Reproduced from Journal of Environmental Quality. Published by ASA, CSSA, and SSSA. All copyrights reserved. ukt n odr,20) n neethsfocused has 1991; interest al., and et 2002), Postma Cowdery, 1986; and al., within Puckett et occur Trudell to (e.g., shown aquifers been has Korom Denitrification by (1992). detail in reviewed process a denitrification, by ugssasmlrpten(abs n ee,1996). Resek, use NO and pesticide conditions (Barbash reducing on pattern Under information similar as a and nitrogen suggests 20-fold, of increased than has use States more United the the 1945, in fertilizer since commercial that communication, indicate written (USGS) USGS, 2003) Survey Ruddy, Geological (Barbara States data United Larson 1997). 1996; al., Helsel, and et Mueller Bar- 1996; 1995; Resek, on and (Puckett, bash impacts quality potential surface-water their and ground- over concern generated has 7 .SgeR. aio,W 31 S A xnlcacid. oxanilic OA, USA 53711 WI Madison, Rd., Segoe S. 677 © Processes Watershed doi:10.2134/jeq2005.0109 and (2005). Landscape 34:2278–2292 Reports: Qual. Technical Environ. J. in Published for is *Corresponding paper 2005. this Mar. ([email protected]). 28 in by Received author endorsement names Survey. constitute Geological trade not U.S. does of the and use only purposes The identification 30360. Reston, GA Center, Road, Amwiler National 3039 Norcross, Survey, Geological 413 U.S. Hughes, Survey, W.B. 20192. Geological VA U.S. Puckett, L.J. W and water ground in water. contaminants surface of when fate setting and hydrogeologic transport the investigating understanding of importance the out stream Cl increasing of periods, high-flow during stream dominates chemistry drainage subsurface Cl shallow of Conversely, degradates. concentrations in place decrease causing takes periods, a low-flow greatest exchange during its chemistry had water chemical surface-water Ground on streambed. influence and the of m dominant creek 0.7 upper a the the within not to discharges was ground water that denitrification indicated data but chemical and the Hydrologic age, factor. of controlling use and before depth recharged NO increasing had of water ground Concentrations the pesticide. that persistence this or sam- that limited in suggests aquifer compounds is the degradate in and deeper parent from collected both ples of previous the absence were during The recharged and yr. were 18 that compounds, waters parent ground pesticide in of present of still those concentrations exceeded detected, were greatly they degradates which in samples from all downgradient ( and corn beneath the directly concentrations frequency largest greatest with and Or- water degradate in ground in pesticide Creek, detected and Castle were concentrations Pesticide Cow Carolina. stream, South adjacent County, and angeburg aquifer investigated were shallow pesticides a and surface-water in nitrate of and fate ground- and on Transport pesticides quality. and nutrients of application S,CS,SSSA CSSA, ASA, hr scniun ocr vrptnilipcso widespread of impacts potential over concern continuing is There Ϫ ,NO al irt (NO nitrate larly dsra use idespread e mays Zea 3 Ϫ rnpr n aeo irt n etcds yrgooyadRiparian and Hydrogeology Pesticides: and Nitrate of Fate and Transport etcds n etcd erdts hs eut point results These degradates. pesticide and pesticides, , . il hr hywr ple.I almost In applied. were they where field L.) ABSTRACT farclua hmcl,particu- chemicals, agricultural of 3 Ϫ n aiu rai pesticides, organic various and ) 3 Ϫ Ϫ ngon ae erae with decreased water ground in ,NO 3 Ϫ scnetdt N to converted is 3 Ϫ etcds n pesticide and pesticides, , ar .Pcet n .BinHughes Brian W. and Puckett* J. Larry concentrations oeProcesses Zone 2 gas 2278 ieesmyb iie ysvrlhdoelgcfac- hydrogeologic the several by around limited from be NO studies may that tiveness concluded zone and riparian States United 13 remove of to results zones riparian of NO effectiveness the predict water ground to lithology NO riparian to link that findings “concep- models that extrapolate tual concluded (2000) al. to et Devito difficult areas. other similar it in conducted making been had settings, studies He most that processes. felt also biogeochemical hy- on that consider controls adequately concluded drogeologic to and failed had zones research riparian previous in processes moval Puckett 1996; Hill, 1993; plant 2002). al., al., and et et denitrification Haycock (e.g., through uptake water ground from aeso h iwsenUie tts(akofet (Kalkhoff States United midwestern al., the et surface and of 2001) (Kalkhoff al., waters et Kolpin waters 1999; al., ground et Burkart 1998; in pesticides organic et Accinelli 2001). 1968; al., Chesters, acidic and under (Armstrong particularly conditions processes, microbial than tant below on information paths inadequate still flow is some there of deep research, spite recent In along zones. reducing water organic-rich shallower, ground move- (v) of and ditches; and ment drains of use extensive to due NO low of containing water concentrations ground older NO with waters reactions remove enriched slow completely even along allowing in to times paths residence denitrification flow long total ground-water (ii) (i) aquifer; upgradient include the factors These tors. o ta. 92 hple 93 ogee l,1994; such impor- pesticides, al., more some be et may least transformations Loague at abiotic atrazine, For 1993; as 2001). Chapelle, al., et 1992; (McMa- Vinther al., aquifers in et depth with hon decrease to shown been o n/rmcoilppltos hc eeal have generally which populations, microbial and/or bon nteaiiyo iainbfe oe ormv NO remove to zones buffer riparian of ability the on ainrtsmyb iie ytelc fognccar- organic of lack the by limited be biotransfor- Fur- may that 2001). rates suggest al., mation studies et of number Vinther a 1992; either al., thermore, al., in et et (Wehtje than McMahon zones zone saturated 1983; soil or shallow unsaturated deep the the in rates faster biotransformation much that are shown have water ground et Devito by envisioned (2000). model al. conceptual of type the a oe nawd nuhrneo etnst develop to settings of range enough wide a in zones ian yrgooi otoso NO on controls hydrogeologic o;EA taesloi cd C,mxmmcnaiatlevel; contaminant maximum MCL, acid; ethane-sulfonic ESA, bon; Abbreviations: il(96 eiwdNO reviewed (1996) Hill eetsreso h curneaddsrbto of distribution and occurrence the of surveys Recent tde ftetasotadft fpsiie in pesticides of fate and transport the of Studies 3 3 Ϫ Ϫ narneo adcps”Pcet(04 examined (2004) Puckett landscapes.” of range a in yaisaencsayt mrv u blt to ability our improve to necessary are dynamics F,clrfurcro;DC isle rai car- organic dissolved DOC, chlorofluorocarbon; CFC, 3 Ϫ i)bpsigo iainzones riparian of bypassing (iv) ; 3 Ϫ 3 Ϫ ii iuino NO of dilution (iii) ; 3 Ϫ rnfrainadre- and transformation rnpr hog ripar- through transport 3 Ϫ eoa effec- removal 3 Ϫ 3 Ϫ – Reproduced from Journal of Environmental Quality. Published by ASA, CSSA, and SSSA. All copyrights reserved. sdt oe h esnlyhg ae al nagricultural in table water high seasonally the are lower ditches and to tiles used Drain Paleaquults). semi- Typic siliceous, thermic active, (fine-loamy, as Rains and (1988) Paleudults), Aquic thermic Oxyaquic DeFrancesco subactive, thermic siliceous, by (fine-loamy, subactive, Noboco classified Paleudults), siliceous, were Soils (fine-loamy, sand. site clayey Goldsboro sand study and sand, coarse the silty sand, very at by to underlain upland are coarse horizons; areas organic (1984). some by and al. beds shell underlain with et interbedded is McCartan floodplain by described The 2). discontin- limestone, and (Fig. thin sandy a deposits is uous site calcareous the at encountered and unit characterized deepest clay, is The site sand, study interbedded the by at several geology and areas Near-surface wooded of fields. consists and dis- 1), (Fig. and Creek Castle system flow shallow streams. of nearby the much to through charges 1996); moves (Aucott, water systems the flow inter- regional shallow, of and series mediate, a comprising stratified, is system water eligaufr yacniigui,cmrsn variety a ranging conductivities comprising hydraulic 3 unit, from estimated confining un- with other materials, a and of by aquifer Floridan aquifers the surficial derlying The from thick. separated m 12 is to aquifer up typically 1984) al., et (McCartan iilwtrtbeaufri opsdo Pleistocene-age, of deposits composed floodplain Holocene-age eroded and is deposits relief, terrace low aquifer coastal of sur- water-table The series swamps. a ficial and of streams area low-gradient with an escarpments in 1), (Fig. Carolina eoete ece h daetcreek. adjacent the reached levels they undetectable before pesticide to the mineralized selected be and and would pesticides aquifer degradates (ii) shallow the and the zone, in in riparian times denitrification travel of Our NO cause long contaminants. (i) to system these due ground-water of that fate were setting and hydrogeologic hypotheses transport the and of the role aquifer in the surficial determine objective to a specific was One in stream. degradates connected hydraulically their and cides NO of of fate fate and and transport long-term the pesticides. natural long many about the how known in to little is Consequently, persist 2003). as al., et actually information (Kalkhoff environment may little compounds is these there but contami- nants, organic of McMahon degradation significant rates and in flow result ground-water (1983) may slow pesticides that al. the suggested (1992) et when al. Wilson et exactly wells. know the to reached difficult is it inter- screened vals, variable-length sam- yr with they 33 wells Because domestic to collection. pled 2 sample from of recharged time have the before to persisted dated had water pesticides ground et selected in Spurlock that showed recently, (2000) More al. concentrations. based classification tritium post-1953 results and on pre- their a to However, limited and were frequency. age detection ground-water on pesticide (1995) information al. et direct Kolpin provided compounds. parent the concen- the than and frequency tration of greater in degradates persisted often her- that bicides chloroacetanilide and revealed triazine used have commonly most 2003) 1998, al., h td iei ato ar am daett Cow to adjacent farm, dairy a of part is site study The h td rai oae nOagbr ony South County, Orangeburg in located is area study The transport the examined we here reported study the In ϫ 10 Ϫ 5 o2.8 to 3 Ϫ n h essec fslce pesti- selected of persistence the and , ϫ TD AREA STUDY 10 Ϫ 4 md UKT UHS RNPR N AEO IRT N PESTICIDES AND NITRATE OF FATE AND TRANSPORT HUGHES: & PUCKETT Ϫ 1 3 Ϫ Act,19) h ground- The 1996). (Aucott, ol ermvdbe- removed be would a ple slqi hmclfriie otehyfeda a at field ha hay kg 340 the ha provided to kg fertilizer 220 of chemical rate liquid as applied nitrogen commercial 1996, was and in that manure indicate animal records areas of Farm form fertilizer. crop chemical the the in site to study applied the of is written USGS, Fertilizer Ruddy, 2003). (Barbara P communication, Mg 36 1997 and N during Mg deposition 185 totaled atmospheric inputs and manure, phosphorus fertilizer, and as nitrogen station, streamgaging USGS incise is surface. and wide floodplain chan- m stream 6 The about straightened is area. been nel study has the throughout creek channelized The and the forest. with of riparian floodplain vicinity 200-m-wide deciduous a the a has In Creek Castle water. Cow and site, ground study drains it discharging tile as reaches through or Creek drainage ditches Castle subsurface Cow shallow Conse- to as 2003b). either moving 2003a, water 3.4 (Wolock, only most streamflow for quently, total account of to 4.3% estimated h been to cm has 7.4 flow overland at and high relatively is permeability yr mm 1200 approximately tiled. not are that soils drained ( Pine areas. ebcd ,- a ple otehyfeda aeo 0.8 of rate a at field hay the to ha applied kg 0.7, was ha 1.3, records, of 2,4-D kg rates farm herbicide at 0.6 field to corn and and the according 0.9, to metolachlor, applied 1996, atrazine, were in which ametryn, 2,4-D, site herbicides the study Pesticides included the (Naomi 230 2003). simazine at metolachlor, communication, kg used 10 kg written and 380 USGS, chlorpyrifos, atrazine, Nakagaki, kg 250 kg alachlor, 600 kg of consisted 1997 ah opiig2 apigprs eeisaldi transect a in installed were ports, sampling 27 comprising each, eesi h utpr el eemaue sn portable a 1988). using al., measured et were (Winter wells manometer multiport the water whereas in tape electric as levels an serve using to measured 5-cm-diameter were 3 the wells in and PVC levels 2 this Water Sites of wells. Well reference wells multiport water-level other was at Two it installed wells. where were multiport type de- depths the at install wells m sampler to water-table 3 difficult multiport to the deepest 1 completed to the were below similar generally wells was These Construc- above. wells installed. scribed also these were of screen tion 1.5-m-long a with wells 2). (Fig. increasing and depth interval (I with shallowest the numerals at Roman beginning using V) Castle labeled through were Cow intervals Individ- in screened upgradient. were order ual beginning sites increasing in 7) Well proceeding and through (1996). Creek Landon (1 and numerically Delin labeled proce- a by flow following constructed outlined ground-water were dure wells of These 2). direction and 1 predominant (Fig. the to parallel n lnteisalto ftescn ewr fwells. of network second map the water-table of a develop installation to the used plan was and levels water of moni- toring subsequent and installation well during collected mation hoie(V)pp ih15mln lte V screens. PVC slotted 1.5-m-long with pipe (PVC) These chloride polyvinyl table. threaded 5-cm-diameter, water with the constructed ground- were in wells of fluctuations seasonal direction and predominant flow water the determine to installed etcd s nteCwCsl re aese during watershed Creek Castle Cow the in use Pesticide 62-km the Within 17.5 is temperature average Annual tmliotWl ie hog ,5c-imtrPVC 5-cm-diameter 7, through 4 Sites Well multiport At ee utpr el ihtret iesmln ports sampling five to three with wells multiport Seven ntesme f19,1 hlo ae-al el were wells water-table shallow 15 1996, of summer the In Ϫ 1 fatv nrdet oisciie eeapplied. were insecticides no ingredient; active of Pinus ae apeCollection Sample Water Ϫ 1 Ϫ p. re r rw naeswt poorly with areas in grown are trees spp.) Ϫ aueapidt h onfedi 1996 in field corn the to applied Manure . 1 2 1 fntoe n 1 gha kg 310 and nitrogen of o ateCekwtrhdaoethe above watershed Creek Castle Cow fatv nrdet epciey The respectively. ingredient, active of METHODS Ϫ 1 OesyadEel 92.Soil 1992). Ezell, and (Owensby eo h surrounding the below m 2 d Њ ,adpeiiainis precipitation and C, Ϫ 1 Wlc,1997), (Wolock, Ϫ 1 phosphorus. Infor- 2279 Reproduced from Journal of Environmental Quality. Published by ASA, CSSA, and SSSA. All copyrights reserved. i.1 oainmpadara htgah(eodd2 e.19)o h td iesoiglctoso motn adcp etrsand features landscape important of locations showing site study the of 1995) Feb. 22 (recorded photograph aerial and map Location 1. Fig. 2280 h td rnetA–A transect study the ؅ h td rneti hw ncosscinve nFg 2. Fig. in view cross-section in shown is transect study The . .EVRN UL,VL 4 OEBRDCME 2005 NOVEMBER–DECEMBER 34, VOL. QUAL., ENVIRON. J. Reproduced from Journal of Environmental Quality. Published by ASA, CSSA, and SSSA. All copyrights reserved. ethrzn rmSts2ad6(i.2 eesre nomntrn fe xrcino -8sldpaecartridges; solid-phase C-18 on extraction after monitoring 0.018 into selected sorted were were analyses these 2) for Samples (Fig. diffraction. X-ray 6 by and 2 and Sites bulk from horizons ment ac,p,adtmeaue tblzd(oeb ta. 1995). al., et (Koterba stabilized temperature, and pH, tance, utpevria etosuigaUG H8 et-nert a esrd nrai a acltda h difference acid the hydrochloric as to calculated exposed was rating was Teflon C calibrated a 3-L sample inorganic on a based measured; duplicate discharge and recorded to was A converted were nozzle and station NJ). hourly streamgaging Teflon the using at 7.9-mm (C) levels carbon Water a total bottle. for in with analyzed was sampler collected sample depth-integrat- each ing DH-81 were of USGS 1); aliquot were a using samples (Fig. sections samples vertical multiple creek Surface-water 1996, the October weekly. and through collected transect 1996 well February from the downstream during km of 1 intersection about station the streamgaging September a through at 1995 1998, October from monthly proximately ni il aaees nldn isle O dissolved continuing including pumping parameters, with field volumes were until well wells three least sampling, at Before of purged contamination. cross prevent to io uigwsdsaddatrec utpr a sampled was multiport each after the and discarded cleaned 1995) was was al., tubing used et tubing Viton was (Koterba Teflon protocols tubing The standard Viton to head. according of pump section peristaltic the 30.5-cm stainless in a the and to attached tubing was steel tubing using Teflon sampled pump. were peristaltic wells protocols a multiport The standard 1995). al., using et sampled (Koterba were The 1998. wells August and large-diameter 1998, April 1997, November result in a samplers as reach. occurred the have within test may discharge to that ground-water transect, discharge of well in multiport changes 168- the a for within bracketing sites reach five at m-long 1969) Somers, and (Buchanan meter uv.O e.19,fo a esrdwt current a with measured was flow 1998, Dec. 3 On curve. A–A transect study the along locations well sample and units Hydrogeologic 2. Fig. eietsmlscletdfo aiu itntv sedi- distinctive various from collected samples Sediment ae ape eecletdfo o ateCeka-t rvd ecito fmnrlg tsvrlpit across points several at mineralogy of description a provide to ap- Creek Castle Cow from collected were samples Water rudwtrsmlswr olce rmtemultiport the from collected were samples Ground-water Ͻ 1- ␮ -iefatosadaaye o mineralogy for analyzed and fractions m-size eietAnalyses Sediment UKT UHS RNPR N AEO IRT N PESTICIDES AND NITRATE OF FATE AND TRANSPORT HUGHES: & PUCKETT 2 pcfcconduc- specific , aorpyms pcrmty(CM)wt eetdion selected with chro- (GC–MS) gas by spectrometry chlorpyrifos matography–mass and cyanazine, tebuthiuron, meton, eotn iisfrteecmonsrne rm001to 0.001 from ranged compounds these for limits reporting 8ognccmons(ebr 01 nldn acetochlor, pro- including simazine, deethylatrazine, 2001) atrazine, metolachlor, (Reuber, alachlor, compounds organic 88 ec,K Tbe1.TeNQ apewsaaye for analyzed was sample NWQL The 1). (Table KS rence, ewe oa n rai Hde n tr,1984). Stern, and (Hedges C organic content and C total organic between which after C, inorganic remove Lakewood, to Elantach, fumes (CE separate analyzer A elemental locations. Erba these Carlo at a aquifer the of thickness the oteUG rai eerhLbrtr OL nLaw- in (ORL) other Laboratory the Research and Organic NWQL the USGS to the shipped to was bottle One bottles. n remn 99 iha,19;Wrhwe l,1987). al., 0.7- et Wershaw 1993; (Fishman Fishman, spectrometry 1989; infrared Friedman, and and ion oxidation by persulfate anions by DOC analyzed and spectroscopy, methods, were colorimetric by plasma nutrients silica chromatography, were coupled and analyses Cations inductively and acid. cation by nitric pesticides, for with collected nutrients, preserved samples by anions, in carbon; analyzed cations, (NWQL) organic were for Laboratory Samples Quality CO, Water field. Denver, National the USGS carbon in the organic measured dissolved were for alkalin- and ity used conductance, pH, was Temperature, samples). filter [DOC] silver (a filters ape o nlsso etcdswr itrdthrough filtered were pesticides of analyses for Samples ae ape eeflee hog 0.45- through filtered were samples Water ␮ ae-ls ie itr notoabr baked-glass amber, two into filters fiber baked-glass m ␮ gL ؅ nFg 1. Fig. in Ϫ 1 h R apewsaaye o 3compounds 23 for analyzed was sample ORL The . ae apeAnalysis Sample Water ␮ nitrocellulose m 2281 Reproduced from Journal of Environmental Quality. Published by ASA, CSSA, and SSSA. All copyrights reserved. td r rsne nTbe2. Table in presented are study 98.Rslswr orce o ouiiyi apewtradPumr 92.Sml gswr sindo h basis the on assigned were ages Sample 1992). Plummer, and water sample in solubility al., for et corrected (Busenberg were samplers Results glass 1998). of headspaces in extraction agdfo 0.05 from ranged apetp iepro ain nosNtinscro WLORL NWQL carbon Nutrients Anions Cations period Time type Sample re-fmgiuegetrta hs tteNQ,ad(etnadVgl 91 lce-ahee ta. 1998). al., et Blicher-Mathiesen 1981; Vogel, and (Heaton to discharges water ground the until and solution NWQL, in an remain the about will at were those ORL the than by greater analyzed order-of-magnitude compounds Reporting for simazine. and limits atrazine acid as ethane-sulfonic well and as degradates, (OA) (ESA) acid oxanilic their and lachlor, oebr19 eeaaye ygscrmtgah fe a hoaorpywt eeto ii f03p kg pg 0.3 of limit detection a with chromatography gas after chromatography gas by analyzed were 1997 November rudwtrNvme 97XXXXXX X X NA X NA‡ X X X X X analyzed were ORL labeled those and CO, analytes. Denver, respective in the Laboratory Quality for Water analyzed National Not X USGS ‡ the at analyzed were NWQL labeled samples Pesticide 1997 † November monthly 1998, 1995–September October water Ground study. water the Surface during periods time various at collected samples surface-water and ground- in determined Analytes 2. Table the of periods time 2002). various al., during et collected Puckett surface- resulting and 1981; Meyer nitrogen samples ground- of in 1990; water measured amount al., groups the Analyte et estimate 1993). (Thurman al., to extraction et cartridges used after were solid-phase water quantitation C-18 (HPLC) and on detection chromatography diode-array liquid ana- with were high-performance analytes by latter The of limits, lyzed separately. reporting error reported the an are in have differences results of and Because temperatures degradates. laboratory for at meto- alachlor, acetochlor, including Method† 1998) al., et (Kolpin chromotography. liquid high-performance HPLC, spectrometry; origin chromatography–mass or gas Use GC–MS, † name Chemical 2-chloro-2 HPLC degradate herbicide 2-chloro- HPLC acid 2-[(2-ethyl-6-methylphenyl)(ethoxymethyl)amino]-2-oxoacetic degradate herbicide Alachlor acid (OA) sulfonic acid 2-[(2-ethyl-6-methylphenyl)(ethoxymethyl)amino]-2-oxoethane oxanilic Acetochlor study. acid this ethane-sulfonic for Acetochlor Laboratory Research Organic Acetochlor the by analyzed products name degradation Common herbicide and Herbicides 1. Table 2282 ynzn -[-hoo6(tyaio-,,-rai--laio--ehlpointiehriieGC–MS herbicide 2-chloro- propionitrile 2-[[4-chloro-6-(ethylamino)-1,3,5-triazin-2-yl]amino]-2-methyl HPLC 2-chloro-4-(1-carbamoyl-1-methyl-ethylamino)-6-ethylamino- degradate herbicide HPLC 2-hydroxy-4-(ethylamino)-6-(isopropylamino)- 2-chloro-4-ethylamino-6-isopropylamino- Metolachlor 2-(ethylamino)-4-isopropylamino-6-methyl-thio- amide Cyanazine degradate herbicide Cyanazine acid 2-amino-4-chloro-6-(ethylamino)- 2-[(2,6-diethylphenyl)(methoxymethyl)amino]-2-oxoacetic 2-amino-4-chloro-6-(isopropylamino)- (HA) Hydroxyatrazine acid sulfonic 2-[(2,6-diethylphenyl)(methoxymethyl)amino]-2-oxoethane (DIA) Deisopropylatrazine (DEA) Deethylatrazine Atrazine Ametryn OA Alachlor ESA Alachlor ebty 2-tert-butylamino-4-ethylamino-6-methylthio- 2-chloro-4,6-bis(ethylamino)- 2-chloro-4,6-bis(isopropylamino)- HPLC 2-chloro- HPLC 2,4-bis(isopropylamino)-6-(methylthio)- 2,4-bis(isopropylamino)-6-methyoxy- degradate herbicide 4-amino-6-(1,1-dimethylethyl)-3-(methylthio)-1,2,4-triazin-5(4 degradate herbicide 2-[(2-ethyl-6-methylphenyl)(2-methoxy-1-methylethyl)amino]-2-oxoacetic Terbutryn Simazine Propazine 2-[(2-ethyl-6-methylphenyl)(2-methoxy-1-methylethyl)amino]-2- Propachlor Prometryn Prometon Metribuzin OA Metolachlor ESA Metolachlor tteUG rai eerhLbrtr nLwec,KS. Lawrence, in Laboratory Research Organic USGS the at (ESA) isle N Dissolved 2 n ri rudwtrsmlscletdin collected samples ground-water in Ar and ␮ pi 98XXXXXNA NA NA X X X X NA NA X X X X X X X X X X X X X X X 1998 August 1998 April monthly 1998, 1997–March April weekly 1996, February–October gL isle Gases Dissolved Ϫ 1 o aetcmonst 0.2 to compounds parent for acetamide xehnsloi cd(metolachlor) acid acid oxoethanesulfonic .EVRN UL,VL 4 OEBRDCME 2005 NOVEMBER–DECEMBER 34, VOL. QUAL., ENVIRON. J. N N N ؅ -(ethoxymethyl)- -(2-ethyl-6-methylphenyl)- iorplctnld ebcd GC–MS herbicide -isopropylacetanilide -6 ؅ -diethyl- N (ehxmty)aeaiiehriieGC–MS herbicide -(methoxymethyl)-acetanilide N ␮ s (-ty--ehlhnlaeaiehriieGC–MS herbicide -(2-ethyl-6-methylphenyl)acetamide tizn ebcd GC–MS herbicide -triazine gL s s tizn ebcd GC–MS herbicide -triazine tizn ebcd erdt GC–MS degradate herbicide -triazine Ϫ 1 s N tizn ebcd GC–MS herbicide -triazine s tizn ebcd erdt GC–MS degradate herbicide -triazine (-ehx--ehlehl ebcd GC–MS herbicide ethyl) -(2-methoxy-1-methyl s tizn ebcd GC–MS herbicide -triazine s tizn ebcd GC–MS herbicide -triazine F-1adCC1,ad10p kg pg 1.0 and CFC-12, and CFC-11 au ne nutapr irgnamshr n eeflame were and atmosphere appa- nitrogen ultra-pure sampling an steel under stainless ratus a using 1997 November in lected hrfr,cnetain fN of atmosphere concentrations the Therefore, with equilibrates and body surface-water a lme,19) ape eeaaye yelectron-capture and by (Busenberg analyzed were ampoules Samples glass 1992). borosilicate Plummer, 62-cc in sealed CC1) CF (CFC-11), al., et Vogel 1981; Vogel, and (Heaton denitrification from ne otcniin,teN the conditions, most Under s s tizn ebcd GC–MS herbicide -triazine tizn ebcd erdt HPLC degradate herbicide -triazine ape o nlsso h hoolooabn CFCl chlorofluorocarbons the of analyses for Samples s tizn ebcd GC–MS herbicide -triazine hoolooabnAeDating Age Chlorofluorocarbon 2 s Cl H tizn ebcd erdt GC–MS degradate herbicide -triazine -n ebcd GC–MS herbicide )-one 2 CC1) n C and (CFC-12), 2 a rdcdb denitrification by produced gas Organic 2 (acetochlor) (acetochlor) simazine) cyanazine, (atrazine, (cyanazine) (alachlor) (alachlor) (atrazine) propazine) (atrazine, (metolachlor) n rgssdsovdin dissolved gases Ar and Ϫ 2 F 1 3 o F-1 (Busenberg CFC-113 for Cl 3 CC13 eecol- were (CFC-113) Pesticides† Ϯ 2to4%. Ϫ 1 for 3 Reproduced from Journal of Environmental Quality. Published by ASA, CSSA, and SSSA. All copyrights reserved. ihnte18mln ec a bu 2 about was reach 168-m-long the within idws02 m pe- 0.21 sampling was 1998 September riod through 1995 October the eepce o temta eevsground-water discharge receives ground-water that overall stream Therefore, a discharge. would for discharges drain expected tile be no during with were flow period low-flow in changes the increase these This site, error. transect measurement within well de- the discharge from down- section stream Although 68-m-long the overall. through somewhat 85-m-long creased and 13.4% site the transect by through the from increased 22% upstream reach as the of much section as by discharge that increased indicated 1998 December during creek the temwtr(al )wr Ca were 3) (Table water stream s s HCO n O and ac fgon-ae icag samjrcompo- Ca major Conversely, time. a that at as baseflow stream discharge of impor- nent ground-water increased the of and flow, tance zone stream riparian the lowest sediments deeper underlying at of the of were period content carbonate pH, the the reflecting with during along maximum analytes, a two these of trations icag .902 .301 .10.003–10.7 166.7–916.7 0.32–7.55 0.21 304.2 1.13 0.19 345.8 1.03 0.03 233.3 1.29 0.21 341.7 1.21 0.59 341.7 0.97 Discharge DOC NO P Total Cl Mn PO SiO Na NH SO Fe K Mg Ca HCO rmtl ri icags ocnrtoso O,Cl DOC, dis- of drainage Concentrations the discharges. subsurface of drain shallow tile dilution from by to water due ground flow, charging high of periods during tem eea iiu uigtepro flws etyarzn curddrn eid fhg lwin flow high of periods during occurred deethylatrazine the lowest from of period samples the in during minimum than a at stream were stream, the beneath depth H65667066675.4–7.4 6.7 6.6 7.0 are concentrations range All Three-year † 6.6 years Three October–December 6.5 July–September April–June January–March O 1995 October pH Creek, Castle Cow from collected Constituent samples 78 in constituents selected of concentrations and discharge Stream 3. Table 1992). Plummer, atmo- and cor- of (Busenberg chronology pressures, pressures a partial partial with spheric equilibrium temperature, recharge CFC for of rected comparison a of Ϫ Ϫ icag nt r m are units discharge ؉ 2 Ϫ 2 2 h eindshreo o ateCekduring Creek Castle Cow of discharge median The 1 1 h nltshvn h ags ocnrtosin concentrations largest the having analytes The ؉ hog etme 1998.† September through 4 2 ؉ 2 4 3 2 ؉ 3 Ϫ ؉ 4 Ϫ 2 ؉ Ϫ ؉ Tbe3.Cmaioso icag tfv onson points five at discharge of Comparisons 3). (Table m 3 Ϫ 3 Ϫ Ϫ 2 n SiO and , 1 hc eelwri rudwtrsmlsat samples ground-water in lower were which , . ufc ae Hydrology Water Surface ufc ae Chemistry Water Surface 3 2 s 3 Ϫ 2. 2. 5711411433.6–278.6 98.7–338.5 121.4 56.6–158.1 73.9–213.2 234.4 69.9–449.1 65.6–950.6 190.6–381.3 131.5 121.4 160.9 274.5 231.3 467.1 259.4 143.1 85.7 158.8 336.8 516.3 208.8 260.9 128.6 136.4 156.6 244.0 374.3 671.9 237.5 128.6 133.9 156.6 253.9 247.0 368.8 256.3 108.2 165.3 194.6 262.2 303.1 eea hi oetconcentrations lowest their at were s ␮ Ϫ 964. 175. 3223.9–104.2 2.55–104.8 43.2 41.1–127.5 46.0 80.2 50.0 58.8 84.3 41.7 53.7 74.0 43.8 46.0 82.3 39.6 33.2 82.3 1 n agdfo .0 o1. m 10.7 to 0.003 from ranged and , .334 .414 .41.07–6.43 0.32–1.81 0.10–0.87 2.14 0.555–7.16 0.65 0.30 2.06 1.43 0.61 0.22 1.60 2.14 0.97 0.22 1.65 3.43 0.65 0.31 2.42 1.43 0.32 0.36 3.04 1 o L mol smaue ttetm fsml collection. sample of time the at measured as RESULTS Ϫ UKT UHS RNPR N AEO IRT N PESTICIDES AND NITRATE OF FATE AND TRANSPORT HUGHES: & PUCKETT 1 ihteecpino H hc si tnaduis isle rai abn(O)i eotdas reported is (DOC) carbon organic dissolved units; standard in is which pH, of exception the with 2 ϩ n HCO and 3 Ϫ ϫ einvlefrteperiod the for value Median Concen- . 10 Ϫ 6 m 2 ϩ Ϫ 3 3 , , atlvl(C)stb h SP 20) However, (2005). USEPA the by set (MCL) level nant n eeol bu n-hr h aiu contami- maximum the one-third about only were and h eotn ii o1.1 above to in just limit reporting from present the ranging was concentrations at Metolachlor samples than 4). 39 more all (Table limit, in samples present reporting were of the compounds 25% the above of 7 detected only were but 23 1996, Octo- through ber February during collected samples water median 3-yr the negligible. from were 10% or about than analytes less inorganic varied other either most of Concentrations 1996). fhg lw u osalwsbufc riaefrom drainage subsurface shallow to due flow, high of nrawy n ihso a Hfmne l,2000). al., et (Hoffman way of rights and roadways on agricul- low their given interesting are tebuthiuron and 42.8 the times 6.5 as great as still were concentrations NO in range (33.6–279 agricultural the tion watershed, widespread the in the use land Given fields. agricultural of influence dominant Cl O the of and Concentrations to discharge. due ground-water again flow, stream edcnrlado ufrs,adtbtirni used is tebuthiuron and turfgrass, on aquatic and in control used is weed also simazine because sources cultural u a nyaot3 ftemxmmarzn con- atrazine maximum the of 3% about only was mum l,19;Byes 01 akofe l,20) Further- 2003). al., et Kalkhoff 2001; Bayless, 1992; al., nysihl rae hnisrpriglmt n t maxi- its and limit, was reporting its deethylatrazine than greater of slightly medi- only concentration their median than The only greater ans. were order-of-magnitude concentrations an maximum about report- the and respective limits, their ing near were deethylatrazine and epnil o raigdehltaie(cao et (McMahon process deethylatrazine degradation creating mediated for biologically responsible the the in for time soil residence insufficient reflecting centration, ua s 1 gad0k,rsetvl,i 97 within 1997) in nonagri- indicate respectively, probably kg, results 0 These watershed. and the kg (10 use tural oe aiu ocnrtoso oharzn and atrazine both of concentrations maximum more, ␮ o L mol mn h 8psiie nlzdi h 9surface- 39 the in analyzed pesticides 88 the Among h eincnetain fclryio,alachlor, chlorpyrifos, of concentrations median The 2 Ϫ nsra ae eegets uigperiods during greatest were water stream in 1 osdrdbcgon MelradHelsel, and (Mueller background considered ␮ o L mol Ϫ 1 emdrltvl ml values small relatively seemed ) ␮ gL Ϫ 1 h eut o simazine for results The . 3 Ϫ concentra- ␮ o L mol Ϫ ,NO 2283 Ϫ 1 3 Ϫ C; , Reproduced from Journal of Environmental Quality. Published by ASA, CSSA, and SSSA. All copyrights reserved. rlywr ttermxmmdrn h itradto mn h ape nlzd rai abncon- carbon organic analyzed; samples the among tion and winter the during maximum their at were erally etcd†( Pesticide† etcd ( Pesticide taie2 3 1 8 5 “ as reported Values ‡ †OA ESA Alachlor Atrazine OA Metolachlor ESA Metolachlor Metolachlor Castle Cow from collected samples surface-water monthly 12 in detected degradates and pesticides selected of Concentrations 5. Table to discharging one- system, about MCLs. flow at shallow their study water the the third during through water surface detected where travels detected largest in (1996), the Aucott concentrations were pesticides although by simazine described any MCLs, and as established area, were atrazine (2005) 1.1 study USEPA study consis- no the are At May the above heads dissipated detected. and and during were had table April degradates water mound time in atrazine the reporting the in no twice, patterns but 1998 its detected These 1997, August was than by maximum Atrazine greater a but limit. slightly at pling, but only samples, three concentration and Alachlor in mound (1999). ground-water detected al. This November, et was 7. Phillips Site ESA in toward by Site 6 reported Site near 7.5 was parent pat- from mound also this the October, ground-water tern application; of following a in degradation months was the to there in 5.3 time, due 0.028 compound the system December, July, At in flow in 6.3 increas- the and 5.4 application, of after to 1997 representation May ing a in with meto- provide 0.25 in to heads was ESA 3 detected metolachlor lachlor of increasing metolachlor was Fig. ratio OA The of in by sample. metolachlor one only pattern samples; followed five a samples, in was ESA eight there in pesticide, dition, detected occurring frequently Again most detection. the of was frequency metolachlor lower con- a were in 0.004 during streambed GC–MS resulting by the 1996, method analyzed in samples heads HPLC the Piezometric for the than zone. order-of-magnitude greater an ian on about contributed was remember samples based 1997 these to for December limits used important during reporting is Creek the It Castle that 5). Cow the (Table above five limit concentrations only reporting at compounds, detected 23 were degradate compounds upgra- for and ac- the analyzed 24 and parent at degradates, and greatest etanilide its was 25 and 1998 atrazine surface 29 lowest March including land pesticides their below through 35 water to 1997 to decreased April 26 37 then and 1997–1998, spring, applications. spring metola- 39 losses following rapid chlorpyrifos, suggesting tebuthiuron, alachlor, and simazine, for chlor, observed pat- were Similar applications. terns pesticide following spring the “ as reported Values † Tebuthiuron Chlorpyrifos Deethylatrazine Alachlor Simazine Atrazine Metolachlor Creek Castle Cow from collected samples surface-water 39 of 25% least at in detected pesticides selected of Concentrations 4. Table 2284 h ae-al lvto n izmti ed gen- heads piezometric and elevation water-table The mn h 2mnhywtrsmlscletdfo to bv adsraea h onrdetedo the of end downgradient the at surface land above or at from collected samples water monthly 12 the Among re uigArl19 hog ac 1998. March through 1997 April during Creek 1998. Feb. 4 on and 1996, October through 1996 February during ϭ xnlcai erdt;ESA degradate; acid oxanilic rudWtrHydrology Water Ground Ͻ Ͻ eels hnterpriglimit. reporting the than less were ” limit. reporting the than less were ” eeto frequency Detection ϭ eeto frequency Detection taesloi cddegradate. acid ethane-sulfonic .EVRN UL,VL 4 OEBRDCME 2005 NOVEMBER–DECEMBER 34, VOL. QUAL., ENVIRON. J. n n ϭ ϭ 9 iiu einMaximum Median Minimum 39) 2 iiu einMaximum Median Minimum 12) hssml otie h raetognccro frac- carbon organic carbon, greatest organic the contained 0.97% sample At this illite. and smectite, chlorite, a oe(ie2i i.2 a rdmnnl quartz predominantly was 2) Fig. a in with 2 sand (Site zone ian and paths streams. flow nearby along the and highs to topographic common at systems enters flow stratified the with tent Creek. Castle Cow toward sam- all was 1998 flow ground-water April and the through persisted potential flow water ground of movement potential in resulted which 6, A–A Section along shown flowlines ground-water and elevations 1976). Water-table (Winter, zones discharge ground-water asso- with commonly ciated condition a streambed, the ad- below depth In stage. surface-water to relative ripar- greater the sistently in surface land above rising level water the to was and field corn the in system flow the of end depth The dient 1998. fall, and summer late the during levels lwsse nterpra oet vrakfo from flow Overbank forest. riparian the in system flow Ͻ Ͻ Ͻ Ͻ Ͻ Ͻ h ukfato ftesalwsdmn nteripar- the in sediment shallow the of fraction bulk The Ͻ Ͻ Ͻ Ͻ Ͻ .10020.03 0.057 0.033 0.045 1.6 1.1 0.012 0.006 0.003 0.010 0.075 0.010 0.01 0.004 0.002 0.002 0.005 0.001† .5 .50.93 0.05 0.2 0.05 0.2 0.2 0.05‡ Ͻ 1- eietChemistry Sediment ␮ lyfato opiigkaolinite, comprising fraction clay m Ј ttesuyst nNvme 1997. November in site study the at Concentration Concentration ␮ ␮ Ͻ Ͻ Ͻ Ͻ gL gL . 0.3 0.14 0.3 0.4 0.2 0.05 0.2 0.2 Ϫ Ϫ 1 1 Reproduced from Journal of Environmental Quality. Published by ASA, CSSA, and SSSA. All copyrights reserved. a ital h aea hti h hlo sample. shallow the in that as same plagioclase. the and virtually quartz was the feldspar with potassium The along and detected dolomite, were calcite, sample, est icaei diint h urzsn,adi h deep- the in and sand, quartz the to addition in gioclase vrg nultemperature. annual 17.3 average of temperature recharge N a the zone. cated through riparian fit the regression beneath linear from A samples in found were N excess 355.3 of contribution 46.4 to of 0 the median from a plus ranged air, equilibrium N excess measured from air–water the the between difference and the as 637.2 992.1 calculated of to median a 464.5 with from ranged concentrations L with 0.04% to 0.02 to decreased then depth. and concentration a 0.21%, with surface of the at near content greatest was carbon 6 Organic Site kaolinite, chlorite. of and mixture illite, a comprising smectite, similar, were 6 Site at was The may chlorite not However, present. they origins. suggesting were agricultural depths, of been dolomite greater have with two and the sand Calcite at quartz present medium dolomite. to and fine calcite was surface the to near 3.1 from ranged concentrations oxygen Dissolved pla- in contained fraction Deeper bulk 0.29%. the to 2, Site 0.39 Novem- at aquifer, to sediment surficial depth the the with in recharge declined ground-water tent of year approximate and directions, flow ground-water elevations, Water-table 3. Fig. Ϫ ocnrtoso rrne rm1. o17.2 to 13.1 from ranged Ar of Concentrations fraction bulk the 2), Fig. in 6 (Site field corn the In e 1997. ber 1 ihamda f15.5 of median a with Ͻ 1- ␮ lyfato nteetodee samples deeper two these in fraction clay m 2 a aibebttelretconcentrations largest the but variable was Ͻ 1- ␮ ␮ isle Gases Dissolved lyfatosa l he depths three all at fractions clay m o L mol ␮ o L mol Ϫ UKT UHS RNPR N AEO IRT N PESTICIDES AND NITRATE OF FATE AND TRANSPORT HUGHES: & PUCKETT 1 ␮ Tbe6.Tedistribution The 6). (Table o L mol Ϫ 1 Tbe6.Ecs N Excess 6). (Table Ϫ 1 Њ 2 ;na h 17.5 the near C; Tbe6.TeN The 6). (Table n rdt indi- data Ar and ␮ o L mol ␮ o L mol Ϫ 1 ␮ with mol Њ Ϫ C 2 2 2 1 , oeoye elto,a euto xdto for- of oxidation of result a as depletion, oxygen some 17.5 ieA N Ar Site h acltdeulbimvleo 297 of value equilibrium calculated the - 556203. 3. 0. NA 1979 1997 1984 NA 201.7 185.8 335.7 1983 1521 1979 135.7 371.4 1988 50.0 335.7 1521 371.4 1981 413.1 33.0 1257 1986 1989 1988 1318 67.9 NA 364.3 0 780.6 1257 0 622.0 1264 1200 “ 1157 1980 as 1496 617.6 reported 15.5 700.0 NA Values 24.4 † 1979 NA 1990 525.9 14.3 1100 26.9 1157 513.3 7-V 1407 1994 302.8 NA 13.7 7-IV 40.3 583.0 13.6 1976 319.3 NA 7-III 50.2 171.4 608.6 1081 44.9 1979 0 7-II 1982 917.5 14.6 1978 242.9 7-I NA 611.6 15.2 274.4 6-IV 89.2 639.1 1014 1974 885.7 65.7 518.6 6-III 635.3 1975 300.2 14.9 1993 209.6 464.5 178.6 6-I 38.2 15.5 15.5 5-IV 33.3 690.5 228.6 13.1 336.6 171.4 28.6 15.9 5-III 658.6 319.4 326.4 5-II 47.9 15.8 645.3 15.6 200.0 5-I 628.1 200.0 145.0 321.4 64.4 4-III 591.8 16.0 90.5 4-II 15.6 653.7 15.1 3-IV 68.3 747.8 59.7 2.5 3-III 654.3 15.9 701.8 3-II 15.9 15.5 2-IV 667.2 16.1 2-III 670.0 602.4 2-II 15.7 16.1 2-I 15.8 1-III 1-II 1-I N Ar, Concentrations 6. Table 297 eentsampled. not were xesN excess hreya fgon-ae ape olce nNovember in collected samples ground-water 1997.† of year charge NO Њ ␮ ,ms ape,atog xc hwdsgsof signs showed oxic, although samples, most C, Ϫ 3 o L mol ( 2 ⌺ eotda 0 eecluae ohv oecs N excess no have to calculated were “0” as reported NO Ϫ Ϫ 3 1 ,adclrfurcro CC-sindre- (CFC)-assigned chlorofluorocarbon and ), ihamda f168 of median a with 2 Ͻ eels hnterpriglmt ausof values limit; reporting the than less were ” xesN Excess ␮ o L mol 2 2 ,NO Ϫ 1 NO Ϫ 3 Ͻ xesN excess , . 7. 1977 178.4 3.6 3 Ϫ ␮ ⌺ o L mol NO 2 reconstructed , ␮ 3 Ϫ o L mol Ϫ 1 Given . F year CFC Assigned 2 “NA” ; Ϫ 2285 1 at Reproduced from Journal of Environmental Quality. Published by ASA, CSSA, and SSSA. All copyrights reserved. tdwt giutrlaes(nesn 93 ukt rtosrmie oprbei l h pi samples. April the all in comparable remained trations Puckett 1993; (Anderson, areas agricultural associ- contaminant with common a ated are both and KCl, as and aiyatiue otentiiaino NH of nitrification the to attributed easily and aaino Fs n osqetyodraprn age apparent older consequently and biodeg- CFCs, and/or of sorption radation in resulting zone, riparian the of itl eo t ee rudwtrms asthrough pass sediments must organic-carbon-rich imme- reducing, water one chemically the ground the than Here, older it. yr 4 below was diately 2 Site from sample est n oiini h lwsse.Seiial,teshallow- the Specifically, system. flow the in position and rie ta fetv ooiyo . n naverage an yr and m 0.143 0.4 of of rate porosity recharge effective long-term an at arrived oesmlsbigdmntdb Ca by dominated being samples zone pad eas fti irfcto,teewsalmost was there nitrification, this of Because upland. oiae yNa by dominated iainzn ape.Teepten np a esrabdwr ufcetyrdcn o Fe for reducing sufficiently were streambed and April the during the that be in indicate can results 6.6 These pH of water. in median patterns a These with samples. 8.0 zone to upland the riparian in 5.0 4.4 of and median a samples, with 5.4 to 3.8 from ranged teme 07m agdfo 90t 97 iha with 1997, to 1990 the in from 1-I ranged Site from m) samples (0.7 the for streambed dates age nine The zone. aibedet h eoiinlhsoyo h eiet.Nvme ape,adCl and samples, November highly was itself sediments. the which of history sediments, depositional the the to due in variable C organic of etdb oe 16)t siaercag rate: recharge estimate to (1967) Vogel by sented et eo h ae al (m), table water the below depth where a oe swl salo h ape tSt ,were 4, Site at samples the ( of suboxic all near as or well suboxic as zone, ian g ae eeodrta xetdbsdo hi depth their on based expected than depth older were and dates age age between correlation ( strong a was there fprst n ehrert o ahsml ot we port, sample each for rate recharge and porosity of iigwt h vryn ufc water. surface overlying and exchange the of with degrees varying mixing to due 1993, of median rudwtraogtesuytasc,wt h iainadFe and riparian the with transect, study the along water ground o2 ri h eps apigpr tSt Tbe6). (Table 1 with increased Site 1 ages at ground-water Site port expected, be sampling at might deepest As piezometer the in shallow yr the 23 to in modern near from usiuigvrosvle o nta ieauevalues literature initial for values various substituting oecssNO cases some ihtesbeun rdcino H of production subsequent the with eehgl aibe rbbyrfetn ieaiainadO and concentrations mineralization Fe relative reflecting of carbon 90% probably Concentrations value. variable, organic about highly Dissolved by were 1999). declined had al., water et ground low NaCl as fertilizer in contaminant a as Na occur immediately Both commonly areas. and fertilized the under of downgradient greatest were concentrations well. as area that in horizons organic to similarly been due have to affected appear 4 Site from Samples dates. and 3), (Fig. system flow the along distance and depth HCO of loss total ripar- the from samples shallow the of All carbon. ganic 2286 r eue h xoeta g rdeteuto pre- equation gradient age exponential the used We rbbytegets ifrne eei H which pH, in were differences greatest the Probably hr eedsic ifrne nteceityof chemistry the in differences distinct were There hoolooabnbsdae fgon ae ranged water ground of ages Chlorofluorocarbon-based ϭ r .2 o h ape ntercag oe Several zone. recharge the in samples the for 0.92) saeaeln-emrcag ae( yr (m rate recharge long-term average is A saei yr, in age is hoolooabnAeDates Age Chlorofluorocarbon rudWtrChemistry Water Ground 3 Ϫ A hra h padsmlswr ufc ae a elndt bu n-hr fthe of one-third about to declined had water surface were samples upland the whereas , ϩ ,Cl ϭ Z ΂ Ϫ Z n NO and , saufrtikes(m), thickness aquifer is Ͻ n r ΃ 64 ln ΂ Z ␮ o L mol Z Ϫ n .EVRN UL,VL 4 OEBRDCME 2005 NOVEMBER–DECEMBER 34, VOL. QUAL., ENVIRON. J. 3 Ϫ sefcieporosity, effective is z oimadCl and Sodium . ΃ ϩ Ϫ 2 ϩ Ϫ 1 ntecliae conigfrtesalNO small the for accounting cultivated the in HCO , 1 nterecharge the in .mda f1.4 of median ). 4 ϩ nfertilizer in ϩ 3 Ϫ n Cl and n in and , Ϫ 1 .By ). z [1] is Ϫ Ϫ O diin NH addition, rto f2021 of tration ytetm fteAgs 98sml olcin NO collection, sample 1998 August the of time the By nslto n o eirfcto oocr therefore occur, to denitrification for and solution in ntal enasmdo h ai fmaue NO measured of basis the on assumed have might been than greater initially somewhat were past the in tions tutdcnetain niaeta NO recon- the that cases few indicate a concentrations In zone. fertilized structed riparian the the in below and depth areas with decreasing centrations r iia oterslsfrmaue NO measured for results the to similar are nterpra zone. riparian the in hr a esfiin rai uidi temsedi- stream in buried C organic sufficient be may there hlo rudwtrsml swl hl Cl while well as sample water ground shallow uuttm eid,cniin t07mbnahthe beneath m 0.7 at conditions periods, time August surface and water ground shallow both in identical tially ainrt nomto o h onfedo 4 gN kg 340 of field corn the for ha information rate cation eet o ateCek(al )a h ieof mea- time that the to similar at were 7) 1997 (Table November in Creek sampling Castle Cow beneath ␮ ae NO water ie n eeol atyacutdfri h excess the in for accounted partly only were 2 and 3 Sites N ehrerts mle -plcto ae,o combi- a or rates, N-application smaller rates, recharge h te ad NO hand, other the h pi 98smln,NO sampling, 1998 April the lndee ute,Fe further, even clined ,Fg 4): Fig. 6, pae n iigwt o NO low with mixing and uptake, ple ol erqie orahtewtrtable water the reach NO ground-water to maximum the for required account to be would applied N a ple n nanme fsmlsecee the exceeded samples of number a fertilizer in where and samples applied upland was shallow the in greatest ue nsraewtr swr ocnrtoso Cl of concentrations were as water, surface in sured 2.5 as much as by MCL times. established (2005) USEPA aino h w.I spriual oeotyta the that noteworthy NO particularly in is decreases It large two. the of nation in.Ti iceac rssbcuetedcessin decreases the because arises discrepancy This tions. NO oebrvle,adteO the and values, November obt t oebrvleadteArlsraewater surface April the and value November its both to calculated the Given yr m 2-III. 0.143 of Site rate recharge at particularly alone, ( ⌺ o L mol 2 2 h nta rrcntutdcnetain fNO of concentrations reconstructed or initial The ocnrtoso NO of Concentrations Ϫ NO aaadteeoetercntutdNO reconstructed the therefore and data ocnrtoswr lona hs fsraewater surface of those near also were concentrations 3 Ϫ 1 n19,w siaeta nyaot1%o the of 10% about only that estimate we 1996, in ocnrtoswr u odntiiain plant denitrification, to due were concentrations 3 Ϫ 2 2 ,bfr eirfcto,cluae s(Table as calculated denitrification, before ), ϩ ocnrtosi hlo rudwtrhdde- had water ground shallow in concentrations Ϫ 1 ocnrtoswr elgbe ttetm of time the At negligible. were concentrations 3 Ϫ nteuln ra eevn etlzr On fertilizer. receiving areas upland the in ⌺ ocnrtosmyb trbtdt larger to attributed be may concentrations NO 4 ϩ ␮ ␮ o L mol ocnrtoswr elgbe iha with negligible, were concentrations 3 Ϫ o L mol 3 Ϫ ϭ onurlz h eutn H resulting the neutralize to 3 Ϫ [NO 3 Ϫ Ϫ Ϫ 1 2 ntesalwsmlsbetween samples shallow the in ocnrtosgnrlywere generally concentrations mle eosrce ground- reconstructed Smaller . ϩ 1 3 Ϫ 3 nterpra oead2.5 and zone riparian the in Ϫ Ϫ a lvtdrltv othe to relative elevated was Ϫ ] 2 1 ϩ ngon ae t07m 0.7 at water ground in n h vial N-appli- available the and , ocnrtoswr essen- were concentrations 2 ϩ nrae akdyi the in markedly increased ocnrto fteshal- the of concentration 3 Ϫ 3 Ϫ [xesN 2[excess 3 Ϫ ocnrtos While concentrations. ngon ae and water ground in aesta recharged that waters 2 3 Ϫ 3 [2] ] Ϫ 2 3 Ϫ ϩ ihcon- with , concentra- concentra- Ϫ oremain to 3 Ϫ concen- concen- ϩ .In Ϫ 3 3 Ϫ 3 Ϫ Ϫ ; Reproduced from Journal of Environmental Quality. Published by ASA, CSSA, and SSSA. All copyrights reserved. oal xetossc sa ie -Iad7II otfo taieadmtlclrwr eetdi ground in detected were metolachlor and atrazine from or (2005). under USEPA located the by ports set sample Most (MCL) 7-III. the level and in contaminant 7-II were Sites in detected at detections compounds as the such were of there exceptions any although of notable samples, concentrations most the in above both limit barely reporting At the were 8). concentrations (Table their 1998 times, April sampling and 4) (Fig. No- 1997 during water vember ground in compounds parent detected rtosi hlo rudwtradsraewtr yio,smzn,adtbtirnas eedetected were also tebuthiuron and simazine, pyrifos, water. surface and water ground shallow in trations ae a iigwt hlo rudwtr hspsi eedtce ntesalws apepr tSt 1-I, Site at port sample shallowest the in detected where were field, corn the from downgradient Cl between immediately similarity possi- the this by supported water; is stream ground bility in shallow C with organic mixing dissolved was the water that likely bacte- Novem- also during iron-reducing is sampled it and water ria, denitrifying ground in support degradates to pesticide ments (b) and nitrate reconstructed and pesticides (a) selected of Concentrations 4. Fig. taieadmtlclrwr h otfrequently most the were metolachlor and Atrazine e 1997. ber UKT UHS RNPR N AEO IRT N PESTICIDES AND NITRATE OF FATE AND TRANSPORT HUGHES: & PUCKETT Ϫ concen- ae.Bt etyarzn n yrxarzn were hydroxyatrazine and deethylatrazine Both water. maximum the exceeded study the during water ground noeocso ntesml ota ie1I oeof None 1-I. Site at port sample the in occasion one on ntemdl ftecek lclr abfrn chlor- carbofuran, Alachlor, creek. the of middle the in metolachlor and Atrazine applied. were pesticides these mn h etcd erdts nytoederived those only degradates, pesticide the Among 2287 Reproduced from Journal of Environmental Quality. Published by ASA, CSSA, and SSSA. All copyrights reserved. in fmtlclrEAwr h ags fayde- any of largest the were concentra- ESA addition, metolachlor In of frequency. that tions half than less at oetsml ot n erae ihdepth. with shal- decreased the and from ports samples sample in de- lowest greatest then were concentra- table generally Deethylatrazine the tions 4). water (Fig. from the depth with samples below creased in port sampling greatest second were generally trations eotn ii,weesmtlclrO a detected was OA metolachlor whereas limit, reporting onsapido h il n1996. in field the on applied pounds eotn ii oamxmmo 1.8 of maximum a to limit reporting etd ecigamxmmo 14.1 of maximum a reaching tected, eoaho n hi erdtsol cone for com- parent accounted the of only respectively, 0.007%, and degradates and 0.002 atrazine about their of sums and the parent basis metolachlor the molar for a than On greater metolachlor. orders two and OA olachlor eoaho erdt ihnn eetosaoethe above detections nine with degradate metolachlor ae ytmwudalwdntiiaint opeeycmn eae sti rudwtrrahsteedof end the reaches water ground this as decade, coming completely to denitrification allow would system water the above just from ranging concentrations at detected bu n re-fmgiuegetrta htfrmet- for that than greater order-of-magnitude one about fhdoytaie(al ) yrxarzn concen- Hydroxyatrazine 8). (Table hydroxyatrazine of etcd†Nvme 97Arl19 iiu einMaximum Median 10 Minimum “ 1998 as April reported 13 Values ‡ †OA 1997 November Atrazine Pesticide† pesticides and 1997, November during collected samples ground-water 24 in detected degradates and pesticides of Concentrations 8. Table 1.58 0.18 0.18 19.7 208.8 172.1 172.1 211.6 241.7 5.7 16.7 0.18 25.0 233.3 0.18 208.8 13.8 186.2 231.3 169.3 218.8 189.0 15.6 200.0 140.0 633.3 1.2 0.06 336.4 33.3 320.0 75.0 27.9 0.06 191.7 – 0.38 338.5 163.6 carbon. organic 3.1 228.1 Dissolved † 1.9 152.3 200.0 0.7 338.5 178.1 21.9 102.9 Creek 333.3 8.3 323.6 1-III 285.7 25.1 1-II 105.7 258.3 – 1-I 3.1 300.1 1.9 131.3 0.7 143.8 278.6 Creek 246.9 202.1 1-III 202.1 1-II 318.6 – 1-I 3.1 1.9 0.7 Creek 1-III 1-II NO 1-I Depth Site and ground- in constituents selected of Concentrations 7. Table 2288 etyarzn 9 9 Deethylatrazine yrxarzn NA 7 Hydroxyatrazine eoaho 6 9 Metolachlor eoaho S NA 9 ESA Metolachlor eoaho A4NA 4 OA Metolachlor lclr10 1 Alachlor abfrn01 0 Carbofuran hoprfs10 1 Chlorpyrifos iaie10 1 Simazine euhuo 0 1 Tebuthiuron eoaho S a h otfeunl detected frequently most the was ESA Metolachlor ehpteie htln rvltmsi h ground- the in times travel long that hypothesized We 98 n uut1998. April August 1997, and November 1998, during collected samples surface-water n2 rudwtrsmlscletddrn pi 98 ny2 fte2 ape olce uigNvme 97wr analyzed were 1997 November during collected samples degradates. 24 acetanilide the and of triazine 22 the Only for 1998. Laboratory April Research Organic during the collected by samples ground-water 29 in ϭ xnlcai erdt;ESA degradate; acid oxanilic m irt rnpr n Fate and Transport Nitrate Ͻ ␮ eels hnterpriglmt N”wr o sampled. not were “NA” limit; reporting the than less were ” 3 DISCUSSION Ϫ o L mol Ϫ O 1 2 ϭ oebr1997 November uut1998 August ␮ taesloi cddegradate. acid ethane-sulfonic pi 1998 April o L mol O†Cl DOC† .EVRN UL,VL 4 OEBRDCME 2005 NOVEMBER–DECEMBER 34, VOL. QUAL., ENVIRON. J. eeto rqec Concentration frequency Detection ␮ Ϫ 1 ␮ gL C gL Ϫ 1 Ϫ ntecase the in 1 hc is which , ␮ Ϫ o L mol Fe Ϫ 1 2 ؉ etain r trbtdete opatutk rto or uptake low-NO plant of to mixing either attributed are centrations iainzn.A elce ntentices nexcess in increase the net the through in halfway reflected about As traversed zone. riparian had by they order-of-magnitude time an field, the hay approximately the by to applied decreased fertilizer as originating trations, N in.Teeoe h eann erae nNO in decreases remaining the Therefore, tions. nte2-rodgon ae ntedshrezn.Even zone. discharge the in water ground 23-yr-old the in bu 7t 1 ftercntutdNO reconstructed the of 41% to 37 about nsalwprin fterpra oewr en by- N being were excess zone Furthermore, riparian the passed. of creek, portions the shallow in beneath present conditions water reducing chemically ground the that meaning in and zone riparian bu o2%o h e eraei NO in decrease net the of 28% to 7 about ly oea ikfrNO for sink a as role a plays n ota 1996). Postma, and Appelo and 1993; temporal (Chapelle, the denitrification of controls extent spatial reactivity micro- its limit processes, may and bial refractory, is commonly C buried organic because addition, In denitrification. limited some supporting of capable conditions local content, scattered matter creating organic high hetero- of This pockets wetland in aquifer. results surficial geneity recent the up scattered make that the the deposits and of variability deposits, nature Holocene-age this floodplain deposits, heterogeneous for terrace the coastal reason Pleistocene-age is One denitrification place. in taken has tion in changes N excess observed the However, NO hypothesis. the and of limited the is oxic, is denitrification NO aquifer widespread surficial for the potential of most Because zone. NO remove aepretgs ecnepc hta oetm nthe in these time some by at that decreased expect can are we percentages, mid-1980s same the since NO recharged larger the if h iainzn ihtesalwgon ae.More water. ground shallow the with zone riparian the motnl,NO importantly, ac.A hw nFg n al ,lreNO large 6, abun- Table and greater 4 in Fig. is in C shown As organic dance. where zone riparian the of 2 lhuhlmtdi h padaes denitrification areas, upland the in limited Although a,hwvr eirfcto a con o only for account can denitrification however, gas, 3 3 Ϫ Ϫ a o opeeyrmvd edn orejection to leading removed, completely not was ocnrtosaogtefo ahadi the in and path flow the along concentrations 2 esrmnsidct htsm denitrifica- some that indicate measurements Ͻ Ͻ Ͻ Ͻ Ͻ Ͻ Ͻ Ͻ Ͻ Ͻ Ͻ 0.001‡ 0.002 0.2 0.002 0.2 0.2 0.002 0.003 0.004 0.005 0.01 3 Ϫ ntesalwaufradteriparian the and aquifer shallow the in 3 Ϫ 3 Ϫ eandi rudwtrblwthe below water ground in remained 3 Ϫ ocnrtosi g in concentrations aesta eetyrcagdin recharged recently that waters 3 Ϫ Ͻ Ͻ Ͻ Ͻ Ͻ Ͻ Ͻ Ͻ Ͻ Ͻ Ͻ ␮ gL .0 0.15 0.001 .0 0.021 0.002 . 1.8 0.2 .0 0.25 0.002 . 14.1 0.2 . 1.0 0.2 .0 0.007 0.002 .0 0.007 0.003 .0 0.004 0.004 .0 0.013 0.005 .10.02 0.01 2 ntesalwportions shallow the in a consfronly for accounts gas Ϫ 1 on w round 3 Ϫ concentrations 3 Ϫ concentra- 3 Ϫ trthat ater concen- 3 Ϫ con- Reproduced from Journal of Environmental Quality. Published by ASA, CSSA, and SSSA. All copyrights reserved. t lwpt,w ilseNO see will we path, flow its ntdSae eg,Kli ta. 00 akofe l,N sampling m) (0.7 shallow the from samples for al., date et age Kalkhoff dis- midwestern 2000; of the al., period in et Kolpin stable water (e.g., surface relatively States degradates and a United their water potential. during the and ground reach discharge reported pesticides in stream have strong numerous that a of studies recent presence indicating of number year, a the with to out degradates their depths various or is at Creek. pesticides made water measurements Castle of Head ground Cow streambed. source location, direct m, this a 0.7 at not than least greater at depths that, espe- at indicates and stream all zone, the virtually riparian beneath of the cially from absence samples The in streambed. values. pesticides the small into relatively concentrations directly pesticide to discharge reduce and to time zone sufficient moderately cesses ( in times results residence field system long flow corn ground-water the the configuration the of from location this At downgradient originated. they where far very migrated htteprn opud rterdgaae aeeta lwpt htalw NO allows that path flow ential have degradates their or compounds parent the that his- depositional the Finally, applied. were why they for pa where accounts of part, in concentrations and the degradation, pesticide study, increased as This this degra- detected system. Where slower in compounds. assumed flow parent their the the to than within com- rates due it dation times be parent degradates, may residence the effective is it the of the or water degradation in of pound, ground continued decrease in case of a presence is result the their drainage the In that artificial of argued yr. for effect bio- be water bypassing 18 might Creek, ground Castle to Cow in to up fields persist cultivated periods the may practice OA) this ESA, metolachlor of deethylatra- metolachlor result and (atrazine, metolachlor, net compounds The hydroxyatrazine, indicate water. these zine, results excess minor of Our remove with true. some to be and that to creek, appears adjacent this the exceptions be- reached levels they undetectable their fore to mineralized and be pesticides to allow degradates would system ground-water ec ftedgaae.gncCaeiaeut ospotwdsra denitrifi- widespread support to inadequate are C ganic contain which of most zone, the riparian near the persis- in depth the layer at for cial accounted sands degradates. have the coarser-grained to of uplands, likely tence the not is parent parents the the of of transformation continued Therefore, those compounds. than the more whereas greater or limit one orders-of-magnitude commonly reporting were the concentrations above degradate just were often NO some creek. August the beneath water ground in occur may n NO and nteodro h 2 o140 to 120 the of order the on 3 o700 to 430 nsra NO in-stream mletadwr nyaotoeqatro htmgtrfettepouto ftedgaae eas of because degradates the of production the reflect might NO what given of expected be one-quarter about only were and smallest ae eet h tem oeitniesuyo ise l,1999). al., et lips in- potential the which to degree of the determine study study to intensive the at site more required be would A processes zone stream. hyporheic the beneath water osbe oee,ta h NO the that however, possible, ae stersl fdntiiaini h pe . aewtrsmls niae htte a o enin been not had they that indicates samples, face-water decrease greatest the that m fact NO 0.7 upper The in the streambed. in the denitrification of of result the as water raetifuneo ufc-ae hmsr tta eoaho S,t h aetcmon uigthe during compound parent the to ESA, metolachlor that at NO chemistry its surface-water surface-water had time, on water ground influence though even greatest why explain to helps rae ngon-ae NO ground-water in creases h etcd n etcd erdt eut ge f1.% niaigta rudwtrwscontributing was water ground that indicating 13.4%, of agree results degradate pesticide and pesticide The nsieo hspritne hr sltl evidence little is there persistence, this of spite In the in times travel long that hypothesized also We ti motn ont hta es uigArlad20) hrfr,teasneo,o eaieysmall relatively or of, absence the Therefore, 2003). and April during least at that note to important is It 3 Ϫ etcdsadPsiieDegradates Pesticide and Pesticides 3 Ϫ curddrn h uutlwfo eidboerdto oocrt esrbeetn.The extent. measurable a to occur to biodegradation period low-flow August the during occurred ocnrtoso bu 00t 1600 to 1000 about of concentrations ␮ o L mol 3 Ϫ concentrations. Ϫ 3 Ϫ 1 a eoe rmsalwground shallow from removed was eet o ateCek ti also is It Creek. Castle Cow beneath 3 Ϫ Ͼ ocnrtosi eprground deeper in concentrations 0y) iigdgaainpo re eevsgon ae rmteajcn aqui- adjacent the from water ground receives Creek pro- degradation giving yr), 20 3 Ϫ UKT UHS RNPR N AEO IRT N PESTICIDES AND NITRATE OF FATE AND TRANSPORT HUGHES: & PUCKETT ocnrtoswr ttheir at were concentrations 3 Ϫ ␮ 3 Ϫ o L mol ocnrtoswl affect will concentrations 3 Ϫ ocnrtoso bu 03.Terltvl ag ufc-ae concentrations surface-water large relatively The 2003). about of concentrations erae ilb nyof only be will decreases Ϫ 1 htw observed, we that etcompound rent ␮ o L mol Ϫ 1 iie rmtecliae ilst o ateCreek. Castle Cow to fields cultivated the from ticides otudrtesrabd i)tefc httedissolved the that fact the (ii) streambed, the under port discharge in increase net a confirmed winter 168-m-long in a charge in points various at flow of Measurements through- positive consistently were streambed the the under within water of exchange active is there that and fer osra lw utemr,()terltvl modern relatively the (i) Furthermore, flow. stream to riparian the in layer reducing shallow the beneath pass oyo h eiet htmk ptesriilaquifer surficial the up make that sediments the of field tory corn the from far migrated not have pesticides the such processes slow for time more allows time ground-water residence in increase an in resulting Another rate, zone. recharge riparian the in from processes directly geochemical drainage subsurface shallow route to is r itr ffnrgandsns it,adcasin clays and sediments silts, These sands, well. finer-grained as of mixture role a important are very a plays al., et Kalkhoff 1999; the al., in et occur (Phillips and zone soil mediated shallow biologically are processes ain h ore-rie eiet rvd prefer- a provide or- sediments coarser-grained of The amounts cation. small The C. organic of amounts small ( thin a and creek, ditches and drains sea- tile a requiring with table, setting water hydrologic high sonally low-gradient a is this First, ocnrtoso etcd erdtsi h aesur- same the in degradates pesticide of concentrations akofe l,20) oto h eeatdegradation relevant the of Most 2003). al., et Kalkhoff fpsiie eosre ntesrn r indicative are spring the in observed we pesticides of rnfrainpoessi h hlo olzn (Phil- zone soil shallow the in processes transformation h hlo olzn ogeog fe plcto for application after enough long zone soil shallow the rat nlec h rnpr n aeo NO of fate and transport the influence to area rwn esn(rm02 nMyt . nNovember) in 7.5 to May in 0.25 (from season growing nrae ntertoo etcd erdts uhas such degradates, pesticide of ratio the in increases 2 eea ie feiec niaeta o Castle Cow that indicate evidence of lines Several eea yrgooi atr obn ntestudy the in combine factors hydrogeologic Several ocnrto esrdteewsvrulytesame the virtually was there measured concentration uoffloigapiain Pilp ta. 1999; al., et (Phillips applications following runoff yrgooi Controls Hydrogeologic Ͻ hc)ceial euigsurfi- reducing chemically thick) m 1 3 Ϫ ngon ae to water ground in 3 Ϫ n pes- and 2289 Reproduced from Journal of Environmental Quality. Published by ASA, CSSA, and SSSA. All copyrights reserved. ltigcoe oterpra oesmlsadtoelwfo eid oeNO it some where period, Creek low-flow Castle Cow to transported was those water and samples zone riparian between the to cluster samples closer a stream (July–September) plotting in months with low-flow or the groupings, during water line collected ground a two on the fall samples Creek fgon-ae ape.I l he aes o ateinzn eiet,ohrpoessacutdfrmore for accounted processes other sediments, zone spe- ian reduced other or C organic sufficient of absence the Castle Cow panels, three all In samples. groupings ground-water distinct of stream two the the between with falling evident, again still samples are chemistry group- water three of the ings panel, chemistry combined the In zone. spoone eas h Cl the not because although panel, pronounced “ANIONS” as the in discernible also n rnstwr Na more toward much trends is chemistry and water the area upland otdcnevtvl onrdetit h iainDntiiainwsntasrn otoln atrin factor controlling strong a not was Denitrification riparian the into trans- downgradient part, most conservatively the for areas are, ported cultivated area the upland from directly the water in drainage fertilizer surface when flow, stream riparian higher of the periods in during hand, water Ca other “CAT- by ground the dominated 5, in is Fig. stream shown zone period, 5 in As low-flow the stream. Fig. panel ground- during the in IONS” that different to is diagram of data sources these Piper importance water of relative the the in illustrate shown streambed. samples the of water m exchange (January–March) 0.7 months that high-flow upper the confirm during the in collected 1, in not Site occurring but at is stream water the ground in deeper found pesticides presence the 1998. numerous (iii) September of and through value, 1995 equilibrium air-water October the chemistry, as surface-water and ground- of diagram Piper 5. Fig. 2290 h ae-hmsr aafrtecekadgon-wtrta a otrcnl asdbnahteriparian the beneath passed recently most has that water ground- and creek the for data water-chemistry The ϩ ,K 2 ϩ ϩ hra ntecultivated the in whereas , n Mg and , Ϫ .EVRN UL,VL 4 OEBRDCME 2005 NOVEMBER–DECEMBER 34, VOL. QUAL., ENVIRON. J. n NO and 2 ϩ hsptenis pattern This . 3 Ϫ ple in applied variable ie ihsraewtri h teme.Drn the During streambed. the in water surface with mixed isrqie ospotti rcs.Ee nteripar- NO the in Even process. this support to required cies elcsteuln rudwtrceityt greater a to chemistry degree. ground-water upland the reflects h rnpr n aeo NO of fate and transport the water surface of signature chemical the stream, the to sub- shallow shunting actively are drains tile and ditches ground discharging by influenced strongly is chemistry interpretation Our samples. upland the to closer plotting oead hs a iia hmclsgaue nthe On signature. chemical similar a has thus, and, zone 3 Ϫ osta i eirfcto,adNO and denitrification, did than loss CONCLUSIONS 3 Ϫ a oti h streambed, the in lost was 3 Ϫ tti td iedeto due site study this at 3 Ϫ nground in Reproduced from Journal of Environmental Quality. Published by ASA, CSSA, and SSSA. All copyrights reserved. ciel,C,G iel,A iai n .Ctzn.20.Arzn and Atrazine 2001. Catizone. P. and Vicari, A. Dinelli, G. C., Accinelli, n aubecmet ntemanuscript. the on comments reviews their valuable for and reviewers anonymous two Dubrovsky, and Neil Flury, Capel, Markus Paul LaBaugh, James thank We Pro- gram. (NAWQA) Assessment Water-Quality National Survey, stream low of periods during flow. concentrations flow, lower stream high and of NO periods during of degradates setting their concentrations and hydrogeologic larger the in of result dynamics subsurface high-flow These shallow during periods. whereas chemistry stream year, dominates the drainage of periods low- the layer great- flow during its chemistry reducing has surface-water water on chemically influence Ground est stream. the the reach beneath and there pass to riparian NO water for the flowpaths preferential below provide negligible zone sediments to reduced Coarse be to concentrations. degradates pes-their ground- most and for Long ticides time zone. sufficient allow riparian times to residence the directly water bypassing contaminants route steam, ditches the NO and of fate drains and Tile transport the on ences waters. residence surface adequate reach they guarantee before compounds these eliminate sufficiently to in may processes establishing natural transport zones times, By their buffer streams. limiting that wide to in role water have important ground may potentially zones the buffer out appli- of points point the cation not from have downgradient far degradates very pesticide migrated and not fact pesticides the were these Furthermore, that use. ground they their older (ii) before deeper, recharged this suggests limited; water (iii) aquifer or is deep; the persistence that transported col- this in samples (i) positions in that deeper compounds these from of lected stud- absence degradates various The note the to for ied. MCLs important no is are were it there However, detected that MCLs. pesticides the the below all well water, persis- ground their were in of but spite tence In study MCLs. the their one-third during about detected only largest the were ter be NO will uncertain large zones these still hyporheic reducing and is in riparian It the effective eutrophication. how to po- the contribute is and there decade, NO next surface-water for major the tential over a stream the represent reach NO not high this water, Because do the issue. drinking health Since concentrations for MCL. used large the rarely times these only 2.5 is about aquifer to surficial up were water NO maximum MCL; the half surface-water NO on of tions water ground of NO impact the limiting eoaho erdto nsbol.Bo.Fri.Sis3:9–0.Kli,DW,DA olb,adEM hra.19.Psiie in Pesticides 1995. Thurman. E.M. and Goolsby, D.A. D.W., Kolpin, 33:495–500. Soils Fertil. Biol. subsoils. in degradation metolachlor hssuywscnutda ato h ..Geological U.S. the of part as conducted was study This influ- strong exert site the at factors Hydrogeologic wa- surface in concentrations simazine and Atrazine 3 Ϫ ocnrtos oee,telretconcentra- largest the However, concentrations. 3 Ϫ esrdi ufc ae eeol about only were water surface in measured ACKNOWLEDGMENTS REFERENCES UKT UHS RNPR N AEO IRT N PESTICIDES AND NITRATE OF FATE AND TRANSPORT HUGHES: & PUCKETT 3 Ϫ 3 Ϫ 3 Ϫ ocnrtost increase to concentrations concentrations. ocnrtosi ground in concentrations 3 Ϫ rudwtrshould water ground 3 Ϫ 3 Ϫ n pesticides. and n pesticides and 3 Ϫ nground in abs,JE,adEA ee.19.Psiie ngon water: ground in Pesticides 1996. Resek. E.A. and J.E., Barbash, eio .. .Ftgrl,AR il n .Aaea 00 Nitrate 2000. Aravena. R. and Hill, A.R. Fitzgerald, D. K.J., Devito, Wayland. J.E. and Bartholomay, R.C. Plummer, L.N. E., Busenberg, uebr,E,adLN lme.19.Ueo chlorofluorocarbons of Use 1992. Plummer. 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Water Oklahoma. central 28:2257–2283. of Res. system terrace and alluvium hmcl ngon ae ftemdetr S:Rltosto Relations USA: midwestern the of water ground in chemicals dinitrogen from estimated groundwater in degassing and trification Netherlands. the Rotterdam, Balkema, A.A. pollution. and 03 ebcdsadhriiedgaainpout nUpper in products degradation herbicide and Herbicides 2003. prevalence The herbicides: chloroacetanilide of Degradation 1998. 22:743–755. Qual. 22:340–346. Ambio perspectives. European corridors: river York. New Sons, & Wiley John 3 n CCl and F 2 F 2 shdooi rcr n g-aigtos The tools: age-dating and tracers hydrologic as ) 2291 Reproduced from Journal of Environmental Quality. Published by ASA, CSSA, and SSSA. All copyrights reserved. ukt,LJ 95 dniyn h ao ore fntin water nutrient of sources major the Identifying 1995. L.J. Puckett, nation’s the in Nutrients 1996. Helsel. D.R. and D.K., Mueller, solid- Automated 1993. Thurman. E.M. and Milles, M.S. Atrazine M.T., Meyer, 1992. 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