Distribution Of Heavy Metals And Their Chemical Speciation Of Tungsten Mine Area Soil In South Of Jiangxi Province

Mining of mineral resources has processing of mineral resources make various associated heavy metals release to the surface environment, becoming an important source of soil heavy metal pollution and the mining impacting the soil ecosystem of mining area seriously.For investigating the current status of soil pollution of heavy metals such as Pb,Cr,Mn,Zn,Cu and Cd, the soil samples were collected in the tungsten mining areas. The concentrations of Pb,Cr,Mn,Zn,Cu and Cd in the samples were measured by the inductively coupled plasma atomic emission spectrometry(ICP-AES) and the degree of pollution based on evalution factor of the National Environment Quality Standard for Soil.Chemical fractions of heavy metals and main influencing factors were also analyzed by BCR sequential extraction procedure,and the correlation between chemical frations distribution and soil physical chemical properties were investigated,then. The spatial distribution and the source of the heavy metal concentrations in this area was estimated by Kriging interpolation model. The activities of urease, catalase and invertase in these surface samples were also assessed,which further confirmed the existence of heavy metals soil pollution.It was demonstrated that the average values of all the heavy metal concentrations were much higher than the threshold values of the National Environment Quality Standard for Soil and the mean concentrations of Pb,Cr,Zn,Cu and Cd in surface soils were as 2.264,1.06,1.326,0.647 and 17.7times high as their threshold values of the National Environment Quality Standard for Soil. The mean concentrations of Pb,Cr,Zn,Cu and Cd in middle soils were as 1.228、0.923、0.942、0.416 and 14.33 times high as their threshold values of the National Environment Quality Standard for Soil.Strong spatial correlations were observed for Pb, Cr,Mn, Cu, Zn and Cd distributions. The optimal fitting models of heavy metals were gaussian model, Cd has the highest precision fitting model.The heavy metals of surface soil were originated from the tailings piled up the tail of the migration of heavy metals in the ore.Pb and Mn was dominated mainly by the reducible,residual fraction,Cr existed by the oxidizable,residual fraction, while Cu,Zn and Cd were mostly by its residual fraction. Except Cr, content of acid soluble state Pb, Mn, Cu, Zn, Cd were highest,the most lively, the largest biological effectiveness in surface soil.There were a certain relationship between soil heavy metal forms and cation exchange capacity, p H value, the total heavy values.The soil enzyme activities were estimated to be as low as 7%-93%, 5%-86% and 11%-90% of their background values for the urease, catalase and invertase, respectively, which further confirmed the existence of heavy metals soil pollution. Multivariate stepwise regression analysis between heavy metal contents and soil enzyme activities displayed that the coefficient between the heavy metal and the enzyme activity was different. Among them, the invertase was the most sensitive. In addition, principle component analysis pointed out that enzyme activities in mining soils were feasible indicators to assess changes in soil environmental quality caused by heavy metals pollution.