Palmer Michael J, Chételat John, Richardson Murray, Jamieson Heather E, Galloway Jennifer M
Department of Geography and Environmental Studies, Carleton University, Ottawa K1S 5B6, Canada.
Department of Geography and Environmental Studies, Carleton University, Ottawa K1S 5B6, Canada; Environment and Climate Change Canada, National Wildlife Research Centre, Ottawa K1A 0H3, Canada.
Sci Total Environ. 2019 Sep 20;684:326-339. doi: 10.1016/j.scitotenv.2019.05.258. Epub 2019 May 21.
The seasonal variation in lake water arsenic (As) and antimony (Sb) concentrations was assessed in four small (<1.5km) subarctic lakes impacted by As and Sb emissions from legacy mining activities near Yellowknife, Northwest Territories, Canada. Substantial variation in As concentrations were measured over the two-year period of study in all but the deepest lake (maximum depth 6.9m), including a four-fold difference in As in the shallowest lake ([As]: 172-846μgL; maximum depth 0.8m). Arsenic concentrations were enriched following ice cover development in the three shallowest lakes (50-110%) through a combination of physical and biogeochemical processes. Early winter increases in As were associated with the exclusion of solutes from the developing ice-cover; and large increases in As were measured once oxygen conditions were depleted to the point of anoxia by mid-winter. The onset of anoxic conditions within the water column was associated with large increases in the concentration of redox sensitive elements in lake waters (As, iron [Fe], and manganese [Mn]), suggesting coupling of As mobility with Fe and Mn cycling. In contrast, there was little difference in Sb concentrations under ice suggesting that Sb mobility was controlled by factors other than Fe and Mn associated redox processes. A survey of 30 lakes in the region during fall (open-water) and late-winter (under-ice) revealed large seasonal differences in surface water As were more common in lakes with a maximum depth <4m. This threshold highlights the importance of winter conditions and links between physical lake properties and biogeochemical processes in the chemical recovery of As-impacted subarctic landscapes. The findings indicate annual remobilization of As from contaminated lake sediments may be inhibiting recovery in small shallow lakes that undergo seasonal transitions in redox state.
在加拿大西北地区耶洛奈夫附近，受遗留采矿活动中砷和锑排放影响的四个小型（<1.5公里）亚北极湖泊中，评估了湖水砷（As）和锑（Sb）浓度的季节性变化。在为期两年的研究期间，除了最深的湖泊（最大深度6.9米）外，所有湖泊中都测量到了砷浓度的显著变化，包括最浅湖泊中砷含量有四倍差异（[As]：172 - 846μg/L；最大深度0.8米）。通过物理和生物地球化学过程的综合作用，三个最浅湖泊在冰盖形成后砷浓度升高（50 - 110%）。初冬时砷的增加与溶质从正在形成的冰盖中排除有关；到冬季中期，一旦氧气条件耗尽至缺氧状态，砷含量大幅增加。水柱内缺氧条件的出现与湖水中氧化还原敏感元素（砷、铁[Fe]和锰[Mn]）浓度的大幅增加有关，表明砷的迁移与铁和锰的循环存在耦合关系。相比之下，冰下锑浓度差异不大，这表明锑的迁移受铁和锰相关氧化还原过程以外的因素控制。对该地区30个湖泊在秋季（开放水域）和冬末（冰下）的调查显示，最大深度<4米的湖泊中，地表水砷的季节性差异更大更为常见。这个阈值凸显了冬季条件以及湖泊物理性质与生物地球化学过程之间的联系在受砷影响的亚北极景观化学恢复中的重要性。研究结果表明，受污染湖泊沉积物中砷的年度再迁移可能会抑制小型浅水湖泊的恢复，这些湖泊在氧化还原状态上会经历季节性转变。
