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 external mercury input to the ocean. We estimate that the river mercury export could be responsible for a net annual export of 350 (interquartile range: 52–640) Mg mercury across the coastal–open-ocean boundary, although there is still high uncertainty around this estimate. Our results show that river export is the largest source of mercury to coastal oceans worldwide, and continued mercury risk modelling should incorporate the impact of rivers.

汞是一种强效的神经毒性物质，每年造成 250,000 名智力障碍。在世界范围内，沿海渔业通过鱼类消费导致大部分人类接触汞。最近的全球汞循环和风险模型将海洋中的所有汞负载归因于大气沉降。然而，新的区域研究指出，河流汞出口到沿海海洋也可能对海洋的汞负担造成重大影响。在这里，我们构建了一个前所未有的高空间分辨率数据集，用于估计全球河流汞和甲基汞的出口。我们发现，河流每年向沿海海洋输送 1,000（最小 - 最大：893–1,224）镁汞，是大气沉降量的三倍。此外，随着气候变化而变得越来越普遍的高流量事件，占出口的很大比例。沿海海洋占整个海洋体积的 0.2%，但接收到海洋外部汞输入的 27%。我们估计，河流汞出口可能导致沿海 - 远洋边界每年净出口 350（四分位距：52-640）镁汞，尽管这一估计仍然存在很大的不确定性。我们的结果表明，河流出口是全球沿海海洋的最大汞来源，持续的汞风险建模应纳入河流的影响。我们估计，河流汞出口可能导致沿海 - 远洋边界每年净出口 350（四分位距：52-640）镁汞，尽管这一估计仍然存在很大的不确定性。我们的结果表明，河流出口是全球沿海海洋的最大汞来源，持续的汞风险建模应纳入河流的影响。我们估计，河流汞出口可能导致沿海 - 远洋边界每年净出口 350（四分位距：52-640）镁汞，尽管这一估计仍然存在很大的不确定性。我们的结果表明，河流出口是全球沿海海洋的最大汞来源，持续的汞风险建模应纳入河流的影响。