HYDROGEOLOGIC CHARACTERIZATION OF

THOMAS SPRING, JEFFERSON COUNTY, ALABAMA

Watercress Darter National Wildlife Refuge

GEOLOGICAL SURVEY OF ALABAMA

Berry H. (Nick) Tew, Jr.

State Geologist

HYDROGEOLOGIC CHARACTERIZATION OF THOMAS SPRING, JEFFERSON COUNTY, ALABAMA

By Marlon R. Cook, Dorina Murgulet,

and Alana L. Rogers

Partial funding for this project was provided by the U.S. Fish and Wildlife Service.

Tuscaloosa, Alabama 2014

ii

TABLE OF CONTENTS Introduction ........................................................................................................................... 1 Physiographic, stratigraphic, and hydrogeologic settings ..................................................... 2 Land use/land cover ............................................................................................................... 5 Spring discharge, physical properties, and chemical composition ........................................ 6 Nutrients........................................................................................................................... 12 Nitrate ........................................................................................................................ 12 Phosphorus................................................................................................................. 13 Metallic constituents ........................................................................................................ 13 Organic constituents......................................................................................................... 15 Isotopic composition........................................................................................................ 16 References cited ............................................................................................................... 19

ILLUSTRATIONS

Figure 1. Topography and assessment areas including drainage/recharge areas for Thomas and Glen Springs .............................................................................. 3

Figure 2. Geology in the Thomas and Glen Springs area ................................................... 5 Figure 3. Land-use/land-cover for the Thomas and Glen Spring assessment

area....................................................................................................................... 7 Figure 4. Thomas Spring physical and chemical parameters.............................................. 9 Figure 5. Piper trilinear diagram showing major ion composition of water

collected from Thomas Spring and Trussville wells............................................ 10 Figure 6. Stiff diagrams for the selected Trussville groundwater samples

(FW, W-7, P-2, and W-10) and the Thomas Spring sample (ThS) ..................... 11 Figure 7. Cross plot of the δD and δ18O isotope data relative to the GMWL

and TLMWL ........................................................................................................ 18

TABLES

Table 1. Concentrations (µg/L) of metallic constituents detected in the water sample from Thomas Spring ............................................................................................ 14

INTRODUCTION

The hydrogeologic assessment of Thomas Spring by the Geological Survey of

Alabama (GSA) was commissioned by the U.S. Fish and Wildlife Service to characterize

geologic, hydrologic, and geochemical conditions in Thomas Spring. The assessment

consists of an evaluation of available hydrogeologic data and collection of stream and

spring discharge data and water samples. The purpose of the assessment was to determine

stratigraphic and structural controls for occurrence of the spring, groundwater recharge

characteristics to determine spatial and volumetric characteristics of spring discharge,

general water quality and contaminant impacts, and age dating of spring discharge to

determine groundwater migration patterns.

Watercress Darter NWR was established to protect Thomas Spring, one of only 4

known locations where the watercress darter was found naturally. Uplands around the

spring contain a mixture of mature pine and hardwoods and dense understory of

vegetation. The small size of the refuge (24 acres) and its location in a suburban setting

does not provide for a diversity of wildlife. The primary purpose of the refuge is the

protection of Thomas Spring and its population of watercress darters (U.S. Fish and

Wildlife Service, 2014).

The first population of watercress darters was collected at Glenn Springs in 1964.

Additional field work has resulted in the location of three other populations: Thomas

Spring (1976), Roebuck Springs (1978) and Seven Springs (2002). The greater

Birmingham metropolitan areas encompass all of these sites, which are threatened with

groundwater pollution and the presence of extensive impervious surfaces (e.g., roads,

parking lots, and roofs), which divert water away from the recharge area of the springs’

aquifers and lessens flows. In 1970, the Service officially recognized the watercress

darter as an endangered species (U.S. Fish and Wildlife Service, 2014).

Little is known about the history of Thomas Spring, where Watercress Darter NWR

is located, although it was apparently dammed up for about 20 years prior to the

discovery of watercress darters. The damming of Thomas Spring created excellent habitat

for the darters by providing slow-moving backwater that allowed dense aquatic

vegetation to become established (U.S. Fish and Wildlife Service, 2014).

1

Although care was taken in collecting the water samples as close as possible to

the groundwater inflow point, excessive algae in the pond made it impossible to

determine the exact location of the inflow point. Therefore, unless the spring discharge

rate is very high, samples likely represent a mixture of fresh groundwater with pounded

water. Furthermore, during rain events, mixing of the spring water with meteoric water

will likely occur in the pond. Nevertheless, a localized source of recharge can be

attributed to the spring based on the isotope signature. The oxygen and hydrogen isotopes

indicate that recharge to the investigated aquifers originates mainly locally. A more

distant source of recharge may be possible through preferentially longer flowpaths along

connected fractures.

PHISIOGRAPHIC, STRATIGRAPHIC AND HYDROGEOLOGIC SETTINGS

Thomas Spring is located in the Alabama Valley and Ridge section of the Valley

and Ridge physiographic Province and the Birmingham-Big Canoe Valley physiographic

district (Sapp and Emplaincourt, 1975). The Birmingham-Big Canoe Valley district is a

narrow limestone valley, about 4 to 8 mi wide, developed on a faulted anticlinorium with

shale, sandstone, and chert outcroppings (Sapp and Emplaincourt, 1975). Elevations in

this area vary from 298 to 1,522 feet (U.S. Geological Survey, National Elevation Dataset

(NED) Digital Elevation Model (DEM), 1999). The drainage/recharge area for Thomas

Spring, located towards the southwest of the Birmingham-Big Canoe Valley, is bounded

eastward by Red Mountain, which serves as a surface-water and groundwater divide (fig.

1). Elevations in the designated area vary between 535 ft on the southwest margin to 778

ft atop Sand Mountain (U.S. Geological Survey, National Elevation Dataset (NED)

Digital Elevation Model (DEM), 1999). Steeper slopes are characteristic of the eastern

part of the study area (13 to 5%) grading to more gentle slopes towards the west

including the spring (4-0.5%). After an exhausted search of well records and the study

area it was found that no wells were available in the area. Therefore, a potentiometric

surface map could not be constructed to determine groundwater flow patterns. However,

based on the topography of the spring area and the surface water drainage (northeast-

southwest), the probable Thomas Spring aquifer recharge and spring drainage area was

determined to cover about 350 acres (fig. 1). Although limited to surface characteristics

2

Figure 1.—Topography and assessment areas including drainage/recharge areas for Thomas and Glen

Springs.

(such as drainage pathways), the identified drainage/recharge area offers some insight on

the source of recharge waters and potential sources of contamination.

The spring and drainage/recharge area are situated towards the southwest

terminus of the Birmingham anticlinorium. Geologic units outcropping in the delineated

drainage/recharge area are the Chickamauga Limestone, the Copper Ridge Dolomite of

the Knox Group, the Knox Group undifferentiated, the Kimbrell member of Conasauga

Formation, and the Conasauga Formation (fig. 2).

The Chickamauga Limestone, a light- to dark-gray fossiliferous limestone,

comprises the eastern-most extremity of the drainage/recharge area, and occurs as a

narrow band along the Red Mountain ridge (fig. 2). In the southeastern part (Greenwood

quadrangle), this formation was described to be in part fenestral, shaly, and stylonodular

(Ward and Osborne, 2006). On the northeastern side of the drainage/recharge area

(Bessemer quadrangle), the Chickamauga Limestone consists of variably fossiliferous

3

limestone, calcareous siltstone, calcareous shale, and minor greenish-gray bentonite with

a laminated to bioturbated texture (Osborne and Rindsberg, 2001).

The Knox Group in Alabama can consist of several units including the Late Cambrian

Copper Ridge Dolomite and the Early Ordovician Chepultepec Dolomite, Longview

Limestone, Newala Limestone, and Odenville Limestone. Most of the Thomas Spring

recharge/drainage area is underlain by Copper Ridge Dolomite (Knox Group) outcrops in

the northeastern part (the Bessemer quadrangle), consisting of light- to medium-gray,

laminated to stromatolitic, to brecciated, finely crystalline cherty dolomite (fig. 2) A

small part of the drainage/recharge area, in the southwestern part (in the Greenwood

quadrangle), is underlain by undifferentiated Knox Group (fig. 2) (Raymond and others,

2003) (Osborne and Rindsberg, 2001). The Knox Group undifferentiated, consists of

chert nodules and stringers, and beds within the light- to medium-gray, finely to medium

crystalline dolomite (Ward and Osborne, 2006). The Kimbrell member of Conasauga

Formation comprises a small part of the drainage/recharge area (fig. 2). However, the

spring resides on the outcrop of this formation (fig. 2). In the Greenwood quadrangle,

Kimbrell member consists of dark-gray micritic limestone and limey dolomite (Ward and

Osborne, 2006). Some dolomite containing common to abundant dark-gray chert as platy

and irregular stringers, nodules, and masses has also been identified in this member

(Ward and Osborne, 2006). The Conasauga Formation, comprising a very small part of

the drainage/recharge area in the Bessemer quadrangle (fig. 2), consists of interbedded

dark-gray shale and micritic limestone in the lower part; dark-gray stylonodular,

bioclastic, and oolitic limestone in the middle and upper parts; and dolomite in the most

upper part (Osborne and Rindsberg, 2001).

Based on geologic and physiographic settings, it can be inferred that Thomas

Spring waters originate from the Valley and Ridge aquifer which in this area is

characterized by Middle to Upper Cambrian sedimentary rocks. Geologic units capable of

yielding adequate quantities of water in this area consist of dolomite, limestone, and chert

with little primary porosity and permeability.

4

However, secondary porosity and permeability is characterized by leached fossils,

bedding plane conduits, abundant fractures, and karst development. Surface-water

discharge, flow directions, and groundwater recharge and migration pathways are

influenced by karst terrains and complex folds and faults characteristic of the Valley and

Ridge.

Figure 3.—Geology in the Thomas and Glen Springs area.

LAND-USE/LAND-COVER

In recent decades, human-generated processes have been the dominant force in

shaping landscape patterns in the United States. Adverse anthropogenic impacts on

environment are mainly the result of inappropriate distribution and placement of

industrial, commercial, agricultural, high intensity residential, and other human

developments. Polluted effluents resulting from developed areas can degrade surface

water and indirectly groundwater quality wherever there is a connection between the two

entities. In order to identify potential contamination threats to Thomas Spring, the 2010

National Agricultural Statistics Service (NASS) U.S. Department of Agriculture (USDA)

5

Cropland Data Layer (CDL) for Alabama was employed. These data were incorporated

into a Geographic Information System (GIS) and ten Level II land-use/land-cover

(LULC) classes, depicted in figure 3, were identified for the Five Mile Creek-Valley

Creek Watershed that include Thomas Spring and the probable drainage/recharge area.

The classification includes crops, pasture/hay/grass, open water, developed/open space

and low intensity, developed/medium and high intensity, barren, mixed forest, shrubland,

woody and herbaceous wetlands, and grassland herbaceous (fig. 3). Most of the

watershed area is dominated by forest and developed (open space and low intensity) land

uses (fig. 3). In the drainage/recharge area residential uses make up approximately 76.3%

and mixed forest accounts for 17.8% (fig. 3). The rest of the area (5.9%) is covered by, in

order of decreasing coverage area, shrubland, pasture/hay/grass, grassland herbaceous,

and crops. Anthropogenic contamination from sewage and septic sources and other

sources of household or commercial origin is expected in areas like the Thomas Spring

recharge/drainage area.

SPRING DISCHARGE, PHYSICAL PROPERTIES, AND CHEMICAL COMPOSITION

Groundwater samples were collected during two site visits in February and June,

2010 to identify seasonal changes on groundwater quality. Major element analysis was

conducted on the sample collected in February. Physical parameters and stable isotope of

hydrogen (δ18O) and oxygen (δD) samples were collected during both visits. Aqueous

samples for Chlorofluorocarbon (CFCs) and sulphur hexafluoride (SF6) groundwater

dating were collected in June. Samples were collected in the spring pond from a boat

using a Wildco Beta subsurface water sampler. The sampler was lowered into the deepest

part of the spring where direct groundwater discharge was most likely to occur. The

sampler was allowed to fill and was closed at sampling depth using a messenger and line.

The source of groundwater and surface water in the Thomas Spring area is

precipitation, which averages about 56 inches per year (Southeast Regional Climate

Center, 2009). Availability and distribution of this water are controlled by processes,

which include overland flow into streams and lakes, evaporation into the atmosphere,

transpiration by vegetation, and infiltration into the subsurface as groundwater recharge.

The surface hydrology of the project area is dominated by Valley Creek and tributaries

characterized by flashy runoff over relatively impermeable Paleozoic rocks. The

6

groundwater system is characterized as relatively shallow, fractured, Paleozoic carbonate

aquifers with widespread karst development. Groundwater yields are highly variable due

to locally variable porosity and permeability that affect the water-bearing characteristics

of aquifer.

Figure 3.--Land-use/land-cover for the Thomas and Glen Spring assessment area.

Thomas Spring discharge was measured downstream from the spring pond during

four field assessments in 2009 and 2010. Discharge varied from 0.21 to 0.66 cubic feet

per second (cfs) (135,360 to 426,240 gallons per day (gpd)). Spring recharge

(groundwater) was estimated using a simple volumetric/area method. Recharge was

estimated to be 10.3 inches per year or about 18 percent of annual precipitation.

Physical properties assessed in-situ include temperature (T), hydrogen ion activity

(pH), specific conductivity (SC), oxydo-reduction potential (ORP), and total dissolved

solids (TDS). Hydrogen ion activity in an aqueous solution is controlled by interrelated

chemical reactions that produce and consume hydrogen ions (Hem, 1985). The reaction

of dissolved carbon dioxide with water is one of the most important mechanisms in

establishing pH in natural-water systems. Spring water collected during the winter

7

sampling events exhibited slightly acidic pHs (6.5 and 6.2) and specific conductance

characteristic of groundwater originating from carbonate aquifers like those described

herein (474 and 454 microsiemens per centimeter [μS/cm]). Water collected during the

summer sampling event had neutral pH (7.2), and slightly lower SC (390 μS/cm). Total

dissolved solids (TDS) in the summer sample were 255 milligrams per liter [mg/L]). An

increase in pH was noted between the winter and summer events. However, this is

accompanied by a decrease in SC between the two seasons. While there is no positive

correlation between pH and SC, the measured SC values suggest the presence of water-

rock reactions and limestone/dolomite dissolution that release Ca2+, Mg, and HCO32- ions

in solution. This is further supported by the analytic results of the water sample collected

in January that reveal the presence of elevated Ca2+, Mg, and HCO32- concentrations

(58.1, 21.1, and 272 mg/L, respectively). Physical and chemical parameters indicate that

the spring source water originates from groundwater moving through carbonate-rock

aquifers (for example, Knox Group and Conasauga Formation).

More than 90 percent of the dissolved solids in groundwater can be attributed to

eight ions: sodium (Na2+), calcium (Ca2+), potassium (K+), magnesium (Mg2+), sulfate

(SO42-), chloride (Cl-), bicarbonate (HCO3

-), and carbonate (Co32-) (Fetter, 1994). The

quantity of major cations and anions determines water types, which are generally used to

characterize groundwater quality.

The absence of water wells within the drainage/recharge area prevented a

comprehensive characterization of groundwater flow and geochemical evolution. Due to

this limitation, groundwater chemistry, collected by the GSA Groundwater Assessment

Program in 2010, from four wells situated in Trussville has been used as surrogates, in an

effort to evaluate the source of recharge to Thomas Spring. Groundwater geochemical

evolution can be assessed by evaluating the major anion and cation concentrations. The

major ionic composition of water collected from Thomas Spring, as illustrated by the

Piper and Stiff diagrams in figs. 5 and 6, is dominated by Ca2+, HCO3-, and Mg2+ ions.

Similar to the Piper diagram, the Stiff diagram reveals these three elements as the

dominant ions that have roughly equal importance in the shape of the plot (fig. 6).

8

223 272

18

0.003

7.96.2

232

21.19.1

0.05

1.3

58.1

7.1 7 12.8

0.04

436

0.08

261

0.03

454

0.001

0.01

0.1

1

10

100

1000

Alkalin

ity

HCO3 Ba Ca Cl

Conduc

tivity pH DO Fe

Hardn

ess K M

g Na

NO3

as N

O3 Pb

SO4 Sr

TDS

COD

TOC

Surfa

ctan

ts (m

g M

BAS/L)

Physical and chemical parameters

Co

nc

en

tra

tio

ns

(m

g/L

)

Figure 4. -- Thomas Spring physical and chemical parameters.

Similarly to groundwater samples collected from the Tuscumbia Fort Payne and

the Bangor Limestone aquifers in the Trussville area, carbonate has not been detected in

the Thomas Spring water but bicarbonate concentrations have relatively high

concentrations (100 to 199 mg/L in Trussville samples and 272 mg/L in Thomas Spring)

(fig. 4). Furthermore, as observed with the Trussville samples, there is good correlation

between pH, HCO3-, Ca2+, Mg2+, and SC in the Thomas Spring water indicating the

ongoing dissociation of carbonic acid into CO2 and HCO3-. The presence of Mg2+ in

higher concentrations (fig. 4) in the Thomas Spring sample indicates that dolomite (Mg-

carbonates) contributes more solutes to groundwater feeding Thomas Spring compared to

that in the investigated Trussville carbonate aquifers (figs. 5, 6). This agrees with the

higher frequency of occurrence of dolomite in the aquifers present in the spring

drainage/recharge area (see the geology section).

Water hardness, defined as the content of metallic ions that react with sodium

soaps to produce solid soaps or produce mineral scales when evaporated, was 232 mg/L

CaCO3 in Thomas Spring water, which according to the Durfor and Becker (1964)

9

Figure 5.--Piper trilinear diagram showing major ion composition of water collected from Thomas Spring and Trussville wells (modified from Cook and Murgulet, 2011).

classification is classified as very hard. Groundwater in the investigated Trussville

samples varies between moderate to hard (Cook and Murgulet, 2011).

The presence of Cl- and NO3- concentrations (9.1 and 7.1 mg/L, respectively) (fig. 4)

higher than the baseline concentrations in these groundwaters, indicates the presence of

anthropogenic contamination. In the investigated drainage/recharge area agricultural

lands are spatially limited. However, given the high percentage of residential land uses in

this area, sources of groundwater and surface water contamination are probably

associated with sewer breakthrough. This is also confirmed by the Cl/NO3- ratio higher

than one (1.3) (for example, higher chloride concentrations are generally associated with

septic contamination) (Alhajjar and others, 1990). Furthermore, elevated levels of

chemical oxygen demand (COD) and total organic carbon (TOC) were recorded in the

10

Figure 6.-- Stiff diagrams for the selected Trussville groundwater samples (FW, W-7, P-

2, and W-10) and the Thomas Spring sample (ThS).

spring (fig. 4), indicating the existence of water with abundant organic matter. The

geochemical similarity of the Thomas Spring and Trussville samples indicates that the

source water to this spring comes from groundwater hosted by carbonate aquifers such as

those in the drainage/recharge area. Furthermore, the higher Mg2+concentration measured

in the spring sample suggests that groundwater discharging at the investigated spring

originates from a more localized origin as oppose to a regional one.

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NUTRIENTS

Excessive nutrient enrichment is a major cause of water-quality impairment. Excessive

concentrations of nutrients, primarily nitrogen and phosphorus, in the aquatic

environment may lead to increased biological activity, increased algal growth, decreased

dissolved oxygen concentrations at times, and decreased numbers of species (Mays,

1996). Nutrient-impaired waters are characterized by numerous problems related to

growth of algae, other aquatic vegetation, and associated bacterial strains. Blooms of

algae and associated bacteria can cause taste and odor problems in drinking water and

decrease oxygen concentrations to euthrophic levels. Toxins also can be produced during

blooms of particular algal species. Nutrient-impaired water can dramatically increase

treatment costs required to meet drinking water standards. Nutrients discussed in this

report are nitrate (NO3-N) and phosphorus (P-total). Large amounts of algae were

NITRATE

The U.S. EPA Maximum Contaminant Level (MCL) for nitrate in drinking water

is 10 mg/L. However, there is currently no MCL for nitrate related to fish and wildlife.

Typical nitrate (NO3 as N) concentrations in streams vary from 0.5 to 3.0 mg/L.

Concentrations of nitrate in streams without significant nonpoint sources of pollution

vary from 0.1 to 0.5 mg/L. Streams fed by shallow ground water draining agricultural

areas may approach 10 mg/L (Maidment, 1993). Nitrate concentrations in streams

without significant nonpoint sources of pollution generally do not exceed 0.5 mg/L

(Maidment, 1993).

The critical nitrate concentration in surface water for excessive algae growth is

0.5 mg/L (Maidment, 1993). The 0.5 mg/L nitrate criterion was exceeded in the sample

collected from Thomas Spring, with a nitrate as nitrogen (NO3 as N) concentration of

1.58 mg/L. This excessive nitrate is manifested in the spring pond where large amounts

of algae were observed during each field assessment.

PHOSPHORUS

Phosphorus in streams originates from the mineralization of phosphates from soil

and rocks or runoff and effluent containing fertilizer or other industrial products. The

principal components of the phosphorus cycle involve organic phosphorus and inorganic

12

phosphorus in the form of orthophosphate (PO4) (Maidment, 1993). Orthophosphate is

soluble and is the only biologically available form of phosphorus. Since phosphorus

strongly associates with solid particles and is a significant part of organic material,

sediments influence water column concentrations and are an important component of the

phosphorus cycle in streams.

The natural background concentration of total dissolved phosphorus is

approximately 0.025 mg/L. Phosphorus concentrations as low as 0.005 to 0.01 mg/L may

cause algae growth, but the critical level of phosphorus necessary for excessive algae is

around 0.05 mg/L (Maidment, 1993). Although no official water-quality criterion for

phosphorus has been established in the United States, total phosphorus should not exceed

0.05 mg/L in any stream or 0.025 mg/L within a lake or reservoir in order to prevent the

development of biological nuisances (Maidment, 1993). In many water bodies,

phosphorus is the primary nutrient that influences excessive biological activity. These

streams are termed “phosphorus limited.”

The 0.05 mg/L phosphorus criterion was not exceeded for total phosphorus at

Thomas Spring as it was below the detection limit of 0.02 mg/L.

METALLIC CONSTITUENTS

The U.S. Environmental Protection Agency (USEPA) compiled national

recommended water quality criteria for the protection of aquatic life and human health in

surface water for approximately 150 pollutants. These criteria are published pursuant to

Section 304(a) of the Clean Water Act (CWA) and provide guidance for states and tribes

to use in adopting water quality standards (USEPA, 2012). The criteria were developed

for acute (short-term exposure) and chronic (long-term exposure) concentrations. Table 5

shows metals and their recommended acute and chronic maximum concentrations.

Numerous metals are naturally present in streams in small concentrations.

However, toxic metals in streams are usually a result of man’s activities. Water samples

collected from Thomas Spring were analyzed for selected metallic constituents. Table 1

shows recommended criteria for protection of aquatic life maximum concentrations and

sample concentrations that exceed the. Metals detected in water samples can occur

naturally as a result of the erosion of fine grained sediments. This is probably true of iron

and zinc concentrations observed at Thomas Spring (table 1). Lead was the only other

13

metal on the criteria list that was detected. The lead concentration (2.7 µg/L) exceeded

the chronic maximum concentration; however adequate data to determine chronic

conditions are currently unavailable. Although not included in USEPA criteria, barium,

magnesium, strontium, and rubidium were also detected. The former three are common in

Alabama waters, however rubidium is rarely detected and is used in the chemical and

electronics industries. Although not a metallic constituent, pH is included in table 5 due

to its importance in the occurrence and solubility of metals. pH was slightly acidic,

relative to the USEPA criteria.

Table1.-- Concentrations (µg/L) of metallic constituents detected in the water sample from Thomas Spring.

Metallic constituent

USEPA standards for protection of aquatic

life (µg/L)

Analyzed concentrations Sample ThS-1

(µg/L)

Acute Chronic ThS-1 Aluminum 750 87 BDL

Arsenic 340 150 BDL

Cadmium 2.0 0.25 *BDL

Chromium (Cr3)

570 74 BDL

Copper 4.67 n/a BDL

Cyanide 22 5.2 BDL

Iron n/a 1,000 29.7

Lead 65 2.5 2.7

Mercury 1.4 0.77 BDL

Nickel 470 52 BDL

pH n/a 6.5-9.0 6.4

Selenium n/a 5.0 BDL

Silver 3.2 n/a BDL

Zinc 120 120 2.6

* BDL = below detection limit. **Chromium reported as total chromium and is assumed to be primarily Cr3.

14

ORGANIC CONSTITUENTS

Organic compounds are commonly used in our society today. Frequently, these

compounds appear in streams and groundwater aquifers. Many of these compounds are

harmful to human health and to the health of the aquatic environment. Selected organic

constituents including total organic carbon, oil and grease, and phenols were analyzed

from sample ThS-1 collected at Thomas Spring in order to make a general determination

of the presence of organic anthropogenic contaminants in the drainage/recharge area.

Total organic carbon (TOC) analysis is a well-defined and commonly used methodology

that measures the carbon content of dissolved and particulate organic matter present in

water. Many water utilities monitor TOC to determine raw water quality or to evaluate

the effectiveness of processes designed to remove organic carbon.

Some wastewater utilities also employ TOC analysis to monitor the efficiency of

the treatment process. In addition to these uses for TOC monitoring, measuring changes

in TOC concentrations can be an effective surrogate for detecting contamination from

organic compounds (e.g., petrochemicals, solvents, pesticides). Thus, while TOC analysis

does not give specific information about the nature of the threat, identifying changes in

TOC can be a good indicator of potential threats to a hydrologic system (USEPA, 2005).

Typical TOC values for natural waters vary from 1 to 10 mg/L (Mays, 1996). The TOC

concentration in sample ThS-1 was 12.8 mg/L, which exceeds the value for natural

waters. Elevated TOC in Thomas Spring probably originates from contaminated urban

runoff in the drainage/recharge area.

Phenols are used in the production of phenolic resins, germicides, herbicides,

fungicides, pharmaceuticals, dyes, plastics, and explosives (USGS, 1992-96). They may

occur in domestic and industrial wastewaters, natural waters, and potable water supplies.

The USEPA has set its water quality criteria, which states that phenols should be limited

to 10,400 µg/L (micrograms per liter) (10.4 mg/L) in lakes and streams to protect humans

from the possible harmful effects of exposure (USEPA, 2009). Phenols cause acute and

chronic toxicity to freshwater aquatic life. Phenols are common in waters in urban

environments; however phenol in sample ThS-1 was below the detectable limit.

Oil and grease includes fatty matter from animal and vegetable sources and from

hydrocarbons of petroleum origin. Due to the types of land use in the Thomas Spring

15

discharge/recharge area oil and grease was expected, however no oil and grease was

detected.

Surfactants are compounds that lower the surface tension (or interfacial tension)

between two liquids or between a liquid and a solid. Surfactants are used as detergents,

wetting agents, emulsifiers, foaming agents, and dispersants and are routinely deposited

in numerous ways on land and into water systems, whether as part of an intended process

or as industrial and household waste. Some of them are known to be toxic to animals,

ecosystems, and humans, and can increase the diffusion of other environmental

contaminants. Detection of surfactants is an indicator of the presence and movement of

other contaminants into surface water or groundwater. Surfactants were detected in

Thomas Spring discharge (0.04 mg MBAS/L). This is another indication of urban

contamination of the spring. However, no maximum contaminant level has been

established by the USEPA.

ISOTOPIC COMPOSITION

As part of this investigation water samples from Thomas Spring were analyzed

for anthropogenic and natural and stable isotopes such as chlorofluorocarbon (CFCs) and

sulphur hexafluoride (SF6) and oxygen (δ18O), and hydrogen (δD), respectively. These

analyses provide essential measurements to identify the environment from which

groundwater originates and constrains the period of time during which recharge occurred.

Hydrogen and oxygen isotopes are best used in tracing sources of groundwater since they

integrally compose the water molecule (Cook and Herczeg, 1999). These measurements

provide information about recharge and discharge processes, and are successfully used in

delineating recharge areas (Cook and Herczeg, 1999).

Ocean derived atmospheric waters are depleted in heavy isotopes (18O and 2H)

relative to the standard mean ocean water (SMOW). δ18O and δD isotopic composition of

precipitation depends on the fraction of water remaining in the air mass from which the

rain or snowfall is derived (Ellis and Mahon, 1977). Abundances of oxygen and hydrogen

isotopes are measured relative to an accepted standard SMOW or Vienna SMOW

(VSMOW) (Craig, 1961). The isotopic composition of the water is expressed in terms of

the relative difference of the ratio of heavy to light isotopes in the sample compared to

that of SMOW. The resulting compositional values are stated as positive (enriched) or

16

negative (depleted) percentages relative to VSMOW. The average isotopic variation of

global precipitation is defined by a linear regression of δD as a function of δ18O. Craig

and Gordon (1965) estimated the mean worldwide isotope composition of precipitation to

be δ18O = -4 per mil (‰) and δ D = -22 ‰. The worldwide average correlation between

hydrogen and oxygen isotope ratios in precipitation is given by the equation δD = 8 δ18O

+ 10‰, called the Global Meteoric Water Line (GMWL).

Groundwater samples for the oxygen and hydrogen stable isotope analyses were

collected during three site visits, November 2009 (ThS1), January (ThS2), and June

(ThS3) 2010. The δD and δ18O values ranged between -26.6 to -24.5 ‰ and -5.1 to -4.7

‰, respectively. The heavier δD and δ18O values were recorded in samples collected

during the winter (November 2009-January 2010) sampling events (-25.3 and -24.5‰

and -4.8 and -4.7‰, respectively). More depleted isotope signatures were measured in the

summer sample (-26.6 and -5.1‰, respectively). The weighted annual (3-year) δ18O and

δD mean values of precipitation collected from Tuscaloosa, Alabama are -4.7‰ and -

24.3‰, respectively (Lambert and Aharon, 2009). Water samples collected from Thomas

Spring during winter are very similar to those reported by Lambert and Aharon (2009).

Summer values are slightly depleted. The summer isotope signature is very similar to the

Trussville values collected during the same sampling event (fig. 7). The closer similarity

of the winter samples isotope signature to the meteoric signature (TLMWL) may indicate

the greater precipitation input to surface water (Thomas Spring) during the winter. Some

evaporation may be associated with sample ThS1 as it plots below the TLMWL (fig. 7).

On the other hand, during the summer when precipitation rates are lower, groundwater

has a greater input to the spring pond. Therefore, samples collected during the winter

event may be more representative of mixed groundwater and meteoric water. However, a

limited input of meteoric water can be assumed given the high mineral content of water

collected in January (see geochemistry section). Apparent ages estimated using both

CFCs and SF6 dating tools can be affected by factors such as introduced air, recharge

temperature, and degradation of CFCs. In high organic content environments CFCs are

degraded by microbial activity. Furthermore, microbial degradation of CFCs takes place

in anoxic waters with sulfate-reduction or methanogenesis. CFC-11 is the most degraded

17

CFCs compound. Degradation leads to a decrease in concentration and age

underestimation (Kazemi and others, 2006).

Age-dating using CFCs and SF6 for Thomas Spring was not successful, due to

unknown sources of contamination that resulted in sample super saturation with respect

to atmospheric equilibrium and degradation of dating compounds. The presence of

nitrate, surfactant, COD, and TOC contents in the spring water are all indicators of

contamination that make CFCs and SF6 age dating impossible. However, correlation of

these data with Trussville age data determined during the same investigation time and

using the same tools helps derive an approximate age for groundwater discharging at

Thomas Spring. Physical parameters and ionic concentrations characteristic of Thomas

Spring water are very similar to those recorded for the Bangor Limestone waters in the

GMWL: δD = 8δ18O + 10‰

Tuscaloosa LMWL:

δD = 7δ18O + 9‰

Trussville and Thomas Spring water:

δD = 6δ18O + 2‰

-35

-33

-31

-29

-27

-25

-23

-21

-6 -5.8 -5.6 -5.4 -5.2 -5 -4.8 -4.6 -4.4 -4.2 -4

δ18O (‰ VSMOW)

δD (

‰ V

SM

OW

)

TP-2

TP-3

TP-1

Figure 7.-- Cross plot of the δD and δ18O isotope data relative to the GMWL and

TLMWL.

18

Trussville area (Cook and Murgulet, 2011). Groundwater ages in the Bangor Limestone

aquifer are approximately 19±2 years (Cook and Murgulet, 2011).

Regression models using calcium concentrations and available groundwater age

data have been used to project groundwater ages for samples where age-data were not

available (Robinson, 2004). This method requires knowledge of the hydrologic settings

from which samples were collected. For example, projection of groundwater ages has to

be conducted only for aquifers similar in nature. Using the age-data and calcium

concentration for the Bangor Limestone aquifer (18.5±2 years and 60 mg/L) and the

calcium concentrations recorded at Thomas Spring (58.1 mg/L), groundwater age at the

spring was estimated to be approximately 18±2 years. Based on the two age-dates and

specific conductivities, direct measurements of the dissolved solids in solution, for the

Bangor Limestone (18.5±2 and 19.5±2 and 340 and 282 μS/cm) and the specific

conductivity recorded at Thomas Spring (390 μS/cm), groundwater discharging at

Thomas Spring may be roughly 17.7±2 years. Therefore, using both, calcium

concentrations and specific conductivities, the average age of groundwater discharging at

Thomas Spring is approximately 18 years. These estimates are determined assuming that

carbonate dissolution contributes most of the ions in solution and the dissolution rates are

similar on both aquifers.

REFERENCES CITED

Alhajjar, B.J., Chesters, G., Harkin, J.M., 1990, Indicators of chemical pollution from

septic systems, Ground Water 28:559–568.

Cook P.G. and Herczeg A.L. (1999) Environmental Tracers in Subsurface Hydrology.

Kluwer Academic Press, Boston, 529 pp.

Cook, M. R., and Murgulet D., 2011, Groundwater hydrogeologic characterization,

preservation, and development in the Trussville area, Jefferson and St. Clair

Counties: Geological Survey of Alabama Open-file Report- in review.

Craig, H., 1961, Standard for reporting concentrations of deuterium and oxygen-18 in

natural water: Science, v. 133, p. 1833-1834.

Craig H. and Gordon L. I. (1965) Deuterium and oxygen 18 variations in the ocean and

the marine atmosphere. Marine Geochemistry, Narragansett Marine Laboratory,

University of Rhode Island, V. 3, 277-374.

19

Durfor, C. N., and Becker, Edith, 1964, Public water supplies of the 100 largest cities in

the United States, 1962, U.S. Geological Survey Water-Supply Paper 1812, 364 p.

Ellis, A. J., and Mahon, W. A. J., 1977, Chemistry and geothermal systems: Academic

Press, New York, 75 p.

Fetter, C. W., 1994, Applied hydrogeology, Third Edition: New York, New York,

Macmillan, Inc., 691 p.

Hem, J. D., 1985, Study and interpretation of the chemical characteristics of natural

waters (3rd ed.): U.S. Geological Survey Water Supply Paper 2254, 264 p.

Kazemi, G.A., Lehr, J.H., Perrochet, P., 2006, Groundwater Age. John Wiley & Sons,

New York.

Lambert, W. J., and Aharon, P., 2009, Oxygen and hydrogen isotopes of rainfall and

dripwater at DeSoto Caverns (Alabama, USA): Key to understanding past

variability of moisture transport from the Gulf of Mexico; Geochimica et

Cosmochimica Acta 74 (2010) 846–861.

Osborne, W.E. and Rindsberg, A.K., 2001, Geologic Map of the Bessemer 7.5-Minute

Quadrangle, Jefferson County, Alabama, Quadrangle Series Map QSM-20-2001,

Geological Survey of Alabama.

URL: http://www.ogb.state.al.us/gsa/QS_results.aspx?PubID=QS20

Robinson, J. L., 2004, Age and source of water in springs associated with the

Jacksonville Thrust Fault Complex, Calhoun County, Alabama: U.S. Geological

Survey Scientific Investigation Report 2004-5145, 27 p.

Sapp, C. D., and Emplaincourt, Jacques, 1975, Physiographic regions of Alabama:

Alabama Geological Survey Special Map 168.

Southeast Regional Climate Center, 2009, Historical Climate Summaries for Alabama,

URL http://www.sercc.net/climateinfo/historical/historical_al.html, accessed

February 11, 2009.

Ward, E.W. and Osborne, W.E., 2006, Geologic Map of the Greenwood 7.5-Minute

Quadrangle, Jefferson and Shelby Counties, Alabama, Quadrangle Series Map

QSM-44-2006, Geological Survey of Alabama.

URL: http://www.ogb.state.al.us/gsa/QS_results.aspx?PubID=QS44

20

U.S. Geological Survey, 1999, National Elevation Dataset (NED) Digital Elevation

Model (DEM); URL: http://seamless.usgs.gov/

21

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P.O. Box 869999 Tuscaloosa, Alabama 35486-6999

205/349-2852

Berry H. (Nick) Tew, Jr., State Geologist

A list of the printed publications by the Geological Survey of Alabama can be obtained from the Publications Office (205/247-3636) or through our web

site at http://www.gsa.state.al.us/.

E-mail: publications@gsa.state.al.us

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