Key Laboratory of Reservoir Aquatic Environment, Chongqing Institute of Green and Intelligent Technology, Chinese Academy of Sciences, Chongqing, 400714, China.
University of Chinese Academy of Sciences, Beijing, 100049, China.
Environ Sci Pollut Res Int. 2020 Oct;27(29):37099-37113. doi: 10.1007/s11356-020-08935-6. Epub 2020 Jun 24.
Throughout continents, reservoirs tend to have elevated methylmercury (MeHg) concentration transformed from mercury (Hg/total Hg). This impact may be pronounced in the reservoir with less velocity of water during the charging period resulted in the deposition of sediments. In sediments on favorable conditions, methylation may be enhanced by the decomposition of flood organic material, which can release Hg and enhance microbial activity. However, much less is known about the transfer ratio of Hg and its form MeHg from sediment to biota in the hydrological reservoir during the dam charging phase. The objective of our study was to understand the interrelationship between total Hg and MeHg in two key components sediment and fish in the reservoir ecosystem. This study was performed at the Three Gorges Reservoir (TGR) located on upstream of the Yangtze River in China. At the TGR charging phase, during winter time, the water level was high due to blockade of water by Three Gorges Dam (TGD). Sediment and fish samples were collected in winter season for total Hg, MeHg, and several ancillary parameters. The results showed that total Hg in sediment samples of the winter season were ranged from 6.2 ± 0.001 to 193.3 ± 0.001 × 10 mg/kg, with an average value of 53.76 ± 51.80 × 10 mg/kg, and for MeHg was ranged from 12.1 ± 0.04 to 348.7 ± 0.16 × 10 ng/g, with an average value of 98.96 ± 93.07 × 10 ng/g. Total Hg and MeHg in fish samples of the winter season were from 42.48 ± 6.71 to 166 ± 52.56 ng/g, with an average value of 76.22 ± 31.23 ng/g, and from 21.09 ± 2.31 to 61.60 ± 13.30 ng/g, with an average value of 37.89 ± 11.96 ng/g. The relationship of total Hg and MeHg concentrations in fish to those of sediments from corresponding sites showed a negative relationship. This might include a strong association of total Hg with an inorganic component of sediment (e.g., bound to sulfides or coprecipitated with other metal oxides such as manganese and iron). The average concentration of fish MeHg found in this study, at rates greater than 1.72 g/day, was estimated hazardous to human health. This study concludes sediment was acting as sequestrate for total Hg and MeHg in TGR. The bioaccumulation of total Hg and MeHg in fish was not controlled by sediment further investigation about pathological routes and dietary habits of fish needed to be identified for total Hg and MeHg study in TGR.
在各大洲，水库中的甲基汞（MeHg）浓度往往高于汞（Hg/总 Hg）。这种影响在充水期间水流速度较慢的水库中可能更为明显，导致沉积物的沉积。在有利条件下的沉积物中，洪水有机物质的分解可能会增强甲基化作用，从而释放汞并增强微生物活性。然而，人们对在大坝充水阶段水文水库中汞及其形态 MeHg 从沉积物向生物群转移的比例知之甚少。我们的研究目的是了解三峡水库（TGR）生态系统中两个关键组成部分沉积物和鱼类中总汞和 MeHg 之间的相互关系。本研究在中国长江上游的三峡水库（TGR）进行。在 TGR 充水阶段，冬季由于三峡大坝（TGD）的蓄水，水位很高。冬季采集了沉积物和鱼类样本，以测定总汞、MeHg 和其他一些辅助参数。结果表明，冬季沉积物样本中的总汞含量范围为 6.2±0.001 至 193.3±0.001×10mg/kg，平均值为 53.76±51.80×10mg/kg，MeHg 含量范围为 12.1±0.04 至 348.7±0.16×10ng/g，平均值为 98.96±93.07×10ng/g。冬季鱼类样本中的总汞和 MeHg 含量范围为 42.48±6.71 至 166±52.56ng/g，平均值为 76.22±31.23ng/g，21.09±2.31 至 61.60±13.30ng/g，平均值为 37.89±11.96ng/g。来自相应地点的沉积物与鱼类中总汞和 MeHg 浓度之间的关系呈负相关。这可能包括总汞与沉积物中的无机成分（例如，与硫化物结合或与其他金属氧化物如锰和铁共沉淀）之间的强烈关联。本研究中发现的鱼类 MeHg 的平均浓度，按每天 1.72g 以上的速度计算，估计对人类健康有害。本研究得出结论，沉积物是三峡水库中总汞和 MeHg 的隔离剂。鱼类中总汞和 MeHg 的生物累积不受沉积物控制，需要进一步研究鱼类的病理途径和饮食习惯，以确定三峡水库中总汞和 MeHg 的研究。
