Using regional characteristic amendments to modify heavy metal contaminated soil of Guangxi, South China

In this study we compared the efficiency of four kinds of amendments (silkworm excrement, coconut husk, red mud, sepiolite) and their mixtures to immobilize the heavy metals present in a contaminated acidic soil (Pb:420 mg . kg(-1); Zn : 334 mg . kg(-1)) and to influence several enzymatic activities. The results showed that, silkworm excrement, coconut husk and their mixtures, which had high pH and/or high content of organic matter, reduced exchangeable Pb in the soil by 18% to 46%, and reduced available Zn by 24% to 35%, which was more efficacious than single sepiolite. The complex of silkworm excrement and red mud had a great influence on soil pH, while coconut husk increased the content of organic matter in soil significantly.