DISTRIBUTIONS OF MERCURY AND METHYLMERCURY IN SEDIMENTS OF MIN-ZHE COASTAL AREA AND INFLUENCING FACTORS

Both surface and cores sediments were taken in the Min-Zhe coastal area in the spring cruise of National Natural Science Foundation of China in June, 2012. Distributions of mercury and methylmercury (MeHg) contents and their influencing factors are systematically analyzed in combination with the contents of major element, grain-size and TOC of the sediments and the concentration of sulfate in pore-water. It is revealed that, (1) Mercury and MeHg are enriched in the sediments in the Min-Zhe coastal area (the alongshore area of the southern Hangzhou Bay, Zhejiang). Methylations in cores in the mud area mainly observed in the shallow depth from surface (the depths are 0~15 cm and 0~13 cm respectively in north and south area). (2) In Min-Zhe coastal mud area, MeHg mainly comes from in situ methylation. Any changes in depth or other environmental conditions may lead MeHg to transfer or relocate in diagenetic process. (3) Influencing factors of methylation and content distributions of mercury and MeHg in sediments include contaminant, circumfluence, grain-size, the content of TOC and the activity of sulfate-reducing bacteria. Contaminant primarily controls the content of mercury in the sediment. Circumfluence dominates the distribution of mercury content. Grain-size affects the degree of enrichment of MeHg. The effect of TOC content on methylation is not obvious in surface sediments of this study. In cores, the content of TOC can not only promote the methylation, but also inhibit it, mainly depending on the type of organic matters in sediments. The activity of sulfate-reducing bacteria is one of the main controlling factors of mercury methylation.