[Speciation change of heavy metals during composting process of chicken manure]

In high-temperature and aerobic condition, speciation of heavy metals were studied during composting process of chicken manure and maize straw. The results showed that total weight of composting material was reduced and content of heavy metals was increased during composting process. No significant changes were found in total amount of heavy metals during composting process. The speciation of heavy metals could be affected significantly by composting. Ni and Cd's percentages of Fe-Mn oxides fraction increased by 5.0%-8.7%. Cu and Cr's percentages of organic fraction were increased by 14.1%-19.1% and 22.0% -28.7%, respectively. Hg, Pb, As, Zn's percentages of residual fraction were increased by different extents. Hg, Pb, Cr, As, Cu, and Zn's percentages of stable fraction all increased. The increasing range of Cu was the highest, which was 10.9%. Composting could reduce the biological activity and toxicity of heavy metals. The inoculating complex microbial strains had no significant influence on the speciation of heavy metals in chicken manure.