Biogeochemical processes in northern peatland ecosystems are influenced by seasonal temperature fluctuations that are changing with the climate. Methylmercury (MeHg), commonly produced in peatlands, affects downstream waters; therefore, it is important to understand how temperature transitions affect mercury (Hg) dynamics. We investigated how the freeze-thaw cycle influences belowground peat pore water total Hg (THg), MeHg, and dissolved organic carbon (DOC). Four large, intact peat columns were removed from an ombrotrophic peat bog and experimentally frozen and thawed. Pore water was sampled across seven depths in the peat columns during the freeze-thaw cycle and analyzed for THg, MeHg, and DOC concentrations. Freezing results showed increased concentrations of THg below the ice layers and limited change in MeHg concentrations. During thawing, THg concentrations significantly increased, whereas MeHg concentrations decreased. Limited bromide movement and depth decreases in THg and DOC concentrations were associated with increased bulk density and degree of humification in the peat. The experiment demonstrates the effects of the freeze-thaw cycle on Hg concentrations in northern peatlands. Changes to freeze-thaw cycles with climate change may exacerbate Hg cycling and transport processes in peatland environments.

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实验性冻融过程中泥炭柱孔隙水中的汞动力学

北部泥炭地生态系统中的生物地球化学过程受到随气候变化的季节性温度波动的影响。通常在泥炭地中产生的甲基汞 (MeHg) 会影响下游水域；因此，了解温度转变如何影响汞 (Hg) 动力学非常重要。我们研究了冻融循环如何影响地下泥炭孔隙水总 Hg (THg)、MeHg 和溶解有机碳 (DOC)。四个大的、完整的泥炭柱从嗜碱性泥炭沼泽中取出，并进行实验性冷冻和解冻。在冻融循环期间，对泥炭柱中七个深度的孔隙水进行采样，并分析 THg、MeHg 和 DOC 的浓度。冷冻结果显示冰层以下的 THg 浓度增加，而甲基汞浓度的变化有限。在解冻过程中，THg 浓度显着增加，而 MeHg 浓度降低。溴化物运动受限以及 THg 和 DOC 浓度的深度降低与泥炭中堆积密度和腐殖化程度的增加有关。实验证明了冻融循环对北部泥炭地中汞浓度的影响。随着气候变化的冻融循环变化可能会加剧泥炭地环境中的汞循环和运输过程。