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 mu g/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. (C) 2010 Elsevier B.V. All rights reserved.