Table Of ContentSOILPROCESSESREGULATINGTHEFATEOFCHLOROPHENOLSIN
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,
