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1、DevelopmentsinEarth&EnvironmentalSciences,7MarkO.BarnettandDouglasB.Kent(Editors)r2008ElsevierB.V.AllrightsreservedDOI10.1016/S1571-9197(07)07015-2Chapter15ArsenicSpeciationinSolidPhasesofGeothermalFields12,43MarcoA.Alsina,IanSaratovsky,Jean-Franc-oisGaillardand1,PabloA.Pa
2、ste´n1DepartamentodeIngenierı´aHidra´ulicayAmbiental,PontificiaUniversidadCato´licadeChile,Santiago6904411,Chile2DepartmentofChemistry,NorthwesternUniversity,Evanston,IL60208,USA3DepartmentofCivilandEnvironmentalEngineering,NorthwesternUniversity,Evanston,IL60208-3109,USA4Pr
3、esentaddress:InorganicChemistryLaboratory,OxfordOX13QR,UKABSTRACTThefateofAsingeothermalsystemsiscontrolledbytheinteractionofseveralgeochemicalandbiologicalprocesses,suchasdissolution,precipitation,dilution,volatilization,sorption,biomineralization,andbiocatalysis.Althought
4、heseinteractionsremainpoorlyunderstood,thedistinctivemicro-andmolecular-scalefingerprintsofprocessesoccurringatthesolid–waterinterfacearesheddingnewlightonthesecomplexsystems.ThemicroscopicandmolecularspeciationofAsingeothermaldepositsoffersvaluableinformationaboutitschemica
5、levolution,theprocessesinwhichitisinvolved,andthereactivityofthesolidmaterialsformed.TheamorphousandhydrousnatureofmosthotspringmineralsrenderstheapplicationofconventionalidentificationmethodsbasedonX-rayorelectrondiffractionchallenging.ThischapterpresentsabriefreviewofAsing
6、eothermaldepositsandsomeofourownrecentresultsonhotspringdepositsintheElTatiogeothermalfield.WeusedX-rayabsorptionspectroscopytoinvestigatethespeciationofAsinsintermaterialandinbiologicalmats.OurresultssuggestthatFeoxyhydroxidesplayanimportantroleincontrollingtheconcentration
7、ofAsinbothsolidmedia.Althoughitisrecognizedthatmicrobialpopulationsingeo-thermalsystemsmaycatalyzetherapidoxidationofAs(III)toAs(V),itisstillunclearwhethermicrobialcatalysisand/orbiomineralizationcontroltheforma-tionofFeoxyhydroxides.UnderstandingtheassociationbetweenAsandF
8、eCorrespondingauthor.Tel.:+56-2-3545872;Fax:+56-2-3545876;E-mail:ppasten@ing.puc.