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ASL Conference 2011
Azra Daud
Winthrop Prof. Carolyn Oldham
Dr Suzanne McDonald
³Inside Informal, Outside Stormy´
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Motivation
Aims
Introduction
Approach
Methodology
Challenges
Outcomes
Take home message
OUTLINES
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DOC controls geochemical andecological processes in aquatic
ecosystems.
Quantifying and characterising DOC,
including its spatial and temporal
variability, is critical to understand itsrole in these processes.
Metal-humic issue can be acute in
wetland affected by acid sulfate soils
or acid mine drainage, whichfrequently contain high DOC and
metal concentrations under low pH
conditions.
MOTIVATION
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5.8 x 106 ha
in Australia 0.76%
Potential ASS
Actual ASS
INTRODUCTION
Sunday, March 04, 2012 5
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ASS are of major environmental concern for many wetlands
and is made up of oxidisable sulfidic material, usually pyrite,FeS2 (Green et al ., 2006)
INTRODUCTION
Iron is one of the main
weathering products of pyrite, Fe2SO4 (Peiffer et
al ., 1999)
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INTRODUCTION
Swan Coastal Plain, 180 km south of
Perth, Western Australia ~30 ha
Hot dry summers (16 ± 30¶C) and
Cool wet winter (7 ± 17¶C)
Rainfall: ~700 mm
Evaporation: ~1500 mm A
A¶
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Field measurement : pH, EC, ORP, Temp, depth
Laboratory analysis : HPSEC, UV-vis, TOC, cation
exchange, fractionation, phenanthroline, ICP-AES
Survey work ± site elevation
Collecting meteorological data from BOM, WA
Damkohler number Water and chemical mass balance
Reaction rate
APPROACH
Inside:
Outside:
Model:
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METHODOLOGY
DOM
Natural Organic Matter
Humus Undecomposed Matter
Humin Humic Substances
Humic Acid Fulvic Acid
0.45 µm membrane
syringe filter
DOC
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METHODOLOGY
Pure
Sample
DOC
Characterization
Laboratory
Analysis
0.45 µm filter
SRFAFe Total TOC
APHA
Method5310A
5 310C
SECSUVA
Phenanthroline
pH adjustment
LOI
254 nm
Optimum
510 nm
Without Fe
With
known Fe(20 ± 1000
mg/L)
Mw
Mn
3 years sampling
August 09 ± July 11
Seasonal
High water table
Low water table
CE RF
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CHALLENGES & SOLUTIONS
1. Loss on ignition method was not applicable for [C] measurement
(negative reading of [C] ± TOC analysis).
2. TOC Standard Method 5310A was not consistent, and no similarity
as compared to Method 5310C. Optimisation was performed and
results were validated (5 months).
3. Results by phenanthroline method were not in the range.
Modification was undertaken. Reduce sample volume, 1:10 ratio to
standard).
4. Purification of carbon by reverse osmosis did not succeed.
Aggregation problem occur, less [C] were measured. (CationExchange and Rapid Fractionation).
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TAKE HOME MESSAGES
1. Multiple tools analysis provides different view of characterisingDOC and provides improved understanding in the variability of
DOC characteristics and reactivity.
2. When dealing with waters and organic matter under variable pHs,
method validation is very CRUCIAL !
3. Surface and ground water in an aquatic system do not always
exhibit similar behavior spatially and temporally, especially under
high variability of DOC, heavy metals and pHs.
4. Results have flagged significant remarks on handling naturalwaters affected by ASS.
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ACKNOWLEDGEMENT
Funding Malaysian Ministry of Higher Education (Tuition)
Universiti Tun Hussein Onn Malaysia (Stipend)
Australian Government (Natural Heritage Trust Regional (project 53454)
Curtin Water Quality Research Centre (Laboratories)
People Adam Lilicrap
Bibhash Nath
Daniel Boland
Laura Ellis
SESE postgrads
Family
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THANK YOU«
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CHALLENGES : [DOC] and [FET]
0
2
4
6
810
12
14
16
18
2 4 4.5 6 8
D O C ( m g / L
)
pH
1.5 mL
3.0 mL
5.0 mL
HTC
0
5
10
15
20
25
30
35
40
1 3 5 7
D O C ( m g / L )
Bores
1.5 mL, 3%
3.0 mL, 4%
HTC
0
10
20
30
40
50
60
70
80
2 4 4.5 6 8
D O C ( m g / L )
pH
1.5 mL
3.0 mL
5.0 mL
HTC
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RESULTS AND DISCUSSION : PAPER 1 & 2
50 mg/L C from International Humic Substances Society Suwannee
River Fulvic Acid with different known concentrations of Fe
0
20
40
60
80
100
120
100010000100000
A b s 2
5 4 nm
Mw
1000mg/L Fe
200mg/L Fe
100mg/L Fe
80mg/L Fe
60mg/L Fe
40mg/L Fe
20mg/L Fe
Without Fe
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RESULTS AND DISCUSSION : PAPER 1
Trends of pH, Fe and DOC across
wetland in wet season (2009)
0
10
20
30
40
50
60
70
0
1
2
3
4
5
6
7
8
9
Bore1
Bore2
Bore3
Bore4
Bore5
Bore6
Bore7
Bore8
SWN SWS
pH Fe DOC
p H
Sample
F e ,D O C ( m g
/ L )
Sample DOC Fe pH Mw SUVA
Name Wet Oxidation
High Temp
Catalytic (mg/L) at pH 7
Bore 1 8.0 - 19.8 8.0 4.92 8.1 2492 1.26 0.22
Bore 3 36.5 - 37.2 31.0 0.19 7.9 3074 1.13 1.44
Bore 5 2.6 - 4.3 3.4 62.14 3.2 1379 3.46 0.77
Bore 7 18.0 - 20.1 16.0 19.92 2.9 1670 3.06 3.04
SUVA
values for
waters in
Bore 1, 3,
5 and 7
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RESULTS AND DISCUSSION : PAPER 1
0
20
40
60
80
100
120
100010000
A b s 2 5 4 nm
MwBore1 pH7 Bore2 pH7 Bore3 pH7 Bore4 pH7 Bore5 pH7Bore6 pH7 Bore7 pH7 Bore8 pH7 N pH7 S pH7
i ii
0
20
40
60
80
100
120
100010000
A b s 2 5 4 nm
Mw
Bore1 pH8.09 Bore2 pH8.43 Bore3 pH7.90 Bore4 pH8.25 Bore5 pH3.17
Bore6 pH8.48 Bore7 pH2.93 Bore8 pH8.22 N pH2.69 S pH2.76
i ii
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METHOD:BACKGROUND
Physicochemical parameters:
pH
Loss on ignition
Electrical conductivity
Temperature
Oxidation reduction (redox) potential
Chemical analysis: Fe
DOC
Al
QA/QC:
Sample collected Samples were stored on ice, transferred to
the laboratory and then stored in the darkat 4oC until analysis.
Depth to groundwater (relative to LocalDatum) was measured prior to samplecollection.
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BACKGROUND
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RESULTS AND DISCUSSION
Trends of pH, Fe andDOC across wetland in
wet season (2009)
Trends of pH, Fe andDOC across wetland in
wet season (2010)
0
10
20
30
40
50
60
70
0
1
2
3
4
5
6
7
8
9
Bore1
Bore2
Bore3
Bore4
Bore5
Bore6
Bore7
Bore8
SWNSWS
pH Fe DOC
p H
Sample
F e ,D O C ( m g / L )
0
10
20
30
40
50
60
70
0
1
2
3
4
5
6
7
8
9
Bore1
Bore2
Bore3
Bore4
Bore5
Bore6
Bore7
Bore8
SWN SWS
pH Fe DOC
Sampl
F e ,D O C ( m g / L )
p H
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ASS are of major environmental concern for many wetlands
and is made up of oxidisable sulfidic material, usually pyrite,
FeS2 (Green et al ., 2006)
INTRODUCTION
Iron is one of the main
weathering products of pyrite (Peiffer et al ., 1999)
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METHODOLOGY
Size Exclusion Chromatography (SEC)
Chromatographic method (molecules in
solution are separated by size)
Also known as permeation gel method
Use organic solvent as a mobile phase
Provide good molar mass distribution for
polymers
Principles:
A very large molecule will elute earlier when
mobile phase passed through the column.
A small molecule will elute late when the
pore- and interparticle volume passed throughthe column.
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BACKGROUND
FeS2(s) + O2 SO42- + Fe(II)
Fe(II) + S22-
(dissolved)
(slow)
+ O2
(a)
(a¶)
(b)
+ O2
(c)
(oxidized)
(fast)
+F
eS2(s)
Fe(III) Fe(OH)3 (s)
(soluble)
Releasing
additional acidity
and new Fe(II)
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BACKGROUND
DOM
Natural Organic Matter
Humus Undecomposed Matter
Humin Humic Substances
Humic Acid Fulvic Acid
0.45 micron filter DOC
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RESULTS AND DISCUSSION
SampleDOC
Fe pH Mw SUVA
Name Wet Oxidation High Temp Catalytic (mg/L) at pH 7
Bore 1 8.0 - 19.8 8.0 8.1 2492 1.26 0.22
Bore 3 36.5 - 37.2 31.0 7.9 3074 1.13 1.44
Bore 5 2.6 - 4.3 3.4 3.2 1379 3.46 0.77
Bore 7 18.0 - 20.1 16.0 2.9 1670 3.06 3.04
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Site Description
Small seasonally inundated wetland in the MinningupWetland Chain
10 km south of Bunbury
Mediterranean type climate (wet and dry)
Average annual rainfall : 850 mm (May-Oct) and 130 mm
(Nov-Apr)
Air temperature : 8.2o
C (July) - 27.6o
C (Feb) Annual potential evaporation : 1400 -1600 mm
BACKGROUND