Effect of sulphur on soil Cu/Zn availability and microbial community composition.

Successful phytoremediation depends mainly on the bioavailability of copper (Cu) and zinc (Zn) in the soil. We studied the potential effects of sulphur (S) amendment on mobility of copper, zinc and microbial community composition in soil under laboratory conditions. The results showed that with S application at 20 g S kg(-1), soil pH decreased about 3 units and the solubility of the Cu and Zn significantly increased after 64 days of incubation. The concentration of Cu in Cu-accumulator Elsholtzia splendens shoots and roots increased with S treatment. Concentration of Cu in the shoots was 156.5 mg kg(-1) under S treatment. It was 2.5 times of without application of S. PCR-denaturing gradient gel electrophoresis (PCR-DGGE) fingerprint analysis revealed that there were certain groups of acidophilic soil bacteria in the soil after addition of S. We found specific clones such as 1 (from biofilter-treating hydrogen sulfide and methanol) and 4 (from metal-rich and acidic River Tinto) in the soil with S treatment. The above results indicated that S facilitated the mobility of Cu and Zn by soil microorganism and provided a basis for further studies of S-assisted phytoremediation.