富里酸和铜的络合的原位检测理论预测和实验结果的比较

Insitustudyofbindingofcopperbyfulvicacid:ComparisonofdifferentialabsorbancedataandmodelpredictionsMingquanYana,*,DeborahDryerb,GregoryV.Korshinc,MarcF.BenedettidaDepartmentofEnvironmentalEngineering,CollegeofEnvironmentalSciencesandEngineering,PekingUniversity,TheKeyLaboratoryofWaterandSedimentSciences,MinistryofEducation,Beijing100871,ChinabHazen&Sawyer,498SeventhAvenue,NewYork,NY10018,UnitedStatescDepartmentofCivilandEnvironmentalEngineering,UniversityofWashington,Box352700,Seattle,WA98195-2700,UnitedStatesdUniv.ParisDiderot,SorbonneParisCite´,IPGP,UMR-CNRS7154,Paris,FrancearticleinfoArticlehistory:Received7June2012Receivedinrevisedform9October2012Accepted10October2012Availableonline22October2012Keywords:AbsorbanceComplexationCopperFulvicacidInsitumethodsModelabstractThisstudyexaminedthebindingofcopper(II)bySuwanneeRiverfulvicacid(SRFA)usingthemethodofdifferentialabsorbancethatwasusedatenvironmentally-relevantconcentrationsofcopperandSRFA.ThepH-andmetal-differentialspectrawerepro-cessedvianumericdeconvolutiontoestablishcommonalitiesseeninthechangesofabsorbancecausedbydeprotonationofSRFAanditsinteractionswithcopper(II)ions.SixGaussianbandsweredeterminedtobepresentinboththepH-andCu-differentialspectra.Theirmaximawerelocated,intheorderofincreasingwavelengthsat208nm,242nm,276nm,314nm,378nmand551nm.ThebandswiththesemaximaweredenotedasA0,A1,A2,A3,A4andA5,respectively.Propertiesofthesebandswerecomparedwiththoseexistinginthespectraofmodelcompoundssuchassulfosalicylicacid(SSA),tannicacid(TA),andpolystyrenesulfonicacid-co-maleicacid(PSMA).WhilenoneofthefeaturesobservedindifferentialspectraofthemodelcompoundwereidenticaltothosepresentinthecaseofSRFA,GaussianbandsA1,A3andpossiblyA2wereconcludedtobelargelyattributabletoacombinationofresponsesofsalicylic-andpolyhydroxyphenolicgroups.Incontrast,bandsA4andA5weredetectedinthedifferentialspectraofSRFAonly.Theirnatureremainstobeelucidated.Toexaminecorrelationsbetweentheamountofcopper(II)boundbySRFAandchangesofitsabsorbance,differentialabsorbancesmeasuredatindicativewavelengths250nmand400nmwerecomparedwiththetotalamountofSRFA-boundcopperestimatedbasedonVisualMINTEQcalculations.ThisexaminationshowedthatthedifferentialabsorbancesofSRFAinawiderangeofpHvaluesandcopperconcentrationswerestronglycorrelatedwiththeconcentrationofSRFA-boundcopper.Theapproachpresentedinthisstudycanbeusedtogenerateinsituinformationconcerningthenatureoffunctionalgroupsinhumicsubstancesengagedininteractionswithmetalsions.Thisinformationcanbeusefulforfurtherelaborationanddevelopmentofdetailedtheo-reticmodelsthatdescribethecomplexationofmetalsintheenvironment.ª2012ElsevierLtd.Allrightsreserved.*Correspondingauthor.Tel.:þ861062755914/81;fax:þ861062756526.E-mailaddress:[e-mail](M.Yan).Availableonlineat(2013)588e5960043-1354/$eseefrontmatterª2012ElsevierLtd.Allrightsreserved.(DOM)affectstheenvironmentalfate,bioavailabilityandtoxicityofmanyheavymetals(Benedettietal.,1995;LeenheerandCroue,2003;Jouvinetal.,2009;YangandvandenBerg,2009;Bakenetal.,2011;Cabaniss,2011;Janotetal.,2011).TechniquestoquantifyDOMemetalsinteractionsareverydiverse(Brulandetal.,2000;Bucketal.,2007;ChristlandKretzschmar,2007;Hoffmannetal.,2007;Baietal.,2008;Jouvinetal.,2009;Jimenezetal.,2010;Wuetal.,2012).FrequentlytheyemployexaminationofchangesofDOMfluorescencecausedbyDOMinteractionswithmetalionsandinterpretationofsuchchangesbasedoneitheranalyticalexpressionsapplicabletorelativelysimpleDOMemetalcomplexationmodels(e.g.,RyaneWeberexpression)orstatisticalPARAFAC-baseddeconvolutionofthedata(RyanandWeber,1982;Coble,1996;EstevesdaSilvaetal.,1998;Baietal.,2008;Ohnoetal.,2008;YamashitaandJaffe,2008;Mora´nVieyraetal.,2009;Park,2009;Seredy
nska-Sobeckaetal.,2011;Wuetal.,2011,2012).IncontrastwiththewideuseoffluorescencemethodsthaninterpretthebehaviorofNOMfluorophoresconstitutingarelativelysmallsubsetofNOMfunctionalgroups(PullinandCabaniss,1995;Coble,1996;Lusteretal.,1996;Ohnoetal.,2008;YamashitaandJaffe,2008;Marangetal.,2009),effectsofDOMemetalionsinteractionsonNOMchromophoresthatrepresentawiderensembleofDOMfunctionalgroupshavenotbeenexaminedinadequatedetail(Korshinetal.,1997;Twardowskietal.,2004;Baietal.,2008;Helmsetal.,2008;Heretal.,2008;Park,2009).Whilerecentresearchhasdemon-stratedthepresenceofprominentandinterpretablechangesofDOMabsorbancespectraassociatedwithdeprotonationofDOMmolecules(Dryeretal.,2008),thecomplicationinusingtheabsorbancespectroscopyforascertainingDOMemetalinteractionsisthattheabsorbancespectraofDOMarefeaturelessanddonotdeemedtobeamenabletosameinvestigationapproaches(e.g.,fluorescencequenching,PAR-AFAC)asthosethathaveusedtoprocessfeature-richexci-tation/emissionmatricesofDOM.ChangesofthefeaturelessabsorbancespectraofDOMassociatedwithDOMinteractionswithhalogensandoxidantscanbetrackedusingtheconceptofdifferentialspectroscopy(Janotetal.,2010;Maureretal.,2010).Thisapproa