Chemosphere66(2007)1821–1828 www.elsevier.com/locate/chemosphere PolychlorinatedbiphenylcontaminationtrendsinLakeHartwell, SouthCarolina(USA):Sedimentrecoveryprofilesspanning twodecades JohnD.Sivey,CindyM.Lee * Department of Environmental Engineering and Science, Clemson University, 342 Computer Court, Anderson, SC 29625, USA Received25May2006;receivedinrevisedform24August2006;accepted5September2006 Availableonline7November2006 Abstract Toassesstheca.20-yearpolychlorinatedbiphenyl(PCB)contaminationtrendsinLakeHartwell,SC,sedimentcoresfromtheTwelve MileCreekarmwerecollectedinJuly2004attwosites(G30andG33)firstsampledinthemid-1980s.Congener-specificPCBdataasa functionofdepthfromthesediment–waterinterfaceforthe2004sedimentsampleswerecomparedtodataobtainedfrom1987and1998 samplestakenfromthesamelocations.DespitemodestdecreasesintotalPCBlevelsneartheG30sediment–waterinterface,historical increasesinaveragedegreesofchlorinationmayelevatetheoveralltoxicriskatthissite.UnlikeG30,themorerapidrecoveryinthenear- surfacesedimentofG33suggeststhattheeffectivenessoftheU.S.EPAnaturalattenuationrecordofdecisionissite-specificandisunli- kelytoresultinuniformsurfacesedimentrecoverythroughoutthemostcontaminatedregionsofLakeHartwell. � 2006 Elsevier Ltd. All rights reserved. Keywords: PCBs;Naturalattenuation;Congener-specificanalysis;Reductivedechlorination;Aroclors 1. Introduction Polychlorinatedbiphenyls(PCBs)arepersistentorganic pollutants with significant bioaccumulation potentials in environmental systems. Despite the cessation of domestic productioninthelate1970s,sitescontaminatedwithPCBs continuetoposeathreattohumanandecosystemhealth. Inaquaticsystems,PCBpartitioningandtransformations areafunctionofmolecular-level(i.e.,congener-level)prop- erties and structure (Erickson, 1986; Farley et al., 1994). ThetoxicologicaleffectsofPCBsalsovaryatthecongener level (Safe, 1992). The variability observed in the physio- chemical properties of PCBs suggests a differential parti- tioning (i.e., weathering) of congeners in multiphase environmental systems (Burkard et al., 1985; Dunnivant et al., 1988). Evidence of PCB physiochemical weathering in near-surface sediments in the Twelve Mile Creek arm * Correspondingauthor.Tel.:+18646561006;fax:+18646560672. E-mail address: LC@clemson.edu (C.M.Lee). 0045-6535/$ - see front matter � 2006 Elsevier Ltd. All rights reserved. doi:10.1016/j.chemosphere.2006.09.013 of Lake Hartwell (the current study site) was reported by Farleyetal.(1994).Atthissite,thedegreeofPCBchlori- nationinshallowsedimentswasobservedtoincreasewith increasingdistancedownstreamofthesource.Duringsedi- ment resuspension and transport events, the preferential sorptionofhigherchlorinatedcongenersandvolatilization oflowerchlorinatedcongenerswereproposedasthedom- inant PCB weathering mechanisms (Dunnivant et al., 1988). AerobicandanaerobicPCBdegradationprocesseshave been reported inlaboratoryinvestigations (Abraham et al., 2002;Master et al., 2002). Typically, PCBs with up to four chlorine atoms are susceptible to aerobic biotransforma- tions.Inanaerobicenvironments,reductivedechlorination is the most commonly reported PCB biotransformation mechanism (Bedard and Quensen, 1995; Pakdeesusuk et al., 2003). Reductive dechlorination of PCBs is a two- electron transfer mechanism in which chlorine atoms on the biphenyl moiety are replaced with hydrogen atoms (NiesandVogel,1991).Reductivedechlorinationtypically