DISTRIBUTION OF TOTAL MERCURY AND METHYLMERCURY IN THE SEDIMENT OF THE NANSI LAKE, CHINA

The objectives of this study were to determine the contents of total mercury (THg) and methyl mercury (MMHg) in order to understand the geochemical relationships between mercury (Hg) and mineral phases of the sediment of the Nansi Lake. Twenty samples of surface sediment were collected and analyzed for the THg and MMHg contents. The results indicated that the average THg content was 0.089 mg/kg but that levels ranged from 0.025 to 0.168 mg/kg in the sediment. In addition, the content of THg in the sediment was significantly and positively correlated with the contents of clay and total organic carbon (TOC), respectively. Thus, the TOC content and the grain size of sediment dominated the distribution of THg in the sediment. The MMHg content in the sediment ranged from 0.033 to 0.764 ng/g and averaged 0.268 ng/g. Moreover, the content of MMHg was significantly and positively correlated with the contents of THg, clay, and TOC, respectively. Therefore, the MMHg content in the sediment of the Nansi Lake was primarily controlled by the THg content and the organic material content in fine-grained sediments. The methylation rate of Hg (%MMHg) in the sediment ranged from 0.096 to 0.476%, generally lower than 0.5%. The %MMHg showed a significant and positive relationship with the content of THg, but a weak relationship with the contents of clay and TOC. Thus, the %MMHg was primarily limited by the supply of Hg. In addition, regressions analysis indicated that the AVS content in the sediment limited the metylation rate.