國外鹵素地球化學(xué)測量綜述Introduction

Halogensareagroupofelementsthatarefoundintheperiodictable,includingfluorine(F),chlorine(Cl),bromine(Br),iodine(I)andastatine(At).Theyareessentialcomponentsofmanymineralsandrocks,andplayanimportantroleingeochemicalprocesses.HalogenshavebeenusedastracerstostudyvariousaspectsoftheEarth'ssystems,suchastheoriginoforedeposits,volcanicandhydrothermalsystems,andthecyclingofhalogensintheatmosphereandoceans.Inthisreview,wesummarizethecurrentstatusandrecentadvancesinthemeasurementofhalogensingeochemicalsystems.

MethodsforHalogenAnalysis

Themeasurementofhalogenscanbedoneusingawiderangeofmethods,includingionchromatography,inductivelycoupledplasmamassspectrometry(ICP-MS),atomicabsorptionspectroscopy,neutronactivationanalysis,andtheuseofhalogen-sensitiveelectrodes.Eachofthesemethodshasitsownadvantagesandlimitations,andthechoiceofmethoddependsonthesamplematrixandtherequiredprecisionandaccuracy.

ICP-MSisoneofthemostwidelyusedmethodsfortheanalysisofhalogensingeologicalsamplesduetoitshighsensitivityandlowdetectionlimits.However,itrequiresacomplexsamplepreparationprocess,andtheanalysiscanbeaffectedbymatrixeffectsandinterferencesfromotherelements.Ionchromatographyisasimplerandfastermethodfortheanalysisofhalogens,butithaslowersensitivityandrequirestheuseofexpensivestandards.

Neutronactivationanalysishasbeenusedtoanalyzehalogensfordecades,particularlyfortheanalysisofiodineinseawaterandbiologicalsamples.However,thismethodhaslimitationsintermsofsamplesizeandtheneedforspecializedfacilities.Halogen-sensitiveelectrodesareafastandsimplemethodformeasuringhalogensinaqueoussolutions,buttheyarepronetointerferencesfromotherions.

ApplicationsofHalogenAnalysisinGeochemistry

Theanalysisofhalogenshasbeenusedinvariousgeochemicalapplications,suchasthetracingoffluidsinhydrothermalsystemsandoredeposits,thedeterminationofhalogenratiosinoceansedimentsandrocks,andthestudyofvolcanicsystems.

Oneimportantapplicationofhalogenanalysisisthedeterminationoftheoriginandevolutionofhydrothermalfluids,whichcanbeusedtoidentifythesourceofmineraldeposits.Theuseofhalogenratios,particularlytheBr/ClandI/Clratios,hasbeenshowntobeeffectiveindifferentiatingbetweenhydrothermallyderivedfluidsandthosederivedfromsurfacewaterormeteoricwater.

ThestudyofthecyclingofhalogensintheEarth'ssystemsisanotherimportantapplicationofhalogenanalysis.TheanalysisofhalogenratiosinoceansedimentsandrockshasprovidedinsightsintotheevolutionoftheEarth'satmosphereandthecyclingofhalogensbetweentheatmosphere,oceans,andland.TheBr/Clratio,forexample,hasbeenusedasatracerforthedepositionofhalogensintheoceans,whiletheI/Clratiohasbeenusedtotracethetransportofiodineintheatmosphere.

Halogenanalysishasalsobeenusedtostudyvolcanicsystems,particularlyinthedeterminationofthesourceandoriginofvolcanicgases.Halogenratiosinvolcanicgasescanprovideimportantinformationonthecompositionofthemantleandtheprocessesthatleadtothegenerationofmagma.

ChallengesandFutureDirections

Despitetheadvancesinthemeasurementofhalogensingeologicalsamples,therearestillchallengesandlimitationsthatneedtobeaddressed.Onemajorchallengeistheneedforaccurateandprecisereferencematerialsforhalogenanalysis.Thedevelopmentofnewreferencematerialsandtheimprovementofexistingoneswouldgreatlyenhancetheaccuracyandcomparabilityofhalogenmeasurementsbetweendifferentlaboratories.

Anotherchallengeistheneedforbetterunderstandingofthebehaviorofhalogensincomplexgeologicalsystems.Theuseofmultiplehalogenratios,suchasBr/Cl,I/Cl,andF/Cl,canprovideinsightsintotheoriginandevolutionofgeologicalfluids,buttheinterpretationoftheseratiosrequiresabetterunderstandingofthepartitioningandfractionationofhalogensindifferentgeologicalenvironments.

Conclusion

Halogensplayanimportantroleingeochemicalprocesses,andtheiranalysishasprovidedvaluableinsightsintotheEarth'ssystems.Themeasurementofhalogenscanbedoneusingawiderangeofmethods,eachwiththeirownadvantagesandlimitations.Halogenanalysishasbeenusedinvariousapplications,suchasthetracingoffluidsinhydrothermalsystems,thedeterminationoftheoriginandevolutionofoceansediments,andthestudyofvolcanicsystems.Furtheradvancesinhalogenanalysiswillrequirethedevelopmentofbetterreferencematerialsandabetterunderstandingofthebehaviorofhalogensincomplexgeologicalsystems.Inadditiontotheapplicationsmentionedabove,halogenanalysishasalsobeenusedinthestudyofatmosphericchemistry,mineralogy,andenvironmentalgeochemistry.

Inatmosphericchemistry,halogenanalysishasbeenusedtostudythecyclingofhalogensbetweentheatmosphereandthebiosphere.Forexample,measuringtheI/Brratioinatmosphericaerosolscanprovideinformationonthetransportofiodineandbrominebetweentheoceanandtheatmosphere,whichcanaffecttheproductionofozoneandotherreactivegases.

Inmineralogy,halogenanalysiscanprovideinformationontheoriginandevolutionofminerals.Halogenratiosinmineralscanbeusedasageindicators,sincedifferentgeologicalprocessescanaffectthepartitioningandfractionationofhalogens.Forexample,themeasurementoftheCl/Kratioinpotassiumfeldsparcanbeusedtodeterminetheageofrocksandminerals.

Inenvironmentalgeochemistry,halogenanalysishasbeenusedtostudythefateandtransportofcontaminantsingroundwaterandsoils.Halogenratiosingroundwatercanprovideinformationonthesourceandmigrationofcontaminants,suchaschlorinatedsolventsandpesticides.ThemeasurementoftheBr/Clratioinsoilscanprovideinsightsintotheaccumulationandmobilityofhalogensinterrestrialenvironments.

Despitethemanyapplicationsofhalogenanalysis,therearestillimportantchallengesthatneedtobeaddressedinthefuture.Onechallengeistheneedforbetterstandardsandreferencematerialsforhalogenanalysis.Theaccuracyandcomparabilityofhalogenmeasurementsdependontheavailabilityandqualityofreferencematerials,whichcanbedifficulttoobtainforrareorlow-abundancehalogens.

Anotherchallengeistheneedforbetterunderstandingofthebehaviorofhalogensincomplexgeologicalsys