†Department of Environmental Health, Harvard School of Public Health, Boston, Massachusetts 02215, United States.
‡Department of Environmental Science, Rutgers University, 14 College Farm Road, New Brunswick, New Jersey 08901, United States.
Environ Sci Technol. 2015 May 19;49(10):5965-72. doi: 10.1021/es506274x. Epub 2015 May 5.
Methylmercury (MeHg) is the only species of mercury (Hg) to biomagnify in aquatic food-webs to levels that are a widespread concern for human and ecological health. Here we investigate the association between dissolved organic matter (DOM) in seawater and Hg speciation and uptake using experimental data and field measurements from Long Island Sound (LIS) and the Northwestern Atlantic continental margin. We measured differences in DOM composition across sampling stations using excitation emission matrix fluorescence spectroscopy and further separated DOM into terrestrial and marine components using Parallel Factor Analysis (PARAFAC). Highest MeHg concentrations were found in the estuarine stations (LIS) with highest DOM concentrations due to enhanced external inputs from the watershed and rivers. For stations on the shelf and slope, MeHg in plankton increased linearly with a decreasing fraction of fluorescence attributable to DOM components with a terrestrial rather than marine origin. These results are corroborated by experimental data showing higher MeHg uptake by cells in the presence of predominantly marine DOM compared to terrestrial DOM. Highest fractions of dissolved gaseous mercury were also found at stations with the highest marine DOM content, suggesting a greater reducible fraction of divalent inorganic Hg. These data suggest DOM composition is a critical driver of Hg reactivity and bioavailability in offshore marine waters.
甲基汞（MeHg）是唯一在水生食物链中发生生物放大作用的汞（Hg）物种，其浓度达到了对人类和生态健康广泛关注的水平。在这里，我们使用长岛海峡（LIS）和北大西洋大陆架的实验数据和现场测量结果，研究了海水中溶解有机质（DOM）与 Hg 形态和摄取之间的关系。我们使用激发发射矩阵荧光光谱法测量了不同采样站之间 DOM 组成的差异，并进一步使用平行因子分析（PARAFAC）将 DOM 分离成陆地和海洋成分。由于流域和河流的外部输入增强，在具有最高 DOM 浓度的河口站（LIS）中发现了最高的 MeHg 浓度。对于大陆架和斜坡上的站点，浮游生物中的 MeHg 浓度随荧光归因于陆地而非海洋来源的 DOM 成分的比例降低而呈线性增加。实验数据也证实了这一结果，表明在主要为海洋 DOM 存在的情况下，细胞对 MeHg 的摄取更高。在具有最高海洋 DOM 含量的站点中，也发现了最高比例的溶解气态汞，这表明二价无机 Hg 的可还原分数更大。这些数据表明，DOM 组成是近海海洋水中 Hg 反应性和生物利用度的关键驱动因素。
