Thawing Arctic permafrost is releasing massive amounts of terrestrial mercury (Hg) into the Arctic shelf, which is expected to form a Hg sink in sediments. Here we analyzed the coupling roles of terrestrial input and biological processes in varying mineral/organic matrix-related Hg sequestration and deposition on the East Siberian Arctic shelf (ESAS), using Pearson and partial correlation analysis. Results show that the occurrence of Hg in the Laptev Sea under the Lena River-dominated input exhibits strong correlations with the organic carbon (OC) content and sediment specific surface area. This indicates that the prolonged riverine loading processes facilitate Hg sequestration by organic/mineral matrices and these land-derived mineral-OC-Hg complexes remain stable during cross-shelf transportation. By contrast, the comparative samples with coastal erosion-dominated Hg input in the western East Siberian Sea shows limited Hg complexation, primarily due to the absence of regulation by riverine processes and/or the high sedimentation rates. The correlations between Hg and OC source proxies (δ13C and lignin) indicate that these matrix-free Hg could be more readily sequestrated by the marine OC, which facilitates its deposition via the biological pump. While unexpectedly low Hg abundance in the Chukchi Sea may indicate that the effective biological scavenging of Hg sequestration could be constrained by insufficient terrestrial Hg input. Our findings of the matrix-related Hg sequestration by mineral and/or OC association in this study may shed light on the biogeochemical cycle of Hg in the Arctic aquatic regime, which could reduce the methylmercury formation in water column, and the methylation within sediments needs further exploration.

中文翻译：

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陆地输入和生物过程驱动了东西伯利亚北极陆架中不同的矿物/有机基质相关的汞封存和沉积


北极永久冻土层的融化正在将大量的陆地汞（Hg）释放到北极陆架中，预计将在沉积物中形成汞汇。在这里，我们使用皮尔逊和偏相关分析分析了东西伯利亚北极陆架（ESAS）上不同矿物/有机基质相关的汞封存和沉积中陆地输入和生物过程的耦合作用。结果表明，以勒拿河为主的输入下，拉普捷夫海中汞的赋存与有机碳（OC）含量和沉积物比表面积具有很强的相关性。这表明，长期的河流装载过程促进了有机/矿物基质对汞的封存，并且这些陆源矿物-OC-汞复合物在跨陆架运输过程中保持稳定。相比之下，东西伯利亚海西部以海岸侵蚀为主的汞输入的比较样本显示出有限的汞络合，这主要是由于缺乏河流过程的调节和/或高沉积率。 Hg 和 OC 源代理（δ13C 和木质素）之间的相关性表明，这些无基质的 Hg 更容易被海洋 OC 封存，从而促进其通过生物泵沉积。虽然楚科奇海汞丰度出乎意料地低，但可能表明汞封存的有效生物清除可能受到陆地汞输入不足的限制。我们在这项研究中通过矿物和/或有机碳结合与基质相关的汞封存的发现可能有助于了解北极水生系统中汞的生物地球化学循环，这可以减少水体中甲基汞的形成以及沉积物内的甲基化需求进一步探索。