Investigation and evaluation of heavy metal pollution in cultivated land in Huishui County, Guizhou Province

This paper has collected 5013 surface soil samples to determine the contents of Cd, Hg, As, Pb, Cr, Cu, Ni, Zn, and pH values, and has chosen single factor pollution index method and ground accumulation index method to evaluate the status of heavy metal pollution in crop-soil and has carried out some correlation analysis and principal component analysis to study the current situation of heavy metal pollution in cultivated soil of Huishui County, Guizhou Province. The results show that: ①The excess rates of soil heavy metal elements As, Cd, Cr, Cu, Hg, Ni, Pb, and Zn were 8.74%, 34.51%, 3.83%, 0.56%, 1.56%, 0.24%, 0.04%, and 1.60% respectively. And the mean values of Cd(k₁=1.46) and Hg(k₁=1.60) exceeded the background values of soil layer A of Guizhou Province. ② The order of average individual Pi from small to large is presented as: Cu(0.20) < Pb(0.22) < Ni(0.26) < Hg(0.27) < Zn(0.31) < Cr(0.44) < As(0.50) < Cd(1.70), and the mean Pi of Cd and As was larger. The mean value of Ig of heavy metal elements from small to large is Cu(-1.24) < Ni(-1.18) < As, Pb(-0.99) < Zn(-0.93) < Cr(-0.71) < Hg(-0.05) < Cd(0.04), and Cd and Hg have higher Ig pollution degree. ③ The correlation analysis has showed that the correlations between As, Hg and the other six heavy metals are weak, which indicate that they have different sources while Cd is strongly correlated with Cr, Ni, Pb, and Zn, indicating that it may have homology. The principal component analysis shows that Cd, Pb, Zn, Cr, and Ni originated from natural and transportation sources, and were mainly controlled by upper Carboniferous Dapu Formation-Huanglong Formation(C_1-2d+C₂h), Lower Carboniferous(C1j+C₁s+C₁x+C₁dw) and Upper Devonian Gelaohe-Gaopochang Formation(D₃g+D₃gp) and SN-trending and EW-trending faults. The Cu and Ni come from agricultural factors and natural sources, and the As and Hg come from natural sources and coal-burning sources.