An Experimental Study On Speciation Distribution For Zn, Cd, Ni, Pb In Oasis Soil

The problem of the heavy metal pollution of soil bring broad attention from the environmental researcher. However, the biology toxicity of heavy metal not only lies on its gross contents, but also are influenced by its speciation distribution largely and different speciation bring different environmental effect. So, the research of the distribution rule and effect factors of the speciation of soil heavy metal is very significant.in this paper,we used field and pot experiments and Tessier A sequential extraction method to study the speciation distributions and effect factors of Cd, Pb, Ni, Zn in oasis soil.The experiment results indicates that in oasis soils, distribution coefficient of RES-Zn> distribution coefficient of Fe-Mn-Zn> distribution coefficient of OM-Zn> distribution coefficient of CA-Zn>distribution coefficient of EXC-Zn;distribution coefficient of RES-Cd > distribution coefficient of CA-Cd>distribution coefficient of Fe-Mn-Cd > distribution coefficient of OM-Cd > distribution coefficient of EXC-Cd;distribution coefficient of RES-Ni> distribution coefficient of OM-Ni> distribution coefficient of Fe-Mn-Ni>distribution coefficient of CA-Ni> distribution coefficient of EXC-Ni;distribution coefficient of RES-Pb>distribution coefficient of Fe-Mn-Pb > distribution coefficient of OM-Pb > distribution coefficient of CA-Pb" distribution coefficient of EXC-Pb.in a word,Zn,Cd,Ni,Pb is mainly in residual fraction in oasis soils;though Cd is also mainly in residual fraction,the distribution coefficient of Cd is lower than the distribution coefficient of Zn, Ni,Pb in oasis soils.Cd is mainly in residual fraction, carbonate fraction and Fe-Mn oxides fraction in oasis soils.In experimental soils, distribution coefficient of Fe-Mn-Zn > distribution coefficient of CA-Zn> distribution coefficient of RES-Zn> distribution coefficient of OM-Zn> distribution coefficient of EXC-Zn;distribution coefficient of CA-Cd> distribution coefficient of Fe-Mn-Cd > distribution coefficient of EXC-Cd > distribution coefficient of OM-Cd > distribution coefficient of RES-Cd;distribution coefficient of Fe-Mn-Ni> distribution coefficient of CA-Ni> distribution coefficient of OM-Ni>distribution coefficient of RES-Ni> distribution coefficient of EXC-Ni;distribution coefficient of Fe-Mn-Pb > distribution coefficient of CA-Pb > distribution coefficient of RES-Pb> distribution coefficient of OM-Pb > distribution coefficient of EXC-Pb.in a word,Zn,Pb,Cd is mainly in carbonate fraction and Fe-Mn oxides fraction;Ni is mainly in carbonate fraction , Fe-Mn oxides fraction and organic fraction.With the increase of the contents of Zn,Cd,Ni,Pb in oasis experimental soils, thecontents of Zn,Cd,Ni,Pb of exchangeable fraction, carbonate fraction, Fe-Mn oxides fraction, and organic fraction increased obviously, the contents of Zn,Cd,Ni,Pb of residual fraction increased unobviously;the contents of Zn,Cd,Ni,Pb of exchangeable fraction,and organic fraction increased obviously;the contents of Zn,Cd,Ni,Pb of carbonate fraction and Fe-Mn oxides fraction increased extremely obviously.With the increase of the contents of Zn,Cd,Ni,Pb in oasis experimental soils, the distribution coefficient of Zn,Cd,Ni,Pb of residual fraction decreased obviously;the distribution coefficient of Zn,Cd,Ni,Pb of organic fraction decreased obviously or decreased;the distribution coefficient of Zn, Pb of exchangeable fraction increased obviously,the distribution coefficient of Cd of exchangeable fraction increased unobviously,the distribution coefficient of Ni of exchangeable fraction increased obviously at first,then decreased;the distribution coefficient of Zn, Pb of carbonate fraction increased obviously, the distribution coefficient of Ni of carbonate fraction increased obviously at first and then increased unobviously, the distribution coefficient of Cd of carbonate fraction increased obviously at first and then increased unobviously,the distribution coefficient of Cd of carbonate fraction might decreased at last;the distribution coefficient of Cd,Pb,Zn of Fe-Mn oxides fraction increased obviously at first and then decreased obviously,the distribution coefficient of Ni of Fe-Mn oxides fraction increased obviously.