micrometer) ! 1 Average Grain Sirc (micrometer) f

Nomalized lron vr. Average Grain SÏze (Hengrha 1s.)

025 7 A

- -- -

Normalized Chmmium vs. Average Grain Size i : (Hengska Ir.)

50 100 150 O 50 1 û0 150

Averape Grain Size (micmmcbcr) Average Grain Size (micrometer)

Normalized Zinc vr Average Grain Sirc (Hmgsha 1s.)

4 5 7 . -

Nomalized Copper vs. Average Grain Size (iiengsha 1s.)

I Average Grain Size (micmrnekr)

1 0 2

50 100 150 MO Average Grain Sire (micmmehr)

Nonnalbed Nkkel vs. Averiige Graln She (Hengrha l n ]

- - . - - -A-- - -- . .

! Nomalhed Lead vs. Avemge Graln Slze

I ; a - - -- - (Hengsha 1s)

16 -

# ' 0.0 1 ' 0.0

O 50 1 0 0 150 m ! ; O 50 1 W 150 200

Average Grain Sim (micromcer) i ! Avenge Grain Sue (mirromter)

Normallzed Mangantre n Average Graln Slze (Hmgsha h.)

. - . - - - - - - -- . . - .- .- -. . . O

25 j

O M 100 150 m r i Average Grain Size (micrometer)

Normallzed Anenlc vr. Avecage Graln Slze

- . (Hengsha Is.) O8oT -

O 50 100 1 5 0 200 j Average Graln Slze (mlcrometer)

Nonnallzcd CIdmlum v s Average Gmln Slze (Hangsha 1s.)

, 0 x 1 I

1 O J O 50 1 0 0 150 200

I Avetage Gmln Size (micmmetar) I

O 2 4 6 8 1

PH

1 Normalizeâ Chromium vs. pH (Hengsha k.)

- . . . . - - . .

Nonnalizd Zinc vs. pH (Hengrha Ir.) (Hengsha Ir.)

Nonnalized Nickel w. pH Normalized Lead vs. pH (Hengsha 1s.) (Hengsha 1s.) - - - .-----a --- - - - -- - - - - -

O

O

Nonnalized Manganese vs. pH (Hengsha 1s.)

- -. - .

Nonnalized Cadmium vs. pH (Hengsha 1s.)

Nonnalizd Arsenic vs. pH (Hengsha 1s.)

0 7 1 - - - - - -

O