A warmer climate is predicted to accelerate the export of mercury (Hg) from Siberian rivers to the Arctic Ocean, yet there is a dearth of process-oriented studies on the speciation and fate of Hg in the shelf sea system. Here, we present data on total Hg (HgT) and methylmercury (MeHg) in Laptev Sea surface sediments along a cross-shelf transect starting at the mouth of the Lena River. Concentrations of HgT along the 330 km cross-shelf transect ranged within a fairly narrow span from 480 to 150 pmol g⁻¹ d.w., while concentrations of MeHg decreased one hundredfold from 13 pmol g⁻¹ d.w. near the Lena river to 0.095 pmol g⁻¹ d.w. in the more distall stations. The highest concentrations of HgT and MeHg were observed close to the river delta and were associated with a high supply of organic carbon (OC). Enrichment of the OC normalized HgT concentration (HgT_OC) and depletion of the OC normalized MeHg concentration (MeHg_OC) across the shelf suggests bulk OC content to not be the only driver of the HgT and MeHg spatial distributions. Based on correlations observed between HgT_OC and MeHg_OC and proxies for sediment physics and organic matter pools we suggest the spatial distribution of Hg and MeHg to also be influenced by hydrodynamic sorting of riverine-derived material. For MeHg, depletion of the MeHg_OC across the shelf is likely driven by the trapping of terrestrial MeHg in sediments close to the river delta before it is degraded in the water column.

预计气候变暖将加速汞 (Hg) 从西伯利亚河流向北冰洋的出口，但缺乏对大陆架海系统中汞的形态和归宿的过程导向研究。在这里，我们展示了拉普捷夫海表层沉积物中总汞 (HgT) 和甲基汞 (MeHg) 的数据，这些数据沿着从勒拿河河口开始的跨陆架横断面。沿 330 公里跨陆架横断面的 HgT 浓度范围在 480 至 150 pmol g ^-1 dw的相当窄的范围内，而 MeHg 的浓度从Lena 河附近的13 pmol g ^-1 dw降低了 100 倍至 0.095 pmol g ^{- 1}dw 在更远的站。在河流三角洲附近观察到最高浓度的 HgT 和 MeHg，并且与大量有机碳 (OC) 供应有关。OC 归一化 HgT 浓度 (HgT _OC ) 的富集和 OC 归一化 MeHg 浓度 (MeHg _OC ) 在整个货架上的消耗表明大量 OC 含量不是 HgT 和 MeHg 空间分布的唯一驱动因素。根据观察到的 HgT _OC和 MeHg _OC之间的相关性以及沉积物物理和有机物池的替代物，我们建议 Hg 和 MeHg 的空间分布也受河流衍生材料的流体动力学分选的影响。对于 MeHg，去除 MeHg _OC 陆架上的甲基汞可能是由陆地甲基汞在河流三角洲附近的沉积物中在其在水体中降解之前被捕获而驱动的。