humic substance-lake-1

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SourcesandHaloaceticAcid/TrihalomethaneFormationPotentialsofAquaticHumicSubstancesintheWakarusaRiverandClintonLakenearLawrence,Kansas

MICHAELL.POMES,*,†CYNTHIAK.LARIVE,‡E.MICHAELTHURMAN,†W.REEDGREEN,§WILLIAMH.OREM,|COLLEENE.ROSTAD,#TYLERB.COPLEN,|BENJAMINJ.CUTAK,‡ANDANNM.DIXON‡

U.S.GeologicalSurvey,4821QuailCrestPlace,Lawrence,Kansas66049,DepartmentofChemistry,TheUniversityofKansas,Lawrence,Kansas66045,U.S.GeologicalSurvey,401HardinRoad,LittleRock,Arkansas72211,U.S.GeologicalSurvey,956NationalCenter,12201SunriseValleyDrive,Reston,Virginia22192,andU.S.GeologicalSurvey,408FederalCenter,Denver,Colorado80225-0046

Gramquantitiesofaquatichumicsubstances(AHS)wereextractedfromtheWakarusaRiver-ClintonLakeReservoirsystem,nearLawrence,KS,tosupportnuclearmagneticresonance(NMR)experimentalstudies,reportconcentrationsofdissolvedorganiccarbon(DOC)andAHS,definesourcesoftheAHS,anddetermineiftheAHSyieldsufficientquantitiesofhaloaceticacids(HAA5)andtrihalomethanes(THM4)thatexceedU.S.EnvironmentalProtectionAgency(EPA)MaximumContaminantLevels(MCL)indrinkingwater.AHSfromtheWakarusaRiverandClintonLakeoriginatedfromriparianforestvegetation,reflectedrespectiveeffectsofsoilorganicmatterandaquaticalgal/bacterialsources,andboreevidenceofbiologicaldegradationandphotodegradation.AHSfromtheWakarusaRivershowedtheeffectofterrestrialsources,whereasClintonLakehumicacidalsoreflectedaquaticalgal/bacterialsources.Greateramountsofcarbonattributabletotannin-derivedchemicalstructuresmaycorrespondwithhigherHAA5andTHM4yieldsforClintonLakefulvicacid.Priortoappreciableleaf-fallfromdeciduoustrees,thecombined(humicandfulvicacid)THM4formationpotentialsfortheWakarusaRiverapproachedtheproposedEPATHM4StageIMCLof80µg/L,andthecombinedTHM4formationpotentialforClintonLakeslightlyexceededtheproposedTHM4StageIIMCLof40µg/L.Finally,AHSfromClintonLakecouldaccountformost(>70%)oftheTHM4concentrationsinfinishedwaterfromtheClintonLakeWaterTreatmentPlantbasedonSeptember23,1996,THM4results.

IntroductionAquatichumicsubstances(AHS)havebeensubjectedtovariousnuclearmagneticresonance(NMR)techniques(1H,13C,31P,and15N)togaininformationonthetypesand

numbersofconstituentfunctionalgroups(1).Asdefinedby

Thurman(2),AHSarecolored,polyelectrolytic,nonvolatileorganicacidsthatrangeinmolecularweightfrom500to>10,000daltonsandareisolatedfromwaterbysorptionontoXADresinsorcomparableprocedures.HumicacidsconsistofcomponentsofAHSthatprecipitatewhenthesamplepHisdecreasedto1.0,whereasfulvicacidsremaininsolution.WiththeprotonationofmostcarboxylicacidgroupsatpH1.0,themorehydrophobichumicacidsprecipitatebecauseoftheirsmallercarboxylicacidcontentandgreatermolecularweight.Overall,AHScommonlyconstituteabout50%ofthedissolvedorganiccarbon(DOC)inawatersamplefilteredthrougha0.45-µmfilter.

Recently,researchershavedevelopednoveltechniquesinvolvingNMRtoexaminethephysicalandstructuralpropertiesofAHSonfinerscales.Thecombinationofspectraleditingtechniquesandmodifiedpulsed-fieldgradientex-perimentsinvolvingprotonNMR-deriveddiffusioncoef-ficients(3)oftheSuwanneeRiver(GA)fulvicacidstandard(4,5)yieldedradiiofgyrationcomparabletovaluesreportedbysmall-angleX-rayscattering(6,7).Additionally,theuseof113CdNMRhasallowedthemeasurementofCd2+exchange

ratesforSuwanneeRiverfulvicacid(8,9).

ExperimentswiththeseNMRtechniques,aswellassolid-state13CNMR,onpreviouslyuncharacterizedAHS,likethose

intheWakarusaRiver-ClintonLakeReservoirsystemnearLawrence,KS,havethepotentialtoconsumerelativelylargequantitiesofsamplemass(75-200mgperexperiment).Additionally,atleast500mgpersamplecanbeconsumedbyclassicalcharacterizationtechniquesthatincludeel-ementalanalysis,titration,Fouriertransforminfraredspec-troscopy(FTIR),δ13Cdetermination,anddeterminationof

ligninoxidationproducts(LOP)(2).SuchcharacterizationtechniquesyielddetailedinformationaboutthesourceofAHSinlakeandreservoirsettings(10-12),andwhetherwaterpercolatedthroughthesoil(13)priortoreachingtheriverorreservoir.Onenewercharacterizationtechnique,thedeterminationofhaloaceticacid(definedtoincludemono-,di-,trichloracetic,mono-,anddibromoaceticacid;HAA5)andtrihalomethane(definedtoincludebromodichlo-romethane,dibromomonochloromethane,bromoform,andchloroform;THM4)formationpotentialsofAHS(11,12)candetermineifAHSyieldsufficientconcentrationsofHAA5andTHM4toraiseregulatoryconcernsundertheDisinfectionByproductsRule(14).Thus,gramquantitiesofAHSarerequiredtosupportNMRexperimentsandcharacterizationefforts.ThispaperdescribestheextractionofgramquantitiesofAHSfromtheWakarusaRiver-ClintonLakeReservoirsystem,nearLawrence,KS,reportsconcentrationsofDOCandtheproportionsofDOCaccountableasAHS,definessourcesoftheAHS,andpresentsadeterminationofwhethertheHAA5andTHM4formationpotentialsoftheAHSaresufficienttocreateregulatoryconcerns.TheSeptember10-October10timeofsamplecollectiontookplacebeforeanyappreciableleaf-falloccurredfromdeciduoustreesandrepresentsatimeofminimalterrestrialinputtotheriver-reservoirsystem.Workinothersettingshasshownthatsource