Chemical Form Transformation Characteristics And Influencing Mechanism Of Heavy Metals In Moso Bamboo Forest

In order to clarify the characterization method of metal effectiveness and chemical form of heavy metals in the soil of Moso bamboo forest;Elucidated the migration rule of colloidal particles in heavy metal contaminated soil;Explored the mechanism of morphological transformation of heavy metals in rhizosphere soil.This paper takes the soil of Moso bamboo forest as the research object,through the experimental methods of the field sampling,the test of the indoor leaching column and root box test method,systematically clarifying the morphological transformation characteristics and mechanism of heavy metals in Moso bamboo forest soil.The research results mainly include:（1）The extraction amount of available Pb and Zn in soil has significant difference due to the difference of extractant.Among them,EDTA,HNO₃ and HCl showed the largest extraction amount of heavy metals Pb and Zn,while NH4 OAc and NaNO3 showed the smallest extraction amount of heavy metal Pb,as well as the extraction amount of heavy metals Zn with NH4 OAc and H2 O.The main chemical forms of heavy metal Pb in soil are mainly iron manganese oxide bound state and residue state,while Zn mainly exists in exchange state and residue state.The effective state Pb have fine correlation with the heavy metal content of Moso bamboo shoots except NaNO₃,CaNO₃ and H₂O,and all the extractions of the effective Zn have fine correlation.The effective Pb and Zn extracted from acid extractant and chelating agent could be used to characterize the bioavailability of heavy metals in this soil.（2）The particle size in soil is mainly concentrated in the range of more than 50 m,and the content of heavy metals is relatively high in less than 50 m.Under the simulated acid rain of pH 3,4 and 5.6,the heavy metal Pb and Zn in the soil were mainly adsorbed on the colloid particles in the migration process.Under three different pH leaching,the migration of colloid particles in the filtrate accounted for more than 80%of the total migration,and the migration efficiency of Zn was the most obvious.（3）The rhizosphere effect of Moso bamboo leads to the difference in the form of different heavy metals in the rhizosphere and non rhizosphere soil.In the chemical speciation of heavy metals Pb and Zn,the reductive state,the reductive state,crystalline Fe oxide-bound and residue content were relatively high,the rhizosphere soil acid respectively bound Pb,Zn,organic Pb and crystalline Fe oxide-bound Zn was significantly higher than that in non rhizosphere soil.The transformation of soil heavy metal forms is closely related to soil organic carbon,soil microbial biomass carbon and soil enzyme activity,which depends on the effect of root exudates and rhizosphere microorganisms.