Transfer of heavy metals from compost to red soil and groundwater under simulated rainfall conditions.

It is well known that compost can be polluted with heavy metals. A self-designed soil column system was used to clarify the leaching or residue of heavy metals when compost was added to red soil. Less than 4% of Cu and more than 58.3% of Zn were transferred to groundwater. Maximum concentrations of Cu and Zn in leachate were 22 and 246 microg/L, respectively. pH in leachate decreased during 6.75-11.25 h, comparing with the control. Electrical conductivity was higher in the treatment of compost polluted by both Cu and Zn than that polluted only by Cu. Over 75.3% of Cu and 78.2% of Zn remained in the residual formation. Maximum bioavailability parameters in soil were 0.099 for Cu and 0.160 for Zn. Long-term field experiments with cycling application are needed to study the cycling effect on heavy metal residue in soil or leaching to the groundwater in the future.