简介：Co,Ni,CrandVin25typicalsoilsofChinawerefractionatedintoexchangeable,carbonatebound(calcareoussoils),Mnoxidebound,organicallybound,amorphousFeoxidebound,crystallineFeoxideboundandresidualformsusingaseven-stepsequentialextractionprocedure,soastostudythedistributionofchemicalformsofthesemetalsaswellastheeffectsofsoilproipertiesonthedistribution.TheresultsshowedthatmostofsoilCo,Ni,CrandVwerepresentinresidualforms,andthedistributionratioaveraged48.2%forCo,53.0%forNi,81.5%forCrand68.7%forV.Thespeciationofheavymetalswasgreatlyinfluencedbysoilphysico-chemicalpropertiesandthechemistryofelements.Theresultsalsoindicatedthattherecoveryofmetalelementsbythesequentialextractionprocedurewassatisfactory,withtherelativedifferencebetweenthesumofsevenformsandthetotalcontentinsoilsaveraging9.5%forCo,12.8%forNi,6.6%forCrand7.2%forV.

简介：ThedistributionandtransformationofaddedandnativeNiinpurplesoilswereinvestigatedwithbothsequentialextractionprocedureandisotopictracertechnique.ThedistributionofaddedandnativeNiwasgreatlydependentonsoilproperties.LowsoilpHwasfavorableforsolubleplusexchangeable(EX)Fraction,whileFe/MnoxidesandclayforFe/Mnoxidebound(OX)andresidual(RES)fractions.TheaddedNi,however,hasnotyetreachedthedistributionequilibriumuptothe150thdayafterincubation.ThiswasreflectedinthefactthattheproportionofEXfractionfromaddedNiwas150%-600%asmuchasthatofnativeNi,whilethatofRESfractionwasonlyabout80%,Onceenteringsoil,theappliedsolubleNiwasrapidlytransformedintootherfractions,buttheorganiccomplexe(OM)fractionofaddedNiwasrelativelystableduringincubation.Thecarbonatebound(CAB)fractionshowedaprogressiveincreaseandattainedapeakvalueafter0-14dofincubationandthereafterdecreasedgradually.TheoccurrencetimeofthispeakadvancedasinitialsoilpHincreased.butthepeakwoulddisappearwheninitialsoilpHwashigherthan7.5(orcontainingfreeCaCO3).ThetransformationprocessesoftheEX,OXandRESfractionscouldbedescribedbyElovichandtwo-constantrateequations,andtheratewerepositivelycorrelatedwithsoilpH,CECandclay.ThesefindingcouldexplainwhytherearedifferencesinecologicalandenvironmentaleffectsofNiindifferentsoilsandatvariousintervals.