Lagrangian Sampling for Emerging Contaminants Through an Urban Stream Corridor in Colorado

LAGRANGIAN SAMPLING FOR EMERGING CONTAMINANTS THROUGHAN URBAN STREAM CORRIDOR IN COLORADO1

Juliane B. Brown, William A. Battaglin, and Robert E. Zuellig2

ABSTRACT: Recent national concerns regarding the environmental occurrence of emerging contaminants (ECs)have catalyzed a series of recent studies. Many ECs are released into the environment through discharges fromwastewater treatment plants (WWTPs) and other sources. In 2005, the U.S. Geological Survey and the City ofLongmont initiated an investigation of selected ECs in a 13.8-km reach of St. Vrain Creek, Colorado. Seven siteswere sampled for ECs following a Lagrangian design; sites were located upstream, downstream, and in the out-fall of the Longmont WWTP, and at the mouths of two tributaries, Left Hand Creek and Boulder Creek (whichis influenced by multiple WWTP outfalls). Samples for 61 ECs in 16 chemical use categories were analyzed and36 were detected in one or more samples. Of these, 16 have known or suspected endocrine-disrupting potential.At and downstream from the WWTP outfall, detergent metabolites, fire retardants, and steroids were detectedat the highest concentrations, which commonly exceeded 1 lg ⁄ l in 2005 and 2 lg ⁄ l in 2006. Most individual ECswere measured at concentrations less than 2 lg ⁄ l. The results indicate that outfalls from WWTPs are the largestbut may not be the sole source of ECs in St. Vrain Creek. In 2005, high discharge was associated with fewer ECdetections, lower total EC concentrations, and smaller EC loads in St. Vrain Creek and its tributaries as com-pared with 2006. EC behavior differed by individual compound, and some differences between sites could beattributed to analytical variability or to other factors such as physical or chemical characteristics or distancefrom contributing sources. Loads of some ECs, such as diethoxynonylphenol, accumulated or attenuated depend-ing on location, discharge, and distance downstream from the WWTP, whereas others, such as bisphenol A, werelargely conservative. The extent to which ECs in St. Vrain Creek affect native fish species and macroinverte-brate communities is unknown, but recent studies have shown that fish respond to very low concentrationsof ECs, and further study on the fate and transport of these contaminants in the aquatic environment iswarranted.

(KEY TERMS: emerging contaminants; St. Vrain Creek; Lagrangian sampling; water quality; wastewater treat-ment plant; urban stream corridor; attenuation; analytical variability.)

Brown, Juliane B., William A. Battaglin, and Robert E. Zuellig, 2009. Lagrangian Sampling for Emerging Con-taminants Through an Urban Stream Corridor in Colorado. Journal of the American Water Resources Associa-tion (JAWRA) 45(1):68-82. DOI: 10.1111 ⁄ j.1752-1688.2008.00290.x

1Paper No. JAWRA-07-0182-P of the Journal of the American Water Resources Association (JAWRA). Received December 19, 2007;accepted August 1, 2008. ª 2008 American Water Resources Association. Discussions are open until August 1, 2009.

2Respectively, Hydrologist and Research Hydrologist (Brown and Battaglin), U.S. Geological Survey, Colorado Water Science Center, Den-ver Federal Center, MS 415, Lakewood, Colorado 80225; and Aquatic Ecologist (Zuellig), U.S. Geological Survey, Fort Collins Science Center,2150 Centre Avenue, Building C, Fort Collins, Colorado 80526 (E-Mail ⁄ Brown: [email protected]).

JAWRA 68 JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION

JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION

Vol. 45, No. 1 AMERICAN WATER RESOURCES ASSOCIATION February 2009

INTRODUCTION

During the last 20 years, land use in the GreatPlains portion of the St. Vrain Creek basin, in north-central Colorado (Figure 1), has shifted substantiallyfrom largely undeveloped native grassland, pasture,and agricultural land to urban and suburban land,particularly in and around the cities of Longmontand Boulder, Colorado. The increase in human popu-lation associated with this shift has increased vol-umes of treated wastewater effluent that isdischarged to area streams. Additionally, between1986 and 1998 impervious surfaces increased 32% inthe region, whereas irrigated cropland decreased by33% and wetlands decreased by 65% (American For-ests, 2001). Typically, changes in land cover can leadto increased urban runoff, decreased natural attenua-tion of discharge and filtering by wetlands, altera-tions in discharge conditions and water quality

(Sprague et al., 2006), and ultimately degraded bio-logical communities (Paul and Meyer, 2001).

During the last two decades new wastewater treat-ment plant (WWTP) technologies and instream resto-ration efforts have been implemented by the city ofLongmont to improve aquatic habitat and water qual-ity in St. Vrain Creek (Zuellig et al., 2007). TheWWTP improvements primarily addressed facilitycapacity and the reduction of elevated metals, nutri-ents, and suspended-sediment concentrations. Recentregional and national reconnaissance studies haveindicated the presence of previously undocumentedcontaminants indicative of human sources down-stream from WWTPs (Ternes, 2001; Kolpin et al.,2002; Heberer and Adam, 2005; Sprague and Battag-lin, 2005). These wastewater-related contaminantsinclude antioxidants, detergents and detergentmetabolites, disinfectants, fire retardants, fragrances,insect repellants, pharmaceuticals (prescription andnonprescription drugs), pesticides, plasticizers,

FIGURE 1. St. Vrain Creek Basin, Colorado, With Land Use and Sampling Stations.

LAGRANGIAN SAMPLING FOR EMERGING CONTAMINANTS THROUGH AN URBAN STREAM CORRIDOR IN COLORADO

JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION 69 JAWRA

polycyclic aromatic hydrocarbons, and steroidal com-pounds and are referred to hereafter as ‘‘emergingcontaminants’’ (ECs). ECs can be released to theaquatic environment through industrial and munici-pal wastewater discharges, storm drains, agriculturaland urban runoff, and individual or multi-facilitysewage disposal systems. Until recently, the extent towhich these contaminants occurred in the aquaticenvironment was not well known and the toxicologi-cal ramifications with regard to humans or wildlifewere largely unknown (Daughton, 2001). However,recent studies have shown that exposure to someECs, even at very low concentrations, can result inendocrine disruption and histological and immunolog-ical alterations in wildlife and humans (Colbornet al., 1993; McLachlan, 2001; Petrovic et al., 2002;Hoger, 2003; Bernet et al., 2004; Hoeger et al., 2004;Arslan et al., 2007). Identifying the occurrence, distri-bution, and fate of ECs in urban streams will aidcommunities in addressing source-control and reduc-tion efforts to safeguard human and aquatic health.

In this paper we describe the occurrence and trans-port of selected ECs in St. Vrain Creek through thecity of Longmont under two different hydrologic con-ditions. Stream samples were collected during thetwo events by using a longitudinal Lagrangian sam-pling design. Dye tracer studies conducted just priorto each sampling event were used to estimate traveltimes during each event. Discharge and field mea-surements were collected and water samples wereanalyzed by the U.S. Geological Survey (USGS)National Water Quality Laboratory (NWQL) for aseries of ECs that are indicative of wastewater byusing methods described in Zaugg et al. (2002).

Study Area and Site Selection

St. Vrain Creek flows east from sources along theeast side of the Continental Divide and eventuallyjoins the South Platte River, in north-central Colo-rado (Figure 1). The main mountainous headwaterstreams, North and South St. Vrain Creeks, are pri-marily forested until they converge downstream nearthe town of Lyons to form St. Vrain Creek. Down-stream from Lyons, St. Vrain Creek primarily flowsthrough grassland, pastures, and agricultural areasand the city of Longmont on its way to the confluencewith the South Platte River.

Seven sites were selected for water-chemistry sam-pling along a 13.8-kilometer (km) reach of the St.Vrain Creek within the city of Longmont: two sitesupstream from the Longmont WWTP outfall (Sites 1and 2); two sites at the mouths of key tributaries,Left Hand Creek and Boulder Creek (Sites 3 and 6);one site at the Longmont WWTP outfall (Site 4); and

two sites on St. Vrain Creek downstream from theWWTP outfall (Sites 5 and 7) (Figure 1). The mostupstream site (Site 1) is located at the western edgeof Longmont just east (downstream) from AirportRoad, and it represents the upstream, primarily non-urban inputs to the creek before it enters the Long-mont area. This site is influenced by the small townof Lyons approximately 13.2 km upstream and thesurrounding agricultural community. Site 2 isapproximately 5.8 km downstream from Site 1 andimmediately upstream from the Longmont WWTPoutfall; it represents inputs from the urban and agri-cultural areas before the input of treated wastewatereffluent. Left Hand Creek (Site 3) is one of the twolargest tributaries entering St. Vrain Creek in thestudy reach. Left Hand Creek enters St. Vrain Creekjust upstream from the Longmont WWTP outfall; it isinfluenced by the upstream communities of James-town and Ward, some historical mining, and subur-ban development and agricultural activities aroundLongmont. Site 4 is the WWTP outfall and the flow iscomposed of treated wastewater effluent from theCity of Longmont Water and Wastewater Depart-ment. Site 5 is approximately 1 km downstream fromthe Longmont WWTP outfall and represents the inte-gration of the WWTP effluent and St. Vrain Creek(tributaries do not intervene between the outfall andthis site). Boulder Creek (Site 6) is the other majortributary and it enters St. Vrain Creek approximately7.5 km downstream from the Longmont WWTP out-fall and is influenced by upstream operations ofBarker Dam, the town of Nederland, historicalmining, and WWTP inflows from the urban areas ofBoulder, Superior, Louisville, Lafayette, and Erie,and by the surrounding suburban and agriculturalland. The WWTP for Boulder is approximately 23 kmupstream from Site 6. Site 7 is just downstream fromthe confluence of Boulder Creek, approximately7.9 km downstream from the Longmont WWTP andapproximately 72.6 km from the confluence with theSouth Platte River.

Data Collection

A Lagrangian sampling design, which follows thesame parcel of water as it moves downstream, wasused for each sampling event (Zuellig et al., 2007).Tracer tests with Rhodamine-WT dye were used todetermine the time-of-travel between sample-collec-tion sites (Kilpatrick and Wilson, 1989). For thisstudy, time-of-travel was defined as ‘‘the amount ofelapsed time for the dye peak to travel between twomonitoring sites’’ (Zuellig et al., 2007). Travel-timeestimates were made 9 and 15 days prior to the dateof sample collection in April 2005 and March 2006,

BROWN, BATTAGLIN, AND ZUELLIG


respectively. Minor adjustments were made to thedye travel-time estimates to account for differences inflow conditions during the times of sample collection(Zuellig et al., 2007). In 2005, under higher flow con-ditions than in 2006, times of travel were estimatedas 345 min between Sites 1 and 2, 65 min betweenSites 2 and 5, and 235 min between Sites 5 and 7. In2006, times of travel were estimated as 825 minbetween Sites 1 and 2, 45 min between Sites 2 and 5,and 290 min between Sites 5 and 7. Stream velocityand travel times can increase or decrease duringlower flow conditions depending on stream channelmorphology. Uncertainty in the estimates of traveltime can be introduced by errors in the measurementof dye concentrations.

Stream samples analyzed for ECs were collected atspecific times calculated from the travel-time datausing standardized depth- and width-integrating tech-niques and processed and preserved on-site usingmethods described in the USGS National Field Manual(variously dated). Samples were analyzed by the USGSNWQL for 61 ECs (Table 1) according to methodsdescribed in Zaugg et al. (2002). Field measurements,including dissolved oxygen, pH, specific conductance,water temperature, and discharge, were obtained atthe time of sample collection. The complete dataset ispresented in Zuellig et al. (2007). Most of the 61 ECsare commercially synthesized compounds or their deg-radation products, but a few such as phenol, skatol,and the steroids can originate from natural sources.

The analytical results consisted of unqualified con-centrations, E coded (or estimated) concentrations,and nondetections [reported as less than the labora-tory reporting level (LRL) for the particular com-pound]. Estimated concentrations include those thatare below or above the calibration curve, concentra-tions for compounds with average recoveries that areless than 60%, or concentrations of compounds rou-tinely detected in laboratory blanks (Furlong et al.,2001). Both unqualified concentrations and E codedconcentrations are used in the calculation of sum-mary statistics (Table 1) and contaminant loads(Tables 2 and 3).

Quality Control and Quality Assessment

Quality-control samples were collected as part ofthis study, including one field blank, one replicate,and one laboratory spike during each sampling event.In 2005, phenol was detected in the field blank andin 2006 methyl salicylate and naphthalene weredetected in the field blank. All phenol results for2005 and naphthalene results for 2006 were consid-ered contaminated. Results for methyl salicylate anal-yses were qualified as acceptable because all results

were nondetectable and the estimated value in theblank (0.0170 lg ⁄ l) was much smaller than the LRL(<0.5 lg ⁄ l). To facilitate between-year comparisons,no phenol or naphthalene results were further ana-lyzed as part of this study, though the summary dataare included in Table 1 for reference.

In 2005, percent difference between environmentaland replicate samples ranged from 0 to 57.5% withan overall median percent difference of 9.1 for the 31detected ECs, excluding phenol (Table 1). In 2006,percent difference between environmental and repli-cate samples ranged from 6.2 to 30.4% with an over-all median percent difference of 15.8 for the threedetected ECs, excluding naphthalene (Table 1).

Field and laboratory spike recovery data for the ECsadded to environmental sample water and laboratoryreagent water at known concentrations are shown inTable 1. Percent recoveries are determined by dividingthe measured concentration in the environmental orlaboratory sample by the known concentration in theadded spike solution. Greater than 60% of most con-stituents (57 of 61) were recovered for the field or labo-ratory spikes for one or both sampling events. Onlyfour constituents, b-stigmastanol, d-limonene, isopro-pylbenzene, and tetrachloroethylene, had environmen-tal and laboratory spike recoveries less than 60% forone or both sampling events, indicating generally poorrecovery and increased uncertainty in quantification.Of these four constituents, only b-stigmastanol wasdetected in an environmental sample. For the 2005event, field spike recoveries ranged from 44.1 to171.9% and laboratory recoveries ranged from 19.2 to102.2% with overall mean and median recoveries of75.3 and 82.7%, respectively. For the 2006 event, fieldspike recoveries ranged from )22.5 to 206.1% and thelaboratory recoveries ranged from 7.6 to 102.3% withoverall mean and median recoveries of 72.2 and 78.3%,respectively. The relatively wide range of recoveries isnot atypical for analysis of these types of compounds(Lee et al., 2004).

Differences between paired environmental and rep-licate samples and field and laboratory spike recover-ies could be attributed to analytical variability,contamination in the environmental sample, contami-nation of the spike solution, or variability in recover-ies owing to differences in physical or chemicalproperties of the ECs (Zaugg and Leiker, 2006).

RESULTS

Of the 61 ECs analyzed for, 36 were detected inone or more samples (Table 1); two of these ECs(naphthalene and phenol) were excluded from further



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ive,

top

ical

an

ti-i

nfl

am

mato

ry,

cigare

ttes

,co

ugh

dro

ps,

lin

imen

t,m

outh

wash

-0

0.5

--

⁄-97.5

⁄112.1

91.6

⁄74.6

No

np

resc

rip

tio

nd

ru

g58-0

8-2

Caff

ein

eB

ever

ages

,d

iure

tic,

mob

ile

⁄bio

deg

rad

able

-10

0.5

0.1

85

(0.7

4)

16.2

⁄-90

⁄106.1

87.1

⁄87

486-5

6-6

Cot

inin

eP

rim

ary

nic

otin

em

etabol

ite

-3

1.0

0.1

45

(0.3

3)

6.1

⁄-87.5

⁄117.2

35.6

⁄39.2

119-3

6-8

Met

hyl

sali

cyla

teL

inim

ent,

food

an

dbev

erage

ad

dit

ive,

UV

-abso

rbin

glo

tion

,to

pic

al

an

ti-i

nfl

am

mato

ry

-0

0.5

--

⁄-97.5

⁄105.8

93.6

⁄83.8

Pest

icid

e314-4

0-9

Bro

maci

lH

erbic

ide,

>80%

non

crop

usa

ge

ongra

ssan

dbru

shY

00.5

--

⁄-106.3

⁄125.5

-⁄9

8.4

63-2

5-2

Carb

ary

lIn

sect

icid

e,cr

opan

dgard

enu

se,

low

per

sist

ence

Y0

1.0

--

⁄-125

⁄105.4

82.7

⁄102.3

86-7

4-8

Carb

azo

leIn

sect

icid

e,m

an

ufa

ctu

rin

gd

yes

,ex

plo

sives

,lu

bri

can

ts-

00.5

--

⁄-86.3

⁄102.3

81.2

⁄83.6

2921-8

8-2

Ch

lorp

yri

fos

Inse

ctic

ide,

dom

esti

cp

est

an

dte

rmit

eco

ntr

olY

00.5

--

⁄-93.8

⁄113.1

80.5

⁄76.8

333-4

1-4

Dia

zin

onIn

sect

icid

e,>

40%

non

agri

cult

ura

lu

se,

an

ts,

flie

sY

00.5

--

⁄-101.3

⁄123.1

91

⁄84.1

5989-2

7-5

d-L

imon

ene

Fu

ngic

ide,

an

tim

icro

bia

l,an

tivir

al,

fragra

nce

inaer

osol

s-

00.5

--

⁄-48.8

⁄28.8

25

⁄13.9

57837-1

9-1

Met

ala

xyl

Her

bic

ide,

fun

gic

ide,

mil

dew

,bli

gh

t,p

ath

ogen

s,gol

fan

dtu

rf-

10.5

<0.2

5(0

.066)

)1.5

⁄-100

⁄143.8

96.4

⁄100.1

51218-4

5-2

Met

olach

lor

Her

bic

ide,

ind

icato

rof

agri

cult

ura

ld

rain

age

Y0

0.5

--

⁄-93.8

⁄126.3

87.7

⁄95

134-6

2-3

N,N

-die

thyl-

met

a-

tolu

am

ide

(DE

ET

)In

sect

icid

e,u

rban

use

s,m

osqu

ito

rep

elle

nt

-8

0.5

0.1

42

(0.3

7)

0⁄-

87.5

⁄125.3

88.6

⁄92.8

1610-1

8-0

Pro

met

onH

erbic

ide

(non

crop

)ap

pli

edp

rior

tobla

ckto

p-

00.5

--

⁄-101.3

⁄126.3

88.4

⁄90.1

Pla

stic

izer

80-0

5-7

Bis

ph

enol

AM

an

ufa

ctu

rin

gp

olyca

rbon

ate

resi

ns,

an

tiox

idan

t,fl

am

ere

tard

an

tY

7(4

)1.0

0.2

50

(0.5

2)

26.2

⁄15.8

101.3

⁄105.6

24.9

⁄24.5

115-8

6-6

Tri

ph

enyl

ph

osp

hate

Pla

stic

izer

,re

sin

,w

ax,

fin

ish

,ro

ofin

gp

ap

er,

flam

ere

tard

an

t-

90.5

0.0

52

(0.1

9)

6.7

⁄6.2

100.1

⁄108.5

85

⁄87.2

Po

lycy

cli

ca

ro

ma

tic

hy

dro

ca

rb

on

s(P

AH

)90-1

2-0

1-M

eth

yln

ap

hth

ale

ne

2-5

%gaso

lin

e,d

iese

lfu

elor

cru

de

oil

-0

0.5

--

⁄-91.3

⁄87.9

70.5

⁄50.2

581-4

2-0

2,6

-Dim

eth

yln

ap

hth

ale

ne

Die

sel⁄

ker

osen

e,tr

ace

ingaso

lin

e-

00.5

--

⁄-90

⁄93.4

62

⁄40.4

91-5

7-6

2-M

eth

yln

ap

hth

ale

ne

2-5

%gaso

lin

e,d

iese

lfu

elor

cru

de

oil

-0

0.5

--

⁄-87.5

⁄86

61.2

⁄42.3



TA

BL

E1.

Con

tin

ued

.

Ch

em

ica

lA

bst

ra

ct

Serv

ices

Nu

mb

er

Co

mp

ou

nd

Na

me

(co

mm

on

na

me)

Pro

ba

ble

Use

so

rS

ou

rces(1

)E

DP

1T

NO

D(n

=14)

LR

L(2

)

(lg

⁄l)

Med

ian

Va

lue

(3)

(ma

xim

um

va

lue)

(lg

⁄l)

2005

⁄2006

Dif

feren

ce

Betw

een

En

vir

on

men

tal

Sa

mp

lea

nd

Rep

lica

te(%

)

2005

⁄2006

Fie

ldS

pik

eR

eco

very

(%)

2005

⁄2006

La

bo

ra

tory

Sp

ike

Reco

very

(%)

84-6

5-1

9,

10-A

nth

raqu

inon

eM

an

ufa

ctu

rin

g⁄t

exti

les

dye,

seed

trea

tmen

t,bir

dre

pel

len

t-

00.5

--

⁄-100

⁄122.5

87.5

⁄89.6

120-1

2-7

An

thra

cen

eW

ood

pre

serv

ati

ve,

inta

r,d

iese

l,or

cru

de

oil,

com

bu

stio

np

rod

uct

Y0

0.5

--

⁄-82.5

⁄95.8

77.8

⁄72

50-3

2-8

Ben

zo[a

]pyre

ne

Reg

ula

ted

PA

H,

use

din

can

cer

rese

arc

h,

com

bu

stio

np

rod

uct

Y0

0.5

--

⁄-67.5

⁄60.3

71.3

⁄53.6

206-4

4-0

Flu

oran

then

eC

omp

onen

tof

coal

tar

an

dasp

halt

-1

0.5

<0.2

5(0

.0086)

-⁄-

86.3

⁄91.3

84.3

⁄78.3

92-2

0-3

Nap

hth

ale

ne

Fu

mig

an

t,m

oth

rep

elle

nt,

majo

rgaso

lin

eco

mp

onen

t-

5(4

)0.5

0.0

23

(0.0

27)

)9.1

⁄-(5

)89.3

⁄-73.5

⁄-

85-0

1-8

Ph

enan

thre

ne

Man

ufa

ctu

rin

gex

plo

sives

,ta

r,d

iese

l,cr

ud

eoi

l,co

mbu

stio

np

rod

uct

Y2

0.5

<0.2

5(0

.013)

-⁄-

90

⁄92.3

84.3

⁄74.3

129-0

0-0

Pyre

ne

Com

pon

ent

ofco

al

tar

an

dasp

halt

Y0

0.5

--

⁄-86.3

⁄88.8

83.6

⁄78.4

So

lven

t78-5

9-1

Isop

hor

one

Sol

ven

tfo

rla

cqu

er,

pla

stic

,oi

l,si

lico

n,

resi

n-

00.5

--

⁄-102.5

⁄114.3

94.8

⁄87.1

98-8

2-8

Isop

rop

ylb

enze

ne

(cu

men

e)M

an

ufa

ctu

rin

gof

ph

enol

⁄ace

ton

e,fu

els

⁄pain

tth

inn

er-

00.5

--

⁄-62.5

⁄37.6

44.9

⁄29.1

127-1

8-4

Tet

rach

loro

eth

ene

Sol

ven

t,d

egre

ase

r,vet

erin

ary

an

thel

min

tic

Y0

0.5

--

⁄-47.5

⁄21.6

19.2

⁄7.6

Ste

ro

id360-6

8-9

3-b

-Cop

rost

an

olC

arn

ivor

efe

cal

ind

icato

r-

92.0

0.5

25

(1.2

3)

18

⁄-60

⁄77.8

60.4

⁄49.3

83-4

6-5

b-S

itos

tero

lP

lan

tst

erol

Y6

2.0

0.6

00

(1.3

0)

36.9

⁄-62.5

⁄66.3

40.4

⁄48.9

19466-4

7-8

b-S

tigm

ast

an

olP

lan

tst

erol

-5

2.0

0.5

30

(1.6

0)

57.5

⁄-44.1

⁄75.3

48.7

⁄51.5

57-8

8-5

Ch

oles

tero

lF

ecal

ind

icato

r,p

lan

tst

erol

-9

2.0

0.8

84

(2.4

5)

22.7

⁄-55.6

⁄74.4

61.4

⁄54.5

Not

es:

ED

P,

end

ocri

ne

dis

rup

tin

gp

oten

tial

(kn

own

orsu

spec

ted

);L

RL

,la

bor

ato

ryre

por

tin

gle

vel

;T

NO

D,

tota

ln

um

ber

ofd

etec

tion

sin

clu

din

gall

esti

mate

dvalu

es(e

stim

ate

dco

nce

ntr

ati

ons

incl

ud

eth

ose

that

are

bel

owor

abov

eth

eca

libra

tion

curv

e,co

nce

ntr

ati

ons

for

com

pou

nd

sw

ith

aver

age

reco

ver

ies

less

than

60%

,or

con

cen

trati

ons

ofco

mp

oun

ds

rou

tin

ely

det

ecte

din

labor

ato

rybla

nk

s(F

url

ong

eta

l.,

2001);

UV

,u

ltra

vio

let;

Y,

yes

;-,

no

data

avail

able

,n

otca

lcu

late

d,

orn

otap

pli

cable

.C

onst

itu

ents

not

det

ecte

dd

uri

ng

eith

erth

e2005

or2006

sam

ple

even

tsh

own

ingra

yte

xt.

(1) C

omp

oun

ds

pu

rpor

ted

tobe

pot

enti

al

orsu

spec

ted

end

ocri

ne

dis

rup

tors

(In

stit

ute

for

En

vir

onm

ent

an

dH

ealt

h,

2005)

an

d(o

r)li

sted

onW

WF

Can

ad

a’s

Web

Gu

ide

toE

nd

ocri

ne

Dis

rup

tin

gC

hem

icals

,acc

esse

don

May

9,

2008

at

htt

p://w

ww

.ww

fcan

ad

a.o

rg/s

ate

llit

e/h

orm

one-

dis

rup

tors

/sci

ence

/ed

clis

t.h

tml

an

d(o

r)fr

oma

list

ofw

ides

pre

ad

pol

luta

nts

wit

hen

doc

rin

e-d

isru

pti

ng

effe

cts

from

Ou

rS

tole

nF

utu

rew

ebp

age

(htt

p://w

ww

.ou

rsto

len

futu

re.o

rg/b

asi

cs/c

hem

list

.htm

,la

stacc

esse

don

May

9,

2008).

(2) L

RL

s,d

eriv

edfr

omlo

ng-t

erm

met

hod

det

ecti

onli

mit

s,w

ere

imp

lem

ente

dst

art

ing

Feb

ruary

1,

2006.

Pri

orto

this

tim

ete

mp

orary

inte

rim

rep

orti

ng

level

s(I

RL

s),

der

ived

du

r-in

gor

igin

al

met

hod

vali

dati

on,

wer

ein

effe

ct(Z

au

gg

eta

l.,

2002;

Zau

gg

an

dL

eik

er,

2006).

(3) M

edia

nvalu

eses

tim

ate

du

sin

gU

SG

SM

ult

iple

Det

ecti

onL

imit

stati

stic

sad

d-o

nto

mod

eld

istr

ibu

tion

sof

mu

ltip

ly-c

enso

red

data

.T

his

pack

age

isan

ad

d-o

nto

S-P

LU

S�

6.1

for

Win

dow

sP

rofe

ssio

nal

Ed

itio

n(R

elea

se1).

Non

det

ect

valu

esw

ere

rece

nso

red

tole

ssth

an

the

lon

g-t

erm

met

hod

det

ecti

onli

mit

(i.e

.,h

alf

the

LR

Lor

IRL

)fo

ran

aly

sis

pu

r-p

oses

.L

og-p

robabil

ity

med

ian

valu

esre

por

ted

.D

ata

wer

en

ottr

an

sfor

med

.(4

) Sel

ecte

dco

mp

oun

ds

had

fin

al

sam

ple

size

less

than

14

du

eto

bla

nk

con

tam

inati

on,

incl

ud

ing

bis

ph

enol

A(n

=13),

nap

hth

ale

ne

(n=

10),

an

dp

hen

ol(n

=7).

(5) N

ap

hth

ale

ne

resu

lts

from

2006

sam

ple

even

tan

dp

hen

olre

sult

sfr

om2005

sam

ple

even

tw

ere

con

sid

ered

con

tam

inate

dd

ue

toqu

ali

tyco

ntr

olre

sult

san

dn

otfu

rth

eran

aly

zed

;w

hil

eth

e2005

nap

hth

ale

ne

an

d2006

ph

enol

resu

lts

are

pre

sen

ted

inth

ista

ble

,th

eyare

excl

ud

edfr

omfu

rth

eran

aly

ses

toall

owfo

rco

mp

ari

son

sbet

wee

nyea

rs.

(6) V

eld

hoe

net

al.

,2006.

(7) H

erzk

eet

al.

,2007.



analysis due to blank contamination in one of the twoyears of sampling. Twenty-five ECs were not detectedat any of the sites during either sampling event. Thenumber of detections was slightly higher for the 2006event, which was sampled at a lower flow than the2005 event (Table 2, Figure 2). Measured dischargefrom the WWTP outfall and Left Hand Creek was notsubstantially different between sampling events; how-ever, the measured discharges in 2005 on St. VrainCreek and Boulder Creek were two to ten times ashigh as in 2006. Concentrations of detected ECs weregenerally low in St. Vrain Creek and Left HandCreek upstream from the WWTP outfall, highest inthe WWTP outfall, and generally decreased down-stream from the WWTP outfall, although an increasein concentrations at Site 7 (downstream fromthe Boulder Creek inflow) was observed for someconstituents.

Patterns of detection and concentrations of ECsand chemical use categories upstream and down-stream from the Longmont WWTP, at the outfall,and from the two sampled tributaries varied consider-ably by location, year, and discharge (Figures 2 and3). For example, in 2005 only one nonprescriptiondrug, caffeine, was detected upstream from theWWTP outfall, whereas in 2006, 12 ECs in nine cate-gories were detected upstream from the WWTP out-fall. At the WWTP outfall (Site 4), 30 ECs in 13categories were detected in 2005, and 31 ECs in 13categories were detected in 2006. All but three of theECs in the WWTP outfall (ethoxyoctylphenol, metal-axyl, and 4-tert-octylphenol) were found in bothyears. Downstream from the WWTP outfall at Site 5,20 ECs in 12 categories were detected in 2005, and31 ECs in 14 categories were detected in 2006. Fur-ther downstream at Site 6 (Boulder Creek), 19 ECs in10 categories were detected in 2005, and 23 ECs in11 categories were detected in 2006. At Site 7 (the

furthest downstream), 21 ECs in 11 categories weredetected in 2005, and 26 ECs in 13 categories weredetected in 2006.

At the WWTP outfall (Site 4) detergent metabo-lites, fire retardants, steroids, fragrances, and antiox-idants were the five most frequently detected ECcategories in both years (Figure 2). Of the 36 ECsdetected during one or both sample events, 16 havebeen identified as having known or suspected endo-crine-disrupting potential (Table 1). In both years,detergent metabolites, fire retardants, and steroidswere detected at the highest concentrations at Sites4, 5, 6, and 7 (Figure 3). Total concentrations forthese three categories at these four sites frequentlyexceeded 1 lg ⁄ l in 2005 and always exceeded 2 lg ⁄ lin 2006. Most individual ECs were measured at con-centrations less than 2 lg ⁄ l; the exceptions werediethoxynonylphenol (12.4 lg ⁄ l), tris(2-butoxyethyl)phosphate (9.37 lg ⁄ l), hexahydrohexamethyl-cyclo-pentabenzopyran (2.54 lg ⁄ l), cholesterol (2.45 lg ⁄ l),and 4-nonylphenol (2.27 lg ⁄ l) (Table 1; Figure 3).Sixty-five to 71% of the analytical results from thetwo sampling events were reported to be below theLRL.

Estimates of total measured EC concentrations(and load) are not specifically relevant to toxicity butmay be associated with or related to potential for eco-system effects. These quantities also are useful forsite-to-site and year-to-year comparisons. Total mea-sured concentrations of ECs were greater for the2006 sampling event than for the 2005 event at allsites (Table 2). During the 2006 event, there was alarger relative reduction (42%) in total concentrationbetween Site 5, the first site downstream from theWWTP outfall, and Site 7, the most downstream site,than the reduction that occurred in 2005 (23%). Thedifferences in relative reductions between 2005and 2006 could be related to the frequencies of

TABLE 2. Summary of Number of Detections, Discharge, Total Concentration, and Total Load ofDetected Wastewater-Related Contaminants by Sample Event, St. Vrain Creek and Tributaries

Left Hand Creek and Boulder Creek, Near Longmont, Colorado, April 2005 and March 2006.

Site No.

2005 2006

NOD1Discharge

(m3 ⁄ s)

TotalConcentration1

(lg ⁄ l)

TotalLoad1,2

(g ⁄ day) NOD1Discharge

(m3 ⁄ s)

TotalConcentration1

(lg ⁄ l)

TotalLoad1,2

(g ⁄ day)

1 0 1.20 0 0 2 0.12 0.219 2.272 1 1.55 0.06 7.8 9 0.25 2.84 61.13 (Tributary) 0 0.13 0 0 1 0.12 0.03 0.34 (WWTP) 30 0.38 29.3 967 31 0.35 41.4 1,2555 20 2.12 6.12 1,123 31 0.76 23.4 1,5286 (Tributary) 19 2.46 6.54 1,392 23 1.29 13.7 1,5287 21 4.39 4.72 1,791 26 2.08 13.5 2,414

Notes: NOD, number of detections; WWTP, wastewater treatment plant.1Excludes phenol and naphthalene from both years.2Loads computed for detected compounds only (excludes all nondetected data, includes estimated data).



TA

BL

E3.

Mass

Bala

nce

Su

mm

ary

ofD

etec

ted

Em

ergin

gC

onta

min

an

tsby

Sam

ple

Even

t,S

t.V

rain

Cre

ekan

dT

ribu

tari

esL

eft

Han

dC

reek

an

dB

ould

erC

reek

,N

ear

Lon

gm

ont,

Col

orad

o,A

pri

l2005,

an

dM

arc

h2006.

Co

mp

ou

nd

Na

me

(co

mm

on

na

me)

2005

Accu

mu

late

dL

oa

db

yS

ites

(g⁄d

ay

)2006

Accu

mu

late

dL

oa

db

yS

ites

(g⁄d

ay

)

Lo

gK

ow

(Lo

gP

)

Sit

es

2+

3+

4S

ite

5

%D

iffe

ren

ce

Sit

es

5+

6S

ite

7

%D

iffe

ren

ce

Sit

es

2+

3+

4S

ite

5

%D

iffe

ren

ce

Sit

es

5+

6S

ite

7

%D

iffe

ren

ce

Accu

mu

late

dD

isch

arg

e(m

3⁄s

)2.0

62.1

24.5

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constituent detection. In 2005, between Sites 5 and 7,there was an increase in the number of constituentsdetected from 20 to 21, whereas in 2006 there was adecrease from 31 to 26 (Table 2).

Whereas total concentrations decreased below theWWTP outfall as ECs traveled downstream via dilu-tion and other mechanisms, total loads increaseddownstream with increasing discharge (Figures 4 and5; Table 2). During both the 2005 and 2006 samplingevents, discharge was conservative; flows differed byless than 5% between Site 5 and the sum of Sites 2,3, and 4 and between Site 7 and the sum of Sites 5and 6. In 2005, the WWTP discharge was equal to18% of the flow at Site 5, whereas in 2006 it equaled46% of the flow at Site 5. In 2005, the outflow fromthe Longmont WWTP comprised 86% of the totalmeasured EC load at Site 5, and 54% at Site 7. In2006, the outflow from the Longmont WWTP con-tained 82% of the total EC load at Site 5, and 52% atSite 7 (Table 2). In 2005 and 2006, the total EC loadsfrom Boulder Creek (Site 6) were larger than theloads contributed by the Longmont WWTP (Figure 4;Table 2), and total EC load was not transported con-servatively. In both years, total EC load increasedbetween 13 and 14% between (the sum of loads at)Sites 2, 3, and 4 and at Site 5. Total EC load thendecreased between (the sum of loads at) Sites 5 and 6and Site 7 by 29% in 2005 and by 21% in 2006. TotalEC load was higher in 2006 (the lower flow year)than in 2005 (Figure 4; Table 2).

The accuracy of the load estimates could beaffected by error in the discharge measurements anduncertainty associated with the analytical results.Most discharge measurements used for this studyhave a quality rating of ‘‘fair to good’’ and should bein error by no more than 5-8% (Rantz et al., 1982).The exceptions are discharge measurements for Site3, which are rated ‘‘poor’’ and may be in error bymore than 8%, and discharge measurements for Site7, which are rated ‘‘good’’ with errors of 2-5%. Thelimited quality control data collected by this studyindicate that analytical variability may introduceuncertainty in the measured concentrations that arelarger than 10% and which could consequently affectthe load calculations.

Certain individual ECs exhibited largely conserva-tive behavior, whereas others accumulated or attenu-ated downstream from the WWTP outfall (Table 3).For example, in 2006, the Longmont WWTP contrib-uted 72% of the load of bisphenol A at Site 5 (Fig-ure 5), and the load at Site 5 was approximately thesame as (4.8% greater) the sum of the loads at Sites2, 3, and 4. Similarly conservative behavior wasrecorded downstream where the load at Site 7 wasapproximately the same as (0.4% less) the sum of theloads at Sites 5 and 6. Some ECs behaved differently

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FIGURE 2. Number of Emerging Contaminants Detected, by Chemical Use Category, During (A) 2005 and (B) 2006 Sampling Events,St. Vrain Creek and Tributaries Left Hand Creek and Boulder Creek, Longmont, Colorado (see Figure 1 for site locations).

FIGURE 3. Concentration of Emerging Contaminants, by Chemical Use Category, and Discharge Detected During (A) 2005 and (B) 2006Sampling Events, St. Vrain Creek and Tributaries Left Hand Creek and Boulder Creek, Longmont, Colorado (see Figure 1 for site locations).



at different locations. For example, in 2005, the Long-mont WWTP contributed 66% of the load of caffeineat Site 5, where the load was greater (14%) than thesum of the loads from Sites 2, 3, and 4; but fartherdownstream the load at Site 7 was less (14%) thanthe sum of the loads at Sites 5 and 6 (Figure 5).Selected ECs showed substantial attenuation as theytraveled downstream from the WWTP outfall. Forexample, in 2006, the Longmont WWTP contributed84% of the load of diethoxynonylphenol at Site 5,where the load was greater (10.7%) than the sum ofthe loads from Sites 2, 3, and 4; but the load at Site 7

was much less (37.3%) than the sum of the loads atSites 5 and 6 (Figure 5; Table 3).

DISCUSSION

The results indicate that outfalls from WWTPs arethe largest, but are likely not the sole, sources of ECsto St. Vrain Creek. Additional potential sources ofECs not identified during this study could include

FIGURE 4. Discharge (A and C) and Total Measured Contaminants Load (B and D) During 2005 and 2006Sampling Events, St. Vrain Creek and Tributaries Left Hand Creek and Boulder Creek Near Longmont, Colorado.



ground water, seepage from bank storage and indi-vidual sewage disposal systems, storm drains, non-point runoff, and atmospheric deposition. During the2005 and 2006 sampling events, discharge wasconservative and streamflows differed by less than5% between Site 5 and the sum of Sites 2, 3, and 4and between Site 7 and the sum of Sites 5 and 6.Therefore, relative changes in EC loads are mostlikely related to factors other than differences instreamflow. In 2005 and 2006, the total EC loadsincreased along the Longmont urban corridor byapproximately 13-14%. The increase in loads betweenthe sum of Sites 2, 3, and 4 (the WWTP outfall) andSite 5 (downstream of the WWTP outfall) may indi-

cate contributions of ECs either from upstream of theWWTP or from the WWTP directly that were too lowto be detected individually. ECs might also be con-tributed to the stream between the outfall and Site 5(a distance of about 1 km), though no specific sourceswere identified.

Further downstream, the concentrations andloads of most measured ECs attenuated. For exam-ple, in 2006 the percent difference between the sumof loads from Sites 5 and 6 was greater than theSite 7 load for 30 compounds (10 of which differedby more than 20%) and less than the Site 7 loadfor two compounds (one of which differed by morethan 20%); the other 27 ECs were not detected at

FIGURE 5. Loads of (A) Bisphenol A, (B) Caffeine, and (C) Diethoxynonylphenol, During 2005 or 2006Sampling Events, St. Vrain Creek and Tributaries Left Hand Creek and Boulder Creek Near Longmont, Colorado.



all three sites and naphthalene and phenol wereexcluded. In 2005, the percent difference betweenthe sum of loads from Sites 5 and 6 was greaterthan the Site 7 load for 18 compounds (two ofwhich differed by more than 20%) and less thanthe Site 7 load for seven compounds (three of whichdiffered by more than 20%); the other 34 ECs werenot detected at all three sites and naphthalene andphenol were excluded (Table 3). The amount ofattenuation (percent difference between the sum ofloads from Sites 5 and 6 and the Site 7 load) wasgreater in 2005 (29%) than in 2006 (21%), eventhough 2006 had lower flow conditions and corre-spondingly slower travel times that would promotedegradation, volatilization, biological uptake, oradsorption. This apparent decrease in attenuationin 2006 may be the result of reduced dilution bythe stream resulting in more frequent detection ofECs downstream from the WWTP outfall. Total con-centration and total load of ECs were higher atSite 7 in 2006 than in 2005, even though dischargewas 53% less. Physical and chemical characteristicssuch as stream temperature, that could affect howcontaminants behave as they travel downstream,varied by compound. Additionally, partitioning tosediment may result in attenuation of selected ECs.ECs, such as the steroids, have relatively high octa-nol-water partitioning coefficients (Kow) and wouldbe expected to adsorb to sediments, whereas others,like the nonprescription drugs caffeine and cotinine,have very low Kow values and would be expected toremain in solution (Table 3). However, a consistentpattern between Kow values and attenuation oraccumulation of ECs was not found in this study.Analytical variability may have influenced theobserved differences in loads, as some contaminantsthat were detected at relatively high concentrationssuch as b-stigmastanol have relatively poor analyti-cal reproducibility (Table 1).

Substantial attenuation of many wastewater-derived contaminants in a large effluent-dominatedriver was noted by Fono et al. (2006), but in that sys-tem, travel times were measured in days rather thanminutes. In the studied portion of St. Vrain Creek,there was evidence of various levels of attenuationfor most ECs (Figures 4 and 5; Table 3). In St. VrainCreek, the amount of attenuation observed was notsufficient to prevent aquatic biota from being exposedcontinuously to a wide range of ECs downstreamfrom the Longmont WWTP and in Boulder Creeknear the confluence with St. Vrain Creek (Table 3).St. Vrain Creek harbors native fish species andmacroinvertebrate communities that have declined orare absent in other parts of the South Platte RiverBasin (Zuellig et al., 2007). The extent to which ECsin St. Vrain Creek affects these organisms is

unknown, but recent studies have shown that fishcan respond to very low concentrations of someorganic or estrogenic contaminants (Brian et al.,2007; Quiros et al., 2007).

ACKNOWLEDGMENTS

The authors acknowledge those from the USGS and from theCity of Longmont who helped with field work. Additionally, com-ments provided by Jennifer L. Flynn, Betty Palcsak, and Allan D.Druliner (USGS Colorado Water Science Center), Lori Sprague(USGS National Water Quality Assessment Program), and CalvinYoungberg (City of Longmont Water and Wastewater Department)were greatly appreciated.

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Lagrangian Sampling for Emerging Contaminants Through an Urban Stream Corridor in Colorado

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