Laboratoire Géosciences Environnement Toulouse, CNRS/Institute for Research and Development/Université Paul Sabatier-Toulouse III, 31400 Toulouse, France;
EcoLab, Université de Toulouse, CNRS, National Polytechnic Institute, 31400 Toulouse, France.
Proc Natl Acad Sci U S A. 2018 Dec 11;115(50):E11586-E11594. doi: 10.1073/pnas.1811957115. Epub 2018 Nov 26.
Midlatitude anthropogenic mercury (Hg) emissions and discharge reach the Arctic Ocean (AO) by atmospheric and oceanic transport. Recent studies suggest that Arctic river Hg inputs have been a potentially overlooked source of Hg to the AO. Observations on Hg in Eurasian rivers, which represent 80% of freshwater inputs to the AO, are quasi-inexistent, however, putting firm understanding of the Arctic Hg cycle on hold. Here, we present comprehensive seasonal observations on dissolved Hg (DHg) and particulate Hg (PHg) concentrations and fluxes for two large Eurasian rivers, the Yenisei and the Severnaya Dvina. We find large DHg and PHg fluxes during the spring flood, followed by a second pulse during the fall flood. We observe well-defined water vs. Hg runoff relationships for Eurasian and North American Hg fluxes to the AO and for Canadian Hg fluxes into the larger Hudson Bay area. Extrapolation to pan-Arctic rivers and watersheds gives a total Hg river flux to the AO of 44 ± 4 Mg per year (1σ), in agreement with the recent model-based estimates of 16 to 46 Mg per year and Hg/dissolved organic carbon (DOC) observation-based estimate of 50 Mg per year. The river Hg budget, together with recent observations on tundra Hg uptake and AO Hg dynamics, provide a consistent view of the Arctic Hg cycle in which continental ecosystems traffic anthropogenic Hg emissions to the AO via rivers, and the AO exports Hg to the atmosphere, to the Atlantic Ocean, and to AO marine sediments.
中纬度人为汞 (Hg) 排放物和排放物通过大气和海洋输送到达北极海洋 (AO)。最近的研究表明，北极河流 Hg 的输入可能是 AO 中 Hg 的一个被忽视的来源。然而，对代表 AO 淡水输入 80%的欧亚河流 Hg 的观测几乎不存在，这使得对北极 Hg 循环的牢固理解受到阻碍。在这里，我们对两条大型欧亚河流——叶尼塞河和北德维纳河的溶解 Hg (DHg) 和颗粒 Hg (PHg) 浓度和通量进行了全面的季节性观测。我们发现春季洪水中 DHg 和 PHg 通量很大，随后秋季洪水中又出现了第二个脉冲。我们观察到欧亚和北美的 Hg 通量到 AO 以及加拿大 Hg 通量到更大的哈德逊湾地区的水与 Hg 径流关系明确。对泛北极河流和流域的外推得出了向 AO 输送的总 Hg 河流通量为 44 ± 4 Mg/年（1σ），与最近基于模型的估计值 16 至 46 Mg/年以及基于 Hg/溶解有机碳 (DOC) 观测的估计值 50 Mg/年一致。河流 Hg 预算，以及最近对苔原 Hg 吸收和 AO Hg 动态的观测，为北极 Hg 循环提供了一个一致的观点，即大陆生态系统通过河流将人为 Hg 排放物输送到 AO，而 AO 将 Hg 释放到大气中，释放到大西洋和 AO 海洋沉积物中。
