The Arctic plays a critical role in the global Hg cycle as both a sink of Hg and, in response to rapid global warming, an emerging source of Hg due to release from permafrost and glaciers. Human activities have led to significant mercury (Hg) contamination in the Arctic over many decades, potentially impacting the health of Arctic ecosystems and indigenous people. Thus, it is crucial to understand the sources and transformations of Hg in the Arctic in order to predict how Hg behaves as emissions and the global climate change. Here we examine Hg stable isotopes in atmospheric particulate Hg (PHg), gaseous elemental Hg (GEM) and surface snow in the high Arctic (Alert, Canada) during polar spring from 2011 to 2015, in order to trace the sources of atmospheric Hg and its fate in Arctic surface environment. Isotope signatures of GEM (δ²⁰²Hg = 0.67 ± 0.24‰, Δ¹⁹⁹Hg = −0.23 ± 0.04‰, Δ²⁰⁰Hg = −0.06 ± 0.04‰, 2SD) are similar to the average Northern Hemisphere background, suggesting that GEM in the high Arctic atmosphere is well mixed with those from lower latitudes. Surprisingly, the isotope composition of PHg has negative Δ¹⁹⁹Hg, which is similar to GEM but distinct from the positive Δ¹⁹⁹Hg typically observed for oxidized Hg species elsewhere. Furthermore, Hg in surface snow shows more negative MIF than PHg, indicating post-depositional loss of Hg via photoreduction. We suggest that PHg is primarily sourced from in situ oxidation of GEM and subsequent scavenging by particles, and thus inherited the isotope composition of GEM when the oxidation is near-complete. The photoreduction re-emission of Hg from snow is strongly affected by Hg speciation, but the overall extent of re-emission (20 ± 31%) is lower than previous estimations for other locations, suggesting potentially a greater loading of Hg to Arctic ecosystem via snowmelt.

北极在全球汞循环中发挥着关键作用，它既是汞的汇，也是应对全球快速变暖的一个新兴的汞来源，这是由于从永久冻土和冰川中释放出来的。几十年来，人类活动导致北极出现严重的汞 (Hg) 污染，可能影响北极生态系统和土著人民的健康。因此，了解北极汞的来源和转化对于预测汞作为排放和全球气候变化的行为至关重要。在这里，我们检查了 2011 年至 2015 年极地春季高北极地区（Alert，加拿大）大气颗粒汞 (PHg)、气态元素汞 (GEM) 和地表雪中的汞稳定同位素，以追踪大气汞的来源和它在北极表面环境中的命运。GEM 的同位素特征 (δ²⁰² Hg = 0.67 ± 0.24‰, Δ ¹⁹⁹ Hg = -0.23 ± 0.04‰, Δ ²⁰⁰ Hg = -0.06 ± 0.04‰, 2SD) 与北半球平均背景相似，表明北极高大气层的 GEM 混合良好与那些来自低纬度的人。令人惊讶的是，PHg 的同位素组成具有负的 Δ ¹⁹⁹ Hg，这与 GEM 相似，但不同于其他地方通常观察到的氧化 Hg 物种的正 Δ ¹⁹⁹ Hg。此外，地表雪中的 Hg 比 PHg 显示出更多的负 MIF，表明沉积后通过光还原损失了 Hg。我们建议 PHg 主要来自原位GEM 的氧化和随后的颗粒清除，因此在氧化接近完成时继承了 GEM 的同位素组成。雪中​​汞的光还原再排放受 Hg 物种形成的强烈影响，但再排放的总体范围 (20 ± 31%) 低于先前对其他地点的估计，这表明通过以下方式对北极生态系统的汞负荷可能更大融雪。