U.S. Department of the Interior

U.S. Geological Survey

Scientific Investigations Report 2013–5200

Prepared in cooperation with the San Antonio River Authority

Detections, Concentrations, and Distributional Patterns of 

Compounds of Emerging Concern in the San Antonio River 

Basin, Texas, 2011−12
Front cover, View of the San Antonio River oriented upstream in San Antonio, Texas (photograph taken on 

November 14, 2013, by Michael B. Nyman, U.S. Geological Survey).

Back cover:

Top, View of the San Antonio River oriented upstream in San Antonio, Texas (photograph taken on 

November 14, 2013, by Michael B. Nyman, U.S. Geological Survey).

Bottom right, U.S. Geological Survey hydrographers collecting water sample for analysis of compounds

of emerging concern (photograph taken on May 31, 2011, by Chiquita S. Lopez, U.S. Geological Survey).

Bottom left, Equipment used for measuring field properties during water sample collection (photograph

taken on May 31, 2011, by Chiquita S. Lopez, U.S. Geological Survey).
Detections, Concentrations, and 

Distributional Patterns of Compounds of 

Emerging Concern in the San Antonio River 

Basin, Texas, 2011−12

By Stephen P. Opsahl and Rebecca B. Lambert

Prepared in cooperation with the San Antonio River Authority

Scientific Investigations Report 2013–5200

U.S. Department of the Interior

U.S. Geological Survey
U.S. Department of the Interior

SALLY JEWELL, Secretary

U.S. Geological Survey

Suzette M. Kimball, Acting Director

U.S. Geological Survey, Reston, Virginia: 2013

Suggested citation:

Opsahl, S.P., and Lambert, R.B., 2013, Detections, concentrations, and distributional patterns of compounds of 

emerging concern in the San Antonio River Basin, Texas, 2011−12: U.S. Geological Survey Scientific Investigations 

Report 2013–5200, 44 p., http://dx.doi.org/10.3133/sir20135200. 

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as noted in the text. Permission to reproduce copyrighted items must be secured from the copyright owner.

ISSN 2328-031X (print)

ISSN 2328-0328 (online)

ISBN 978 1 4113 3723 7
iii

Contents

Abstract ..........................................................................................................................................................1

Introduction ....................................................................................................................................................2

Purpose and Scope .............................................................................................................................3

Description of Study Area ..................................................................................................................3

Previous Studies and Background Information ..............................................................................8

Wastewater Compounds ...........................................................................................................8

Pharmaceuticals .......................................................................................................................14

Steroidal Hormones and Sterols ............................................................................................14

Methods ........................................................................................................................................................14

Collection of Streamflow Data .........................................................................................................14

Collection and Processing of Water-Quality Samples .................................................................14

Sample Analyses ................................................................................................................................14

Quality Assurance ..............................................................................................................................15

Detections and Concentrations of Compounds of Emerging Concern ..............................................17

Detections and Concentrations of Individual Compounds .........................................................17

Detections and Concentrations for Each Synoptic Sampling Event .........................................22

Distributional Patterns of Compounds of Emerging Concern ..............................................................33

Distributional Patterns of Wastewater Compounds ....................................................................33

Basin-Wide Distributional Patterns ................................................................................................37

Summary .......................................................................................................................................................39

References Cited .........................................................................................................................................41

Appendixes

1. Physicochemical Properties and Wastewater Compounds Analyzed in WaterQuality Samples Collected from the San Antonio River Basin, Texas, 2011–12 ..............56

2. Physicochemical Properties and Pharmaceuticals Analyzed in Water-Quality 

Samples Collected from the San Antonio River Basin, Texas, 2011–12 ............................56

3. Physicochemical Properties, Steroidal Hormones, and Sterols Analyzed in 

Water-Quality Samples Collected from the San Antonio River Basin, Texas, 

2011–12 ........................................................................................................................................56

4. Quality-Assurance Data for Wastewater Compounds, Pharmaceuticals, Steroidal 

Hormones, and Sterols Analyzed in Water-Quality Samples Collected from the 

San Antonio River Basin, Texas, 2011–12 ..............................................................................56

5. Concentrations of Wastewater Compounds Summed for Each Compound 

Subclass Measured in Water-Quality Samples Collected from the San Antonio 

River Basin, Texas, 2011–12 .....................................................................................................56
iv

Figures

1. Maps showing locations of wastewater discharge and water-quality sampling 

sites in the San Antonio River Basin, 2011–12 ........................................................................4

2. Graph showing the number of detections of wastewater compounds in 33 waterquality samples collected from the San Antonio River Basin, 2011–12 ............................18

3. Graph showing the number of detections of pharmaceuticals in 34 water-quality 

samples collected from the San Antonio River Basin, 2011–12 .........................................20

4. Graph showing the number of detections of steroidal hormones and sterols in 

34 water-quality samples collected from the San Antonio River Basin, 2011–12 ...........21

5. Graphs showing the number of detections in water-quality samples collected 

from the San Antonio River Basin during synoptic sampling event 1, March–May 

2011, of A, wastewater compounds, B, pharmaceuticals, C, steroidal hormones, 

and D, sterols ..............................................................................................................................23

6. Graphs showing the concentrations in water-quality samples collected from 

the San Antonio River Basin during synoptic sampling event 1, March–May 2011, 

of A, wastewater compounds, B, pharmaceuticals, C, steroidal hormones, and 

D, sterols .....................................................................................................................................24

7. Graphs showing the number of detections in water-quality samples collected 

from the San Antonio River Basin during synoptic sampling event 2, October–

November 2011, of A, wastewater compounds, B, pharmaceuticals, C, steroidal 

hormones, and D, sterols ..........................................................................................................26

8. Graphs showing the concentrations in water-quality samples collected from the 

San Antonio River Basin during synoptic sampling event 2, October–November 

2011, of A, wastewater compounds, B, pharmaceuticals, C, steroidal hormones, 

and D, sterols ..............................................................................................................................27

9. Graphs showing the number of detections in water-quality samples collected 

from the San Antonio River Basin during synoptic sampling event 3, April–May 

2012, of A, wastewater compounds, B, pharmaceuticals, C, steroidal hormones, 

and D, sterols ..............................................................................................................................28

10. Graphs showing the concentrations in water-quality samples collected from 

the San Antonio River Basin during synoptic sampling event 3, April–May 2012, 

of A, wastewater compounds, B, pharmaceuticals, C, steroidal hormones, and 

D, sterols .....................................................................................................................................30

11. Graphs showing the number of detections in water-quality samples collected 

from Ecleto Creek at the Ecleto site in the San Antonio River Basin, January–

July 2012, of A, wastewater compounds, B, steroidal hormones, and C, sterols ...........31

12. Graphs showing the concentrations in water-quality samples collected at the 

Ecleto site on Ecleto Creek in the San Antonio River Basin, January–July 2012, of 

A, wastewater compounds, B, steroidal hormones, and C, sterols ..................................32

13. Map showing relative concentrations and proportions of individual subclasses 

of wastewater compounds in water-quality samples collected during synoptic 

sampling event 1 from the San Antonio River Basin, March–May 2011 ..........................34

14. Map showing relative concentrations and proportions of individual subclasses 

of wastewater compounds in water-quality samples collected during synoptic 

sampling event 2 from the San Antonio River Basin, October–November 2011 .............35

15. Map showing relative concentrations and proportions of individual subclasses 

of wastewater compounds in water-quality samples collected during synoptic 

sampling event 3 from the San Antonio River Basin, April–May 2012 ..............................36
v

Tables

1. Wastewater discharge sites in the San Antonio River Basin, Texas ..................................6

2. Water-quality sampling sites in the San Antonio River Basin, Texas, 2011–12 .................7

3. Wastewater compounds, pharmaceuticals, steroidal hormones, and sterols 

analyzed in water-quality samples collected from the San Antonio River Basin, 

Texas, 2011–12 ..............................................................................................................................9

4. Laboratory reporting levels, total number of detections, and concentration 

ranges for wastewater compounds in 33 water-quality samples collected from 

the San Antonio River Basin, Texas, 2011–12 .......................................................................19

5. Laboratory reporting levels, total number of detections, and concentration 

ranges for pharmaceuticals in 34 water-quality samples collected from the San 

Antonio River Basin, Texas, 2011–12 ......................................................................................20

6. Laboratory reporting levels, total number of detections, and concentration 

ranges for steroidal hormones and sterols in 34 water-quality samples collected 

from the San Antonio River Basin, Texas, 2011–12 ..............................................................22

Conversion Factors

Inch/Pound to SI

Multiply By To obtain

Length

foot (ft) 0.3048 meter (m)

mile (mi) 1.609 kilometer (km)

Area

acre 4,047 square meter (m2

)

acre 0.004047 square kilometer (km2

)

square mile (mi2

) 259.0 hectare (ha)

square mile (mi2

) 2.590 square kilometer (km2) 

Flow rate

cubic foot per second (ft3

/s) 0.02832 cubic meter per second (m3/s)

million gallons per day (Mgal/d) 0.04381 cubic meter per second (m3

/s)

Vertical coordinate information is referenced to the North American Vertical Datum of 1988 

(NAVD 88).

Horizontal coordinate information is referenced to the North American Datum of 1983 (NAD 83).

Altitude, as used in this report, refers to distance above the vertical datum.

Specific conductance is given in microsiemens per centimeter at 25 degrees Celsius (μS/cm at 

25 °C).

Concentrations of chemical compounds in water are given in either micrograms per liter (μg/L) 

or nanograms per liter (ng/L).

Detections, Concentrations, and Distributional Patterns of 

Compounds of Emerging Concern in the San Antonio River 

Basin, Texas, 2011−12

By Stephen P. Opsahl and Rebecca B. Lambert

Abstract

During 2011–12, the U.S. Geological Survey, in 

cooperation with the San Antonio River Authority, evaluated 

detections, concentrations, and distributional patterns of 

selected compounds of emerging concern (hereinafter referred 

to as “CECs”) from water-quality samples (hereinafter referred 

to as “samples”) collected at a total of 20 sampling sites 

distributed throughout the San Antonio River Basin, Texas. 

Of the 54 wastewater compounds analyzed, 32 were detected 

in at least one sample collected from the San Antonio River 

Basin, and 22 of those compounds were not detected in any 

samples. The flame retardants tris (2-chloroethyl) phosphate 

and tris (dichloroisopropyl) phosphate, both possible 

endocrine disruptors, were the most frequently detected 

wastewater compounds with 28 of the 33 samples analyzed 

for wastewater compounds having measureable concentrations 

of those compounds. Of the 13 analyzed pharmaceuticals, 

4 compounds were detected in a least one sample. 

Carbamazepine, an anticonvulsant, was the most frequently 

detected prescription pharmaceutical with 24 detections in 

34 samples analyzed for pharmaceuticals. Of the 17 steroidal 

hormones, 4 were detected in at least one sample from the San 

Antonio River Basin. Estrone was detected in 9 of 34 samples 

analyzed for steroidal hormones, making it the most frequently 

detected steroidal hormone. Of the 4 sterols, all 4 were 

detected in at least one sample from the San Antonio River 

Basin. Cholesterol, detected in 19 of 34 samples analyzed for 

sterols, was the most frequently detected sterol.

Three synoptic sampling events were completed as 

part of this study. The first and second synoptic sampling 

events included samples collected at the same 12 sampling 

sites. During the first and second synoptic sampling events, 

the lowest number of detections (2 and 0, respectively) and 

the lowest total concentrations of all measured compounds 

(0.62 and not measureable, respectively) occurred in 

samples collected at the Macdona site (Medina River near 

Macdona, Tex.). The highest number of detections (21 and 

23, respectively) and highest total concentrations of all 

measured compounds (7.75 and 3.97 micrograms per liter 

[μg/L], respectively) occurred in samples collected at the 

SAR Elmendorf site (San Antonio River near Elmendorf, 

Tex.). The third synoptic sampling event included samples 

collected at seven sites that were added to the study after 

the first two synoptic sampling events were completed. 

During the third synoptic sampling event, the lowest number 

of detections (two) and the lowest total concentration 

(0.14 μg/L) of compounds were measured in samples collected 

at the North Prong site (North Prong Medina River above 

confluence Wallace Creek near Medina, Tex.). The highest 

number of detections (21) occurred at the SAR Mitchell 

site (San Antonio River at Mitchell Street, San Antonio, 

Tex.). The Dos Rios site (the Dos Rios wastewater treatment 

plant outfall at San Antonio, Tex.) had the highest total 

concentration of all measured compounds (4.37 μg/L) in the 

third synoptic sampling event. Because Ecleto Creek flows 

only intermittently at the Ecleto site (Ecleto Creek near 

Runge, Tex.), samples from the Ecleto site were collected at 

different times than were samples from the other sites and 

were not included in a synoptic sampling event. The presence 

of wastewater compounds at the Ecleto site indicates that at 

least some wastewater compounds can be introduced into 

surface waters in rural parts of the San Antonio River Basin 

during runoff or because of onsite wastewater system seepage. 

The steroidal hormone and sterols detected at the Ecleto site, 

including estrone, cholesterol, beta-sitosterol, and betastigmastanol, likely were derived from cattle waste rather than 

from wastewater effluent.

The distributional patterns of detections and 

concentrations of individual compounds and compound 

classes show the influence of wastewater-treatment plant 

(WWTP) outfalls on the quality of water in the San Antonio 

River Basin. In the Medina River Subbasin, the minimal 

influence of wastewater is evident as far downstream as 

the Macdona site. Downstream from the Macdona site, the 

Medina River receives treated municipal wastewater from 

both the Medio Creek Water Recycling Center site from an 

unnamed tributary at the plant and the Leon Creek Water 

Recycling Center site from Comanche Creek at the plant, 

and corresponding increases in both the number of detections 
2 Detections, Concentrations, and Distributional Patterns of Compounds of Emerging Concern in the San Antonio River Basin

and the total concentrations of all measured compounds at all 

downstream sampling sites were evident. Similarly, the San 

Antonio River receives treated municipal wastewater as 

far upstream as the SAR Witte site (San Antonio River at Witte 

Museum, San Antonio, Tex.) and additional WWTP outfalls 

along the Medina River upstream from the confluence of the 

Medina and San Antonio Rivers. Consequently, all samples 

collected along the main stem of the San Antonio River 

had higher concentrations of CECs in comparison to sites 

without upstream WWTPs. Sites in urbanized areas without 

upstream WWTPs include the Leon 35 site (Leon Creek at 

Interstate Highway 35, San Antonio, Tex.), the Alazan site 

(Alazan Creek at Tampico Street, San Antonio, Tex.), and the 

San Pedro site (San Pedro Creek at Probandt Street, at San 

Antonio, Tex.). The large number of detections at sites with 

no upstream wastewater source demonstrated that CECs 

can be detected in streams flowing through urbanized 

areas without a large upstream source of treated municipal 

wastewater. A general lack of detection of pharmaceuticals 

in streams without upstream outfalls of treated wastewater 

appears to be typical for streams throughout the San Antonio 

River Basin and may be a useful indicator of point-source 

versus nonpoint-source contributions of these compounds 

in urban streams. Observations of lower concentrations of 

compounds at the furthest downstream sampling sites in the 

basin indicate some natural attenuation of these compounds 

during transport; however, a more focused assessment is 

needed to make this determination.

Introduction

Advancements in laboratory analytical techniques 

have provided the capability to identify large numbers of 

previously unrecognized organic compounds derived from 

wastewater treatment plants (WWTPs), industrial effluent, 

runoff from urban and agricultural land cover, land application 

of human and animal waste, and onsite wastewater treatment 

systems (Richardson and Ternes, 2011). Such organic 

compounds are commonly referred to as “compounds 

of emerging concern” (CECs) and include wastewater 

compounds, pharmaceutical drugs (hereinafter referred to as 

“pharmaceuticals”), and natural and synthetically produced 

hormones (Glassmeyer and others, 2005; Focazio and others, 

2008). Prior studies have demonstrated that many of these 

compounds are commonly detectable in surface waters 

(Kolpin and others, 2002; Oblinger and others, 2007; Haack, 

2009; Lawrence and LaFontaine, 2010; Lee and others, 2011; 

Reif and others, 2012) and groundwater (Barnes and others, 

2008; Katz and others, 2010). Some of these compounds are 

known or suspected endocrine disrupters (Lintelmann and 

others, 2003) that can interfere with normal endocrine system 

functions responsible for regulating various developmental 

processes in the body (U.S. Environmental Protection Agency, 

2012). The potential for individual CECs or some combination 

of CECs to affect human health and aquatic life remains 

poorly understood, and most CECs remain unregulated (U.S. 

Environmental Protection Agency, 2012); however, data on 

the detection and concentration of CECs are becoming more 

widely available, providing managers and policy makers with 

more information that may be used for water treatment and 

water resource management.

Understanding the sources and fate of CECs at the river 

basin scale is important to water resource managers. Pointsource discharges from WWTPs are a primary source of CECs 

to urban streams (Kolpin and others, 2004). Nonpoint sources 

such as seepage from onsite wastewater treatment systems 

(Katz and others, 2010), leakage from sewer lines (Lawrence 

and LaFontaine, 2010), urban runoff (Marklund and others, 

2005), agricultural and livestock operations (Chambers 

and Leiker, 2006), and atmospheric deposition (Schuetzle 

and others, 1975; Peck and Hornbuckle, 2006; Ligocki and 

others, 1985a, b) also represent common pathways for CECs 

to enter the environment. The fate of CECs in streams is 

partially determined by natural attenuation processes including 

sorption to sediments (Tolls, 2001; Kolpin and others, 2002), 

microbial decomposition (Yamamoto and others, 2009), and 

photochemical degradation (Carlos, 2012; Klamerth and 

others, 2010). 

San Antonio and surrounding municipalities in Bexar 

County, Texas, are in a rapidly urbanizing region in the San 

Antonio River Basin (fig. 1) (U.S. Census Bureau, 2013), 

and patterns of water usage have changed as a result of this 

rapid urbanization (Texas Instream Flow Program and San 

Antonio River Authority, 2009). As the San Antonio area 

continues to grow, increases in residential and commercial 

development likely will enhance runoff into streams during 

storm events and increase chemical loads into the drainage 

network (Ockerman and McNamara, 2003). Although 

there are multiple WWTPs in the San Antonio area, other 

municipalities, both upstream from and downstream from 

San Antonio, also represent potential sources of CECs to 

the San Antonio River system (fig. 1, table 1). To better 

understand the quality of surface water in the San Antonio 

River Basin, the U.S. Geological Survey (USGS), in 

cooperation with the San Antonio River Authority, evaluated 

detections, concentrations, and distributional patterns of 

selected compounds of emerging concern (hereinafter referred 

to as “CECs”) from water-quality samples (hereinafter referred 

to as “samples”) collected at sampling sites distributed 

throughout the San Antonio River Basin, Tex., during 2011–

12. Each wastewater discharge site has a wastewater facility 

name, a National Pollutant Discharge Elimination System 

(NPDES) identifier, and a short name (table 1), and each 

sampling site has a USGS station number, USGS station name, 

and short name (table 2). In this report, the short names listed 

in tables 1 and 2 are used for referring to wastewater discharge 

sites and sampling sites, respectively. Map identifiers (tables 1, 

2) cross referenced to the short names are provided on all of 

the map-based figures in the report.
Introduction 3

Purpose and Scope

This report summarizes the number of detections, 

concentrations, and distributional patterns of wastewater 

compounds, pharmaceuticals, steroidal hormones, and sterols 

analyzed in samples collected from 20 sampling sites along 

streams throughout the San Antonio River Basin, Tex., 

during 2011–12. Results are presented for 54 wastewater 

compounds, 13 pharmaceuticals, 17 steroidal hormones, 

and 4 sterols. The report presents data for the number of 

detections and concentrations of individual compounds from 

all samples collectively and for the number of detections 

and concentrations of individual compounds and compound 

classes for each of three synoptic sampling events. The report 

also describes basin-wide distributional patterns of detections 

and concentrations of all compounds to provide insight into 

the potential sources and transport of compounds from streams 

in the San Antonio River Basin.

Description of Study Area

The San Antonio River drains an area of approximately 

4,180 square miles and extends about 240 miles from its 

headwaters northwest of San Antonio to the confluence of 

the San Antonio and Guadalupe Rivers (San Antonio River 

Authority, 2013) (fig. 1). The Guadalupe River drains into the 

San Antonio Bay and the Gulf of Mexico downstream from 

where the San Antonio River flows into the Guadalupe River. 

The San Antonio River Basin drains parts of the following 

counties: Atascosa, Bandera, Bexar, Comal, DeWitt, Goliad, 

Guadalupe, Karnes, Kendall, Kerr, Medina, Refugio, Victoria, 

and Wilson. Much of the population in the study area resides 

in Bexar County where San Antonio is located. Major 

subbasins of this basin include the Medina River Subbasin, 

the Upper San Antonio River Subbasin, the Cibolo Creek 

Subbasin, and the Lower San Antonio River Subbasin 

(fig. 1). 

Wastewater processing facilities in the San Antonio River 

Basin include WWTPs and water recycling centers (WRCs), 

both of which treat municipal wastewater and discharge it to 

streams. There are outfalls of treated municipal wastewater 

throughout Bexar County, and the majority of sampling sites 

were located in Bexar County (fig. 1, table 1, table 2). The 

San Antonio Water System manages WRCs, and estimates 

for discharge by WRCs were provided by the San Antonio 

Water System (Gregg Eckhardt, oral commun., 2013). 

Treated municipal wastewater discharge from Dos Rios WRC 

(map identifier WW07, fig. 1, table 1), the largest WRC in San 

Antonio, averages approximately 75–80 million gallons per 

day (Mgal/d), or 116–124 cubic feet per second (ft3

/s). Treated 

municipal wastewater discharge from Leon Creek WRC (map 

identifier WW13, fig. 1, table 1) averages approximately 

36–38 Mgal/d (56–59 ft3

/s). Treated municipal wastewater 

discharge from the Medio Creek WRC (map identifier 

WW15, fig. 1, table 1) averages approximately 7.5 Mgal/d 

(12 ft3/s). 

Some of the treated municipal wastewater from Dos 

Rios WRC, Leon Creek WRC, and Medio Creek WRC may 

be discharged at the following sites along the San Antonio 

River, where it is used to help maintain base flows (Gregg 

Eckhardt, San Antonio Water System, oral commun., 2013): 

Dos Rios Tuleta (map identifier WW08, fig. 1, table 1), Dos 

Rios Flood Tunnel (map identifier WW09, fig. 1, table 1), Dos 

Rios Rittiman (map identifier WW10, fig. 1, table 1), Dos Rios 

Convention Center (map identifier WW11, fig. 1, table 1), and 

Dos Rios Blue Wing (map identifier WW12, fig. 1, table 1). 

Typical treated municipal wastewater discharges at these sites 

under base flow conditions are 4–5 Mgal/d (6.2–7.7 ft3/s) at 

the Dos Rios Tuleta wastewater discharge site, 0.5–1.0 Mgal/d 

(0.8–1.5 ft3/s) at the Dos Rios Convention Center wastewater 

discharge site, and 0.5 Mgal/d (0.8 ft3/s) at the Dos Rios 

Rittiman wastewater discharge site. The Dos Rios Flood 

Tunnel wastewater discharge site typically is used as a backup, 

and the Dos Rios Blue Wing wastewater discharge site 

currently is (2013) not in operation. 

In the Cibolo Creek Subbasin, there are two wastewater 

discharge sites (map identifiers WW01 and WW02, fig. 1, 

table 1) located in Boerne, Tex. Under normal base flow 

conditions, the discharge from these sites infiltrates the 

stream channel and becomes groundwater recharge within 

about 3 miles downstream from Boerne where Cibolo Creek 

typically goes dry. Farther downstream from WW01 and 

WW02 in the Cibolo Creek Subbasin, there are multiple sites 

of treated municipal wastewater discharge that maintain base 

flow in Cibolo Creek until the confluence of Cibolo Creek 

and the San Antonio River. These sites include the Cibolo 

WWTP (map identifier WW03, fig. 1, table 1) on the main 

stem of Cibolo Creek, the Salitrillo WWTP on Salitrillo 

Creek (map identifier WW04, fig. 1, table 1), and the Upper 

Martinez WWTP (map identifier WW05, fig. 1, table 1) and 

the Martinez II WWTP (map identifier WW06, fig. 1, table 1) 

on Martinez Creek.

The upper parts of the Medina River Subbasin and the 

Ecleto Creek watershed are not affected by WWTPs (fig. 1). 

The North Prong site (map identifier EC01, fig. 1, table 2), in 

the upper part of the Medina River Subbasin, was included 

in the study as a reference site. The North Prong site is in an 

area composed primarily of rangeland with no large upstream 

municipalities and is the northernmost data collection site 

from which samples were collected. The Ecleto site (map 

identifier EC19, fig. 1, table 2), in the Ecleto Creek watershed 

was not part of the three synoptic sampling events; it was 

selected to represent rangeland conditions characteristic of 

much of the San Antonio River Basin. 
Figure 1. Locations of wastewater discharge and water-quality sampling sites in the San Antonio River Basin, 2011–12.

BLANCO

COUNTY

HAYS COUNTY

KERR COUNTY

KENDALL

COUNTY

CALDWELL COUNTY

REAL COUNTY

COMAL COUNTY

BANDERA COUNTY

GUADALUPE COUNTY

GONZALES COUNTY

BEXAR 

COUNTY MEDINA COUNTY

LAVACA COUNTY

UVALDE COUNTY

WILSON COUNTY

DEWITT COUNTY 

ATASCOSA COUNTY

KARNES

COUNTY

VICTORIA COUNTY

FRIO COUNTY

GOLIAD 

COUNTY

LIVE OAK

COUNTY

CA

C

BEE COUNTY

MCMULLEN COUNTY

REFUGIO COU

ARANSAS COU

Ingram

Kerrville

New Bandera Braunfels

Cibolo

Seguin

Castroville

La Coste Nixon

Somerset Stockdale

Devine Natalia Floresville

Cuero

Poth

St. Hedwig

Hondo

Poteet Yorktown Pleasanton

Jourdanton

Karnes City Runge Victoria

Charlotte

Kenedy

Bloom

Three Rivers

Beeville

Refugio

Woodsboro

Lytle

Goliad

Rockport

Boerne

San 

Antonio

Martinez

Creek

WW01

WW02

WW17

Base map modified from U.S. Geological Survey 1:100,000-scale digital dataUniversal Transverse Mercator projection, zone 14North American Datum of 1983

San Antonio River

San Antonio

0 10 20 30 40 MILES0 2010 30 40 KILOMETERS

ECEC2

M

iden

WW01WW02WW17

Boerne WWTPBoerne WWTP and WRCKenedy WWTP

Map 

identifier

Short name

(table 1)

EC01

EC20

97°00'

98°00'

99°00'

30°00'

29°30'

29°00'

28°30'

Medina River Subbasin

Lower San Antonio 

River Subbasin

Cibolo Creek

Subbasin

Upper San Antonio 

River Subbasin

EXPLANATION

San Antonio River Basin bSubbasin boundaryWastewater discharge sitWater-quality sampling sit

WW01

EC01

Canyon

Lake

MedinaLake

Calaveras Lake

Victor Braunig Lake

River

West Prong

Medina River

Alazan Creek

ApacheCreek

San Pedro

Creek

Medio

Creek

Salitrillo

Creek

North Prong

Medina River

Medina River

Guadalupe River

Medina River

San Antoni o River

Salado Creek

EcletoCreek

Cibolo Creek

Escondido Creek

Guadalupe River

Cibolo Creek

Mitchell 

Lake

Leon Creek

TEXAS

San Antonio 

River Basin

Area enlarged
Figure 1. Locations of wastewater discharge and water-quality sampling sites in the San Antonio River Basin, 2011–12.—Continued

Upper San Antonio 

River Subbasin

Medina River Subbasin

Lower San Antonio

River Subbasin

Cibolo Creek Subbasin

KENDALL COUNTY

COMAL 

COUNTY

BANDERA

COUNTY

GUADALUPE

COUNTY

GONZALES

COUNTY

BEXAR COUNTY

MEDINA COUNTY

WILSON COUNTY

ATASCOSA COUNTY

FRIO COUNTY

New

Braunfels

San Antonio

Cibolo

Castroville

La Coste

Stockdale

Lytle

Somerset

Natalia

Floresville

Poth

Schertz

St. Hedwig

Poteet

Pleasanton

Jourdanton

Karnes

City

Charlotte 

Cibolo

Ecleto

Creek

Creek

Salado

Salitrillo

Zarzamora

Creek Creek

Creek

San Pedro

Creek

Apache

Creek Martinez Creek

Calaveras

Lake

Victor 

Braunig Lake

Mitchell

Lake

Comanche

Creek

Alazan Creek

San Antonio River

San Antonio River

Guadalupe River

Cibolo Creek

Leon Creek

Medio Creek

Medina River

Base modified from U.S. Geological Survey 1:100,000-scale digital dataUniversal Transverse Mercator, zone 14North American Datum of 1983

EC02EC03EC04EC05EC06EC07EC08EC09EC10EC11EC12EC13EC14EC15EC16EC17EC18EC19

Map 

identifier

WW03WW04WW05WW06WW07WW08WW09WW10WW11WW12WW13WW14WW15WW16

Cibolo WWTPSalitrillo WWTPUpper Martinez WWTPMartinez II WWTPDos Rios WRCDos Rios TuletaDos Rios Flood TunnelDos Rios RittimanDos Rios Convention CenterDos Rios Blue WingLeon Creek WRCLeon Creek Mitchell LakeMedio Creek WRCFloresville WWTP

Map 

identifier

Short name

(table 1)

0 63 90 63 9 12 KILOMETERS

12 MILES

Ecleto Creek watershedLeon Creek watershedMedio Creek watershedSalado Creek watershedSan Antonio River Basin boundarySubbasin boundaryWastewater discharge site and  map identifier—See table 1Water-quality sampling site and  map identifier—See table 2

EXPLANATION

EC17

WW03

WW03

WW04

WW05

WW06

WW07

WW08

WW09

WW10

WW11

WW12

WW13 WW14

WW15

WW16

EC02

EC03

EC04

EC05

EC06

EC07

EC08 EC09

EC10

EC11

EC12

EC13

EC14

EC15

EC16

EC17

EC18

E

29°30'29°00'

98°30' 98°00'
6 Detections, Concentrations, and Distributional Patterns of Compounds of Emerging Concern in the San Antonio River Basin

Table 1. Wastewater discharge sites in the San Antonio River Basin, Texas.

[NPDES, National Pollutant Discharge Elimination System; NAD 83, horizontal coordinate information referenced to North American Datum of 1983; dd, 

degrees; mm, minutes; ss, seconds; WWTP, wastewater treatment plant; WWTF, wastewater treatment facility; WRC, water recycling center; --, no NPDES 

identifier available. Data from U.S. Environmental Protection Agency (2013a)]

Map 

identifier 

(as shown in 

figs. 1, 13, 

14, and 15)

Short name County Wastewater 

facility name

NPDES 

identifier

WW01 Boerne WWTP Kendall Boerne WWTP TX0024465

WW02 Boerne WWTP and WRC Kendall Boerne WWTP and Recycling Center TX0131831

WW03 Cibolo WWTP Guadalupe Cibolo Creek WWTP TX0077232

WW04 Salitrillo WWTP Bexar Salitrillo Creek TX0053074

WW05 Upper Martinez WWTP Bexar Upper Martinez Creek WWTF TX0024082

WW06 Martinez II WWTP Bexar Martinez II WWTP TX0095583

WW07 Dos Rios WRC Bexar Medina River at plant site TX0077801

WW08 Dos Rios Tuleta Bexar San Antonio River at Tuleta Street --

WW091 Dos Rios Flood Tunnel Bexar San Antonio River at flood tunnel inlet --

WW10 Dos Rios Rittiman Bexar Salado Creek at Rittiman Road --

WW11 Dos Rios Convention Center Bexar San Antonio River at Convention Center --

WW121 Dos Rios Blue Wing Bexar San Antonio River near Blue Wing Road --

WW13 Leon Creek WRC Bexar Comanche Creek at plant site --

WW14 Leon Creek Mitchell Lake Bexar Mitchell Lake TX0065641

WW15 Medio Creek WRC Bexar Unnamed tributary at plant site TX0055689

WW16 Floresville WWTP Wilson Floresville WWTP TX0056227

WW17 Kenedy WWTP Karnes Kenedy WWTF TX0027774

1

Site inactive during the time that samples were collected for all synoptics.
Table 2. Water-quality sampling sites in the San Antonio River Basin, Texas, 2011–12.[USGS, U.S. Geological Survey; NAD 83, horizontal coordinate information referenced to North American Datum of 1983; dd, degrees; mm, minutes; ss, seconds; TCEQ, TexaQuality; IH, interstate highway; WWTP, wastewater treatment plant; SAR, San Antonio River; --, not available]

Map 

identifier 

(as 

shown in 

figs. 1, 13, 

14, 

and 15)

Short name County USGS station number USGS station name Synoptic number Latitude (NAD 83) (dd mm ss

EC01 North Prong Bandera 08178863 North Prong Medina River above confluence Wallace 

Creek near Medina, Tex.

3 29° 51′ 14

EC02 Macdona Bexar 08180700 Medina River near Macdona, Tex. 1,2 29° 20′ 06

EC03 Medio Bexar 08180750 Medio Creek at Pearsall Road, San Antonio, Tex. 1,2 29° 19′ 41

EC04 Leon 35 Bexar 08181480 Leon Creek at IH 35, San Antonio, Tex. 1,2 29° 19′ 48

EC05 Medina Bexar 08181500 Medina River at San Antonio, Tex. 1,2 29° 15′ 51

EC06 Dos Rios Bexar 291407098243701 Dos Rios WWTP Outfall at San Antonio, Tex. 3 29° 14′ 09

EC07 SAR Witte Bexar 08177825 San Antonio River at Witte Museum, San Antonio, Tex. 3 29° 27′ 42EC08 Alazan Bexar 292449098303000 Alazan Creek at Tampico Street, San Antonio, Tex. 3 29° 24′ 49EC09 SAR Mitchell Bexar 08178050 San Antonio River at Mitchell Street, San Antonio, Tex. 3 29° 23′ 35EC10 San Pedro Bexar 08178504 San Pedro Creek at Probandt Street, at San Antonio, Tex. 3 29° 23′ 30

EC11 SAR 410 Bexar 08178565 San Antonio River at Loop 410, San Antonio, Tex. 1,2 29° 19′ 20

EC12 Salado 13 Bexar 08178800 Salado Creek at Loop 13, San Antonio, Tex. 1,2 29° 21′ 26

EC13 SAR Elmendorf Bexar 08181800 San Antonio River near Elmendorf, Tex. 1,2 29° 13′ 20

EC14 SAR Falls City Bexar 08183550 San Antonio River at Highway 181 at Falls City, Tex. 1,2 28° 58′ 38

EC15 Salitrillo Bexar 293025098175700 Salitrillo Creek downstream of Schaeffer Road in 

Converse, Tex.

3 29° 30′ 25

EC16 Martinez St. Hedwig Bexar 08185100 Martinez Creek near Saint Hedwig, Tex. 1,2 29° 26′ 38EC17 Cibolo St. Hedwig Guadalupe 08185065 Cibolo Creek near Saint Hedwig, Tex. 1,2 29° 30′ 05EC18 Cibolo Falls City Karnes 08186000 Cibolo Creek near Falls City, Tex. 1,2 29° 00′ 51EC19 Ecleto Karnes 08186500 Ecleto Creek near Runge, Tex. -- 28° 55′ 13

EC20 SAR Goliad Goliad 08188500 San Antonio River at Goliad, Tex. 1,2 28° 38′ 57
8 Detections, Concentrations, and Distributional Patterns of Compounds of Emerging Concern in the San Antonio River Basin

Previous Studies and Background Information

Wastewater Compounds

WWTPs effectively remove some wastewater compounds 

during treatment, although the efficiency of removal varies on 

the basis of the chemical properties of individual compounds 

and environmental conditions (Loyo-Rosales and others, 

2007; Phillips and others, 2005; Baker and KasprzykHordern, 2013). For example, in a study that examined the 

fate of alkylphenolic compounds in three large WWTPs, the 

efficiency of removal of 4-n-octylphenol and 4-nonylphenol 

ethoxylates ranged from 71.5 percent to 99.1 percent (LoyoRosales and others, 2007). That study also reported that the 

removal efficiency was observed to be greater at a higher 

temperature, presumably the result of enhanced microbial 

transformations stimulated by higher temperatures (LoyoRosales and others, 2007). Phillips and others (2005) reported 

that biological treatment of wastewater removed a higher 

percentage of wastewater compounds than did filtration or 

disinfection processes, and removal efficiency was enhanced 

with higher sludge retention efficiencies. The number of 

individual compounds that may be present in treated municipal 

wastewater remains unknown. 

Certain subclasses of wastewater compounds are 

commonly present in streams including detergent metabolites, 

personal-use compounds, pesticides, industrial compounds, 

disinfection compounds, polycyclic aromatic hydrocarbons 

(PAHs), and flame retardants and plasticizers (Kolpin and 

others, 2002; Lawrence and LaFontaine, 2010; Lee and 

others, 2011). Detergent metabolites present in environmental 

samples generally result from the degradation or metabolism 

of alkylphenol polyethoxylate detergents, widely used as 

cleaning agents during wastewater treatment (Loyo-Rosales 

and others, 2007). Seven detergent metabolites were analyzed 

in this study (table 3), and all are known to be endocrine 

disruptors because of their ability to mimic estrogenic 

hormones (White and others, 1994). Personal-use compounds 

are contained in many widely used personal-use products 

that enter wastewater and thus can be useful wastewater 

indicators (Oblinger and others, 2007). Thirteen personal-use 

compounds representing a broad range of chemical additives 

including flavorants, food preservatives, fragrances, and 

stimulants were analyzed in this study (table 3). Among 

the 9 pesticides analyzed for this study, 3 were herbicides 

(bromacil, metachlor, and prometon), 4 were insecticides 

(carbaryl, carbazole, chlorpyrifos, and diazinon), and 1 was 

a fungicide (metalaxyl) (table 3). A suspected carcinogen, 

the fumigant 1,4-dichlorobenzene is traditionally used as a 

moth repellent and is also classified as a pesticide, although it 

may be appropriately classified as a personal-use compound 

because of its use in urinal cakes (Montgomery and Welkom, 

1990; National Institute of Environmental Health Sciences, 

2011; Reif and others, 2012). Three of the pesticides 

(carbaryl, chlorpyrifos, and diazinon) are known endocrine 

disruptors, and two (1,4-dichlorobenzene and metachlor) are 

suspected endocrine disruptors (table 3) (Reif and others, 

2012). There were 10 industrial compounds representing 

preservatives, antioxidants, solvents, fixatives, dyes, and other 

manufacturing compounds analyzed in this study (table 3). 

One compound, 3-tert-Butyl-4-hydroxyanisole (BHA), is 

a known endocrine disruptor. Two industrial compounds 

analyzed for this study, p-cresol and benzophenone, are 

compounds with suspected endocrine disrupting potential 

(Reif and others, 2012). Tribromomethane and phenol were 

the two disinfectant compounds analyzed in this study. 

Tribromomethane, a potential human carcinogen (table 3), 

is produced as a disinfection byproduct during chlorination 

(U.S. Environmental Protection Agency, 2007). PAHs are 

compounds typically associated with fossil fuels because they 

are constituents of natural gas, oil, and tar (table 3). PAHs also 

are formed during the combustion of carbon-based materials 

and the byproducts of fossil fuel combustion represent one of 

the largest pathways for PAHs into the environment (Nagpal, 

1993). Recent studies have found that coal-tar sealants are 

another major source of PAHs to the environment (Van Metre 

and Mahler, 2010; Mahler and others, 2012). One pathway for 

coal-tar sealants into water and air includes weathering of road 

surfaces followed by aeolian transport or stormwater runoff 

of fine particles containing PAHs. Volatilization is another 

pathway by which PAHs from coal-tar sealants may enter the 

atmosphere (Van Metre and others, 2012). Among the nine 

PAHs analyzed in this study (table 3), benzo[a]-pyrene is a 

potential human carcinogen and a known endocrine disruptor 

that is highly bioaccumulative (U.S. Environmental Protection 

Agency, 2011). Flame retardants and plasticizers are used 

in the manufacture of flame retardants, plastics, resins, wax, 

and other products (Reif and others, 2012) (table 3). Of the 

six flame retardants and plasticizers analyzed in this study, 

tris (2-chloroethyl) phosphate and tris (dichloroisopropyl) 

phosphate are suspected endocrine disruptors.
Table 3. Wastewater compounds, pharmaceuticals, steroidal hormones, and sterols analyzed in water-quality samples collected from the San Anto2011–12.—Continued[LRL, laboratory reporting level; CASRN, Chemical Abstracts Service Registry Number; USGS, U.S. Geological Survey; NWIS, USGS National Water Information System; μgng/L, nanograms per liter; --, not available; PAH, polycyclic aromatic hydrocarbon]

Compound name LRL CASRN Description of use or sources

Wastewater compounds - detergent metabolites

4-Cumylphenol1 0.060 μg/L 599-64-4 Nonionic detergent metabolite 

4-n-Octylphenol1 0.06 μg/L 1806-26-4 Nonionic detergent metabolite 4-Nonylphenol (sum of all 

isomers)1

2 μg/L 84852-15-3 Nonionic detergent metabolite 

4-Nonylphenol diethoxylate 

(sum of all isomers) (NP2EO/NPE02)1

5 μg/L -- Nonionic detergent metabolite 

4-tert-Octylphenol diethoxylate 

(OPE02)1

1 μg/L 2315-61-9 Nonionic detergent metabolite 

4-tert-Octylphenol 

monoethoxylate (OPE01)1

1 μg/L 2315-67-5 Nonionic detergent metabolite 

4-tert-Octylphenol1 0.14 μg/L 140-66-9 Nonionic detergent metabolite 

Wastewater compounds - personal-use compounds

Camphor 0.044 μg/L 76-22-2 Flavor, odorant, ointments 

3-Methyl-1H-indole (Skatole) 0.036 μg/L 83-34-1 Fragrance, stench in feces, and coal tar Acetophenone 0.40 μg/L 98-86-2 Fragrance in detergent and tobacco, flavor in beverages Acetyl hexamethyl 

tetrahydronaphthalene (AHTN)2

0.028 μg/L 21145-77-7 Musk fragrance, persistent and widespread in groundwater 

Caffeine 0.06 μg/L 58-08-2 Stimulant N, N-diethyl-meta-toluamide 

(DEET)

0.06 μg/L 134-62-3 Insecticide, urban uses, mosquito repellent 

Hexahydrohexamethylcyclopentabenzopyran 

(HHCB)

0.052 μg/L 1222-05-5 Musk fragrance, persistent and widespread in groundwater 

Indole 0.08 μg/L 120-72-9 Inert pesticide ingredient, fragrance, in coffee Isoborneol 0.08 μg/L 124-76-5 Fragrance in perfumery, in disinfectants Isoquinoline 0.046 μg/L 119-65-3 Flavors and fragrances d-Limonene 0.08 μg/L 5989-27-5 Fragrance in aerosols, antimicrobial, antiviral, and fungicide Menthol 0.32 μg/L 89-78-1 Cigarettes, cough drops, liniment, mouthwash Triclosan3 0.20 μg/L 3380-34-5 Disinfectant, antimicrobial (concern for acquired microbial resistance) 

Table 3. Wastewater compounds, pharmaceuticals, steroidal hormones, and sterols analyzed in water-quality samples collected from the San Anton2011–12. [LRL, laboratory reporting level; CASRN, Chemical Abstracts Service Registry Number; USGS, U.S. Geological Survey; NWIS, USGS National Water Information System; μgng/L, nanograms per liter; --, not available; PAH, polycyclic aromatic hydrocarbon]
Table 3. Wastewater compounds, pharmaceuticals, steroidal hormones, and sterols analyzed in water-quality samples collected from the San Anto2011–12.—Continued [LRL, laboratory reporting level; CASRN, Chemical Abstracts Service Registry Number; USGS, U.S. Geological Survey; NWIS, USGS National Water Information System; μgng/L, nanograms per liter; --, not available; PAH, polycyclic aromatic hydrocarbon] Compound name LRL CASRN Description of use or sources 

Wastewater compounds - pesticides 1,4-Dichlorobenzene3 0.040 μg/L 106-46-7 Used as an ingredient in urinal cakes, deodorant, disinfectant and chemical intermediate in addition to uses as a general insecticide, moth repellent, fumigant, and germicide 

Bromacil 0.36 μg/L 314-40-9 Uracil compound used as a herbicide for brush control on noncropland areas such as road shoulders. Greater than 80 percent noncrop usage on grass 

Carbaryl (1-naphthylmethylcarbamate)1 0.16 μg/L 63.25-2 Broad-spectrum carbamate insecticide used to control over 100 species of insects on citrus trees, fruit trees, nut trees, cotton, vegetables, forests, lawns, ornamentals, shade trees, an

other crops, as well as poultry, livestock, and pets 

Carbazole 0.03 μg/L 86-74-8 Insecticide, manufacturing of dyes, explosives, and lubricants 

Chlorpyrifos1 0.16 μg/L 2921-88-2 Broad-spectrum, chlorinated organophosphate (OP) insecticide, acaricide, and nematicide used on grain, cotton, field, fruit, nut, and vegetable crops, as well as on lawns, ornamen

plants, and golf course turf. Also registered for direct use on sheep and turkeys, for horse treatment, dog kennels, domestic dwellings, farm buildings, storage bins, and commerciaestablishments as well as nonstructural wood treatments including processed wood produfence posts, and utility poles. Can lead to neurotoxicity 

Diazinon 0.16 μg/L 333-41-5 Nonsystemic organophosphate Restricted Use Pesticide (RUP) for professional pest contro

operator use only. Greater than 40 percent nonagricultural usage on a wide variety of treefruit, row crops, and vegetables. No longer used on golf courses and sod farms because odie-offs of birds that often congregated in these areas. Classified as moderately toxic 

Metalaxyl 0.12 μg/L 57837-19-1 Systemic benzenoid compound used as a pesticide, herbicide, and fungicide. Applied as either a foliar spray, soil treatment, or a seed treatment to control downy mildews. Used 

many different food crops, including tobacoo, ornamentals, conifer, and golf course/turf applications 

Metolachlor3 0.028 μg/L 51218-45-2 Preemergent herbicide used to control certain broadleaf and annual grassy weeds in row cro

fruit and nut trees, highway rights-of-way, and woody ornamentals. General use pesticidthat is an indicator of agricultural drainage 

Prometon 0.12 μg/L 1610-18-0 Herbicide, noncrop only, applied prior to blacktop 

Wastewater compounds - industrial compounds p-Cresol (para-Cresol)3 0.08 μg/L 106-44-5 Wood preservative 

3-tert-Butyl-4-hydroxyanisole (BHA)1 0.6 μg/L 121-00-6 Antioxidant and general preservative 5-Methyl-1H-benzotriazole 1.2 μg/L 136-85-6 Antioxidant in antifreeze and deicers 9,10-Anthraquinone 0.16 μg/L 84-65-1 Manufacturing of dye/textiles, seed treatment, bird repellent Benzophenone3 0.08 μg/L 119-61-9 Fixative for perfumes and soap Isophorone 0.032 μg/L 78-59-1 Used as solvent for paints, tin coatings, agricultural chemicals, and synthetic resins; excellent solvent for vinyl resins, cellulose esters, ethers, pesticides, storing lacquers; pesticide manufacturing

Solvent for lacquer, plastic, oil, silicon, resin
Table 3. Wastewater compounds, pharmaceuticals, steroidal hormones, and sterols analyzed in water-quality samples collected from the San Anto2011–12.—Continued[LRL, laboratory reporting level; CASRN, Chemical Abstracts Service Registry Number; USGS, U.S. Geological Survey; NWIS, USGS National Water Information System; μgng/L, nanograms per liter; --, not available; PAH, polycyclic aromatic hydrocarbon]

Compound name LRL CASRN Description of use or sources

Wastewater compounds - industrial compounds—Continued

Isopropylbenzene (cumene) 0.30 μg/L 98-82-8 Manufacturing phenol/acetone, fuels and paint thinner 

Methyl salicylate 0.044 μg/L 119-36-8 Liniment, food, beverage, UV-absorbing lotion Tetrachloroethene 

(Tetrachloroethylene)4

0.12 μg/L 127-18-4 Solvent and degreaser. Used in drycleaning fluids, degreasing and drying metals and other 

solids; solvent for waxes, greases, fats, oils, gums; manufacturing printing inks and paint removers; preparation of fluorocarbons and trichloroacetic acid; vermifuge; organic synthesis

Triethyl citrate (ethyl citrate) 0.16 μg/L 77-93-0 Cosmetics, pharmaceuticals 

Wastewater compounds - disinfection compounds

Phenol 0.16 mg/L 108-95-2 Antiseptic and disinfectant. Used in pharmaceuticals, germicidal paints, dyes, indicators, 

slimicide, laboratory reagents; phenolic resins; epoxy resins (bisphenol-A), nylon-6, 2,4-Also used as a solvent for refining lubricating oils, preparation of acids and other compo

Tribromomethane (Bromoform)4 0.10 mg/L 75-25-2 Wastewater ozination byproduct. Also used as solvent for waxes, greases, and oils; separati

solids with lower densities, component of fire-resistant chemicals, geological assaying, medicine (sedative), intermediate in organic synthesis, military/explosives

Wastewater compounds - polycyclic aromatic hydrocarbons

1-Methylnaphthalene 0.022 μg/L 90-12-0 2–5 percent of gasoline, diesel fuel, or crude oil 

2,6-Dimethylnaphthalene 0.06 μg/L 581-42-0 Present in diesel/kerosene (trace in gasoline) 2-Methylnaphthalene 0.036 μg/L 91-57-6 2–5 percent of gasoline, diesel fuel, and crude oil. Used in organic synthesis and insecticide

Anthracene4 0.01 μg/L 120-12-7 Wood preservative, component of coal tar pitch volatiles, diesel, or crude oil; used in 

dyes, preparation of phenanthrene, carbazole, anthraquinone, and insecticides, organic semiconductor research

Benzo[a]-pyrene1,4 0.06 μg/L 50-32-8 Regulated PAH and byproduct of incompleted combustion, component of coal tar pitch 

volatiles and used in cancer research

Fluoranthene4 0.024 μg/L 206-44-0 Component of coal tar and asphalt (only traces in gasoline or diesel fuels); used as a researc

chemical. Combustion product

Naphthalene3,4 0.04 μg/L 91-20-3 PAH also known as “camphor tar” and derived from coal tar or crude oil. Used as a fumiga

and moth repellent, in preparation of pesticides, fungicides, dyes, detergents, wetting agesynthetic resins, celluloids, preservatives, and lubricants. Major component (about 10 percent) of gasoline

Phenanthrene4 0.016 μg/L 85-01-8 Used in explosives, dyes, biochemical research, synthesis of drugs, and organic synthesis; 

combustion product

Pyrene4 0.042 μg/L 129-00-0 Research chemical derived from industrial and experimental coal gasification operations. 

Component of coal tar and asphalt (only traces in gasoline or diesel fuel)
Table 3. Wastewater compounds, pharmaceuticals, steroidal hormones, and sterols analyzed in water-quality samples collected from the San Anto2011–12.—Continued [LRL, laboratory reporting level; CASRN, Chemical Abstracts Service Registry Number; USGS, U.S. Geological Survey; NWIS, USGS National Water Information System; μgng/L, nanograms per liter; --, not available; PAH, polycyclic aromatic hydrocarbon] Compound name LRL CASRN Description of use or sources 

Wastewater compounds - flame retardants and plasticizers Tributyl phosphate 0.16 μg/L 126-73-8 Antifoaming agent, flame retardant 

Triphenyl phosphate 0.12 μg/L 115-86-6 Plasticizer, resin, wax, finish roofing paper Tris (2-butoxyethyl) phosphate 0.8 μg/L 78-51-3 Flame retardant Tris (2-chloroethyl) phosphate3 0.10 μg/L 115-96-8 Plasticizer, flame retardant Tris (dichloroisopropyl) phosphate3 0.16 μg/L 13674-87-8 Flame retardant Bisphenol A (BPA) 100 ng/L 80-05-7 Plasticizer 

Pharmaceuticals - nonprescription and metabolites 1,7-Dimethylxanthine (para- Xanthine) 0.10 μg/L 611-59-6 Caffeine metabolite 

Acetaminophen 0.12 μg/L 103-90-2 Analgesic Codeine 0.046 μg/L 76-57-3 Analgesic Cotinine 0.038 μg/L 486-56-6 Nicotine metabolite Diphenhydramine 0.058 μg/L 147-24-0 Antihistamine, antiemetic (antinausea), sleep aid and sedative 

Pharmaceuticals - prescription Thiabendazole 0.06 μg/L 148-79-8 Anthelmintics (used to treat worm infections) 

Albuterol (Salbutamol) 0.08 μg/L 18559-94-9 Antiasthmatic Carbamazepine 0.06 μg/L 298-46-4 Anticonvulsant and antimanic Dehydronifedipine 0.08 μg/L 67035-22-7 Antianginal Diltiazem 0.06 μg/L 42399-41-7 Antihypertensive Sulfamethoxazole 0.091 μg/L 723-46-6 Human antibiotic often used in combination with trimethoprim Trimethoprim 0.034 μg/L 738-70-5 Human antibiotic often used in combination with sulfamethoxazole Warfarin 0.08 μg/L 81-81-2 Anticoagulant. In large concentrations used as a rodenticide for controlling rats and house m

in and around homes, animal and agricultural premises, and commercial and industrial si

Steroidal hormones - natural androgens 11-Ketotestosterone 2 ng/L 564-35-2 Very strong androgen 

4-Androstene-3,17-dione 0.8 ng/L 63-05-8 Testosterone precursor, illicit steroid cis-Androsterone 0.8 ng/L 53-41-8 Testosterone metabolite, commonly used in deer repellent Dihydrotestosterone (DHT) 4 ng/L 521-18-6 Also known as Stanolone. Testosterone metabolites; very strong androgen Epitestosterone 2 ng/L 481-30-1 Human androgen Testosterone 1.6 ng/L 58-22-0 Principal human androgen, strong androgen 
Table 3. Wastewater compounds, pharmaceuticals, steroidal hormones, and sterols analyzed in water-quality samples collected from the San Anto2011–12.—Continued[LRL, laboratory reporting level; CASRN, Chemical Abstracts Service Registry Number; USGS, U.S. Geological Survey; NWIS, USGS National Water Information System; μgng/L, nanograms per liter; --, not available; PAH, polycyclic aromatic hydrocarbon]

Compound name LRL CASRN Description of use or sources

Steroidal hormones - natural estrogens

17-alpha-Estradiol 0.8 ng/L 57-91-0 Low occurrence in humans, common in other species 

17-beta-Estradiol1 0.8 ng/L 50-28-2 Principal estrogen in humans, strong estrogen Equilenin 2 ng/L 517-09-9 Equine estrogen used in hormone replacement therapy Equilin 8 ng/L 474-86-2 Equine estrogen used in hormone replacement therapy Estriol 2 ng/L 50-27-1 Metabolite of 17-beta-estradiol Estrone 0.8 ng/L 53-16-7 Metabolite of 17-beta-estradiol 

Steroidal hormones - synthetic estrogens

17-alpha-Ethynyl estradiol1 0.8 ng/L 57-63-6 Used in oral contraceptives, very strong estrogen 

Mestranol 0.8 ng/L 72-33-3 Used in oral contraceptives, metabolized to ethylnyl estradiol prior to excretion trans-Diethylstilbestrol 0.8 ng/L 56-53-1 Used in pharmaceuticals 

Steroidal hormones - natural progestin

Progesterone 8 ng/L 57-83-0 Principal human progestational hormone 

Steroidal hormones - synthetic progestin

Norethindrone 

(19-Norethisterone)

0.8 ng/L 68-22-4 Used in oral contraceptives 

Sterols - animal

3-beta-Coprostanol 200 ng/L 360-68-9 Animal fecal indicator, useful sewage tracer 

Cholesterol 200 ng/L 57-88-5 Ubiquitous, produced by animals and plants 

Sterols - plant

beta-Sitosterol 4 μg/L 83-46-5 Plant sterol 

beta-Stigmastanol 2.6 μg/L 19466-47-8 Plant sterol 

1Known endocrine disrupting potential (see source reference for more information).2Concern for bioaccumulation and toxicity (see source reference for more information).3Suspected endocrine disrupting potential (see source reference for more information).4Potential human carcinogen (see source reference for more information).5Montgomery and Welkom (1990).6Extension Toxicology Network (EXTOXNET) (1996).7National Pesticide Information Center (2011).8Couper and Logan (2004).9Reif and others (2012).10National Institute of Environmental Health Sciences (2013).11National Institute of Environmental Health Sciences (2011).12Washington State Department of Transportation (2006).13U.S. Environmental Protection Agency (2007).14Nagpal (1993).
14 Detections, Concentrations, and Distributional Patterns of Compounds of Emerging Concern in the San Antonio River Basin

Pharmaceuticals

Pharmaceuticals are chemical substances that are 

manufactured and administered to humans or animals to 

prevent, treat, or cure a variety of physical and mental 

afflictions. Pharmaceuticals are introduced into the 

environment through disposal practices such as flushing 

unused medication, direct excretion, or discharge of effluent 

from pharmaceutical manufacturing facilities (Phillips and 

others, 2010). Pharmaceuticals have been detected in both 

surface water and groundwater and often are associated with 

wastewater (Kolpin and others, 2002, 2004; Barnes and 

others, 2008; Rounds and others, 2009). Rounds and others 

(2009) reported a wide range of removal rates of different 

pharmaceuticals during wastewater treatment, ranging from 

18 percent for carbamazepine to greater than 99 percent for 

acetaminophen, indicating the efficiency of removal during 

wastewater treatment is an important factor in determining 

the concentrations of different pharmaceuticals introduced 

into streams. Many pharmaceuticals are known endocrine 

disruptors and some have been shown to have adverse effects 

on aquatic biota (Lintelmann and others, 2003). A total of 

13 pharmaceuticals were analyzed for this study (table 3). 

Five of the compounds were nonprescription pharmaceuticals 

or metabolites, and eight were prescription pharmaceuticals.

Steroidal Hormones and Sterols

Steroidal hormones are biologically produced chemicals 

that serve a variety of functions in animal and plant 

metabolism. Synthetic hormone derivatives such as anabolic 

steroids and birth-control compounds also are widely used 

by humans (Reif and others, 2012). As with pharmaceuticals, 

both natural and synthetic hormones may be introduced into 

the environment through direct excretion or disposal into 

wastewater systems. Both natural and synthetic hormones 

have been detected in aquatic systems, promoting concerns 

about negative effects on freshwater biota (National Academy 

of Sciences, 1999). For example, feminization of male fish, 

based on increased vitellogen production and production of 

early stage eggs in the testes of male fish, has been observed in 

conjunction with the presence of 17-alpha-ethynyl-estradiol, 

a form of synthetic estrogen (Kidd and others, 2007). For this 

study, 21 natural androgens, natural and synthetic estrogens, 

natural and synthetic progestin, animal sterols, and plant 

sterols were analyzed (table 3).

Methods

Collection of Streamflow Data

Continuous streamflow was measured at USGS 

streamflow-gaging stations by using USGS methods described 

by Rantz and others (1982a, b) and Turnipseed and Sauer 

(2010). A stage-discharge relation (rating) was developed 

on the basis of the discrete discharge measurements at 

each site (Kennedy, 1984; Turnipseed and Sauer, 2010). 

Adjustments were made to site ratings when discrete discharge 

measurements indicated changing channel conditions. 

From the rating, stage data were used to compute discharge 

(Kennedy, 1983). Discrete discharge measurements were 

made in accordance with USGS methods (Rantz and others, 

1982a, b; Turnipseed and Sauer, 2010) preceding waterquality-sample collection. Streams were waded, and velocity 

measurements were made by using rod-mounted acoustic 

velocity meters (Xylem Analytics, 2012). The instantaneous 

discharges at the time the samples were collected are listed 

in appendixes 1–3 and were obtained from stage-discharge 

relations or by making discrete discharge measurements. 

Streamflow data were not used in the analyses but are included 

in appendixes 1–3.

Collection and Processing of Water-Quality 

Samples

Samples were collected at 20 sites in the San Antonio 

River Basin during March 2011–May 2012 (fig. 1, table 2). 

All of the samples were collected and processed by following 

the methods and guidelines described in the “National Field 

Manual for the Collection of Water-Quality Data” (U.S. 

Geological Survey, variously dated). The specific sites where 

wastewater compounds, pharmaceuticals, and steroidal 

hormones and sterols were collected during each synoptic 

sampling event and the dates when samples were collected 

are shown in appendixes 1–3, respectively. With the exception 

of the samples collected at the Ecleto site, all samples were 

collected during base flow or low-flow conditions. At the 

Ecleto site, samples were collected during January–March 

2012 and in July 2012 in response to storm events when 

streamflow sufficient for sampling was generated. Compared 

to the samples collected at the other sites, the samples 

collected at the Ecleto site have different sample collection 

dates for wastewater compounds, pharmaceuticals, steroidal 

hormones, and sterols (apps. 1–3). Multiple samples were 

collected during January–March 2012 at the Ecleto site 

because of processing difficulties associated with sedimentladen storm samples; the large amounts of suspended sediment 

in the samples sometimes clogged the sample-extraction 

cartridges used to process the samples at the National Water 

Quality Laboratory (NWQL) in Denver, Colorado, resulting 

in an insufficient sample volume to analyze for wastewater 

compounds. 

Sample Analyses

Samples were analyzed for selected wastewater 

compounds, pharmaceuticals, steroidal hormones, and 

sterols at the NWQL. Physicochemical properties including 

dissolved oxygen (DO), pH, specific conductance (SC), water 

temperature, and turbidity (apps. 1–3) also were measured 
Methods 15

in the field prior to sample collection by following standard 

USGS protocols (U.S. Geological Survey, variously dated).

Selected wastewater compounds were analyzed by 

using solid-phase extraction and gas chromatography/mass 

spectrometry techniques described in Zaugg and others (2002) 

(app. 1). These compounds include detergent metabolites, 

personal-use compounds, pesticides, industrial compounds, 

disinfection compounds, polycyclic aromatic hydrocarbons, 

flame retardants and plasticizers, and plant sterols (table 3). 

Although the plant sterols beta-sitosterol and betastigmastanol were analyzed with the wastewater-compound 

method, they are discussed in this report along with steroidal 

hormones and related compounds because they more closely 

match natural hormones in terms of function and source. 

The animal sterols 3-beta-coprostanol and cholesterol were 

analyzed by using both the wastewater-compound method and 

the hormones method, but the hormone method was chosen for 

the analysis in this study because of superior detection levels 

(Zaugg and others, 2002; Foreman and others, 2012). 

All of the analytical methods used for this study can 

detect low-level concentrations of wastewater compounds, 

pharmaceuticals, steroidal hormones, and sterols in 

environmental samples such as the samples collected during 

the study. The analytical results from each of these methods 

are described as to whether or not they exceed the long-term 

method detection limits (LT-MDLs) and LRLs. The LT-MDLs 

and LRLs are guidelines that can be used in interpretation 

of data, determining whether or not data will need to be 

censored to minimize the number of false positive detections, 

and to quantify false negative detections within a particular 

set of data (Childress and others, 1999). The LT-MDL is a 

modification of the method detection limit (MDL) analysis 

used by the U.S. Environmental Protection Agency (USEPA) 

(Childress and others, 1999, p. 6). The LT-MDL establishes 

the minimum concentration of a compound that can be 

measured and reported with a 99 percent confidence level 

when the analyte concentration in the sample is greater than 

zero. The LT-MDL is designed to minimize the chance of 

a false positive result (detecting the compound when it is 

not present in the sample), but does not imply accuracy or 

precision of the quantitative measurement (Childress and 

others, 1999). The LT-MDL limits the risk of false positive 

values in a sample, but does not adequately address the 

possibility of false negatives in a sample when the compound 

may be present in the sample but is not detected. The LRL is 

a laboratory quantification limit that generally is two times 

the LT-MDL and is designed to minimize the number of false 

negatives in a dataset (Childress and others, 1999). Because 

information-rich mass spectrometry methods were used to 

augment the identification of the compounds described in this 

report, estimated concentrations less than the LT-MDL were 

considered valid chemical detections (U.S. Geological Survey, 

2010). Detections are reported when the concentration of the 

compound equaled or exceeded the LT-MDL, for qualified 

concentrations less than the LT-MDL, and when the presence 

of the compound was verified but not quantified. In this 

report, compound concentrations are qualified with an “E” 

remark code to indicate that the sample value is estimated if 

the quantification of the analyte is considered by the NWQL 

to be highly variable, if the compound concentration was 

extrapolated below the calibration curve, or if the compound 

concentration was less than the LT-MDL (U.S. Geological 

Survey, 2010). Compounds that were verified, but not 

quantified, are qualified with an “M” remark code. When a 

compound was analyzed and the criteria for a detection were 

not met, the concentration is reported as “not measureable.”

Prescription and nonprescription pharmaceuticals and 

metabolites (table 3) were analyzed by using solid-phase 

extraction and high-performance liquid chromatography/mass 

spectrometry methods and techniques described in Furlong 

and others (2008) (app. 2). The pharmaceutical cotinine was 

analyzed by using both the wastewater-compound method and 

the pharmaceutical method, but the pharmaceutical method 

was chosen for the analysis in this study to be consistent with 

the pharmaceuticals analysis. 

Steroidal hormones and sterols (table 3) were analyzed 

by using the solid-phase extraction, derivatization, and gas 

chromatography with tandem mass spectrometry methods 

described in Foreman and others (2012) (app. 3). Bisphenol 

A also was analyzed by using the hormone analysis, but is 

categorized in this report as a flame retardant and plasticizer 

compound. At the start of the study, the hormone analysis was 

considered a research analytical method, but the method was 

approved by the NWQL for general use on June 21, 2012, and 

documented in Foreman and others (2012). Concentrations 

of steroidal hormones are reported by the NWQL in units of 

nanograms per liter, whereas all other compounds are reported 

in units of micrograms per liter. For use in selected figures (bar 

graphs and pie charts depicting concentrations for different 

compound classes), concentrations of steroidal hormones were 

converted from nanograms per liter to micrograms per liter 

by dividing nanograms per liter by 1,000. Converting all of 

the concentration values to a single unit of measure facilitated 

comparison of results from different compound classes, and 

was necessary when concentrations were summed to compute 

total concentrations.

Quality Assurance

For quality-assurance purposes, several quality-control 

samples, including an equipment blank, two field blanks, and 

two split replicates, were collected to qualify the precision 

and accuracy of the environmental samples collected. The 

equipment blank was collected to determine the extent 

of contamination that might be introduced during sample 

processing in the laboratory and laboratory analysis. The 

field blank samples were collected to determine the extent 

of contamination that might have been introduced during 

sample collection, sample processing, and laboratory analysis. 

Equipment blank and field blank samples were collected and 

processed by using organic-free, deionized water obtained 

from the NWQL and certified to contain nondetectable 
16 Detections, Concentrations, and Distributional Patterns of Compounds of Emerging Concern in the San Antonio River Basin

concentrations of the compounds that were analyzed. Split 

replicate samples were collected along with environmental 

samples to determine the amount, or degree, of variability 

that might have resulted from the procedures used to collect, 

process, and analyze the samples. The quality-control 

samples were analyzed for the same wastewater compound, 

pharmaceutical, and hormone analytical schedules as were 

the environmental samples. Results of the quality-assurance 

analyses are shown in appendix 4. 

Prior to collecting the first environmental sample, an 

equipment blank was collected on March 29, 2011, and 

analyzed for concentrations and surrogate recoveries for 

selected wastewater compounds, pharmaceuticals, steroidal 

hormones, and sterols (app. 4). No pharmaceuticals, steroidal 

hormones, or sterols were detected in the equipment blank; 

four wastewater compounds were detected. The four 

wastewater compounds detected were 4-nonylphenol (all 

isomers) (the presence of 4-nonylphenol was verified but not 

quantified), benzophenone, isophorone, and tetrachloroethene. 

Where quantified, concentrations of these detected compounds 

ranged from an estimated 0.03 micrograms per liter (μg/L) 

for tetrachloroethene to 0.17 μg/L for isophorone (app. 4). 

The laboratory reagent blank data provided by the NWQL 

confirmed no contamination during analysis at the NWQL, 

indicating sample processing in the field was likely the source 

of contamination for these compounds.

Field blank samples were collected on November 1, 

2011, and April 26, 2012, during the second and third synoptic 

sampling events (app. 4). There were detectable concentrations 

of four wastewater compounds in the two field blank samples. 

The four compounds detected in the field blank collected 

on November 1, 2011, at the Leon 35 site (map identifier 

EC04, fig. 1, table 2) were N,N-diethyl-meta-toluamide 

(DEET) (0.01μg/L), 4-nonylphenol (all isomers) (estimated 

concentration of 2 μg/L), benzophenone (0.04 μg/L), and 

isophorone (0.16 μg/L) (app. 4). The only wastewater 

compound detected in the field blank collected on April 26, 

2012, at the North Prong site was isophorone (0.062 μg/L) 

(app. 4). The laboratory reagent blank data provided by the 

NWQL confirmed no contamination during analysis at the 

NWQL, indicating that when these compounds were detected 

in the field blank samples they likely were introduced during 

sample processing in the field. Similar to the results from the 

equipment blank sample, pharmaceuticals, steroidal hormones, 

or sterols were not detected in either of the field blanks.

The equipment blank and field blank results were 

analyzed to determine if any results needed to be rejected and 

not reported because the concentrations in the blank samples 

were greater than the concentrations in the environmental 

samples. For two of the compounds, 4-nonylphenol (all 

isomers) and isophorone, all environmental sample values 

and 2 replicate sample values for these compounds were 

rejected and not reported because the concentrations of 

these compounds in the blank samples were close to or 

exceeded the concentrations measured in the environmental 

samples (app. 1, app. 4). For the remaining compounds 

detected in the blank samples, including benzophenone, 

DEET, and tetrachloroethene, a threshold value of three 

times the concentration measured in the blank samples 

was used to determine whether or not to reject data for an 

individual compound in each field sample because of potential 

contamination as a result of sample handling or analytical 

procedures. The threshold value for benzophenone was 

0.12 μg/L, and environmental sample concentrations less 

than or equal to 0.12 μg/L were rejected and not reported 

(app. 1). Likewise for DEET and tetrachloroethene, with 

threshold values of 0.03 μg/L and 0.09 μg/L, respectively, 

environmental sample concentrations of DEET less than or 

equal to 0.03 μg/L and environmental sample concentrations 

of tetrachloroethene less than or equal to 0.09 μg/L were 

rejected and not reported (app. 1). 

Split replicate samples were collected along with paired 

environmental samples from the Medina site (map identifier 

EC05, fig. 1, table 2, app. 1, app. 4 ) on November 1, 2011, 

and from the SAR Mitchell site (map identifier EC09, fig. 1, 

table 2, app. 1, app. 4) on April 25, 2012. The split replicate 

sample results were compared to the environmental sample 

results by calculating the relative percent difference (RPD) for 

each detected concentration pair by using the equation

RPD = |C1 – C2|/((C1 + C2)/2) x 100, (1)

where

C1 is the detected concentration in the 

environmental sample, and

C2 is the detected concentration in the split 

replicate sample.

RPDs were calculated for only those compound pairs 

with detectable concentrations greater than or equal to the 

LRL in both the environmental and the split replicate sample 

(app. 4). RPDs were not computed for sample pair compound 

concentrations that had one or more nondetected or estimated 

values. RPDs calculated for 11 paired concentrations from 

the sample collected at the Medina site on November 1, 2011, 

ranged from 0.00 to 35.05 percent (app. 4). RPDs of less than 

or equal to 15 percent were used to indicate good agreement 

between the environmental and split replicate sample results 

when concentrations were sufficiently large compared to the 

LRL. Only 4 of the 11 paired concentrations from the Medina 

site exceeded the 15 percent threshold, and most of the values 

exceeding the 15 percent threshold were associated with 

concentrations that were low and close to the LRL. RPDs 

were calculated for 19 paired concentrations from the samples 

collected on April 25, 2012, at the SAR Mitchell site. RPDs 

for these samples ranged from 0.00 to 66.67 percent (app. 4). 

Four of the 19 paired concentrations exceeded the 15 percent 

threshold, and many of these paired concentrations were close 

to the LRL.
Detections and Concentrations of Compounds of Emerging Concern 17

Detections and Concentrations of 

Compounds of Emerging Concern

Detections and Concentrations of Individual 

Compounds

Of the 60 wastewater compounds analyzed by the 

NWQL, 2 compounds (4-nonylphenol and isophorone) 

were rejected and not reported or discussed because of 

contamination of the equipment blank and field blank qualitycontrol samples. Four compounds (beta-sitosterol, betastigmastanol, 3-beta-coprostanol, and cholesterol) included 

in USGS wastewater compound analysis used in this study 

were reclassified as sterols and discussed in association 

with sterols, and cotinine was reclassified and discussed as 

a pharmaceutical (table 3). The compound bisphenol A, a 

plasticizer analyzed in the hormone analysis, was reclassified 

and included in the discussion on wastewater compounds; a 

total of 54 compounds were therefore classified as wastewater 

compounds for the purposes of this report (app. 1). Of these 

54 compounds, 32 were detected in at least 1 sample, and 22 

were not detected in any samples collected during this study 

(fig. 2, table 4). Of the detected compounds, 18 were measured 

at concentrations greater than or equal to the LRL, and 14 

compounds only were detected at concentrations less than the 

LRL. There were 302 detections in the 33 samples analyzed 

for wastewater compounds in the study (app. 1). 

Two of six detergent metabolites, 4-n-octylphenol and 

4-nonylphenol diethoxylate, both known endocrine-disrupting 

compounds (Reif and others, 2012), each were detected in 

at least one sample, yielding a total of nine detections for 

detergent metabolites (fig. 2, table 4). The most commonly 

detected detergent metabolite, 4-nonylphenol diethoxylate, 

was detected in 8 of 33 samples at concentrations ranging 

from an estimated 0.4 μg/L to an estimated 0.8 μg/L. The 

other detergent metabolite, 4-n-octylphenol, was detected 

in one sample on the basis of its mass spectra; however, the 

concentration could not be quantified and it was coded with an 

“M” (app. 1).

There were 88 detections of personal-use compounds, 

and 9 of the 13 personal-use compounds were detected in at 

least one sample (fig. 2, table 4). The most commonly detected 

personal-use compound, DEET (the active ingredient in 

many insect repellents), was detected in 23 of 33 samples at 

concentrations ranging from 0.04 μg/L to 0.34 μg/L. 

There were 19 detections of pesticides, and 3 of 9 

pesticides were detected in at least one sample (fig. 2, table 4). 

The most commonly detected pesticide, 1,4-dichlorobenzene, 

was detected in 8 of 33 samples at concentrations ranging 

from an estimated 0.014 μg/L to 0.065 μg/L. 

There were 62 detections of industrial compounds, and 6 

of 10 individual industrial compounds were detected in at least 

one sample (fig. 2). The most frequently detected industrial 

compound, 5-methyl-1H-benzotriazole (a common component 

of antifreeze), was detected in 19 of the 33 samples at 

concentrations ranging from an estimated 0.1 μg/L to 1.4 μg/L 

(table 4).

There were 13 detections of two different disinfection 

compounds, both of which were detected in at least one 

sample (fig. 2, table 4). Tribromomethane, a disinfection 

byproduct of water treatment (U.S. Environmental Protection 

Agency, 2004, 2007), was detected in 8 of 33 samples at 

concentrations ranging from an estimated 0.01 μg/L to 

0.67 μg/L (table 4). Phenol, a widely used disinfectant, was 

detected in 5 of 33 samples at concentrations ranging from 

0.12 μg/L to 0.25 μg/L. 

There were 11 detections of PAHs, and 5 of 9 PAHs were 

detected in at least one sample (fig. 2, table 4). Phenanthrene 

and fluoranthene, both components of tar and petroleum 

products, were detected more frequently than the other 

PAHs. These compounds were detected in 4 of 33 samples 

at concentrations ranging from an estimated 0.003 μg/L to 

an estimated 0.008 μg/L for phenanthrene and an estimated 

0.003 μg/L to 0.012 μg/L for fluoranthene. 

There were 100 detections of flame retardants and 

plasticizers, and 5 of 6 compounds in this subclass were 

detected in at least one sample (fig. 2, table 4). Bisphenol A 

was the only compound in this subclass that was not detected 

in any of the samples. Detected in 28 of the 33 samples, 

tris (2-chloroethyl) phosphate and tris (dichloroisopropyl) 

phosphate were the most commonly detected compounds in 

the study and had concentrations ranging from an estimated 

0.02 μg/L to 0.52 μg/L and an estimated 0.02 μg/L to 

0.82 μg/L, respectively. Tris (2-chloroethyl) phosphate and 

tris (dichloroisopropyl) phosphate are suspected endocrine 

disruptors (Reif and others, 2012). 

Of the wastewater compounds that were detected, 

the lowest measured concentrations were an estimated 

0.003 μg/L for 3-methyl-1H-indole, fluoranthene, and 

phenanthrene, all of which were less than their respective 

LRLs (table 4). The highest concentration of a wastewater 

compound was measured in the personal-use compound 

hexahydrohexamethyl-cyclopentabenzopyran (HHCB), with 

a concentration measured at 1.90 μg/L. The second highest 

concentration of a wastewater compound in the study was 1.4 

μg/L of the industrial compound 5-methyl-1H-benzotriazole, 

a common component of antifreeze. All of the remaining 

wastewater compounds were measured at concentrations less 

than 1.0 μg/L.
Figure 2. The number of detections of wastewater compounds in 33 water-quality samples collected from the San Antonio River Basin, 2011–12. Lab

(LRLs) for each compound are listed in table 4. 051015202530

Number of detections

Wastewater compound

4-n-Octylphenol 4-Nonylphenol diethoxylate Camphor 3-Methyl-1H-indole Acetophenone Acetyl hexamethyl tetrahydro naphthalene (AHTN) Caffeine N, N-diethyl-meta-toluamide (DEET) Hexahydrohexamethyl-cyclopentabenzopyran (HHCB) Indole Triclosan 1, 4-Dichlorobenzene Bromacil Prometon p-Cresol 5-Methyl-1H-benzotriazole 9, 10-Anthraquinone Benzophenone Methyl salicylate Triethyl citrate Phenol Tribromomethane 1-Methylnaphthalene Fluoranthene Naphthalene Phenanthrene Pyrene Tributyl phosphate Triphenyl phosphate Tris (2-butoxyethyl) phosphate Tris (2-chloroethyl) phosphate Tris (2-dichloroisopropyl) phosphate

Detergent metabolites

(9) 

Pesticides

(19) 

Personal-use compounds 

(88)

Industrial compounds

(62) 

Disinfection compounds

(13) 

Polycyclic aromatic hydrocarbons

(11) 

Flame retardants and plasticizers

(100) 
Detections and Concentrations of Compounds of Emerging Concern 19

Table 4. Laboratory reporting levels, total number of detections, and concentration ranges for wastewater compounds in 33 waterquality samples collected from the San Antonio River Basin, Texas, 2011–12. 

[Wastewater compounds and water-quality data listed in appendix 1. LRL, laboratory reporting level; μg/L, micrograms per liter; M, presence verified but not 

quantified; E, estimated]

Compound LRL

(μg/L)

Total number of 

detections

Range in 

detected compounds

(μg/L)

Detergent metabolites

4-n-Octylphenol1 0.06 1 M

4-Nonylphenol diethoxylate1 5.0 8 E0.4–E0.8

Personal-use products

Camphor 0.044 7 E0.011–0.040

3-Methyl-1H-indole 0.036 8 E0.003–0.540

Acetophenone 0.4 1 0.4

Acetyl hexamethyl tetrahydro naphthalene (AHTN) 0.028 7 E0.007–0.130

Caffeine 0.06 22 E0.02–0.46

N, N-diethyl-meta-toluamide (DEET) 0.06 23 0.04–0.34

Hexahydrohexamethyl-cyclopentabenzopyran (HHCB) 0.052 16 E0.006–1.90

Indole 0.08 2 E0.01–0.09

Triclosan2 0.20 2 E0.02–E0.09

Pesticides

1,4-Dichlorobenzene2 0.040 8 E0.014–0.065

Bromacil 0.36 7 E0.06–0.74

Prometon 0.12 4 E0.02–0.10

Industrial compounds

p-Cresol2 0.08 7 E0.02–0.89

5-Methyl-1H-benzotriazole 1.2 19 E0.1–1.4

9,10-Anthraquinone 0.16 7 E0.02–E0.04

Benzophenone2 0.08 10 0.13–0.26

Methyl salicylate 0.044 6 E0.007–E0.015

Triethyl citrate 0.16 13 E0.02–0.23

Disinfection compounds

Phenol 0.16 5 0.12–0.25

Tribromomethane (Bromoform)3 0.10 8 E0.01–0.67

Polycyclic aromatic hydrocarbons

1-Methylnaphthalene 0.022 1 E0.009

Fluoranthene 0.024 4 E0.003–0.012

Naphthalene 0.040 1 E0.017

Phenanthrene 0.016 4 E0.003–E0.008

Pyrene 0.042 1 E0.006

Flame retardants and plasticizers

Tributyl phosphate 0.16 23 E0.01–0.62

Triphenyl phosphate 0.12 7 E0.01–E0.04

Tris(2-butoxyethyl) phosphate 0.8 14 E0.1–0.7

Tris(2-chloroethyl) phosphate2 0.10 28 E0.02–0.52

Tris(dichloroisopropyl) phosphate2 0.16 28 E0.02–0.82

1

Known endocrine disrupter (Reif and others, 2012).

2

Suspected endocrine disrupter (Reif and others, 2012).

3

Potential human carcinogen (U.S. Environmental Protection Agency, 2007).
20 Detections, Concentrations, and Distributional Patterns of Compounds of Emerging Concern in the San Antonio River Basin

Fourteen nonprescription and prescription 

pharmaceuticals were included in the USGS pharmaceutical 

analysis used in this study. One of the compounds, 

caffeine, was reclassified for this report as a wastewater 

compound (personal-use compound); the remaining 13 

pharmaceuticals were considered pharmaceuticals for the 

purposes of this report (table 3). Of the 13 pharmaceuticals, 

Table 5. Laboratory reporting levels, total number of detections, 

and concentration ranges for pharmaceuticals in 34 water-quality 

samples collected from the San Antonio River Basin, Texas, 

2011–12. 

[Pharmaceuticals and water-quality data listed in appendix 2. LRL, laboratory 

reporting level; μg/L, micrograms per liter; E, estimated]

Compound LRL 

(μg/L)

Total 

number of 

detections

Range in 

detected 

compounds

(μg/L)

Nonprescription

Diphenhydramine 0.058 6 E0.005–E0.015

Prescription

Carbamazepine 0.060 24 E0.005–E0.121

Dehydronifedipine 0.080 13 E0.003–E0.013

Sulfamethoxazole 0.091 15 E0.014–0.267

Figure 3. The number of detections of pharmaceuticals in 34 water-quality samples collected from the San Antonio River Basin, 

2011–12. Laboratory reporting levels (LRLs) for each compound are listed in table 5.

only 4 compounds, 1 nonprescription pharmaceutical 

(diphenhydramine) and 3 prescription pharmaceuticals 

(carbamazepine, dehydronifedipine, and sulfamethoxazole), 

were detected in at least one sample collected from the San 

Antonio River Basin (fig. 3, table 5). There were a total of 58 

detections of pharmaceuticals in the 34 samples analyzed for 

pharmaceuticals in the study. 

0

5

10

15

20

25

30

Number of detections

Diphenhydramine

Carbamazepine

Dehydronifedipine

Sulfamethoxazole

Pharmaceutical compound

Nonprescription

(6) 

Prescription

(52) Detection greater than or

 equal to the laboratory

 reporting level

Detection less than the 

 laboratory reporting 

 level

Number of detections per

 subclass of compound

EXPLANATION

(52)
Detections and Concentrations of Compounds of Emerging Concern 21

Diphenhydramine, primarily used as an antihistamine 

(O’Neil, 2001) and the only detected nonprescription 

pharmaceutical, was detected in 6 of 34 samples at 

concentrations ranging from an estimated 0.005 μg/L to 

an estimated 0.015 μg/L (fig. 3, table 5). Carbamazepine, 

an anticonvulsant and antimanic (mood stabilizing) 

compound (O’Neil, 2001) and the most frequently 

detected prescription pharmaceutical, was detected in 24 

of 34 samples at concentrations ranging from an estimated 

0.005 μg/L to an estimated 0.121 μg/L. Sulfamethoxazole, 

a prescription antibiotic (O’Neil, 2001), was detected 

in 15 of 34 samples at concentrations ranging from an 

estimated 0.014 μg/L to 0.267 μg/L. Dehydronifedipine, an 

antianginal pharmaceutical (O’Neil, 2001), was detected 

in 13 of 34 samples at concentrations ranging from an 

estimated 0.003 μg/L to an estimated 0.013 μg/L. Both 

carbamazepine and sulfamethoxazole were detected at 

concentrations greater than or equal to the LRL in some 

samples, whereas diphenhydramine and dehydronifedipine 

only were detected at concentrations less than the LRL. The 

lowest reported concentration of a pharmaceutical was an 

estimated 0.003 μg/L for dehydronifedipine, and the highest 

concentration was 0.267 μg/L for sulfamethoxazole.

There were 20 measured compounds in the USGS analysis 

of steroidal hormones and sterols used for this study. Bisphenol 

A was analyzed as part of the steroidal hormones and sterols 

method but was classified in this report with the wastewater 

compounds because it is also a plasticizer and an endocrine 

disrupter (U.S. Environmental Protection Agency, 2013b). Two 

plant sterols (beta-sitosterol and beta-stigmastanol) analyzed 

as part of the wastewater compounds method were reclassified 

as sterols, resulting in a total of 17 steroidal hormones and 4 

sterols being analyzed for this report (table 3, app 3). Of the 

17 steroidal hormones, 4 were detected in at least one sample 

from the San Antonio River Basin (fig. 4, table 6). Of the 4 

detected steroidal hormones, 2 were measured at concentrations 

greater than or equal to the LRL, and 2 only were detected at 

concentrations less than the LRL. Of the 4 sterols, all 4 were 

detected in at least one sample from the San Antonio River 

Basin. Both animal sterols were measured at concentrations 

greater than or equal to the LRL, and both plant sterols only 

were detected at concentrations less than the LRL. There were 

a total of 16 detections of steroidal hormones and 41 detections 

of sterols in the 34 samples analyzed for steroidal hormones in 

the study. Steroidal hormones had lower LRLs than wastewater 

compounds, pharmaceuticals, and sterols. A lower LRL 

indicates greater analytical sensitivity and the ability to detect 

compounds at lower concentrations. 

0

2

4

6

8

10

12

14

16

18

20

Number of detections

4-Androstene-3,17-dione

17-alpha-Estradiol

17-beta-Estradiol

Estrone

3-beta-Coprostanol

Cholesterol

beta-Sitosterol

beta-Stigmastanol

Steroidal hormone and sterol compounds

Steroidal hormones - natural androgens

(2)

Steroidal hormones - natural estrogens

(14) 

Sterols - animal

(21)

Sterols - plant

(20)

Detection greater than or

 equal to the laboratory

 reporting level

Detection less than the 

 laboratory reporting 

 level

Number of detections per

 subclass of compound

EXPLANATION

(21)

Figure 4. The number of detections of steroidal hormones and sterols in 34 water-quality samples collected from the San Antonio River 

Basin, 2011–12. Laboratory reporting levels (LRLs) for each compound are listed in table 6.
22 Detections, Concentrations, and Distributional Patterns of Compounds of Emerging Concern in the San Antonio River Basin

Concentrations of steroidal hormones were much lower 

in comparison to sterols (table 6). The steroidal hormone 

4-androstene-3,17-dione occurs naturally and as a synthetic 

steroid and was measured at concentrations ranging from 

an estimated 0.21 nanograms per liter (ng/L) to 2.58 ng/L 

(table 6). The concentration of 17-alpha-estradiol was an 

estimated 0.31 ng/L, and the concentration of 17-beta-estradiol 

ranged from an estimated 0.09 ng/L to 0.43 ng/L. Estrone, 

a metabolite of 17-beta-estradiol, was the most commonly 

detected compound related to estrogen and was detected in 

9 of 34 samples at concentrations ranging from 0.68 ng/L to 

4.50 ng/L. The animal sterol, 3-beta-coprostanol, was detected 

in 2 of 34 samples, and concentrations ranged from 252 ng/L 

to 422 ng/L. Cholesterol was detected in 19 of 34 samples 

at concentrations ranging from 200 ng/L to 1,740 ng/L (fig. 

4, table 6). The two natural plant sterols, beta-sitosterol 

and beta-stigmastanol, were detected in 11 and 9 of the 34 

samples, respectively. The concentrations of beta-sitosterol 

ranged from “M” (presence verified but not quantified) to an 

estimated 1 μg/L, and the concentrations of beta-stigmastanol 

ranged from an estimated 0.1 μg/L to an estimated 0.8 μg/L.

Detections and Concentrations for Each 

Synoptic Sampling Event

The number of detections for all compound classes 

from the first synoptic sampling event (March–May 2011) is 

shown in figure 5. The number of detections of wastewater 

compounds ranged from 2 in samples collected at multiple 

sites to 13 in the sample collected at the Medina site (figs. 1, 

5A). Of the 91 detections of wastewater compounds in the 

first synoptic sampling event, approximately 47 percent 

were greater than or equal to the LRL. The number of 

detections for pharmaceuticals ranged from 0 at multiple 

sites to 3 at multiple sites (fig. 5B). Of the 22 detections of 

pharmaceuticals, concentrations greater than or equal to 

the LRL were measured in approximately 36 percent of the 

samples. The number of detections of steroidal hormones 

ranged from 0 at multiple sites to 2 at multiple sites (fig. 5C). 

Of the 11 detections of steroidal hormones, approximately 

55 percent were greater than or equal to the LRL. The 

number of detections of sterols ranged from 0 at the Macdona 

site (map identifier EC02, fig. 1, table 2) to 4 at the SAR 

Elmendorf site (map identifier EC13, fig. 1, table 2) (fig. 5D). 

Of the 28 detections of sterols, approximately 43 percent were 

greater than or equal to the LRL. 

Total concentrations for the different compound classes 

from the first synoptic sampling event are shown in figure 6. 

Total concentrations of wastewater compounds ranged 

from 0.22 μg/L at the Cibolo Falls City site (map identifier 

EC18, fig. 1, table 2) to 5.86 μg/L at the SAR Elmendorf site 

(fig. 6A). Total concentrations of pharmaceuticals ranged 

from not measureable at multiple sites to 0.37 μg/L at the 

Medio site (map identifier EC03, fig. 1, table 2) (fig. 6B). 

Total concentrations of steroidal hormones ranged from not 

measureable at multiple sites to 0.00493 μg/L at the SAR 

Elmendorf site (fig. 6C). Total concentrations of sterols 

ranged from not measureable at the Macdona site to 1.74 μg/L 

at the SAR Goliad site (map identifier EC20, fig. 1, table 2) 

(fig. 6D). The high concentration of sterols at the SAR 

Goliad site was related to detection only of the animal sterol 

cholesterol. The plant sterol beta-sitosterol was detected in 

this sample, but it was not measurable. When measurement 

data for wastewater, pharmaceutical, steroidal hormone, 

and sterol compounds were grouped together, the Macdona 

site had both the lowest number of total detections (2) and 

the lowest total concentrations (0.62 μg/L), and the SAR 

Elmendorf site had the highest number of detections (21) and 

highest total concentrations (7.75 μg/L).

Table 6. Laboratory reporting levels, total number of detections, 

and concentration ranges for steroidal hormones and sterols in 34 

water-quality samples collected from the San Antonio River Basin, 

Texas, 2011–12. 

[Steroidal hormones, sterols, and water-quality data listed in appendix 3. LRL, 

laboratory reporting level; ng/L, nanograms per liter; μg/L, micrograms per 

liter; M, presence verified but not quantified; E, estimated]

Compound LRL

(ng/L)

Total 

number 

of detections

Range in 

detected 

compounds

(ng/L)

Steroidal hormones - natural androgens

4-Androstene-3,17-dione 0.80 2 E0.21–2.58

Steroidal hormones - natural estrogens

17-alpha-Estradiol 0.80 1 E0.31

17-beta-Estradiol 0.80 4 E0.09–0.43

Estrone 0.80 9 0.68–4.50

Sterols - animal

3-beta-Coprostanol 200 2 252–422

Cholesterol 200 19 200–1,740

Compound LRL

(μg/L)

Total 

number 

of detections

Range in 

detected 

compounds

(μg/L)

Sterols - plant

beta-Sitosterol 4 11 M–E1

beta-Stigmastanol 2.6 9 E0.1–E0.8
Detections and Concentrations of Compounds of Emerging Concern 23

Figure 5. The number of detections in water-quality samples collected from the San Antonio River Basin during synoptic sampling 

event 1, March–May 2011, of A, wastewater compounds, B, pharmaceuticals, C, steroidal hormones, and D, sterols.

0

2

4

6

8

10

12

14

16

18

0

1

2

3

4

5

6

0

1

2

3

4

5

6

0

2

4

6

8

10

12

14

16

18

Number of detections

Macdona

Medio

Leon 35

Medina

SAR 410

Salado 13

SAR Elmendorf

SAR Falls City

Martinez St. Hedwig

Cibolo St. Hedwig

Cibolo Falls City

SAR Goliad

Sampling site short name (table 2)

A. Wastewater compounds

B. Pharmaceuticals

C. Steroidal hormones

D. Sterols

Detection greater than or

 equal to the laboratory

 reporting level 

Detection less than the

 laboratory reporting 

 level 

EXPLANATION
24 Detections, Concentrations, and Distributional Patterns of Compounds of Emerging Concern in the San Antonio River Basin

Figure 6. The concentrations in water-quality samples collected from the San Antonio River Basin during synoptic sampling event 1, 

March–May 2011, of A, wastewater compounds, B, pharmaceuticals, C, steroidal hormones, and D, sterols.

1

0

2

3

4

5

6

Concentration, in micrograms per liter

0

0.1

0.2

0.3

0.4

0

0.001

0.002

0.003

0.004

0.005

0

0.5

1.0

1.5

2.0

Macdona

Medio

Leon 35

Medina

SAR 410

Salado 13

SAR Elmendorf

SAR Falls City

Martinez St. Hedwig

Cibolo St. Hedwig

Cibolo Falls City

SAR Goliad

Sampling site short name (table 2)

A. Wastewater compounds

B. Pharmaceuticals

C. Steroidal hormones

D. Sterols

NM NM

NM

NM

NM NM NM NM

Concentration greater

 than or equal to the

 laboratory reporting

 level 

Estimated concentration

 less than the

 laboratory reporting 

 level

Not measureable or not

 detected

EXPLANATION

NM
Detections and Concentrations of Compounds of Emerging Concern 25

The number of detections for all compound classes for 

the second synoptic sampling event (October–November 

2011) is shown in figure 7. The number of detections of 

wastewater compounds ranged from 0 in samples collected 

at the Macdona site to 17 in the sample collected at the 

SAR Elmendorf site (figs. 1, 7A). Of the 121 detections of 

wastewater compounds in the second synoptic sampling event, 

approximately 31 percent were greater than or equal to the 

LRL. The number of detections of pharmaceuticals ranged 

from 0 at multiple sites to 4 in the sample collected at the 

Medio site (fig. 7B). Of the 23 detections of pharmaceuticals, 

concentrations greater than or equal to the LRL were measured 

in approximately 22 percent of the samples. The number 

of detections of steroidal hormones was 0 at all sites with 

the exception of the SAR Elmendorf site, where there was 

1 detection of a steroidal hormone (estrone) at a concentration 

greater than or equal to the LRL (fig. 7C). The number of 

detections of sterols ranged from 0 at multiple sites to 2 

at multiple sites (fig. 7D). Of the 8 detections of sterols, 

75 percent were for concentrations greater than or equal to the 

LRL. 

The total concentrations for the different compound 

classes from the second synoptic sampling event are shown 

in figure 8. Total concentrations of wastewater compounds 

ranged from not measureable at the Macdona site to 3.29 μg/L 

at the SAR Elmendorf site (figs. 1, 8A). Total concentrations of 

pharmaceuticals ranged from not measureable at multiple sites 

to 0.25 μg/L at the Martinez St. Hedwig site (map identifier 

EC16, fig. 1, table 2) (fig. 8B). Total concentrations of 

steroidal hormones were not measureable at all sites with the 

exception of the SAR Elmendorf site (fig. 8C), which had a 

concentration of 0.00215 μg/L. Total concentrations of sterols 

ranged from not measureable at multiple sites to 0.59 μg/L 

at the SAR Elmendorf site (fig. 8D). When measurement 

data for wastewater compounds, pharmaceuticals, steroidal 

hormones, and sterols were grouped together, the Macdona 

site had the lowest number of detections (zero), and total 

concentrations were not measureable. The SAR Elmendorf site 

had the highest number of detections (23) and the highest total 

concentrations (3.97 μg/L).

The third synoptic sampling event (April–May 2012) 

included collection of samples at seven sites that were 

added to the study after the first 2 synoptic sampling events 

were completed to better characterize CECs in certain 

areas in the San Antonio River Basin (fig. 9). During the 

third synoptic sampling event, the number of detections 

of wastewater compounds ranged from 2 at the North 

Prong site to 18 at the SAR Mitchell site (figs. 1, 9A). Of 

the 84 detections of wastewater compounds during this 

sampling event, approximately 32 percent were detected at 

concentrations greater than or equal to the LRL. The number 

of pharmaceutical detections ranged from 0 at multiple 

sites to 4 at multiple sites (fig. 9B). Of the 13 detections of 

pharmaceuticals, approximately 31 percent were detected at 

concentrations greater than or equal to the LRL. The number 

of detections of steroidal hormones ranged from 0 at multiple 

sites to 2 at the Salitrillo site (map identifier EC15, fig. 1, 

table 2) (fig. 9C). Of the 3 detections of steroidal hormones, 

approximately 33 percent were greater than or equal to the 

LRL. The number of detections of sterols was zero at all sites 

with the exception of the Alazan site (map identifier EC08, 

fig. 1, table 2) which had 1 detection greater than or equal to 

the LRL (fig. 9D).
26 Detections, Concentrations, and Distributional Patterns of Compounds of Emerging Concern in the San Antonio River Basin

Figure 7. The number of detections in water-quality samples collected from the San Antonio River Basin during synoptic sampling 

event 2, October–November 2011, of A, wastewater compounds, B, pharmaceuticals, C, steroidal hormones, and D, sterols. Number of detections

0

2

4

6

8

10

12

14

16

18

0

1

2

3

4

5

6

0

1

2

3

4

5

6

0

2

4

6

8

10

12

14

16

18

Macdona

Medio

Leon 35

Medina

SAR 410

Salado 13

SAR Elmendorf

SAR Falls City

Martinez St. Hedwig

Cibolo St. Hedwig

Cibolo Falls City

SAR Goliad

Sampling site short name (table 2)

A. Wastewater compounds

B. Pharmaceuticals

C. Steroidal hormones

D. Sterols

Detection greater than or

 equal to the laboratory

 reporting level 

Detection less than the 

 laboratory reporting 

 level 

EXPLANATION
Detections and Concentrations of Compounds of Emerging Concern 27

Figure 8. The concentrations in water-quality samples collected from the San Antonio River Basin during synoptic sampling event 2, 

October–November 2011, of A, wastewater compounds, B, pharmaceuticals, C, steroidal hormones, and D, sterols. Concentration, in micrograms per liter

0

0.5

1.0

1.5

2.0

0

0.001

0.002

0.003

0.004

0.005

0

1

2

3

4

5

6

0

0.1

0.2

0.3

0.4

Macdona

Medio

Leon 35

Medina

SAR 410

Salado 13

SAR Elmendorf

SAR Falls City

Martinez St. Hedwig

Cibolo St. Hedwig

Cibolo Falls City

SAR Goliad

Sampling site short name (table 2)

A. Wastewater compounds

B. Pharmaceuticals

C. Steroidal hormones

D. Sterols

NM

NM

NM

NM

NM

NM

NM

NM

NM

NM

NM

NM

NM

NM NM

NM

NM NM NM NM

NM

Concentration greater

 than or equal to the

 laboratory reporting

 level 

Estimated concentration

 less than the

 laboratory reporting 

 level

Not measureable or not

 detected

EXPLANATION

NM
28 Detections, Concentrations, and Distributional Patterns of Compounds of Emerging Concern in the San Antonio River Basin

Figure 9. The number of detections in water-quality samples collected from the San Antonio River Basin during synoptic sampling 

event 3, April–May 2012, of A, wastewater compounds, B, pharmaceuticals, C, steroidal hormones, and D, sterols. Number of detections 0

0

2

4

6

8

10

12

14

16

18

0

2

4

6

8

10

12

14

16

18

1

2

3

4

5

6

0

1

2

3

4

5

6

Sampling site short name (table 2)

North Prong

Dos Rios

SAR Witte

Alazan

SAR Mitchell

San Pedro

Salitrillo

A. Wastewater compounds

B. Pharmaceuticals

C. Steroidal hormones

D. Sterols

Detection greater than or

 equal to the laboratory

 reporting level 

Detection less than the 

 laboratory reporting 

 level 

EXPLANATION
Detections and Concentrations of Compounds of Emerging Concern 29

The total concentrations for the different compound 

classes from the third synoptic sampling event are shown 

in figure 10. Total concentrations of wastewater compounds 

measured during the third synoptic sampling ranged from 

0.14 μg/L at the North Prong site to 4.15 μg/L at the Dos Rios 

site (fig. 1, 10A). Total concentrations of pharmaceuticals 

ranged from no detections at multiple sites to 0.24 μg/L 

at the Salitrillo site (fig. 10B). Total concentrations of 

steroidal hormones ranged from not measureable at multiple 

sites to 0.00491 μg/L at the Salitrillo site (fig. 10C). Total 

concentrations of sterols were not measureable at all sites 

with the exception of the Alazan site (fig. 10D), which had a 

concentration of 0.33 μg/L. When wastewater compounds, 

pharmaceuticals, steroidal hormones, and sterols were grouped 

together, the North Prong site had both the lowest number 

of total detections (two) and lowest total concentrations 

(0.14 μg/L). The highest number of detections (21) occurred 

at the SAR Mitchell site, and the highest total concentration 

(4.37 μg/L) occurred at the Dos Rios site.

A total of 4 samples were collected at the Ecleto 

site (fig. 1), and 2 of these samples were analyzed for 

wastewater compounds (figs. 11A and 12A). At the Ecleto 

site, 2 wastewater compounds were detected in the first 

sample collected, and 4 compounds were detected in the 

second sample collected. Although there were detections of 

wastewater compounds in both samples, concentrations were 

relatively low in samples from the Ecleto site in comparison to 

most other sites (figs. 6A, 8A, and 10A). Three of four samples 

collected at the Ecleto site were analyzed for pharmaceuticals, 

steroidal hormones, and sterols. There were no detections of 

pharmaceuticals in any of the samples collected at the Ecleto 

site. The steroidal hormone estrone, a metabolite of the human 

hormone 17-beta-estradiol, and three sterols were detected in 

the first sample collected at the Ecleto site on January 26, 2012 

(figs. 11B and 11C). The concentration of 17-beta-estradiol in 

this sample was 0.68 ng/L (0.00068 μg/L), which is less than 

the LRL (fig. 12B). There were no steroidal hormones and 

one sterol detected in the second sample and no detections 

of steroidal hormones or sterols in the third sample from the 

Ecleto site. Concentrations of sterols generally were higher 

in samples collected at the Ecleto site (fig. 12C) compared 

to concentrations for these compounds at most other sites 

(figs. 6C, 8C, and 10C). The high concentrations of steroidal 

hormones and sterols at the Ecleto site primarily were a result 

of the presence of natural sterols (cholesterol, beta-sitosterol, 

and beta-stigmastanol).
30 Detections, Concentrations, and Distributional Patterns of Compounds of Emerging Concern in the San Antonio River Basin

Figure 10. The concentrations in water-quality samples collected from the San Antonio River Basin during synoptic sampling event 3, 

April–May 2012, of A, wastewater compounds, B, pharmaceuticals, C, steroidal hormones, and D, sterols.

0

1

2

3

4

5

6

0

0.1

0.2

0.3

0.4

0

0.001

0.002

0.003

0.004

0.005

0

0.5

1.0

1.5

2.0

Concentration, in micrograms per liter

Sampling site short name (table 2)

North Prong

Dos Rios

SAR Witte

Alazan

SAR Mitchell

San Pedro

Salitrillo

A. Wastewater compounds

B. Pharmaceuticals

C. Steroidal hormones

D. Sterols

NM

NM

NM

NM

NM

NM

NM

NM

NM

NM

NM

NM NM

Concentration greater

 than or equal to the

 laboratory reporting

 level 

Estimated concentration

 less than the

 laboratory reporting 

 level

Not measureable or not

 detected

EXPLANATION

NM
Detections and Concentrations of Compounds of Emerging Concern 31

Figure 11. The number of detections in water-quality samples collected from Ecleto Creek at the Ecleto site (table 2) in the San Antonio 

River Basin, January–July 2012, of A, wastewater compounds, B, steroidal hormones, and C, sterols. Number of detections

0

2

4

6

8

10

12

14

16

18

0

1

2

3

4

5

6

0

1

2

3

4

5

6

Date

January 26, 2012 February 22, 2012 March 20, 2012 July 17, 2012

NA NA

NA

NA

A. Wastewater compounds

B. Steroidal hormones

C. Sterols

NA

Detection greater

 than or equal to the

 laboratory reporting

 level 

Detection less than the

 laboratory reporting 

 level

Not analyzed

EXPLANATION
32 Detections, Concentrations, and Distributional Patterns of Compounds of Emerging Concern in the San Antonio River Basin

Figure 12. The concentrations in water-quality samples collected at the Ecleto site (table 2) on Ecleto Creek in the San Antonio River 

Basin, January–July 2012, of A, wastewater compounds, B, steroidal hormones, and C, sterols.

0

1

2

3

4

5

6

0

0.0002

0.0004

0.0006

0.0008

0.0010

0

0.5

1.0

1.5

2.0

2.5

3.0

Concentration, in micrograms per liter

Date

January 26, 2012 February 22, 2012 March 20, 2012 July 17, 2012

NA

NA

NA NA

NM NM

NM

A. Wastewater compounds

B. Steroidal hormones

C. Sterols

Concentration greater

 than or equal to the

 laboratory reporting

 level 

Estimated concentration

 less than the

 laboratory reporting 

 level

Not analyzed

Not measureable or not

 detected

EXPLANATION

NA

NM
Distributional Patterns of Compounds of Emerging Concern 33

Distributional Patterns of Compounds 

of Emerging Concern

Distributional Patterns of Wastewater 

Compounds

Wastewater compounds were classified as detergent 

metabolites, personal-use compounds, pesticides, industrial 

compounds, disinfection compounds, polycyclic aromatic 

hydrocarbons, and flame retardants and plasticizers. To 

qualitatively evaluate the distribution of different subclasses 

of wastewater compounds, the relative proportions of each 

subclass were estimated by summing the concentrations 

of individual wastewater compounds in each subclass and 

comparing them to total concentrations of wastewater 

compounds measured in samples (app. 5). To estimate 

concentrations, all values that met the criteria for a detected 

analyte as explained in the Sample Analysis section were 

included. When there were no reported concentrations for 

any of the individual compounds, the total concentration was 

reported as “not measureable.” The distributional patterns of 

wastewater compound subclasses are qualitatively depicted 

by using pie charts scaled to represent differences in total 

concentrations of wastewater subclasses among the sampling 

sites (figs. 13, 14, and 15). 

During the first and second synoptic sampling events, 

concentrations of PAHs were low compared to some of the 

other subclasses (figs. 13 and 14). Disinfection compounds 

were detected only in samples collected at the Medina site 

during the first synoptic sampling event and in samples 

collected at four sites during the second synoptic sampling 

event (tribromomethane was detected at SAR Falls City, but 

the concentration was too low to be visible on the pie chart). 

Personal-use compounds and flame retardants and plasticizers 

frequently composed substantial proportions of total 

wastewater compound concentrations measured in samples 

collected from the San Antonio River Basin. Personal-use 

compounds and flame retardants and plasticizers were not 

detected in the samples collected at the Macdona site, a site 

which is not downstream from a WWTP discharge location. 

Personal-use compounds and flame retardants and plasticizers 

were present, however, in both samples collected at the Leon 

35 site, another site that is not downstream from WWTP 

discharge sites.

During the first synoptic sampling event, a higher 

proportion of pesticides was measured in samples collected 

at three sites, Leon 35, SAR 410 (map identifier EC11, 

fig. 1, table 2), and Salado 13 (map identifier EC12, fig. 1, 

table 2), compared to the proportion of pesticides measured 

in samples collected at all other sites in the basin (fig. 13). 

During the second synoptic sampling event, samples collected 

at two of the same sites, Leon 35 and Salado 13, again 

contained a higher proportion of pesticides in comparison 

to samples collected from all of the other sites in the basin 

(fig. 14). Bromacil, a herbicide commonly used to control 

weeds along roadsides (Washington State Department 

of Transportation, 2006; Reif and others, 2012), was the 

predominant compound contributing to the high proportions of 

pesticides in samples collected at the Leon 35, SAR 410, and 

Salado 13 sites. 

Downstream from San Antonio, there were similarities 

in the distributional patterns of wastewater compounds along 

the main stem of the San Antonio River (fig. 13). The SAR 

Elmendorf site receives the combined discharge from all of 

the WWTPs in the western part of the basin. During the first 

synoptic sampling event, the concentration of wastewater 

compounds at the SAR Elmendorf site was dominated by 

flame retardants and plasticizers, industrial compounds, 

personal-use compounds, and detergent metabolites. This 

pattern also was observed at the SAR Falls City site (map 

identifier EC14, fig. 1, table 2) and farther downstream at 

the SAR Goliad site although the total concentrations were 

lower at those two downstream sites. During the second 

synoptic sampling event, there was an absence of detergent 

metabolites in the sample collected at the SAR Elmendorf site, 

but disinfectant compounds were present (fig. 14). As with 

the first synoptic sampling event, concentrations were lower 

at the SAR Falls City and SAR Goliad sites, and no industrial 

compounds were measured in the sample collected at the SAR 

Goliad site.

In the Cibolo Creek Subbasin there were both 

similarities and differences in the distributional patterns and 

concentrations of wastewater compounds in comparison to 

sites along the main stem of the San Antonio River. Both 

the Cibolo St. Hedwig site (map identifier EC17, fig. 1, 

table 2) and the Martinez St. Hedwig site are downstream 

from WWTPs (fig. 1). During the first synoptic sampling 

event, the total concentrations of wastewater compounds in 

samples collected at those sites were not as high as those in 

the samples collected at sites along the main stem of the San 

Antonio River including the SAR Elmendorf, SAR Falls City, 

and SAR Goliad sites (fig. 13). During the second synoptic 

sampling event, concentrations at the Cibolo St. Hedwig and 

Martinez St. Hedwig sites were higher than during the first 

synoptic sampling event and closer in concentration to those 

in the samples collected during the second synoptic sampling 

event along the main stem of the San Antonio River including 

the SAR Elmendorf, SAR Falls City, and SAR Goliad sites. 

During both the first and second synoptic sampling events, 

concentrations at the Cibolo Falls City site were lower than 

water-quality samples collected upstream at the Cibolo St. 

Hedwig and Martinez St. Hedwig sites. 
Figure 13. Relative concentrations and proportions of individual subclasses of wastewater compounds in water-quality samples collected during sy

from the San Antonio River Basin, March–May 2011.

BLANCO

COUNTY

HAYS COUNTY

KERR COUNTY

KENDALL

COUNTY

CALDWELL COUNTY

REAL COUNTY

COMAL COUNTY

BANDERA COUNTY

GUADALUPE COUNTY

GONZALES COUNTY

BEXAR 

COUNTY MEDINA COUNTY

LAVACA COUNTY

UVALDE COUNTY

WILSON COUNTY

DEWITT COUNTY 

ATASCOSA COUNTY

KARNES

COUNTY

VICTORIA COUNTY

FRIO COUNTY

GOLIAD 

COUNTY

LIVE OAK

COUNTY

C

BEE COUNTY

MCMULLEN COUNTY

REFUGIO CO

ARANSAS CO

Martinez

Creek

San Antonio River

San Antonio

0 10 20 30 40 MILES0 2010 30 40 KILOMETERS

Medina River Subbasin

Lower San Antonio 

River Subbasin

Cibolo Creek

Subbasin

Upper San Antonio 

River Subbasin

WW03

EC17

E

Subcl Val con Size  Dete Pers Pest Indu Disin Poly FlamSan ASubbaWaste

ide

Water

ide

Canyon

Lake

MedinaLake

Calaveras Lake

Victor Braunig Lake

River

West Prong

Medina River

Alazan Creek

ApacheCreek

San Pedro

Creek

Medio

Creek

Salitrillo

Creek

North Prong

Medina River

Medina River

Guadalupe River

Medina River

San Antoni o River

Salado Creek

EcletoCreek

Cibolo Creek

Escondido Creek

Guadalupe River

Cibolo Creek

Mitchell 

Lake

Leon Creek

97°00'

98°00'

99°00'

30°00'

29°30'

29°00'

28°30'

0.62

2.53 1.39

1.98

5.86

2.46

2.30

0.22

1.36

0.81

1.61

2.34

EC01

EC02

EC03

EC04

EC05

EC06

EC07

EC08 EC09

EC10

EC11

EC12

EC13

EC14

EC15

EC16

EC17

EC18

EC19

EC20

WW01 WW02

WW03

WW04

WW05

WW06

WW07

WW08

WW09

WW10

WW11

WW13 WW12 WW14

WW15

WW16

WW17

Base map modified from U.S. Geological Survey 1:100,000-scale digital dataUniversal Transverse Mercator projection, zone 14North American Datum of 1983

EC01EC02EC03EC04EC05EC06EC07EC08EC09EC10EC11EC12EC13EC14EC15EC16EC17EC18EC19EC20

North ProngMacdonaMedioLeon 35MedinaDos RiosSAR WitteAlazanSAR MitchellSan PedroSAR 410Salado 13SAR ElmendorfSAR Falls CitySalitrilloMartinez St. HedwigCibolo St. HedwigCibolo Falls CityEcletoSAR Goliad

Map 

identifier

Short name

(table 2)

WW01WW02WW03WW04WW05WW06WW07WW08WW09WW10WW11WW12WW13WW14WW15WW16WW17

Boerne WWTPBoerne WWTP and WRCCibolo WWTPSalitrillo WWTPUpper Martinez WWTPMartinez II WWTPDos Rios WRCDos Rios TuletaDos Rios Flood TunnelDos Rios RittimanDos Rios Convention CenterDos Rios Blue WingLeon Creek WRCLeon Creek Mitchell LakeMedio Creek WRCFloresville WWTPKenedy WWTP

Map 

identifier

Short name

(table 1)
Figure 14. Relative concentrations and proportions of individual subclasses of wastewater compounds in water-quality samples collected during sy

from the San Antonio River Basin, October–November 2011.

BLANCO

COUNTY

HAYS COUNTY

KERR COUNTY

KENDALL

COUNTY

CALDWELL COUNTY

REAL COUNTY

COMAL COUNTY

BANDERA COUNTY

GUADALUPE COUNTY

GONZALES COUNTY

BEXAR 

COUNTY MEDINA COUNTY

LAVACA COUNTY

UVALDE COUNTY

WILSON COUNTY

DEWITT COUNTY 

ATASCOSA COUNTY

KARNES

COUNTY

VICTORIA COUNTY

FRIO COUNTY

GOLIAD 

COUNTY

LIVE OAK

COUNTY

CA

C

BEE COUNTY

MCMULLEN COUNTY

REFUGIO COU

ARANSAS COU

Martinez

Creek

San Antonio River

San Antonio

0 10 20 30 40 MILES0 2010 30 40 KILOMETERS

Medina River Subbasin

Lower San Antonio 

River Subbasin

Cibolo Creek

Subbasin

Upper San Antonio 

River Subbasin

WW03

EC17

E

Subclass  Value  in mic scale meas Deterg Person Pestici Industr Disinfe Polycy Flame San AntoSubbasiWastew

identi

Water-q

identi

Canyon

Lake

MedinaLake

Calaveras Lake

Victor Braunig Lake

River

West Prong

Medina River

Alazan Creek

ApacheCreek

San Pedro

Creek

Medio

Creek

Salitrillo

Creek

North Prong

Medina River

Medina River

Guadalupe River

Medina River

San Antoni o River

Salado Creek

EcletoCreek

Cibolo Creek

Escondido Creek

Guadalupe River

Cibolo Creek

Mitchell 

Lake

Leon Creek

97°00'

98°00'

99°00'

30°00'

29°30'

29°00'

28°30'

1.37

0.26

3.29

2.06

1.23

0.26

0.70

0.69

1.31

2.45

1.72

NM

EC01

EC02

EC03

EC04

EC05

EC06

EC07

EC08 EC09

EC10

EC11

EC12

EC13

EC14

EC15

EC16

EC17

EC18

EC19

EC20

WW01 WW02

WW03

WW04

WW05

WW06

WW07

WW08

WW09

WW10

WW11

WW13 WW12 WW14

WW15

WW16

WW17

Base map modified from U.S. Geological Survey 1:100,000-scale digital dataUniversal Transverse Mercator projection, zone 14North American Datum of 1983

EC01EC02EC03EC04EC05EC06EC07EC08EC09EC10EC11EC12EC13EC14EC15EC16EC17EC18EC19EC20

North ProngMacdonaMedioLeon 35MedinaDos RiosSAR WitteAlazanSAR MitchellSan PedroSAR 410Salado 13SAR ElmendorfSAR Falls CitySalitrilloMartinez St. HedwigCibolo St. HedwigCibolo Falls CityEcletoSAR Goliad

Map 

identifier

Short name

(table 2)

WW01WW02WW03WW04WW05WW06WW07WW08WW09WW10WW11WW12WW13WW14WW15WW16WW17

Boerne WWTPBoerne WWTP and WRCCibolo WWTPSalitrillo WWTPUpper Martinez WWTPMartinez II WWTPDos Rios WRCDos Rios TuletaDos Rios Flood TunnelDos Rios RittimanDos Rios Convention CenterDos Rios Blue WingLeon Creek WRCLeon Creek Mitchell LakeMedio Creek WRCFloresville WWTPKenedy WWTP

Map 

identifier

Short name

(table 1)
Figure 15. Relative concentrations and proportions of individual subclasses of wastewater compounds in water-quality samples collected during sy

from the San Antonio River Basin, April–May 2012.

BLANCO

COUNTY

HAYS COUNTY

KERR COUNTY

KENDALL

COUNTY

CALDWELL COUNTY

REAL COUNTY

COMAL COUNTY

BANDERA COUNTY

GUADALUPE COUNTY

GONZALES COUNTY

BEXAR 

COUNTY MEDINA COUNTY

LAVACA COUNTY

UVALDE COUNTY

WILSON COUNTY

DEWITT COUNTY 

ATASCOSA COUNTY

KARNES

COUNTY

VICTORIA COUNTY

FRIO COUNTY

GOLIAD 

COUNTY

LIVE OAK

COUNTY

BEE COUNTY

MCMULLEN COUNTY

REFUGIO C

ARANSAS C

Martinez

Creek

San Antonio River

San Antonio

0 10 20 30 40 MILES0 2010 30 40 KILOMETERS

Medina River Subbasin

Lower San Antonio 

River Subbasin

Cibolo Creek

Subbasin

Upper San Antonio 

River Subbasin

WW03

EC17

Subc Va co Siz Det Per Pes Indu Disi Poly FlamSan ASubbWast

ide

Wate

ide

Canyon

Lake

MedinaLake

Calaveras Lake

Victor Braunig Lake

River

West Prong

Medina River

Alazan Creek

ApacheCreek

San Pedro

Creek

Medio

Creek

Salitrillo

Creek

North Prong

Medina River

Medina River

Guadalupe River

Medina River

San Antoni o River

Salado Creek

EcletoCreek

Cibolo Creek

Escondido Creek

Guadalupe River

Cibolo Creek

Mitchell 

Lake

Leon Creek

97°00'

98°00'

99°00'

30°00'

29°30'

29°00'

28°30'

3.79

0.60

1.84

4.15

3.75

0.20

0.14

EC01

EC02

EC03

EC04

EC05

EC06

EC07

EC08 EC09

EC10

EC11

EC12

EC13

EC14

EC15

EC16

EC17

EC18

EC19

EC20

WW01 WW02

WW03

WW04

WW05

WW06

WW07

WW08

WW09

WW10

WW11

WW13 WW12 WW14

WW15

WW16

WW17

Base map modified from U.S. Geological Survey 1:100,000-scale digital dataUniversal Transverse Mercator projection, zone 14North American Datum of 1983

EC01EC02EC03EC04EC05EC06EC07EC08EC09EC10EC11EC12EC13EC14EC15EC16EC17EC18EC19EC20

North ProngMacdonaMedioLeon 35MedinaDos RiosSAR WitteAlazanSAR MitchellSan PedroSAR 410Salado 13SAR ElmendorfSAR Falls CitySalitrilloMartinez St. HedwigCibolo St. HedwigCibolo Falls CityEcletoSAR Goliad

Map 

identifier

Short name

(table 2)

WW01WW02WW03WW04WW05WW06WW07WW08WW09WW10WW11WW12WW13WW14WW15WW16WW17

Boerne WWTPBoerne WWTP and WRCCibolo WWTPSalitrillo WWTPUpper Martinez WWTPMartinez II WWTPDos Rios WRCDos Rios TuletaDos Rios Flood TunnelDos Rios RittimanDos Rios Convention CenterDos Rios Blue WingLeon Creek WRCLeon Creek Mitchell LakeMedio Creek WRCFloresville WWTPKenedy WWTP

Map 

identifier

Short name

(table 1)
Distributional Patterns of Compounds of Emerging Concern 37

During the third synoptic sampling event, differences 

in wastewater compound concentrations resulted from the 

presence or absence of an upstream wastewater discharge 

location and land use. During this sampling event, 

concentrations of wastewater compounds at three sites 

(North Prong, Alazan, and San Pedro; map identifiers EC01, 

EC08, and EC10, respectively, fig. 1, table 2) that did not 

have large wastewater discharge sites upstream (fig. 15) 

typically were lower compared to the concentrations of 

wastewater compounds at three sites (Dos Rios, SAR Witte, 

and Salitrillo; map identifiers EC06, EC07, and EC15, 

respectively, fig. 1, table 2) that are located downstream 

from wastewater discharge sites. In the sample collected at 

the North Prong site, which is in a largely undeveloped area, 

pesticides and disinfection compounds were detected, but the 

total concentrations of wastewater compounds in the sample 

collected at this site were lower than those measured in the 

samples collected at the Alazan and San Pedro sites, which 

are in a highly urbanized area of San Antonio. Concentrations 

of wastewater compounds in samples collected at the SAR 

Mitchell site were less than the concentrations of wastewater 

compounds measured in samples collected at the SAR Witte 

site, which is upstream from the Mitchell site. 

Basin-Wide Distributional Patterns

The North Prong site is in the uppermost reaches 

of the Medina River Subbasin and is upstream from 

any municipalities. The disinfectant phenol and 

1,4-dichlorobenzene were detected during the third synoptic 

sampling event, although concentrations were low (figs. 

9A, 10A). Detection of CECs at a reference site such as the 

North Prong site is consistent with the report by Barber and 

others (2003), and the source of these compounds at reference 

sites without upstream WWTPs remains uncertain. These 

compounds might be associated with household use and 

could be introduced through nonpoint-source pathways such 

as surface runoff, onsite wastewater treatment systems, or 

aerosols rather than by discharge from WWTPs. 

Minimal concentrations of wastewater compounds 

were measured as far downstream as the Macdona site. 

The detergent metabolite 4-nonylphenol diethoxylate and 

the industrial compound p-cresol were the only wastewater 

compounds detected at the Macdona site in the first synoptic 

sampling event, and none were detected in the second synoptic 

sampling event (app. 1). Because the detergent metabolite 

4-nonylphenol diethoxylate is used in a variety of products 

including deicing agents, detergents, and antiseptic cleaners 

(O’Neil, 2001, p. 1196), sources other than treated municipal 

wastewater may introduce 4-nonylphenol diethoxylate into the 

San Antonio River Basin. The compound p-cresol commonly 

is used as a preservative for treated wood (Zaugg and others, 

2002); p-cresol might have been released to the environment 

by the weathering of preserved wood such as the wood used to 

build docks and piers upstream at Medina Lake.

The highest concentrations of wastewater compounds and 

pharmaceuticals were measured in samples collected during 

the first and second synoptic sampling events from the Medio 

site (fig. 1, table 2), which is about 5 miles downstream from 

the Medio WRC. The confluence of Medio Creek with the 

Medina River downstream from the Macdona site represents 

a substantial input of wastewater compounds to the Medina 

River. The Leon Creek WRC, downstream from the Leon 

35 site, is one of the largest wastewater treatment facilities in 

San Antonio. Leon Creek WRC source water was not sampled 

in this study, but its treated municipal wastewater is discharged 

just upstream from the confluence of Leon Creek with the 

Medina River, representing another source of wastewater 

compounds into the Medina River. The contributions of 

compounds from these two wastewater sources are evident in 

samples collected downstream at the Medina site (figs. 5A–B, 

6A–B, 7A–B, 8A–B).

The Dos Rios WRC (map identifier WW07) is the 

largest wastewater discharger in San Antonio; some of 

its effluent is pumped to the Dos Rios Tuleta wastewater 

discharge site (map identifier WW08), the same location as 

the SAR Witte site (map identifier EC07, fig. 1, table 2), and 

some of the effluent from the Dos Rios WRC is pumped to 

the Dos Rios Convention Center wastewater discharge site 

(map identifier WW11, fig. 1, table 2). The Dos Rios site 

(map identifier EC06, fig. 1, table 2) and the SAR Witte 

site were sampled during the third synoptic sampling event; 

the number of detections and concentrations of wastewater 

compounds at both sites were similar, and pharmaceuticals 

were present in samples collected at both sites (figs. 9A–B, 

10A–B). The large number of detections and concentrations 

of wastewater compounds at the SAR Mitchell site probably 

are related to treated municipal wastewater contributions 

from these upstream sources (figs. 9A–B, 10A–B); however, 

concentrations of wastewater compounds were lower at 

the SAR Mitchell site than at the Dos Rios or Witte sites, 

possibly because of dilution from San Pedro Creek or natural 

attenuation processes. 

There were nine wastewater compounds from five 

compound classes detected in the sample collected at the 

Leon 35 site (fig. 1) during the first synoptic sampling event 

(fig. 5A), even though there is no WWTP upstream from this 

site. There were 11 wastewater compounds representing 5 

compound classes measured in the sample collected at that 

site during the second synoptic sampling event (fig. 7A), 

demonstrating that wastewater compounds can be detected 

in streams flowing through a highly urbanized area without 

a large upstream source of treated municipal wastewater. 

Bromacil was the only pesticide and the most abundant 

compound measured in samples collected at the Leon 35 site 

during the first and second synoptic sampling events (figs. 13 

and 14). 

The Alazan and San Pedro sites are two urbanized 

sites with no large upstream wastewater sources that were 

sampled during the third synoptic sampling event (fig. 1). 
38 Detections, Concentrations, and Distributional Patterns of Compounds of Emerging Concern in the San Antonio River Basin

At the Alazan site, 12 wastewater compounds were detected, 

and at the San Pedro site, 5 wastewater compounds were 

detected (fig. 9A). The pharmaceutical carbamazepine was 

also detected at the San Pedro site (fig. 9B, app. 2). Total 

concentrations of wastewater compounds and pharmaceuticals 

were substantially lower at the Alazan and San Pedro sites 

than at either the Dos Rios site or the SAR Witte site (fig. 15); 

upstream from the Dos Rios and SAR Witte sites there are 

discharges of treated municipal wastewater whereas there are 

no WWTPs above the Alazon and San Pedro sites. Similar to 

the Leon 35 site, the large number of detections of wastewater 

compounds measured in samples collected at the Alazan and 

San Pedro sites demonstrate that wastewater compounds can 

be detected in surface water in a highly urbanized area without 

a known source of treated municipal wastewater. The presence 

of carbamazepine is difficult to explain without an upstream 

source of treated wastewater. It is possible that carbamazepine 

is associated with groundwater seepage from onsite 

wastewater treatment systems or leaky sewer lines. Alazan 

Creek flows into San Pedro Creek, which in turn flows into 

the San Antonio River downstream from the SAR Mitchell 

site (map identifier EC09, fig. 1, table 2), and the San Antonio 

River in turn flows past the SAR 410 site (map identifier 

EC11, fig. 1, table 2). Numerous wastewater compounds 

were detected in samples collected at both the SAR Mitchell 

and SAR 410 sites. Depending on streamflow conditions, 

concentrations may vary for wastewater compounds measured 

in samples collected at sites on the San Antonio River 

downstream from Alazan and San Pedro Creeks, such as 

the SAR Mitchell and SAR 410 sites. For example, during 

relatively wet periods, inflows from Alazan and San Pedro 

Creeks will be larger compared to relatively dry periods, and 

wastewater compounds in the San Antonio River at the SAR 

410 site likely will be diluted by these inflows.

Part of the base flow in Salado Creek is supplied by 

treated municipal wastewater discharged at the Dos Rios 

Rittiman wastewater discharge site. The number of detections 

of wastewater compounds at the Salado 13 site during 

the first and second synoptic sampling events indicates a 

large treated wastewater component (figs. 5A–D, 7A–D). 

The concentrations of both wastewater compounds and 

pharmaceuticals at the Salado 13 site, however, were less than 

the concentrations measured in samples collected at the same 

time from other sites (Medio, SAR 410, and SAR Elmendorf) 

that receive the same treated municipal wastewater. The low 

streamflow and the long distance from the treated municipal 

wastewater discharge location at the Dos Rios Rittiman 

wastewater discharge site to the Salado 13 site might facilitate 

removal through natural attenuation processes.

The Dos Rios WRC (site WW07) discharges a large 

volume of treated municipal wastewater into the Medina 

River just upstream from the confluence of the Medina and 

San Antonio Rivers, and streamflow from this entire drainage 

network flows past the SAR Elmendorf site (fig. 1). Samples 

collected at the SAR Elmendorf site during the first and 

second synoptic sampling events had more detections and 

higher concentrations of wastewater compounds than did 

all sites upstream from the SAR Elmendorf site sampled 

at the same time. The higher concentrations of wastewater 

compounds at the SAR Elmendorf site during the first and 

second synoptic sampling events indicate that the Dos Rios 

WRC likely was discharging wastewater compounds at 

higher concentrations than were the other upstream sources. 

Unaccounted variations in the quantity and quality of 

wastewater discharge and streamflow during the first and 

second synoptic sampling events, however, limit the ability 

to compare the distribution and concentration of wastewater 

compounds among sites.

The distribution of wastewater compounds, 

pharmaceuticals, steroidal hormones, and sterols in the Cibolo 

Creek Subbasin is influenced by a combination of hydrologic 

factors and source inputs. In the city of Boerne, there are two 

WWTPs (fig. 1); however, under normal base flow conditions, 

the discharge from these sites goes into groundwater storage 

approximately 3 miles downstream from the Boerne city 

limits rather than being transported farther downstream. In 

the Cibolo Creek Subbasin near San Antonio, there are four 

large wastewater discharge points including Cibolo WWTP, 

Salitrillo WWTP, Upper Martinez WWTP, and Martinez 

II WWTP (map identifiers WW03, WW04, WW05, and 

WW06, respectively) upstream from the Martinez St. Hedwig 

and Cibolo St. Hedwig sites. The number of detections and 

concentrations of wastewater compounds, pharmaceuticals, 

steroidal hormones, and sterols at the Martinez St. Hedwig 

and Cibolo St. Hedwig sites generally were similar to those in 

samples collected from other sites downstream from known 

wastewater discharge (figs. 5A–D, 6A–D, 7A–D, and 8A–D). 

An examination of the number of detections and total 

concentrations of CECs measured in samples collected from 

Cibolo Creek and the San Antonio River indicates there was 

a pattern of lower total concentrations and fewer detections 

at downstream sites. Total concentrations of all CECs were 

lower at Cibolo Falls City than at the Cibolo St. Hedwig and 

Martinez St. Hedwig sites (figs. 1, 6, and 8). Because this 

reach of Cibolo Creek is known to increase in flow because 

of groundwater discharge, particularly immediately upstream 

from the Cibolo Falls City site (Lizárraga and Wehmeyer, 

2012), dilution by groundwater might be part of the cause of 

lower concentrations of wastewater compounds measured 

at the Cibolo Falls City site. Concentrations of wastewater 

compounds decreased between the SAR Elmendorf site 

and the SAR Falls City site during the first and second 

synoptic sampling events (figs. 13 and 14). Concentrations of 

wastewater compounds from samples collected during the first 

and second synoptic sampling events also further decreased 

between the SAR Falls City site and the SAR Goliad site 

(figs. 13 and 14). These decreases in concentrations may 

be the result of dilution caused by increased flow from 

Cibolo Creek discharging into the San Antonio River 

between the SAR Falls City and SAR Goliad sites (fig. 1). 
Summary 39

The general pattern of downstream decreases in wastewater 

compounds in both the San Antonio River and Cibolo Creek 

indicates that natural attenuation processes may be reducing 

concentrations of wastewater compounds; however, a more 

comprehensive assessment would be needed to quantify 

the effects of such processes on wastewater compound 

concentrations in local streams.

The Ecleto site on Ecleto Creek (fig. 1) was included in 

the study because it drains rangeland with no major population 

centers and provides a representation of a substantial 

proportion of the land cover in the San Antonio River Basin. 

There were two detections of wastewater compounds in the 

first sample collected at the Ecleto site (fig. 11A) including 

the flame retardant tris (dichloroisopropyl) phosphate and 

the herbicide bromacil commonly used to control roadside 

weeds. It is possible that these compounds were introduced 

into Ecleto Creek by runoff during the time of sample 

collection. Four wastewater compounds were detected in 

the second sample collected at the Ecleto site including two 

personal-use compounds, the fragrance acetophenone and 

the insect repellent DEET. Also, the industrial compound 

benzophenone (a fixative for soaps and perfumes) and the 

disinfectant compound phenol were detected in the second 

sample collected at the Ecleto site. The presence of these 

CECs indicates that at least some wastewater compounds can 

be introduced into surface waters in rural parts of the San 

Antonio River Basin during runoff or can result from onsite 

wastewater system seepage. The presence of a natural source 

of phenol, however, cannot be excluded (National Pollutant 

Inventory, 2013). Although detection of estrone often indicates 

human source, estrone has other sources such as female 

cattle, a likely source to Ecleto Creek. Furthermore, the high 

concentrations of steroidal hormones and sterols at the Ecleto 

site were primarily a result of the presence of natural sterols 

(cholesterol, beta-sitosterol, and beta-stigmastanol) in the 

stream that likely were derived from cattle waste rather than 

wastewater effluent.

A general lack of pharmaceuticals at stream sites without 

large known sources of treated wastewater appears to be 

a typical pattern for streams throughout the San Antonio 

River Basin. This finding is supported by the observation 

that the Leon 35, Macdona, North Prong, and Alazan sites 

(figs. 5B, 7B, and 9B) had no detectable concentrations of 

pharmaceuticals. One site with no large upstream wastewater 

treatment facility, San Pedro, only had one detection of 

carbamazepine, the most common pharmaceutical measured 

in the study (fig. 9B, app. 2). Carbamazepine is resistant to 

breakdown during water treatment (Walker and others, 2012), 

and it is possible that an onsite wastewater treatment system 

may be the source of carbamazepine at this site. Although the 

source of carbamazepine at one urban site remains uncertain, 

a general lack of detectable pharmaceuticals may be a 

useful indicator for identifying point- and nonpoint-source 

wastewater contributions to urban streams.

Summary 

Advancements in laboratory analytical techniques have 

provided the capability to identify large numbers of previously 

unrecognized compounds of emerging concern (CECs) in 

streams. Some of these compounds are known or suspected 

endocrine disrupters. Point-source discharges from WWTPs 

are a primary source of CECs to urban streams. Nonpoint 

sources such as seepage from on-site wastewater treatment 

systems, leakage from sewer lines, urban runoff, agricultural 

and livestock operations, and atmospheric deposition also 

represent common pathways for organic compounds to enter 

surface waters. To better understand the quality of surface 

water in the San Antonio River Basin, the U.S. Geological 

Survey (USGS), in cooperation with the San Antonio 

River Authority, evaluated detections, concentrations, and 

distributional patterns of selected compounds of emerging 

concern (hereinafter referred to as “CECs”) from water-quality 

samples (hereinafter referred to as “samples”) collected at 

sampling sites along streams throughout the San Antonio 

River Basin, Texas, during 2011–12.

Results are presented for 54 wastewater compounds, 

13 pharmaceuticals, 17 steroidal hormones, and 4 sterols 

analyzed in samples. Of the 54 wastewater compounds, 32 

were detected in at least 1 sample collected at a site in the San 

Antonio River Basin and 22 compounds were not detected in 

any samples. Detected in 28 of the 33 samples analyzed for 

wastewater compounds, tris (2-chloroethyl) phosphate and 

tris (dichloroisopropyl) phosphate were the most commonly 

detected compounds in the study. Tris (2-chloroethyl) 

phosphate and tris (dichloroisopropyl) phosphate are 

suspected endocrine disruptors. The highest concentration 

of a wastewater compound (1.90 μg/L) was measured from 

the fragrance hexahydrohexamethyl-cyclopentabenzopyran 

(HHCB). The second highest concentration of a wastewater 

compound in the study was 1.4 μg/L of the industrial 

compound 5-methyl-1H-benzotriazole, a common component 

of antifreeze. All of the remaining wastewater compounds 

were measured at concentrations less than 1.0 μg/L. Of the 

13 pharmaceuticals, only 4 compounds, 1 non-prescription 

pharmaceutical (diphenhydramine) and 3 prescription 

pharmaceuticals (carbamazepine, dehydronifedipine, and 

sulfamethoxazole), were detected in at least one sample 

collected from the San Antonio River Basin. Carbamazepine, 

an anti-convulsant and the most frequently detected 

prescription pharmaceutical, was detected in 24 of 34 samples 

analyzed for pharmaceuticals. Of the 17 steroidal hormones, 

4 were detected in at least one sample from the San Antonio 

River Basin. Of the 4 sterols, all 4 were detected in at least 

one sample from the San Antonio River Basin. Estrone, a 

metabolite of 17-beta-estradiol, was the most commonly 

detected compound related to estrogen and was detected in 

9 of 34 samples analyzed for steroidal hormones and sterols. 

Cholesterol was detected in 19 of 34 samples.
40 Detections, Concentrations, and Distributional Patterns of Compounds of Emerging Concern in the San Antonio River Basin

Three synoptic sampling events were completed as 

part of this study. When measurement data for wastewater, 

pharmaceutical, steroidal hormone, and sterol compounds 

from the first synoptic sampling event were grouped together, 

the Macdona site (Medina River near Macdona, Tex.) had both 

the lowest number of total detections (2) and the lowest total 

concentrations (0.62 μg/L), and the SAR Elmendorf site (San 

Antonio River near Elmendorf, Tex.) had the highest number 

of detections (21) and highest total concentrations (7.75 μg/L). 

When measurement data for wastewater compounds, 

pharmaceuticals, steroidal hormones, and sterols from the 

second synoptic sampling event were grouped together, the 

Macdona site had the lowest number of detections (zero), 

and total concentrations were not measureable. The SAR 

Elmendorf site had the highest number of detections (23) and 

highest total concentrations (3.97 μg/L). When wastewater 

compounds, pharmaceuticals, steroidal hormones, and 

sterols from the third synoptic sampling event were grouped 

together, the North Prong site (North Prong Medina River 

above confluence Wallace Creek near Medina, Tex.) had both 

the lowest number of total detections (two) and lowest total 

concentrations (0.14 μg/L). The highest number of detections 

(21) occurred at the SAR Mitchell site (San Antonio River 

at Mitchell Street, San Antonio, Tex.), and the highest total 

concentration (4.37 μg/L) occurred at the Dos Rios site (Dos 

Rios WWTP Outfall at San Antonio, Tex.).

The North Prong site is in the uppermost reaches 

of the Medina River Subbasin and is upstream from 

any municipalities. The disinfectant phenol and 

1,4-dichlorobenzene were detected at the North Prong 

site during the third synoptic sampling event, although 

concentrations were low. These compounds might be 

associated with household use and could be introduced 

through nonpoint-source pathways such as surface runoff, 

onsite wastewater treatment systems, or aerosols rather than 

by discharge from WWTPs. Minimal concentrations of 

wastewater compounds were measured as far downstream 

as the Macdona site where only the detergent metabolite 

4-nonylphenol diethoxylate (a compound used in deicing 

agents, detergents, and antiseptic cleaners) and the industrial 

compound p-cresol were detected in the first synoptic 

sampling; these results indicate sources other than treated 

wastewater might also be introducing 4-nonylphenol 

diethoxylate into the San Antonio River Basin. The compound 

p-cresol commonly is used as a preservative for treated wood; 

p-cresol might have been released to the environment by the 

weathering of preserved wood such as the wood used to build 

docks and piers upstream at Medina Lake.

The confluence of Medio Creek with the Medina River 

downstream from the Macdona site represents a substantial 

input of wastewater compounds to the Medina River. 

Source water from the Leon Creek WRC site on Comanche 

Creek at the plant was not sampled in this study, but its 

treated municipal wastewater is discharged just upstream 

from the confluence of Leon Creek with the Medina River, 

representing another source of wastewater compounds 

into the Medina River. The contributions of compounds 

from these two wastewater sources are evident in samples 

collected downstream at the Medina site (Medina River at 

San Antonio, Tex.). The Dos Rios WRC site on the Medina 

River at the plant is the largest wastewater discharger in San 

Antonio; some of its effluent is pumped to the Dos Rios Tuleta 

wastewater discharge site, the same location as the SAR Witte 

site (San Antonio River at Witte Museum, San Antonio, Tex.), 

and some of the effluent from the Dos Rios WRC is pumped 

to the Dos Rios Convention Center site (San Antonio River at 

the Convention Center). The large number of detections and 

concentrations of wastewater compounds at the SAR Mitchell 

site (San Antonio River at Mitchell Street, San Antonio, 

Tex.) probably are related to treated municipal wastewater 

contributions from these upstream sources.

The Leon 35 site (Leon Creek at Interstate Highway 35, 

San Antonio, Tex.), the Alazan site (Alazan Creek at Tampico 

Street, San Antonio, Tex.), and the San Pedro site (San Pedro 

Creek at Probandt Street, at San Antonio, Tex.) are urbanized 

sampling sites with no large upstream wastewater sources. 

There were multiple detections of wastewater compounds at 

all three sites. The pharmaceutical carbamazepine also was 

detected at the San Pedro site. The large number of detections 

at sites with no upstream wastewater source demonstrated that 

wastewater compounds and pharmaceuticals can be detected 

in streams flowing through a highly urbanized area without a 

large upstream source of treated municipal wastewater. Part of 

the base flow in Salado Creek is supplied by treated municipal 

wastewater discharged at the Dos Rios Rittiman wastewater 

discharge site on Salado Creek at Rittiman Road that also 

receives treated municipal wastewater from WRCs. The low 

streamflow and the long distance from the treated municipal 

wastewater discharge location at the Dos Rios Rittiman site 

to the Salado 13 site (Salado Creek at Loop 13, San Antonio, 

Tex.) might facilitate removal through natural attenuation 

processes.

 Samples collected at the SAR Elmendorf site during the 

first and second synoptic sampling events had more detections 

and higher concentrations of wastewater compounds than 

did all sites upstream from the SAR Elmendorf site sampled 

at the same time. The higher concentrations of wastewater 

compounds at the SAR Elmendorf site during the first and 

second synoptic sampling events indicate that the Dos Rios 

WRC likely was discharging wastewater compounds at 

higher concentrations than were the other upstream sources. 

An examination of the number of detections and total 

concentrations of CECs occurring in Cibolo Creek and the 

San Antonio River indicates there was a pattern of lower 

total concentrations and fewer detections at downstream 

sites. Dilution by groundwater might be part of the cause of 

lower concentrations of wastewater compounds measured 

at the Cibolo Falls City site (Cibolo Creek near Falls City, 

Tex.). Decreases in the San Antonio River may be the result 

of dilution cause by increased flow from Cibolo Creek 

discharging into the San Antonio River between the SAR 

Falls City site (San Antonio River at Highway 181 at Falls 
References Cited 41

City, Tex.) and the SAR Goliad site (San Antonio River at 

Goliad, Tex.). The general pattern of downstream decreases 

in wastewater compounds in both the San Antonio River and 

Cibolo Creek indicates that natural attenuation processes may 

be reducing concentrations of wastewater compounds.

The Ecleto site (Ecleto Creek near Runge, Tex.) 

was not part of the three synoptic sampling events; it was 

included in the study because it drains rangeland with no 

major population centers and provides a representation of a 

substantial proportion of the land cover in the San Antonio 

River Basin. The presence of CECs indicates that at least some 

wastewater compounds can be introduced into surface waters 

in rural parts of the San Antonio River Basin during runoff or 

can result from onsite wastewater system seepage. The high 

concentrations of steroidal hormones and sterols at the Ecleto 

site were primarily a result of the presence of natural sterols 

(cholesterol, beta-sitosterol, and beta-stigmastanol) in the 

stream that likely were derived from cattle waste rather than 

wastewater effluent.

One site with no large upstream wastewater treatment 

facility, San Pedro, had only one detection of carbamazepine, 

the most commonly occurring pharmaceutical measured in 

the study. Carbamazepine is resistant to breakdown during 

water treatment, and it is possible that an onsite wastewater 

treatment system may be the source of carbamazepine at 

this site. Although the source of carbamazepine at one 

urban site remains uncertain, a general lack of detectable 

pharmaceuticals may be a useful indicator for identifying 

point- and nonpoint-source wastewater contributions to urban 

streams.

References Cited

Barber, L.B., Furlong, E.T., Keefe, S.H., Brown, G.K., 

and Cahill, J.D., 2003, Natural and contaminant organic 

compounds in the Boulder Creek watershed, Colorado, 

during high-flow and low-flow conditions, 2000, in Murphy, 

S.F., Verplanck, P.L., and Barber, L.B., eds., Comprehensive 

water quality of the Boulder Creek watershed, Colorado, 

during high-flow and low-flow conditions, 2000: U.S. 

Geological Survey Water-Resources Investigations Report 

03–4045, p. 103–144.

Baker, D.R., and Kasprzyk-Hordern, B., 2013, Spatial 

and temporal occurrence of pharmaceuticals and illicit 

drugs in the aqueous environment and during wastewater 

treatment—New developments: Science of the Total 

Environment, v. 454–455, p. 442–456.

Barnes, K.K., Kolpin, D.W., Furlong, E.T., Zaugg, S.D., 

Meyer, M.T., and Barber, L.B., 2008, A national 

reconnaissance of pharmaceuticals and other organic 

wastewater contaminants in the United States—I) 

Groundwater: Science of the Total Environment, v. 402, 

p. 192–200.

Carlos, Luciano, Martire, D.O., Gonzalez, M.C., Gomis, Juan, 

Bernabeu, Antonio, Amat, A.M., and Arques, Antonio, 

2012, Photochemical fate of a mixture of emerging 

pollutants in the presence of humic substances: Water 

Research, v. 46, p. 4732–4740.

Chambers, D.B., and Leiker, T.J., 2006, A reconnaissance for 

emerging contaminants in the South Branch Potomac River, 

Cacapon River, and Williams River Basins, West Virginia, 

April–October 2004: U.S. Geological Survey Open-File 

Report 2006–1393, 23 p.

Childress, C.J.O., Foreman, W.T., Connor, B.F., and Maloney, 

T.J., 1999, New reporting procedures based on long-term 

method detection levels and some considerations for 

interpretations of water-quality data provided by the U.S. 

Geological Survey National Water Quality Laboratory: U.S. 

Geological Survey Open-File Report 99–193, 19 p.

Couper, F.J., and Logan, B.K., 2004, Drugs and human 

performance fact sheet: Washington, D.C., National 

Highway Traffic Safety Administration, DOT HS 809725.

Extension Toxicology Network (EXTOXNET), 1996, 

Pesticide information profiles (PIPs): Accessed May 9, 

2013, at http://extoxnet.orst.edu/pips/ghindex.html.

Focazio, M.J., Kolpin, D.W., Barnes, K.K., Furlong, E.T., 

Meyer, M.T., Zaugg, S.D., Barber, L.B., and Thurman, 

M.E., 2008, A national reconnaissance for pharmaceuticals 

and other organic wastewater contaminants in the United 

States—II) Untreated drinking water sources: Science of the 

Total Environment, v. 402, p. 201–216.

Foreman, W.T., Gray, J.L., ReVello, R.C., Lindley, C.E., 

Losche, S.A., and Barber, L.B., 2012, Determination of 

steroid hormones and related compounds in filtered and 

unfiltered water by solid-phase extraction, derivatization, 

and gas chromatography with tandem mass spectrometry: 

U.S. Geological Survey Techniques and Methods, book 5, 

chap. B9, 118 p.

Furlong, E.T., Werner, S.L., Anderson, B.D., and Cahill, J.D., 

2008, Methods of analysis by the U.S. Geological Survey 

National Water Quality Laboratory determination of humanhealth pharmaceuticals in filtered water by chemically 

modified styrene-divinylbenzene resin-based solid-phase 

extraction and high performance liquid chromatography/

mass spectrometry: U.S. Geological Survey Techniques and 

Methods, book 5, chap. B5, 56 p.

Glassmeyer, S.T., Furlong, E.T., Kolpin, D.W., Cahill, J.D., 

Zaugg, S.D., Werner, S.L., Meyer, M.T., and Kryak, D.D., 

2005, Transport of chemical and microbial compounds 

from known wastewater discharges—Potential for use as 

indicators of human fecal contamination: Environmental 

Science and Technology, v. 39, p. 5157–5169.
42 Detections, Concentrations, and Distributional Patterns of Compounds of Emerging Concern in the San Antonio River Basin

Haack, S.K., 2009, Antibiotic, pharmaceutical, and 

wastewater-compound data for Michigan, 1998–2005: U.S. 

Geological Survey Scientific Investigations Report 2009–

5217, 36 p.

Katz, B.G., Griffin, D.W., McMahon, P.B., Harden, H., 

Wade, E., Hicks, R.W., and Chanton, J.P., 2010, Fate of 

effluent-borne contaminants beneath septic tank drainfields 

overlying a karst aquifer: Journal of Environmental Quality, 

v. 39, p. 1181–1195.

Kennedy, E.J., 1983, Computation of continuous records of 

streamflow: U.S. Geological Survey Techniques of WaterResources Investigations, book 3, chap. A13, 53 p.

Kennedy, E.J., 1984, Discharge ratings at gaging stations: 

U.S. Geological Survey Techniques of Water-Resource 

Investigations, book 3, chap. A10, 59 p.

Kidd, K.A., Blanchfield, P.J., Mills, K.H., Palace, V.P., Evans, 

R.E., Lazorchak, J.M., and Flick, R.W., 2007, Collapse of 

a fish population after exposure to a synthetic estrogen: 

Proceedings of the National Academy of Sciences, v. 104, 

no. 21, p. 8897–8901.

Klamerth, Nikolaus, Malato, Sixto, Maldonado, M.I., Aguera, 

Amadeo, Fernandez-Alba, A.R., 2010, Degradation of 

fifteen emerging contaminants at μgL-1 initial concentrations 

by mild solar photo-Fenton in MWTP effluents: Water 

Research, v. 44, p. 545–554.

Kolpin, D.W., Furlong, E.T., Meyer, M.T., Thurman, E.M., 

Zaugg, S.D., Barber, L.B., and Buxton, H.T., 2002, 

Pharmaceuticals, hormones, and other organic wastewater 

contaminants in U.S. streams, 1999–2000—A national 

reconnaissance: Environmental Science and Technology, 

v. 36, p. 1202–1211.

Kolpin, D.W., Skopec, M., Meyer, M.T., Furlong, E.T., and 

Zaugg, S.D., 2004, Urban contribution of pharmaceuticals 

and other organic wastewater contaminants to streams 

during differing flow conditions: Science of the Total 

Environment, v. 328, p. 119–130.

Lawrence, S.J., and LaFontaine, J.H., 2010, Occurrence of 

organic wastewater-indicator compounds in urban streams 

of the Atlanta area, Georgia, 2003–2006: U.S. Geological 

Survey Scientific Investigations Report 2010–5209, 

113 p.

Lee, K.E., Langer, S.K., Barber, L.B., Writer, J.H., Ferrey, 

M.L., Schoenfuss, H.L., Furlong, E.T., Foreman, W.T., 

Gray, J.L., ReVello, R.C., Martinovic, D., Woodruff, 

O.P., Keefe, S.H., Brown, G.K., Taylor, H.E., Ferrer, I., 

and Thurman, E.M., 2011, Endocrine active chemicals, 

pharmaceuticals, and other chemicals of concern in 

surface water, wastewater-treatment plant effluent, and 

bed sediment, and biological characteristics in selected 

streams, Minnesota—Design, methods, and data, 2009: U.S. 

Geological Survey Data Series 575, 54 p., with appendixes.

Ligocki, M.P., Leuenberger, Christian, and Pankow, J.F., 

1985a, Trace organic compounds in rain—III. Particle 

scavenging of neutral organic compounds: Atmospheric 

Environment, v. 19, no. 10, p. 1619–1626.

Ligocki, M.P., Leuenberger, Christian, and Pankow, J.F., 

1985b, Trace organic compounds in rain—II. Gas 

scavenging of neutral organic compounds: Atmospheric 

Environment, v. 19, no. 10, p. 1609–1617.

Lintelmann, J., Katayama, A., Kurihara, N., Shore, L., and 

Wenzel, A., 2003, Endocrine disruptors in the environment: 

Pure and Applied Chemistry, v. 75, no. 5, p. 631–681.

Lizárraga, J.S., and Wehmeyer, L.L., 2012, Estimation of 

streamflow gains and losses in the lower San Antonio 

River watershed, south-central Texas, 2006–10: U.S. 

Geological Survey Scientific Investigations Report 2012–

5073, 34 p.

Loyo-Rosales, J.E., Rice, C.P., and Torrents, A., 2007, Fate of 

octyl- and nonylphenol ethoxylates and some carboxylated 

derivatives in three American wastewater treatment plants: 

Environmental Science and Technology, v. 41, no. 19, 

p. 6815–6821.

Mahler, B.J., Van Metre, P.C., Crane, J.L., Watts, A.W., 

Scoggins, M., and Williams, E.S., 2012, Coal-tar-based 

pavement sealcoat and PAHs—Implications for the 

environment, human health, and stormwater management: 

Environmental Science and Technology, v. 46, p. 3039–

3045.

Marklund, Anneli, Andersson, Barbro, and Haglund, Peter, 

2005, Traffic as a source of organophosphorus flame 

retardants and plasticizers in snow: Environmental Science 

and Technology, v. 39, no. 10, p. 3555–3562.

Montgomery, J.H., and Welkom, L.M., 1990, Groundwater 

chemicals desk reference: Chelsea, Mich., Lewis Publishers, 

Inc., 640 p.

Nagpal, N.K., 1993, Ambient water quality criteria for 

polycyclic aromatic hydrocarbons (PAHs), chap. 4.0—

Occurrence in the environment: Province of British 

Columbia Ministry of Environment, Environmental 

Protection Division, accessed September 27, 2013, at 

http://www.env.gov.bc.ca/wat/wq/BCguidelines/pahs/pahs03.htm#P890_30513.

National Academy of Sciences, 1999, Hormonally active 

agents in the environment: Washington, D.C., National 

Academy Press, 430 p. 

National Institute of Environmental Health Sciences, 2011, 

12th report on carcinogens: U.S. Department of Health 

and Human Services, 507 p., accessed August 10, 2012, at 

http://ntp.niehs.nih.gov/ntp/roc/twelfth/roc12.pdf. 
References Cited 43

National Institute of Environmental Health Sciences, 2013, 

Bisphenol A (BPA)—Questions and answers about 

bisphenol A, radio interview with Dr. Linda S. Birnbaum, 

Ph.D., on January 28, 2013: Accessed May 9, 2013, at 

http://www.niehs.nih.gov/health/topics/agents/sya-bpa/.

National Pesticide Information Center, 2011, Pesticide fact 

sheets: Accessed May 9, 2013, at http://npic.orst.edu/ingred/

aifact.html.

National Pollutant Inventory, 2013, Phenol—Sources of 

emissions: Accessed July 6, 2013, at http://www.npi.gov.au/

resource/phenol.

Oblinger, C.J., Gill, A.C., McPherson, A.K., Meyer, 

M.T., and Furlong, E.T., 2007, Occurrence of selected 

pharmaceuticals, personal-use products, organic wastewater 

compounds, and pesticides in the lower Tallapoosa 

River watershed near Montgomery, Alabama, 2005: U.S. 

Geological Survey Scientific Investigations Report 2007–

5266, 23 p.

Ockerman, D.J., and McNamara, K.C., 2003, Simulation of 

streamflow and estimation of streamflow compound loads 

in San Antonio River watershed, Bexar County, Texas, 

1997–2001: U.S. Geological Survey Water-Resources 

Investigations Report 2003–4030, 44 p.

O’Neil, M.J., ed., 2001, The Merck index—An encyclopedia 

of chemicals, drugs, and biologicals (13th ed.): Whitehouse 

Station, N.J., Merck and Company, Inc., 1,735 p.

Peck, A.M., and Hornbuckle, K.C., 2006, Synthetic musk 

fragrances in urban and rural air of Iowa and the Great 

Lakes: Atmospheric Environment, v. 40, no. 32, 

p. 6101–6111.

Phillips, P.L., Smith, S.G., Kolpin, D.W., Zaugg, S.D., Buxton, 

H.T., Furlong, E.T., Esposito, K., and Stinson, B., 2010, 

Pharmaceutical formulation facilities as sources of opioids 

and other pharmaceuticals to wastewater treatment plant 

effluents: Environmental Science and Technology, v. 44, 

no. 13, p. 4910–4916.

Phillips, P.J., Stinson, B., Zaugg, S.D., Furlong, E.T., Kolpin, 

D.W., Esposito, K.M., Bodniewicz, B., Pape, R., and 

Anderson, J., 2005, A multi-disciplinary approach to the 

removal of emerging contaminants in municipal wastewater 

treatment plants in New York State, 2003–2004: World 

Environmental and Water Resources Congress 2007, 

p. 1–30.

Rantz, S.E., and others, 1982a, Measurement and computation 

of streamflow—Volume 1 measurement of stage and 

discharge: U.S. Geological Survey Water-Supply Paper 

2175, 284 p., accessed October 24, 2013, at http://pubs.

usgs.gov/wsp/wsp2175/pdf/WSP2175_vol1a.pdf.

Rantz, S.E., and others, 1982b, Measurement and computation 

of streamflow—Volume 2 computation of discharge: U.S. 

Geological Survey Water-Supply Paper 2175, 631 p., 

accessed October 24, 2013, 2011, at http://pubs.usgs.gov/

wsp/wsp2175/pdf/WSP2175_vol2a.pdf.

Reif, A.G., Crawford, J.K., Loper, C.A., Proctor, Arianne, 

Manning, Rhonda, and Titler, Robert, 2012, Occurrence 

of pharmaceuticals, hormones, and organic wastewater 

compounds in Pennsylvania waters, 2006–09: U.S. 

Geological Survey Scientific Investigations Report 2012–

5106, 99 p.

Richardson, S.D., and Ternes, T.A., 2011, Water analysis—

Emerging contaminants and current issues: Analytical 

Chemistry, v. 83, p. 4614–4648.

Rounds, S.A., Doyle, M.C., Edwards, P.M., and Furlong, 

E.T., 2009, Reconnaissance of pharmaceutical chemicals in 

urban streams of the Tualatin River Basin, Oregon, 2002: 

U.S. Geological Survey Scientific Investigations Report 

2009–5119, 22 p.

San Antonio River Authority, 2013, Understanding the 

San Antonio River Basin: San Antonio River Authority, 

accessed August 7, 2013, at http://www.sara-tx.org/public_

information/understanding_the_basin/.

Schuetzle, D., Cronn, D., Crittenden, A.L., and Charlson, R.J., 

1975, Molecular composition of secondary aerosol and its 

possible origin: Environmental Science and Technology, 

v. 9, no. 9, p. 838–845.

Texas Instream Flow Program and San Antonio River 

Authority, 2011, Instream flow study of the Lower San 

Antonio River and Lower Cibolo Creek—Interim progress 

report and instream flow recommendations: Accessed 

September 26, 2011, at http://www.sara-tx.org/public_

resources/library/documents/LSAR_FINAL_INTERIM_

REPORT_20110831.pdf.

Tolls, Johannes, 2001, Sorption of veterinary pharmaceuticals 

in soils—A review: Environmental Science and Technology, 

v. 35, no. 17, p. 3397–3406.

Turnipseed, D.P., and Sauer, V.B., 2010, Discharge 

measurements at gaging stations: U.S. Geological Survey 

Techniques and Methods, book 3, chap. A8, 87 p. (Also 

available at http://pubs.usgs.gov/tm/tm3-a8/.)

U.S. Census Bureau, 2013, Texas cities lead Nation in 

population growth, Census Bureau reports: Accessed May 

21, 2012, at http://www.census.gov/newsroom/releases/

archives/population/cb13-94.html.

U.S. Environmental Protection Agency, 2004, 2004 edition 

of the drinking water standards and health advisories: 

Washington, D.C., Office of Water, U.S. Environmental 

Protection Agency, EPA 822–R–04–005, 20 p.
44 Detections, Concentrations, and Distributional Patterns of Compounds of Emerging Concern in the San Antonio River Basin

U.S. Environmental Protection Agency, 2007, Technology 

Transfer Network Air Toxics Web site—Bromoform: 

Accessed August 7, 2013, at http://www.epa.gov/ttnatw01/

hlthef/bromofor.html.

U.S. Environmental Protection Agency, 2011, Persistent 

Bioaccumulative and Toxic (PBT) Chemical Program—

Benzo(a)pyrene: Accessed July 7, 2013, at http://www.epa.

gov/pbt/pubs/benzo.htm.

U.S. Environmental Protection Agency, 2012, Endocrine 

Disruptor Screening Program (EDSP)—What are endocrine 

disruptors?: Accessed May 15, 2013, at http://www.epa.gov/

scipoly/oscpendo/pubs/edspoverview/whatare.htm.

U.S. Environmental Protection Agency, 2013a, Permit 

Compliance System (PCS) and Integrated Compliance 

System (ICIS) databases containing information on 

permitted discharge of wastewater into rivers: Accessed 

April 10, 2013, at http://www.epa.gov/enviro/facts/pcs-icis/

index.html.

U.S. Environmental Protection Agency, 2013b, Bisphenol 

A (BPA) action plan summary: Accessed July 7, 2013, 

at http://www.epa.gov/opptintr/existingchemicals/pubs/

actionplans/bpa.html.

U.S. Geological Survey, variously dated, National field manual 

for the collection of water-quality data: U.S. Geological 

Survey Techniques of Water-Resources Investigations, 

book 9, chaps. A1–A9, variously paged. (Also available at 

http://pubs.water.usgs.gov/twri9a.)

U.S. Geological Survey, 2010, Changes to the reporting 

convention and data qualification approaches for selected 

analyte results reported by the National Water Quality 

Laboratory (NWQL): U.S. Geological Survey Office of 

Water Quality Technical Memorandum 2010.07, accessed 

November 13, 2013, at http://water.usgs.gov/admin/memo/

QW/qw10.07.html.

Van Metre, P.C., Majewski, M.S., Mahler, B.J., Foreman, 

W.T., Braun, C.L., Wilson, J.T., and Burbank, T.L., 2012, 

PAH volatilization following application of coal-tarbased pavement sealant: Atmospheric Environment, v. 51, 

p. 108–115.

Van Metre, P.C., and Mahler, B.J., 2010, Contribution of 

PAHs from coal-tar pavement sealcoat and other sources 

to 40 U.S. lakes: Science of the Total Environment, v. 409, 

p. 334–344.

Walker, C.W., Watson, J.E., and Williams, C., 2012, 

Occurrence of carbamazepine in soils under different 

land uses receiving wastewater: Journal of Environmental 

Quality, v. 41, p. 1263–1267, accessed August 19, 2013, at 

http://www.ncbi.nlm.nih.gov/pubmed/22751070. 

Washington State Department of Transportation, 2006, 

Bromacil roadside vegetation management herbicide fact 

sheet: Accessed August 19, 2013, at http://www.wsdot.

wa.gov/NR/rdonlyres/7004073D-DBAD-4BBA-B32D04082C699136/0/bromacil.pdf.

White, Robert, Jobling, Susan, Hoare, S.A., Sumpter, J.P., 

and Parker, M.G., 1994, Environmentally persistent 

alkylphenolic compounds are estrogenic: Endocrinology, 

v. 135, no. l, p. 175–182.

Xylem Analytics, 2012, Sontek argonaut acoustic Doppler 

velocity meter and flowtracker principles of operation: 

Accessed March 1, 2012, at http://www.xylemanalytics.

com/.

Yamamoto, Hiroshi, Nakamura, Yudai, Moriguchi, 

Shigemi, Nakamura, Yuki, Honda, Yuta, Tamura, Ikumi, 

Hirata, Yoshiko, Hayashi, Akihide, and Sekizawa, Jun, 

2009, Persistence and partitioning of eight selected 

pharmaceuticals in the aquatic environment—Laboratory 

photolysis, biodegradation, and sorption experiments: Water 

Research, v. 43, p. 351–362.

Zaugg, S.D., Smith, S.G., Schroder, M.P., Barber, L.B., and 

Burkhardt, M.R., 2002, Methods of analysis by the U.S. 

Geological Survey National Water Quality Laboratory—

Determination of wastewater compounds by polystyrenedivinylbenzene solid-phase extraction and capillary-column 

gas chromatography/mass spectrometry: U.S. Geological 

Survey Water-Resources Investigations Report 01–4186, 

37 p.

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