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PHOTODEGRADATION OF METHYLMERCURY IN LAKES

机译：湖泊中甲基汞的光分解

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摘要

METHYLMERCURY can accumulate in fish to concentrations that threaten human health(1). Fish methylmercury concentrations are high in many reservoirs(2) and acidic lakes(3), and also in many remote lakes(4,5)-a fact that may be related to increased atmospheric deposition of anthropogenically mobilized mercury during the past few decades(6). Although sources of methylmercury to lakes and reservoirs are known(7), in-lake destruction has not been demonstrated to occur at the low concentrations found in most water bodies. Here we report in situ incubations of lake water that show that methylmercury is decomposed by photo-degradation in surface waters. This process is abiotic and the rate is first-order with respect to methylmercury concentration and the intensity of solar radiation. In our study lake, the calculated annual rates of methylmercury photodegradation are almost double the estimated external inputs of methylmercury from rain, snow, streamflow and land runoff, implying the existence of a large source of methylmercury from bottom sediments. Photodegradation could also be an important process in the mercury cycle of other aquatic systems. This discovery fundamentally changes our understanding of aquatic mercury cycling, and challenges the long-accepted view that microbial demethylation dominates methylmercury degradation in natural fresh waters. [References: 24]
机译：甲基汞可能在鱼类中积累到威胁人类健康的浓度（1）。在许多水库（2）和酸性湖泊（3）中，以及在许多偏远的湖泊中（4,5），鱼类甲基汞的浓度都很高，这一事实可能与过去几十年来人为动员的汞在大气中的沉积增加有关（ 6）。尽管已知甲基汞的来源是湖泊和水库（7），但尚未证明在大多数水体中低浓度的情况下会发生湖内破坏。在这里，我们报告了湖水的原位培养，结果表明甲基汞被地表水中的光降解分解。该过程是非生物过程，相对于甲基汞浓度和太阳辐射强度而言，速率是一阶的。在我们的研究湖泊中，计算得出的甲基汞光降解年速率几乎是降雨，降雪，水流和土地径流所估计的甲基汞外部输入的两倍，这意味着存在来自底部沉积物中的大量甲基汞。光降解也可能是其他水生系统汞循环中的重要过程。这一发现从根本上改变了我们对水生汞循环的理解，并挑战了人们长期接受的观点，即微生物脱甲基在天然淡水中占甲基汞降解的主导地位。 [参考：24]

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