Vertical distribution of total mercury and methylmercury in sediment of the Fugong mangrove area at Jiulong River Estuary, Fujian, China.

The concentrations and vertical distributions of total mercury (Hg) and methylmercury (methyl Hg) in the sediment of the Fugong mangrove area, located at the Jiulong River Estuary, Fujian, China, were investigated. The concentrations of total mercury were between 0.12-0.17 and 0.11-40.14 microg/g, while concentrations of methylmercury were between 0.15-1.8 and 0.081-0.58 ng/g (as mercury), in the dry and rainy seasons, respectively. The total mercury concentration was not correlated with the sampling depth. As the depth increased, methylmercury concentrations first increased to their maximum level at a depth of 10-25 cm, and then decreased; this was similar to the vertical distribution characteristics of methylmercury/total mercury ratios. The mangrove ecosystem was considered as a source of methylmercury for adjacent areas, due to the higher average methylmercury concentration in the mangrove sediment than other sediments nearby. Statistically significant logarithmic correlations, conic correlations, and negative correlations were observed for methylmercury and sulfide concentration, sediment organic matter, and sediment pH, respectively.