School of Environment, Hangzhou Institute for Advanced Study, University of Chinese Academy of Sciences, Hangzhou 310024, China; State Key Laboratory of Tibetan Plateau Earth System, Resources and Environment, Institute of Tibetan Plateau Research, Chinese Academy of Sciences, Beijing 100101, China; State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Science, Chinese Academy of Sciences, Beijing 100085, China.
State Key Laboratory of Tibetan Plateau Earth System, Resources and Environment, Institute of Tibetan Plateau Research, Chinese Academy of Sciences, Beijing 100101, China.
Water Res. 2022 Jun 30;218:118474. doi: 10.1016/j.watres.2022.118474. Epub 2022 Apr 16.
Glaciers in the Himalayan region have been receding rapidly in recent decades, drawing increasing concerns about the release of legacy pollutants (e.g., mercury (Hg)). To investigate the distribution, transport and controlling factors of Hg in glacier-fed runoff, from June 2019 to July 2020, a continuous monitoring and an intensive sampling campaign were conducted in the Rongbuk Glacier-fed basin (RGB) on the north slope of Mt. Everest in the middle Himalayas. The total Hg (THg) and methyl Hg (MeHg) concentrations were 1.56 ± 0.85 and 0.057 ± 0.025 ng/L, respectively, which were comparable to the global background levels and were mainly affected by the total suspended particulate matter (TSP). In addition, THg and MeHg showed significant diurnal variations, with peak values appearing at approximately 17:00 (upstream) and 19:00 (downstream). Based on the annual runoff and average Hg concentration, the annual export fluxes of THg and MeHg were estimated to be 441 g and 16 g, respectively. The yields of THg and MeHg in the RGB were 1.6 and 0.06 μg/m/year, respectively. Currently, the annual Hg export of meltwater runoff in the Himalayan region is approximately 337 kg/year. When flowing through the proglacial lake, the THg concentrations decreased by 32% and 15% in the proglacial lake water and in the outlet, respectively, indicating that proglacial lakes had a sedimentation effect on the Hg transport. The Hg export from meltwater runoff in the Himalayas will likely increase considering the meltwater runoff has been projected to increase in the future. Nonetheless, emerging proglacial lakes may exert ambiguous effects on the glacier exported Hg under changing climate. Proglacial lakes could lower the levels and amounts of Hg in the glacier runoff, whereas the outburst of proglacial lakes could lead to an instantaneous release of Hg stored in lake waters and sediments. Our analysis shed light on the environmental impact of glacier retreat in the Himalayas and highlighted the need for integrated monitoring and study of Hg in glacier runoff and glacial lakes.
喜马拉雅地区的冰川在近几十年内迅速消退，这引起了人们对释放遗留污染物（如汞 (Hg)）的日益关注。为了研究冰川融水中 Hg 的分布、迁移和控制因素，我们于 2019 年 6 月至 2020 年 7 月在喜马拉雅山脉中段珠穆朗玛峰北坡的绒布冰川流域（RGB）进行了连续监测和强化采样。总汞 (THg) 和甲基汞 (MeHg) 的浓度分别为 1.56±0.85 和 0.057±0.025ng/L，与全球背景水平相当，主要受总悬浮颗粒物（TSP）的影响。此外，THg 和 MeHg 表现出明显的日变化，峰值出现在大约 17:00（上游）和 19:00（下游）。根据年径流量和平均 Hg 浓度，估算出 THg 和 MeHg 的年排放量分别为 441g 和 16g。RGB 的 THg 和 MeHg 产率分别为 1.6 和 0.06μg/m/年。目前，喜马拉雅地区融水径流量的年 Hg 排放量约为 337kg/年。当融水径流流经冰前湖时，THg 浓度在冰前湖水中和出水口处分别降低了 32%和 15%，表明冰前湖对 Hg 迁移具有沉降作用。考虑到未来融水径流量预计会增加，喜马拉雅地区的融水径流中 Hg 的排放量可能会增加。然而，在气候变化下，新兴的冰前湖可能会对冰川输出的 Hg 产生不确定的影响。冰前湖可能会降低冰川径流中 Hg 的水平和数量，而冰前湖的爆发可能会导致储存在湖水中和沉积物中的 Hg 瞬间释放。我们的分析揭示了喜马拉雅山冰川退缩对环境的影响，并强调了对冰川径流和冰川湖中 Hg 进行综合监测和研究的必要性。
