Abstract: The single and combined effects of bentonite and diammonium phosphate additions on the distribution of fractionated Hg in soil and flowering cabbage grown in mercury (Hg) enriched soil were investigated under field conditions at Wanshan mercury mine in Guizhou Province. The results showed that the applications of bentonite, diammonium phosphate, and their mixture increased the dry biomass of the root and shoot of flowering cabbages compared with the control. Especially, the combined treatment resulted in a significant boost of root and shoot dry biomass (4.7 and 4.8 times higher respectively compared to the control). In this combined treatment case, the biomass Hg content was also significantly lower than the control, while this effect was insignificant in the single compound treatments. The flowering cabbages receiving the treatment of 3% bentonite and 0.5% diammonium phosphate had the lowest Hg content in various tissues. Concerning the combined treatments, chemical analysis of Hg fractions present in soil before and after the remediation period indicated a significant decrease in bioavailable Hg (soluble and exchangeable, specifically sorbed fractions) and Fe/Mnoxide bound Hg content, while the contents of the organic bound and residual Hg fractions were relatively stable. The results from this study may provide new insights and useful information for the remediation of Hg contaminated soil.

Key words: organic carbon content, altitude gradient, temperate forest, oxidoreductase, hydrolase