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Hydrologic control on winter dissolved oxygen mediates arsenic cycling in a small subarctic lake
Limnology and Oceanography ( IF 4.5 ) Pub Date : 2020-08-03 , DOI: 10.1002/lno.11556
Michael J. Palmer 1, 2 , John Chételat 3 , Heather E. Jamieson 4 , Murray Richardson 1 , Marc Amyot 5
Affiliation  

The seasonal development of an ice cover is a characteristic feature of subarctic lakes, yet the biogeochemical cycling of redox sensitive elements under ice, including arsenic (As), is poorly understood. We conducted comprehensive geochemical characterization of lake waters, sediment pore waters and lake sediments over two consecutive years to develop a conceptual model of As, iron (Fe), and sulfur (S) dynamics under ice in a shallow subarctic lake (mean depth 2.0 m) impacted by more than 60 yr of As pollution from local gold mining emissions. Lake sediments were a source of As to overlying waters during both winters when oxygen was depleted from interfacial sediments through the reductive dissolution of As‐bearing Fe (oxy)hydroxides, but the influence on lake water chemistry was distinctly different between years and dependent on winter hydrology of the lake. When the lake was hydrologically disconnected from the upstream watershed, anoxia developed through the entire water column and high concentrations of As (> 100 μ g L−1) and Fe (> 1000 μ g L−1) were measured in lake water. During the second winter, open‐water flow persisted at the lake inlet, which replenished dissolved oxygen in the under‐ice water column, suppressed the upward migration of the Fe and SO4 redox boundaries, and limited sediment As efflux. These findings demonstrate how changing hydrology, specifically ice cover duration, and hydrological connectivity can influence the winter cycling of As, Fe, and S in shallow subarctic lakes.

中文翻译:

冬季溶解氧的水文控制介导了一个小的亚北极湖中的砷循环

冰盖的季节性发展是北极湖的一个特征,但是人们对包括砷(As)在内的冰下氧化还原敏感元素的生物地球化学循环知之甚少。我们连续两年对湖泊水,沉积物孔隙水和湖泊沉积物进行了全面的地球化学表征,以开发浅北极亚冰湖(平均深度为2.0 m)中冰,砷,铁(Fe)和硫(S)动力学的概念模型。 )受到当地金矿开采排放的60多年As污染的影响。在两个冬季,当通过含砷的Fe(羟基)氢氧化物的还原性溶解使界面沉积物中的氧气耗尽时,湖泊沉积物是上覆水的As来源,但是对湖泊水化学的影响在几年间明显不同,并且取决于湖泊的冬季水文学。当湖泊在水文上与上游流域断开连接时,整个水柱和高浓度的砷(> 100 μ克L- -1)和Fe(> 1000  μ克L- -1)在湖水进行测定。在第二个冬季,湖泊入口处的开阔水流持续存在,补充了冰下水柱中的溶解氧,抑制了Fe和SO 4氧化还原边界的向上迁移,并限制了泥沙的外流。这些发现证明了不断变化的水文学,特别是冰覆盖的持续时间以及水文连通性如何影响北极浅水湖泊中As,Fe和S的冬季循环。
更新日期:2020-08-03
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