Rivers as the largest source of mercury to coastal oceans worldwide

Mercury is a potent neurotoxic substance and accounts for 250,000 intellectual disabilities annually. Worldwide, coastal fisheries contribute the majority of human exposure to mercury through fish consumption. Recent global mercury cycling and risk models attribute all the mercury loading to the ocean to atmospheric deposition. Nevertheless, new regional research has noted that the riverine mercury export to coastal oceans may also be significant to the oceanic burden of mercury. Here we construct an unprecedented high-spatial-resolution dataset estimating global river mercury and methylmercury exports. We find that rivers annually deliver 1,000 (minimum–maximum: 893–1,224) Mg mercury to coastal oceans, threefold greater than atmospheric deposition. Furthermore, high flow events, which are becoming more common with climate change, are responsible for a disproportionately large percentage of the export. Coastal oceans constitute 0.2% of the entire ocean volume but receive 27% of the exte...汞是一种强效神经毒性物质，每年可导致25万例智力残疾病例。全球范围内，人类主要通过食用沿海渔业捕捞的鱼类接触汞。近期的全球汞循环与风险模型将所有入海汞负荷均归因于大气沉降。然而，最新区域研究表明，河流向沿海海域输出的汞，对海洋汞总负荷的贡献同样可观。本研究构建了一套前所未有的高空间分辨率数据集，用于估算全球河流汞与甲基汞（methylmercury）的输出通量。研究发现，全球河流每年向沿海海域输送1000（最小值-最大值：893-1224）Mg汞，该数值是大气沉降汞负荷的三倍。此外，随气候变化愈发频发的极端高流量事件，贡献了远超其占比的汞输出份额。沿海海域仅占全球海洋总容积的0.2%，却接收了总输出汞的27%……