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1、METHOD3060AALKALINEDIGESTIONFORHEXAVALENTCHROMIUM1.0SCOPEANDAPPLICATION1.1AnyreferenceinthismethodtoMethod3060"referstothisversionofthatmethod,anddoesnotrefertopreviouslypublishedversions(e.g.,intheSecondEditionofthismanual).WhenpublishedasanewmethodtoSW-846,amethodsnu
2、mberdoesnotincludealettersuffix.EachtimeamethodisrevisedandmadeapartofSW-846update,itreceivesasuffix.However,amethodreferencefoundwithinthetextofSW-846methodsalwaysreferstothelatestversionofthatmethodpublishedinSW-846,evenifthemethodnumberatthatlocationdoesnotincludeth
3、eappropriatelettersuffix.1.2Method3060isanalkalinedigestionprocedureforextractinghexavalentchromium[Cr(VI)]fromsoluble,adsorbed,andprecipitatedformsofchromiumcompoundsinsoils,sludges,sediments,andsimilarwastematerials.ToquantifytotalCr(VI)inasolidmatrix,threecriteriamu
4、stbesatisfied:(1)theextractingsolutionmustsolubilizeallformsofCr(VI),(2)theconditionsoftheextractionmustnotinducereductionofnativeCr(VI)toCr(III),and(3)themethodmustnotcauseoxidationofnativeCr(III)containedinthesampletoCr(VI).Method3060meetsthesecriteriaforawidespectru
5、mofsolidmatrices.Underthealkalineconditionsoftheextraction,minimalreduction2+ofCr(VI)oroxidationofnativeCr(III)occurs.TheadditionofMginaphosphatebuffertothealkalinesolutionhasbeenshowntosuppressoxidation,ifobserved.Theaccuracyoftheextractionprocedureisassessedusingspik
6、erecoverydataforsolubleandinsolubleformsofCr(VI)(e.g.,K2Cr2O7andPbCrO4),coupledwithmeasurementofancillarysoilproperties,indicativeofthepotentialforthesoiltomaintainaCr(VI)spikeduringdigestion,suchasoxidationreductionpotential(ORP),pH,organicmattercontent,ferrousiron,an
7、dsulfides.RecoveryofaninsolubleCr(VI)spikecanbeusedtoassessthefirsttwocriteria,andmethod-inducedoxidationisusuallynotobservedexceptinsoilshighinMnandamendedwithsolubleCr(III)saltsorfreshlyprecipitatedCr(OH)3.1.3ThequantificationofCr(VI)inMethod3060digestsshouldbeperfor
8、medusingasuitabletechniquewithappropriateaccuracyandprecision,forexampleMethod7196(colorimetricallybyUV-VISspectropho
