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SOILPROCESSESREGULATINGTHEFATEOFCHLOROPHENOLSIN WETLANDS By ELISAMARIED'ANGELO ADISSERTATIONPRESENTEDTOTHEGRADUATESCHOOL OFTHEUNIVERSITYOFFLORIDAINPARTIALFULFILLMENT OFTHEREQUIREMENTSFORTHEDEGREEOF DOCTOROFPHILOSOPHY UNTVERSrrYOFFLORIDA 1998 Thisdissertationisdedicatedtomyparents,JeanandMary,andtothememoryofLaura Wall. ACKNOWLEDGEMENTS ThisresearchwasfinanciallysupportedbytheU.S.DepartmentofAgriculture NationalResearchInitiativeCompetitiveGrantsProgram. Sincereappreciationgoestomymajoradvisor,Dr.K.R.Reddy,forproviding almostlimitlessopportunitiesandguidancetohelpmeattainmyprofessionalgoalsover thelastdozenyears.IwouldalsoliketothankDr.P.S.C.Rao,forhelpingmegainthe confidence to go for the brass ring. I sincerely acknowledge my other committee members,Drs.D.P.Chynoweth,J.J.Delfino,D.A.Graetz,andL.T.Ou,foractingasmy rolemodelsasteachersandscientists. Iwouldliketogratefullyacknowledgethecooperationofseveralresearcherswho provided soils usedin the study: Dr. E. Roden (Univ. ofAlabama), Dr. C. Lindau (LouisianaSt. Univ.), Dr. C. Crozier(North CarolinaStateUniv),Dr. J. Richardson (NorthDakotaStateUniv.),Dr.R.Kadlec(WetlandManagementServices,MI),Dr.R. DeLaune(LouisianaSt.Univ),andJ.R.WhiteandM.M.Fisher(Univ.ofFL),andthe statisticalanalysisadviceofJ.M.Harrison(SeniorStatistician,Univ.ofFL). Finally, I would like to thankmy husband, Steven P. Wall, whose love and supportthroughouttheyearshavemadethisendeavorpossible. iii TABLEOFCONTENTS page ACKNOWLEDGEMENTS »« ABSTRACT vii CHAPTERS 1 INTRODUCTION 1 OverviewoftheProblem 1 AerobicandAnaerobicInterfacesinWetlands 4 ChlorophenolsasEnvironmentalPollutants 8 Biodegradation 13 Sorption 21 ObjectivesandHypotheses 26 DissertationFormat 28 2 REGULATORSOFHETEROTROPHICMICROBIALPOTENTIALSIN WETLANDSOILS 30 Introduction 30 MaterialsandMethods 32 SoilCollectionandIncubation 32 SoilChemicalAnalysis 35 AnalyticalMethods 36 DataAnalysis 38 ResultsandDiscussion 38 ChemicalPropertiesofSoils 38 MethaneProductioninWetlandSoils 41 DecompositionofSoilOrganicCUnder DifferentElectronAcceptorReducingConditions 41 RelationshipsBetweenMicrobialActivities andBiologicalandChemicalProperties 54 Conclusions 59 iv 3 REGULATORSOFPENTACHLOROPHENOLDEGRADATIONIN WETLANDSOILS 61 Introduction 61 MaterialsandMethods 63 SoilCollectionandIncubation 63 PentachlorophenolToxicitytoAerobicandAnaerobicSoil Microorganisms 66 InfluenceofElectronAcceptorsonPCPDegradation 66 InfluenceofElectronDonors,Nutrients,and VitaminsonPCPDegradation 68 AnalyticalMethods 69 DataAnalysis 70 Results 71 PentachlorophenolToxicitytoAerobicandAnaerobicSoil Microorganisms 71 InfluenceofElectronAcceptorsonPCPDegradation 71 RelationshipsBetweenPCPDegradationKinetics andSoilProperties 84 InfluenceofElectronDonors,Nutrients,and VitaminsonPCPDegradation 84 Discussion 88 4 MICROBIALACTIVITYEFFECTSONSORPTIONOF CHLOROPHENOLSINSOILS 100 Introduction 100 Theory 102 MaterialsandMethods 105 SoilCollectionandIncubation 105 SorptionExperiments 107 ChemicalAnalysis 108 Results 109 MicrobialActivityEffectsonSoilProperties 109 ChlorophenolSorption 112 RelationshipsBetweenPartitionCoefficientsandSoilProperties 120 Discussion 125 MicrobialActivityEffectsonSoilProperties 125 ChlorophenolSorption 126 5 WETLANDTOXICORGANICFATEMODEL 130 Introduction 130 MaterialsandMethods 130 WetlandToxicOrganicFateModelDevelopment 130 ModelSimulations 139 v ResultsandDiscussion 139 FateofPCPAmendedtoSurfaceWater 139 FateofPCPAmendedtoSubsurfaceWetlandSoils 142 Conclusions 142 6 SUMMARYANDCONCLUSIONS 147 LITERATURECITED 155 BIOGRAPHICALSKETCH 178 vi AbstractofDissertationPresentedtotheGraduateSchool oftheUniversityofFloridainPartialFulfillmentofthe RequirementsfortheDegreeofDoctorofPhilosophy SOILPROCESSESREGULATINGTHEFATEOFCHLOROPHENOLSIN WETLANDS By ElisaMarieD'Angelo December,1998 Chairman:Dr.K.R.Reddy MajorDepartment: SoilandWaterScience Transformationsofagriculturalandindustrialpollutantsinwetlandsdependon the presence and activity of appropriate microbial groups inhabiting the soil, as influencedbyinteractions withtheirphysical andchemical environment. Laboratory research wasconductedusing aspectrumofwetlandsoils, toascertainthedominant regulators of microbial activities, and in turn, how these activities governed biodegradationandsorption ofchlorinatedphenols (CPs). Chorophenols werechosen becausetheyarecommonsoilcontaminants,andlikeotherchlorinatedaromatics,are susceptible to biodegradation under anaerobic conditions that dominate wetland ecosystems. Aerobicrespiration,denitrification,sulfatereduction,andmethanogenesiswere stronglycorrelatedtoavailabilityofelectronacceptors,electrondonors,andmicrobialC. OrganicCmineralizationaveragedthreetimesfasterwithO2ascomparedtoalternate vii electron acceptors, but was not significantly different between anaerobic treatments. Throughmeasurementsofsoilchemicalpropertiesandelectronacceptorloadingrates, therelativecontributionsofdifferentmetabolic groupstoorganicmatterdecomposition canbeestimatedinawetlandprofile. Biodegradationofpentachlorophenol(PCP)wasobservedinmost(80%)wetland soils;however,ratesweresimilarlygovernedbyenvironmentalconditions.Maximum PCPdegradationwasrestrictedtoconcentrationsbetween0.3to10-23umolL",dueto sorption-controlledbioavailability andtoxicityconstraints. Degradation waspromoted underaerobicandmethanogenicconditions,andinhibitedunderdenitrifyingandsulfate reducing conditions. Aerobic PCP degradation produced pentachloroanisole, and methanogenicdegradationyieldedlowerchlorinatedphenolsbyreductivedechlorination. However,>63%oftheseby-productswerelostin30dfromhalfofthesoils.Reductive dechlorinationwashighlycorrelatedtoelectrondonoravailabilityandmicrobialbiomass (94%),andwasenhancedwithamendmentsofprotein-basedelectrondonors,suggesting theroleoffermentativeandhydrolyticbacteria. SorptionofCPswasdescribedbylinearisotherms,andpartitioncoefficientswere highestin low pH and high organic mattersoils, which explained 80% ofvariation betweensorptionmodelsandexperimentalresults.Upto30timesreductioninsorption undermethanogeniccomparedto aerobic conditions was attributedtoeffects on pH, ionic strength, and colloidal concentration. Results predicted that CP mobility, bioavailability,andtoxicitywill behigherundermethanogenicconditionsthanunder aerobicconditions. viii CHAPTER1 INTRODUCTION OverviewoftheProblem Wetlands and aquatic ecosystems are recipients of agricultural chemicals from a numberofpointandnon-pointsources.Wells(1992)quotedthefollowingstatisticsfromthe USEPA and USDA, "Agricultural stresses, largely from excess nutrients, sediments, and pesticides,affect58%oftheimpairedlakeacres,55%ofimpairedstreammiles,and21%of impaired estuarine systems" in the U.S. Recent estimates indicate that pesticides from agriculturalareashavecauseddamagetoalmost5000wetlandsandwaterbodiesintheU.S. (Tarabanetal., 1993; Cooper, 1993). DuringarecentUSDA-ARS sponsored symposium entitled "Agricultural Water Quality Priorities, A Team Approach to Conserving Natural Resources",itwasdeterminedthatthereisaneedtodevelopnewagriculturalmanagement strategies to improve the long-term sustainability of agricultural systems and to reduce agricultural impacts on water quality (Gish and Sadeghi, 1993). One rapidly spreading technology, constructed wetlands, has been found to be effective at attenuating many agricultural,industrial,anddomesticwastewaters(Hammer,1989;Cooper,1993;Kadlecand Knight,1996;Cole,1998).Oneadvantageofconstructedwetlandsisthattheycanbedesigned andmanagedtooptimizeconditionsforremovalofspecifictypesofcontaminants.However, beforeconstructedwetlandscanbeconsideredastreatmentalternatives,informationaboutthe dominantbiogeochemicalprocessesandtheirrespectivecontrollingfactorsisrequired. 1 2 Inrecentyears,researchhasemphasizedwetlandassimilationofnutrients,organics, andsuspendedsolids(KadlecandKnight,1996).Biologicalandchemicalprocessesassociated withthesoilarelargelyresponsibleforwaterqualityimprovement(ReddyandD'Angelo, 1994).Forexample,processessuchasnitrification-denitrification(Reddyetal.,1989;1990a), soilsorptionofphosphorus(OlilaandReddy,1993),andaerobicandanaerobicdecomposition oforganicmatter(D'AngeloandReddy, 1994a) aremajorpathwaysforremovalofthese contaminants. Comparedtotransformationsofnaturally-occurringsubstrates,thereisadearthof informationregardingthefateagriculturalpesticidesinthewetlandenvironment.However, thecapacityofwetlandstoassimilatepesticidesisalsolikelytobedictatedbybiogeochemical pathwaysassociatedwiththesoilandoverlyingwatercolumn(Fig.1.1).Microbialdegradation isgenerallyconsideredthemainpathwayforattenuationofagriculturalchemicals, andis stronglyinfluencedbyenvironmentalconditions.Thepresenceoftheplantrhizospheremay also influence microbial degradation (Walton and Anderson, 1990). Additionally, abiotic processes,suchassoil sorption,haveamajorinfluenceonthebioavailabilityandfateof chemicalsinwetlands,andareaffectedbysoilcharacteristicssuchaspHandorganicmatter content. Althoughthereexistsaconsiderableamountofinformationaboutmostprocesses individually(seebelow),therehavebeenfewattemptstointegrate,orcoupleprocesseswith thegoalofdescribingtheoverallfateofchemicalsincomplexsoil-watersystems. Manyhighlychlorinatedcompoundsaretoxicandpersistentenvironmentalpollutants (BhatnagarandFathepure,1990).Examplesofhighlychlorinatedagriculturalandindustrial chemicals include:2,4,5-trichlorophenoxyaceticacid(2,4,5-T),methoxychlor,aldrin,mirex, toxaphene, eldrin, pentachlorophenol (PCP), hexachlorocyclohexane (lindane), heptachlor,