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Marine pollution, ecotoxicology and sustainability
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METHYLMERCURY CYCLING IN THE BOHAI SEA, YELLOW SEA AND EAST CHINA SEA, CHINA: SOURCES/SINKS AND CONTROLLING FACTORS
Monday 7th @ 1430-1450, Conference Room 7
Yanbin Li* , Ocean University of China, QINGDAO, China
Lufeng Chen, Ocean University of China, QINGDAO, China
Chang Liu, Ocean University of China, QINGDAO, China
Presenter Email: liyanbin@ouc.edu.cn |
| Chinese marginal seas, important regions of the western Pacific Ocean, have been facing a variety of environmental problems, including mercury (Hg) pollution. Although methylmercury (MeHg) has been recognized as the most toxic Hg species in the environment, there is still a lack of knowledge on its cycling in Chinese marginal seas, limiting a sound understanding of Hg cycling in these important regions. To address these needs, we investigated the distribution and methylation/demethylation of Hg in the Yellow Sea (YS), Bohai Sea (BS), and East China Sea (ECS). A decreasing trend from inshore to offshore was observed for total Hg (THg), suggesting the importance of terrestrial discharge; however, the distribution of MeHg was found to be complicated, with several "hot spots" located in both inshore and offshore areas, indicating the importance of in situ production and degradation processes. Methylation in the sediment and demethylation (both photo-mediated and biotic) in the water column were identified as the two most important processes controlling MeHg levels, while SO42-, THg, and dissolved organic matter were found to be the most influential environmental factors. By quantifying the in situ production/degradation, along with river input and exchange with nearby seas, sediment was found to be the most important source of MeHg; meanwhile, the water serves as the largest sink in the three investigated regions. In comparison with other marine systems, a relatively low ecosystem conversion efficiency of inorganic Hg to MeHg, i.e., low MeHg/THg ratios in the water, was observed in these Chinese coastal systems. This may result from the low efficiency of transporting THg from water to the sediment, slow Hg methylation in the sediment, and quick MeHg degradation in the water. The low conversion efficiency of inorganic Hg to MeHg may be one of the convincible reasons for the low Hg levels detected in marine organisms from China, in comparison to the high THg concentrations in the water. |
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