North Slave Research Centre, Aurora Research Institute, Aurora College, Yellowknife, NT, Canada; Department of Geography and Environmental Studies, Carleton University, Ottawa, ON, Canada.
Department of Geography and Environmental Studies, Carleton University, Ottawa, ON, Canada.
Environ Pollut. 2024 Oct 1;358:124480. doi: 10.1016/j.envpol.2024.124480. Epub 2024 Jul 3.
A holistic understanding of the chemical recovery of lakes from arsenic (As) pollution requires consideration of within-lake biogeochemical cycling of As and processes occurring in the surrounding catchment. This study used a watershed mass balance approach, complemented by experimental sediment incubations, to assess the mobility and transport of As within a subarctic watershed (155 km) impacted by more than 60 years of atmospheric mining emissions. The period of record spanned a transition from drought to high streamflow between September 2017 and September 2019, which yielded insights into the interacting effects of hydrology and within-lake biogeochemical cycling of As. Internal loading of As from contaminated lake sediments (25-46 kg As year) and contributions from terrestrial sources (16-56 kg As yr) continue to negatively impact lake water quality (19-144 μg As L), but the relative importance of these loads varies seasonally and inter-annually in response to changing hydrological conditions. Wet conditions resulted in greater transport of As from terrestrial reservoirs and upstream areas, shorter lake water retention time, and increased the downstream export of As. During dry periods, the lake was disconnected from the surrounding watershed resulting in limited terrestrial contributions and longer lake water residence time, which delayed recovery due to the greater relative influence of internal loading from contaminated sediments. This study highlights that changing hydroclimatic regimes will alter trajectories of chemical recovery for arsenic impacted lakes through the coupling of within-lake and watershed transport processes.
要全面了解湖泊砷（As）污染的化学恢复，需要考虑湖泊内 As 的生物地球化学循环以及周围集水区发生的过程。本研究采用流域质量平衡方法，辅以实验沉积物培养，评估了亚北极流域（155km）中 As 的迁移和运输，该流域受到超过 60 年大气采矿排放的影响。记录的时间段跨越了 2017 年 9 月至 2019 年 9 月从干旱到高径流量的转变，这为水文和湖泊内 As 生物地球化学循环的相互作用效应提供了见解。受污染湖底沉积物（25-46kg As 年）和陆地源（16-56kg As yr）的内部 As 负荷继续对湖泊水质（19-144μg As L）产生负面影响，但这些负荷的相对重要性会随着水文条件的变化而季节性和年度性变化。湿润条件导致更多的 As 从陆地储层和上游地区迁移，湖水停留时间缩短，以及更多的 As 向下游输出。在干旱时期，湖泊与周围的集水区断开连接，导致陆地贡献有限且湖水停留时间延长，由于受污染沉积物的内部负荷的相对影响更大，因此会延迟恢复。本研究强调，气候变化将通过湖泊内和流域输运过程的耦合，改变受砷影响的湖泊的化学恢复轨迹。
