Spatial Distribution of Mercury Species in the Topsoils of Ambient Areas Surrounding Xining Urban in Summer

Hg species in soil were analyzed by modified Tessier sequential extraction method to study their spatial distributions in ambient areas surrounding Xining,Qinghai Province. Results indicated that Hg content in the topsoils surrounding Xining ranged from 0.013 to 0.308 mg/kg with large differences among different sampling sites,which was higher in the western areas and lower in the eastern areas. Based on the functional land type of sampling sites,it was found that the mercury content in the soil of industrial area was significantly higher than those of other areas,and Hg content descended as the descending order of agricultural land,highways,abandoned land and forested land. Hg speciation was dominated by residual form,while the carbonate fraction and exchangeable fraction were much lower. The percentage of mercury species in different land types was different between each others. Total mercury,organic and sulfide-bounded fraction and residual fraction were found to have a significant correlation with TOC,but no strong correlation was found between total mercury as well as mercury species and pH value.