Effect of groundwater irrigation on cadmium pollution in surface soil of farmland

The object of this study is to evaluate the clean-up effect of ground water irrigation on soil Cd pollution, and to provide theoretical evidences for engineering management. Soil Cd pollution index and soil microbial biomass were used to evaluate Cd pollution in Zhangshi Irrigation Area. Contents of soil Cd were compared with historic data of the past 13 years to analyse the changes of soil Cd content. The removal rate of cadmium by HC1, DTPA solution and clean water were also analyzed. The results show that after groundwater irrigation for 13 years soil in Zhangshi Irrigation Area is still heavily polluted by Cd although soil Cd content greatly decreased. The highest pollution index is 10.85 and the growth of microbes is inhibited. When soil Cd content in Zhangshi Irrigation Area is relatively high Cd content in the surface soil can be reduced by groundwater irrigation. When Cd content in soil of this area dropped to certain level groundwater irrigation shows no clean-up effect on soil Cd pollution. Chelator and biological measures should be used to speed up the removal of Cd and the restoration of soil ecosystem.