Human exposure to toxic mercury (Hg) is dominated by the consumption of seafood^1,2. Earth system models suggest that Hg in marine ecosystems is supplied by atmospheric wet and dry Hg(ii) deposition, with a three times smaller contribution from gaseous Hg(0) uptake^3,4. Observations of marine Hg(ii) deposition and Hg(0) gas exchange are sparse, however⁵, leaving the suggested importance of Hg(ii) deposition⁶ ill-constrained. Here we present the first Hg stable isotope measurements of total Hg (tHg) in surface and deep Atlantic and Mediterranean seawater and use them to quantify atmospheric Hg deposition pathways. We observe overall similar tHg isotope compositions, with median Δ²⁰⁰Hg signatures of 0.02‰, lying in between atmospheric Hg(0) and Hg(ii) deposition end-members. We use a Δ²⁰⁰Hg isotope mass balance to estimate that seawater tHg can be explained by the mixing of 42% (median; interquartile range, 24–50%) atmospheric Hg(ii) gross deposition and 58% (50–76%) Hg(0) gross uptake. We measure and compile additional, global marine Hg isotope data including particulate Hg, sediments and biota and observe a latitudinal Δ²⁰⁰Hg gradient that indicates larger ocean Hg(0) uptake at high latitudes. Our findings suggest that global atmospheric Hg(0) uptake by the oceans is equal to Hg(ii) deposition, which has implications for our understanding of atmospheric Hg dispersal and marine ecosystem recovery.

人类接触有毒汞 (Hg) 的主要方式是食用海鲜^1,2。地球系统模型表明，海洋生态系统中的汞由大气干湿 Hg( ii ) 沉积提供，而气态 Hg(0) 吸收的贡献则小三倍^3,4。然而，对海洋 Hg( ii ) 沉积和 Hg(0) 气体交换的观测很少⁵，因此提出了 Hg( ii ) 沉积的重要性⁶约束不良。在这里，我们首次展示了表层和深大西洋和地中海海水中总 Hg (tHg) 的 Hg 稳定同位素测量值，并使用它们来量化大气 Hg 沉降路径。我们观察到总体相似的 tHg 同位素组成，中值 Δ ²⁰⁰ Hg 特征为 0.02‰，位于大气 Hg(0) 和 Hg( ii ) 沉积末端成员之间。我们使用 Δ ²⁰⁰ Hg 同位素质量平衡来估计海水 tHg 可以通过 42%（中位数；四分位距，24-50%）大气 Hg( ii ) 总沉降和 58%（50-76%）的混合来解释Hg(0) 总摄取量。我们测量和编制额外的全球海洋汞同位素数据，包括颗粒汞、沉积物和生物群，并观察纬度 Δ ²⁰⁰汞梯度表明高纬度海洋对汞 (0) 的吸收量更大。我们的研究结果表明，海洋对全球大气 Hg(0) 的吸收等于 Hg( ii ) 的沉降，这对我们理解大气 Hg 扩散和海洋生态系统恢复具有重要意义。