School of Earth Sciences and Environmental Engineering, Gwangju Institute of Science and Technology (GIST) , Gwangju 500-712, Republic of Korea.
Department of Environmental Science and Analytical Chemistry, Stockholm University , Stockholm SE-11418, Sweden.
Environ Sci Technol. 2017 Feb 7;51(3):1186-1194. doi: 10.1021/acs.est.6b04238. Epub 2017 Jan 26.
Methylmercury (MeHg) accumulation in marine organisms poses serious ecosystem and human health risk, yet the sources of MeHg in the surface and subsurface ocean remain uncertain. Here, we report the first MeHg mass budgets for the Western Pacific Ocean estimated based on cruise observations. We found the major net source of MeHg in surface water to be vertical diffusion from the subsurface layer (1.8-12 nmol m yr). A higher upward diffusion in the North Pacific (12 nmol m yr) than in the Equatorial Pacific (1.8-5.7 nmol m yr) caused elevated surface MeHg concentrations observed in the North Pacific. We furthermore found that the slope of the linear regression line for MeHg versus apparent oxygen utilization in the Equatorial Pacific was about 2-fold higher than that in the North Pacific. We suggest this could be explained by redistribution of surface water in the tropical convergence-divergence zone, supporting active organic carbon decomposition in the Equatorial Pacific Ocean. On the basis of this study, we predict oceanic regions with high organic carbon remineralization to have enhanced MeHg concentrations in both surface and subsurface waters.
甲基汞（MeHg）在海洋生物体内的积累对生态系统和人类健康构成严重威胁，但海洋表面和次表层中 MeHg 的来源仍不确定。本研究基于航次观测结果，首次报告了西太平洋海域 MeHg 的质量预算。研究发现，表层水中 MeHg 的主要净源是从次表层（1.8-12 nmol/m/yr）垂直扩散。北太平洋的向上扩散通量（12 nmol/m/yr）高于赤道太平洋（1.8-5.7 nmol/m/yr），这导致了北太平洋表层 MeHg 浓度的升高。此外，研究还发现，赤道太平洋 MeHg 与表观耗氧量线性回归的斜率约为北太平洋的两倍。这可以用热带辐合带内表层水的再分布来解释，该过程支持了赤道太平洋海洋中有机碳的有效分解。基于本研究，我们预测高有机碳再矿化的海域在表层和次表层水中的 MeHg 浓度将会升高。
