pg(

y), y gpy 

sediment is flushed through the Barton Springs segment of the Edwards aquifer and springfl

becomes turbid (cloudy). Sediment in urban areas often has high concentrations of hydropho

contaminants, such as DDT, polycyclic aromatic hydrocarbons (PAHs), and lead. In response 

concerns that sediment discharging from the Barton Springs outlets could contain contamina

levels that pose a threat to the health of the salamander or its prey, the U.S. Geological Surv

(USGS), in cooperation with the U.S. Fish and Wildlife Service, collected samples of suspen

sediment discharging from each of the four spring outlets after two rainstorms and analyzed t

suite of hydrophobic contaminants.

Key Findings

Concentrations of DDE and PAHs are lower in suspended 

sediments discharging from the springs than in suspended 

sediments in nearby urban creeks.

Concentrations of PAHs in suspended sediments 

discharging from the springs are low compared to 

sediment-quality guidelines for bed sediments.

Only one organochlorine compound, DDE, was detected 

in suspended sediments discharging from the springs, although other organochlorine com

were detected frequently in suspended sediments from nearby urban creeks. 

Concentrations of trace elements (metals) in suspended sediments discharging from the 

which were elevated relative to concentrations in suspended sediments in urban creeks a

sediment-quality guidelines, are largely related to the natural geochemistry of the sedime

U.S. Department of the Interior

U.S. Geological Survey

USGS Fa

The Barton Springs 

salamander, a completely aquatic species, 

lives in the four spring 

outlets of Barton 

Springs. Note the external gills. The salamanders grow to about 

2.5 inches long. (Photograph courtesy of 

Lisa O’Donnell, City of 

Austin.)

Turbid water discharging from Old Mill Sprin

four Barton Springs outlets, after a heavy ra
N

Apartments

Parking lot

Barton Creek

Barton Creek

Main Barton Spring

Old Mill Spring

Upper Barton Spring

Eliza Spring

Barton Springs

 Pool

Pool house

TEXAS

Area

 enlarged

LOCATION MAP

Direction of flow

bypass

bypass

Trail

Road

Flow by type

Ephemeral

Perennial

Underground

Spring

EXPLANATION

0 300 600 FEET

The Barton Springs system, the fourth largest in Texas, has four main spring outlets: Upper 

Barton Spring, Eliza Spring, Old Mill Spring (also known as Sunken Garden), and Main Barton Spring 

(originally named Parthenia Spring). Upper Barton Spring discharges into a small natural pool; discharge 

from Eliza and Old Mill Springs is retained by structures and then flows into Barton Creek; and Main 

Spring is retained by a dam, forming the 1,000-foot-long Barton Springs Pool. Main Spring discharges 

from a series of orifices in the pool bottom, and the volume of water discharged by this outlet is by far 

the greatest of the four. The average discharge for the whole system is about 53 cubic feet per second 

(ft3/s), or about 34 million gallons per day, but has been as little as 10 ft3/s and as great as 166 ft3/s.

The segment of Barton Creek upstream from Barton Springs Pool flows only after rain or during high 

ground-water levels. It does not flow into Barton Springs Pool but instead is routed around the pool 

through a bypass. In times of flood, however, it overtops the dam separating it from the pool and Main 

Barton Spring, delivering water and sediment from the creek into the pool.

Most of the recharge to the aquifer feeding the Barton Springs system infiltrates through fractures and 

fissures in the beds of five creeks (Slade and others, 1986); recharge from these creeks can take as little 

as several hours to many days to arrive at the springs (Hauwert, 2001). Water discharging from the four 

spring outlets usually is clear, with suspended sediment concentrations of a few milligrams per liter or less. 

After a rain of 1 inch or more, however, spring discharge often becomes turbid, and suspended sediment 

concentrations can exceed 100 milligrams per liter.

Views of Barton Springs pool. Main Barton Spring discharges from beneath the ledge near the lifeguard stand. (Photographs courtesy of David 

Johns, City of Austin.)

Figure 1. Location of Barton Springs system. Suspended sediment samples were collected from the four spring sites shown; the hydrogeologically 

connected springs compose the Barton Springs system. Flow in the creek is from left to right. 
Study Results and What They Mean

During 2000–2002, the USGS collected two 

suspended sediment samples each from Eliza, 

Old Mill, and Upper Barton Springs (fig. 1) as 

part of this study; and collected four suspended 

sediment samples from Main Barton Spring 

as part of a cooperative program with the City 

of Austin. Results for DDE (the only organochlorine detected), selected PAHs, and metals 

are listed in table 1 (back page). Total PAH 

was computed as the sum of 13 parent PAHs 

(MacDonald and others, 2000). Two sedimentquality guidelines developed by MacDonald and 

others (2000) also are shown: The threshold 

effect concentration (TEC) is the concentration 

below which bed sediment is not expected to 

adversely affect benthic biota, and the probable 

effect concentration (PEC) is the concentration 

above which bed sediment is expected to 

adversely affect benthic biota. The guidelines 

were developed to evaluate the toxicity of bed 

sediment, not suspended sediment, but they are 

a useful guideline for evaluating the relative 

contamination of suspended sediment. 

All samples were collected as suspended 

sediments except one sample each from Old 

Mill and Upper Barton Springs, which were 

collected as bed sediment samples for logistical 

reasons. Major-element and grain-size data (not 

shown) indicated that the bed sediment sample 

from Old Mill most likely represented suspended sediment, but that the bed sediment 

sample from Upper Barton did not. In the Upper 

Barton bed sediment sample, concentrations of 

calcium and magnesium (associated with limestone) were much higher than in suspended 

sediment samples, concentrations of aluminum, 

iron, and titanium (associated with clay minerals) and organic carbon were much lower, and 

the bed sediment sample had a much larger 

proportion of sand-size grains (almost 50 percent) than the suspended sediment samples. 

These findings suggest that at Upper Barton, 

suspended sediment discharging from the 

spring is sorted by size after discharge, with 

the larger particles settling next to the spring 

and the smaller clay particles remaining in suspension and being transported downstream by 

springflow.

Contaminant concentrations in discharging 

spring sediments were compared to those in 

suspended sediments collected by the USGS 

in stormflow from two creeks in the Barton 

Springs recharge zone during 2000–2002 as part 

How we collect a suspended 

sediment sample ...

Suspended sediment is isolated from 

water by in-line filtration. Tubing is 

inserted in the spring orifice and pumped 

through a Teflon filter held in either a 

stainless steel filter holder (for analysis of 

organic contaminants) or an acrylic filter 

holder (for analysis of major elements 

and metals) until the filter clogs. The filter 

is removed from the holder, placed in a 

locking plastic bag, and massaged to 

remove the sediment. The filter then is 

replaced in the holder, and more water is 

filtered. Sampling begins once the spring 

water is turbid, generally 12 to 24 hours 

after rainfall, and continues for several 

hours until the turbidity has peaked and 

started to decrease. Details on sample 

collection and processing can be found 

in Mahler and Van Metre (2003).

... and how it’s analyzed.

Samples are analyzed for organochlorine 

compounds, PAHs, and major and trace 

elements (metals) at the USGS National 

Water Quality Laboratory, using the following USGS methods: Organochlorine 

compounds and PAHs are measured by 

dual capillary-column gas chromatography with electron capture detection 

(Foreman and others, 1995; Furlong and 

others, 1996); major and trace elements 

are measured by inductively coupled 

plasma/mass spectrometry (ICP/MS) 

(Briggs and Meier, 2003), except for mercury, which is measured by cold vapor 

atomic adsorption spectroscopy (Brown 

and others, 2003). 

USGS hydrologist Marcus Gary collects 

suspended sediment at Main Barton 

Spring. The sediment has been removed 

from the filter by massaging and has 

collected in the bottom of the locking plastic 

bag. The blue peristaltic pump and the 

stainless steel filter holder are visible in the 

background.

Hydrophobic, or “Water Fearing,” Contaminants and Their Sources

Hydrophobic contaminants are those that, because of their chemical composition, tend 

to adsorb to particles at concentrations of a thousand to a million times greater than 

their concentrations in water. Hydrophobic contaminants detected at very high concentrations in sediment might not be detected in water. Three groups of hydrophobic contaminants (organochlorine compounds, PAHs, and metals) were analyzed for this study. 

Organochlorine Compounds

The most frequently detected organochlorines in the environment are polychlorinated 

biphenyls (PCBs) and the insecticides DDT (and its breakdown products DDE and DDD), 

chlordane, and dieldrin. PCBs were widely used in the 1960s and 1970s in industrial 

equipment; their manufacture was banned in 1978. DDT was banned in 1972 after the 

toxicity and persistence of DDT and its breakdown products were widely publicized 

in Rachel Carson’s (1962) book Silent Spring. Chlordane was used to control termites 

and fire ants until its ban in 1988. Although use of all of these products has been discontinued, they are still detected in suspended sediments in urban creeks and in lake 

sediments.

Polycyclic Aromatic Hydrocarbons

PAHs are the largest class of suspected cancer-causing agents (Björseth and Ramdahl, 

1985). PAHs are produced by incomplete combustion of petroleum, oil, coal, and wood. 

They occur naturally in the environment at very low concentrations, but numerous 

anthropogenic (human-related) sources exist including vehicles, coal and wood fires, 

and power plant emissions. Recent investigations by the City of Austin indicate that 

parking lot sealants containing coal tar might be an important source of PAHs in the 

urban environment (Austin American-Statesman, 2003). Concentrations of PAHs in sediment cores from urban lakes and reservoirs across the Nation increase greatly in more 

recently deposited sediments compared to older sediments (Van Metre and others, 

2000). 

Metals

The metals analyzed for this study are arsenic (actually a metalloid), cadmium, chromium, copper, lead, mercury, nickel, and zinc. Metals occur naturally in all geologic 

settings at a range of concentrations. Anthropogenic sources such as urban runoff, 

smelting, and landfills also deliver metals into the environment. In the urban environment, some common sources of metals are rubber tires (zinc), wheel weights (lead), 

pressure-treated wood (arsenic, chromium, copper), brake pads (copper), and lubricating oil and grease (lead, nickel, zinc).
DDE

TOTAL PAH Eliza Old Mill

Upper Barton

Main Barton

Barton 71

Barton Above

Williamson

0

5

10

15

20

CONCENTRATION, IN MICROGRAMS PER KILOGRAM

0

30,000

60,000

90,000

120,000

150,000

Concentration below TEC

Concentration between TEC and PEC

Concentration above PEC

Nondetection at reporting level

EXPLANATION

of a cooperative program with the City of Austin. The creek sample sites are Barton Creek at 

State Highway 71 (Barton 71), Barton Creek 

above Barton Springs Pool (Barton Above), and 

Williamson Creek at Manchaca Road (Williamson) (fig. 2). Barton 71 is in a relatively undeveloped part of the Barton Creek watershed, and 

Barton Above and Williamson are in more 

intensely developed (urbanized) parts of the 

watershed. Flow-weighted composite samples 

were collected so that concentrations would 

represent an average for the rainstorm; the sediments were analyzed using methods similar to 

those described here for discharging spring sediments (Mahler and Van Metre, 2003).

Organochlorine Compounds

Of the organochlorine compounds analyzed, 

only DDE was detected in discharging spring 

sediments. DDE was detected in at least one 

sample from each spring outlet except Upper 

Barton (fig. 3; table 1). Concentrations were 

low and exceeded the TEC in only one sample. 

In contrast, DDE was detected in every one of 

the surface-water samples collected during the 

sampling period and exceeded the TEC for 

most of the samples collected at the two moreurbanized sites. The occurrence of DDE in 

discharging spring sediments confirms that 

surface-water sediment is transported through 

the aquifer, although the time scale for this 

transport is unknown—discharging sediment 

could have infiltrated the aquifer during the 

sampled event or at an earlier time. The lower 

DDE concentrations detected in spring suspended sediments suggest that contaminated 

sediments in recharge water might be diluted by 

“cleaner” sediments. These cleaner sediments 

could be coming from other, less-developed 

watersheds such as Onion Creek or Bear Creek 

(watersheds feeding the Barton Springs system), from within the aquifer itself, or both. 

Mineralogic differences between recharging 

and discharging sediments (higher aluminum, 

iron, and titanium concentrations in discharging 

sediments indicate more clay minerals and associated iron-oxide coatings) imply that at least 

some proportion of the sediments discharging 

from the aquifer originate from inside the 

aquifer.

Aldrin, chlordane, DDD, DDT, dieldrin, 

endrin, endosulfan, heptachlor, heptachlor 

epoxide, lindane, methoxychlor, mirex, and 

PCB Aroclors 1242, 1254, and 1260 were 

not detected in spring sediments at laboratory 

reporting levels. Reporting levels for any 

individual organochlorine compound in 

suspended sediment vary depending on the 

mass of sediment analyzed, with small sample 

masses usually having higher reporting levels. 

Reporting levels for this study ranged from 1.0 

to 550 micrograms per kilogram (μg/kg); the 

median reporting level for 11 of the compounds 

was 7.0 μg/kg. Five compounds had higher 

median reporting levels: chlordane and the three 

PCB Aroclors (70 μg/kg) and methoxychlor 

(24 μg/kg).

Organochlorine compounds not detected in 

discharging spring sediments were detected in 

some suspended sediment samples from the 

creeks, in some cases at high concentrations. 

For example, chlordane was detected in one 

sample from Barton Above and two from 

Williamson; concentrations in all three samples 

exceeded the PEC of 18 μg/kg (Mahler and 

Van Metre, 2003).

Polycyclic Aromatic Hydrocarbons

Total PAH concentrations associated with 

suspended sediments at the two urbanized surface-water sites were markedly different from 

those at the other sites (fig. 3). Total PAH concentrations at the spring sites and the lightly 

developed surface-water site (Barton 71) were 

all below the TECs. To provide a context for the 

results, concentrations of these samples are similar to those analyzed in a sediment core from 

Mills Lake, a remote lake in Rocky Mountain 

National Park near Estes Park, Colo. (P.C. 

Van Metre, U.S. Geological Survey, unpub. 

data, 1999). In contrast, concentrations of total 

PAH at the two more-urbanized sites are 10 to 

100 times higher than those in Mills Lake. PAH 

concentrations at Williamson, in particular, 

were extremely high, exceeding concentrations 

for all other samples by as much as five times 

(fig. 3). In this case, urbanization appears to 

have increased contamination of surface-water 

sediments by PAHs.

Metals

In contrast to the low concentrations of organochlorine compounds and PAHs in suspended 

sediments discharging from the aquifer, metals 

concentrations were elevated compared to sediment-quality guidelines (fig. 4). Arsenic, chromium, and nickel exceeded the respective TEC 

in eight or more of 10 samples, and nickel 

exceeded the PEC in one sample (table 1). For 

arsenic, chromium, copper, and nickel, the 

median concentration in discharging spring 

sediment exceeded that in the surface-water 

sediments. However, for lead and zinc, two metals shown to be strongly related to urban land 

use (Callender and Rice, 2000), median concentrations in suspended creek sediments exceeded 

those in discharging spring sediments.

Why do discharging spring sediments have 

higher concentrations of metals than suspended 

sediments in creeks, if creek sediments are 

TOWN

 LAKE

LAKE

 AUSTIN AUSTIN

Barton Creek

Creek

Barton 71

Barton Above

Williamson

Williamson

COLORADO

RIVER

TEXAS

AUSTIN

LOCATION MAP

Sampling site and short name

Spring

Dam

Williamson

EXPLANATION

0 3 6 MILES

30o

15'

97o 96o

45'

Figure 2. Locations of sampling sites for suspended sediments in surface water. 

Figure 3. The difference between concentrations of DDE and total PAH in suspended 

sediments discharging from the springs of the 

Barton Springs system (yellow background) and 

in runoff in nearby creeks (blue background) is 

shown. Relative magnitude of concentrations 

was compared to sediment-quality guidelines 

(MacDonald and others, 2000), as indicated by 

symbol color. 
Median concentration for spring or

surface-water suspended sediment

Concentration below TEC

Concentration between TEC and PEC

Concentration above PEC

EXPLANATION

Eliza

Old Mill

Upper Barton

Main Barton

Barton 71

Barton Above

Williamson

Eliza

Old Mill

Upper Barton

Barton 71

Barton Above

Williamson

Main Barton

0

5

10

15

20

25

30

0

100

200

300

TRACE ELEMENT CONCENTRATION,

IN MILLIGRAMS PER KILOGRAM

0

20

40

60

80

0

10

20

30

40

50

60

ARSENIC

NICKEL ZINC

LEAD

0 20,000 40,000 60,000 0 20,000 40,000 60,000 0 20,000 40,000 60,000 0 20,000 40,000 60,000

IRON CONCENTRATION

IN MILLIGRAMS PER KILOGRAM

0 20,000 40,000 60,000 0 20,000 40,000 60,000

0

5

10

15

20

25

30

TRACE ELEMENT CONCENTRATION,

IN MILLIGRAMS PER KILOGRAM

0

10

20

30

40

50

60

0

10

20

30

40

50

60

70

0

20

40

60

80

100

0

100

200

300

0

20

40

60

80

Surface-water suspended

sediment

Barton 71

Barton Above

Williamson

Spring suspended sediment

Main Barton

Eliza

Old Mill

Upper Barton

,

EXPLANATION

ARSENIC NICKEL

LEAD

CHROMIUM

ZINC

COPPER

much more contaminated by organochlorine compounds and PAHs? The 

natural geochemistry of the sediments might be the explanation. Metals 

occur over a wide range of concentrations in geologic materials, but tend 

to concentrate in the iron and manganese hydroxides that sometimes coat 

clay minerals (Hem, 1992). One way to determine if the concentration of 

a metal in sediment is higher than the naturally occurring background 

concentration is to compare the metal concentrations of a suite of sediment samples from a similar geologic setting to the iron concentration. If 

the metal concentration varies proportionately with iron, assumed to have 

a natural source, the metal also is assumed to have a natural source. If 

metal concentrations are graphed in relation to iron concentrations, the 

samples for which the metal concentrations vary proportionately with 

iron concentration will plot along a straight line. Samples that plot above 

the straight line have a disproportionately large concentration of the metal 

in comparison to iron.

All of the metals that were elevated in discharging spring sediments 

compared to suspended sediments in creeks—arsenic, chromium, copper, 

and nickel—correlate well with iron concentration (fig. 5), indicating a 

non-anthropogenic (or natural) source. The few outliers indicate that 

some samples might have an anthropogenic contribution, for example, 

one sample for nickel in Upper Barton (May 8, 2001) and one sample 

for copper in Eliza (November 3, 2000). In general, though, the elevated 

concentrations of most metals in discharging aquifer sediments seem 

to be a natural consequence of high iron concentrations rather than 

pollution.

In contrast, a strong anthropogenic source of lead and zinc is evident 

for suspended sediments at the two urbanized surface-water sites (fig. 5). 

Suspended sediments from Barton Above and Williamson plot in a group 

above the line indicating a proportional variation between iron and these 

two metals; concentrations are more than three times the background concentrations expected on the basis of iron concentrations for some samples, 

quantified by the distance between the straight line and the highest plotted 

points.

Figure 4. Concentrations of selected metals in suspended sediments 

discharging from springs (yellow background) and in surface streams (blue 

background) are compared. Only for lead and zinc, two metals with a 

strong urban source signal (Callender and Rice, 2000), were the median 

concentrations higher in surface-water sediments than in spring sediments. 

Relative magnitude of concentrations was compared to sediment-quality 

guidelines (MacDonald and others, 2000), as indicated by symbol color. 

Figure 5. Correlation of concentrations of different metals to concentration of iron in suspended sediments indicates which samples might have an 

anthropogenic contribution. A linear relation between iron and the other metals is shown by a dashed line. For most metals, spring and surface-water 

sediments plot on that line, indicating that the concentration of the individual metals is proportional to that of iron, and thus probably reflects the natural 

geochemistry of the sediments. A few outliers plot above the line, suggesting an additional, anthropogenic source of the metal for those samples. In 

contrast, for lead and zinc, two metals with a strong urban source signal, most samples from the two urbanized surface-water sites (Barton Above and 

Williamson) plot in a cluster above the line, as indicated by the dashed ovals, while suspended sediments from the springs and Barton 71 plot on the line. 
What Can We Conclude About Sediments Discharging 

From the Springs and Transported in Urban Creeks?

Suspended sediments discharging from Eliza, Old Mill, Upper Barton, 

and Main Barton Springs analyzed for this report show minor effects from 

the urbanization occurring within their watershed. Only one organochlorine compound, DDE, was detected in spring sediments. PAHs were 

detected at concentrations similar to those in nonurbanized environments. 

Concentrations of metals were elevated in many cases relative to the 

TECs, but the elevated concentrations, with only a few exceptions, are 

related to the natural geochemistry of the discharging sediment rather 

than to contamination.

In contrast, concentrations of DDE, PAHs, and lead and zinc were 

higher in suspended sediments collected at two surface-water sites in the 

more-urbanized part of the watershed than they were either in the spring 

sediments or in suspended sediments collected at a surface-water site in a 

less-urbanized part of the watershed. Concentrations of hydrophobic contaminants associated with suspended sediments at the urbanized surfacewater sites were in many cases several times higher than sediment-quality 

guidelines for the health of benthic biota. Although the creeks sampled 

recharge the aquifer feeding Barton Springs, sediments currently (2002) 

discharging from the springs are relatively uncontaminated. Possible reasons include dilution of contaminated sediments by cleaner sediments and 

storage of contaminated recharging sediments in the aquifer. The results 

of the study described in this report indicate that urbanization of the 

watershed has not yet resulted in extensive degradation of the quality of 

sediment discharging from the Barton Springs system.

— B.J. Mahler

References Cited

Austin American-Statesman, 2003, Parking lot contaminant theory explored 

(by R.K.M. Haurwitz, February 4, 2003): Austin, p. A6.

Björseth, Alf, and Ramdahl, T., eds., 1985, Handbook of polycyclic aromatic 

hydrocarbons—Emission sources and recent progress in analytical 

chemistry, v. 2: New York, Marcel Dekker, 432 p.

Briggs, P.H., and Meier, A.L., 2003, The determination of forty-two elements 

in geological materials by inductively coupled plasma/mass spectrometry for NAWQA: U.S. Geological Survey Open-File Report 02–223–I, 

16 p.

Brown, Z.A., O’Leary, R.M., Hageman, P.L., and Crock, J.G., 2003, Mercury 

in water, geologic, and plant materials by continuous flow/cold vapor/

atomic adsorption spectroscopy: U.S. Geological Survey Open-File 

Report 02–223–M, 11 p.

Callender, Edward, and Rice, K.C., 2000, The urban environmental gradient—Anthropogenic influences on the spatial and temporal distributions 

of lead and zinc in sediments: Environmental Science and Technology, 

v. 34, no. 2, p. 232–238.

Carson, Rachel, 1962, Silent spring: Boston, Houghton Mifflin, 386 p.

Foreman, W.T., Connor, B.F., Furlong, E.T., Vaught, D.G., and Merten, L.M., 

1995, Methods of analysis by the U.S. Geological Survey National 

Water Quality Laboratory—Determination of organochlorine pesticides 

and polychlorinated biphenyls in bottom sediment by dual capillarycolumn gas chromatography with electron-capture detection: U.S. 

Geological Survey Open-File Report 95–140, 78 p.

Furlong, E.T., Vaught, D.G., Merten, L.M., Foreman, W.T., and Gates, P.M., 

1996, Methods of analysis by the U.S. Geological Survey National 

Water Quality Laboratory—Determination of semivolatile organic compounds in bottom sediment by solvent extraction, gel permeation chromatographic fractionation, and capillary-column gas chromatography/

mass spectrometry: U.S. Geological Survey Open-File Report 95–719, 

67 p.

Hauwert, N.M., 2001, Research program summary—Groundwater tracing: 

Barton Springs/Edwards Aquifer Conservation District, accessed June 

20, 2003, at URL

 http://www.bseacd.org/graphics/Groundwater_Tracing_Study_R.pdf

Hem, J.D., 1992, Study and interpretation of the chemical characteristics of 

natural water (3d ed.): U.S. Geological Survey Water-Supply Paper 

2254, 263 p. 

MacDonald, D.D., Ingersoll, C.G., and Berger, T.A., 2000, Development 

and evaluation of consensus-based sediment quality guidelines for 

freshwater ecosystems: Archives of Environmental Contamination and 

Toxicology, v. 39, p. 20–31.

Mahler, B.J., and Van Metre, P.C., 2003, A simplified approach for monitoring hydrophobic organic contaminants associated with suspended sediment—Methodology and applications: Archives of Environmental 

Contamination and Toxicology, v. 44, no. 4, p. 288–297.

Slade, R.M., Jr., Dorsey, M.E., and Stewart, S.L., 1986, Hydrology and 

water quality of the Edwards aquifer associated with Barton Springs 

in the Austin area, Texas: U.S. Geological Survey Water-Resources 

Investigations Report 86–4036, 117 p.

Van Metre, P.C., Mahler, B.J., and Furlong, E.T., 2000, Urban sprawl leaves 

its PAH signature: Environmental Science and Technology, v. 34, no. 19, 

p. 4,064–4,070.

Any use of trade, product, or firm names is for descriptive purposes only 

and does not imply endorsement by the U.S. Government.

Information on technical reports and hydrologic data related to this 

study can be obtained from:

District Chief

U.S. Geological Survey Phone: (512) 927–3500

8027 Exchange Dr. FAX: (512) 927–3590

Austin, TX 78754–4733 World Wide Web: 

E-mail: dc_tx@usgs.gov http://tx.usgs.gov/ 

Table 1. Concentrations of organic carbon, DDE, selected PAHs, and metals in suspended sediments discharging from the Barton Springs system

[Concentrations exceeding the TEC shown in blue and one exceeding the PEC shown in red; see text for additional compounds not detected. μg/kg, micrograms per kilogram; mg/kg, milligrams 

per kilogram; I.S., insufficient sediment for analysis; E, estimated; <, less than; TEC, threshold effect concentration (MacDonald and others, 2000); --, not applicable; PEC, probable effect 

concentration (MacDonald and others 2000)]

Spring Date

Organic

carbon

(percent)

DDE

(μg/kg)

Total

PAH

(μg/kg)

Anthracene

(μg/kg)

Fluoranthene

(μg/kg)

Pyrene

(μg/kg)

Benz[a]-

anthracene

(μg/kg)

Chrysene

(μg/kg)

Benzo(a)-

pyrene

(μg/kg)

Arsenic

(mg/kg)

Cadmium

(mg/kg)

Chromium

(mg/kg)

Copper

(mg/kg)

Mercury

(mg/kg)

Nickel

(mg/kg)

Lead

(mg/kg)

Zinc

(mg/kg)

Eliza 11–03–00 I.S. E4.3 E769 E30.3 E105 E89.2 E62.6 E96.3 E107 19.8 0.96 71.8 63.2 0.015 37.7 34.9 138

11–16–01 4.73 <19 E322 E36.1 E37.7 E37.3 E58.2 E4.1 E75.5 23.2 .47 83.3 41.4 I.S. 46.3 32.4 141

Old Mill 05–17–01 2.72 E.2 E102 <10 16.9 12.9 10.3 16.5 12.5 15.7 .19 49.3 23.6 .05 24.6 21.2 67.6

11–16–01 I.S. <12 E302 E24.0 E32.4 E29.2 E37.9 E8.4 E49.4 24.2 .62 94.8 45.0 I.S. 47.1 35.3 160

Upper Barton 05–08–01 I.S. <8.0 E395 E18.5 E53.3 E46.5 E37.3 E27.0 E41.0 13.9 .22 54.2 20.4 I.S. 51.9 17.0 83.4

03–12–02 <.05 <1.0 E80 3.0 13.2 12.1 E6.8 E7.4 E8.2 2.04 .075 11.9 5.06 .02 12.8 6.64 14.4

Main Barton 11–03–00 2.09 E1.0 E177 E5.9 E23.8 E19.4 E12.5 E21.4 E25.0 21.0 .73 68.6 28.6 .07 32.0 22.4 91.3

05–07–01 1.67 <6.0 E360 E21.5 E46.2 E41.2 E36.1 E25.9 E38.1 10.5 .40 36.3 17.6 .08 24.2 12.6 50.4

08–27–01 I.S. <10 E632 E20.4 E98.3 E81.3 E53.4 E59.1 E85.6 18.5 .37 62.6 25.7 I.S. 31.6 23.0 99.7

11–16–01 3.56 E1.3 E328 E16.8 E41.2 E36.3 E33.9 E19.5 E48.4 22.8 .58 82.8 40.8 .07 44.0 31.8 133

TEC -- -- 3.16 1,610 57.2 423 195 108 166 150 9.79 .99 43.4 31.6 .18 22.7 35.8 121

PEC -- -- 31.3 22,800 845 2,230 1,520 1,050 1,290 1,450 33.0 4.98 111 149 1.06 48.6 128 459