Interdisciplinary Research Centre for Agriculture Green Development in Yangtze River Basin, College of Resources and Environment, Southwest University, Chongqing 400716, China.
Chongqing Key Laboratory of Agricultural Resources and Environment, College of Resources and Environment, Southwest University, Chongqing 400716, China.
Int J Environ Res Public Health. 2023 Feb 19;20(4):3681. doi: 10.3390/ijerph20043681.
The particular condition of the water-level-fluctuation zone (WLFZ) in the Three Gorges Reservoir (TGR), the largest hydroelectric reservoir in China, raises great concerns about mercury (Hg) contamination and ecological risk. In addition, previous research found that soil organic carbon (SOC) plays an essential role in controlling Hg distribution and speciation. However, there is minimal information on the Hg storage distribution and their relationships with SOC in the WLFZ in TGR. This study investigated Hg distribution, storage, and their relationships with SOC in the surface soils in WLFZ. The results showed that the total Hg (THg) content in the surface soils ranged from 18.40 to 218.50 ng g, with an average value of 78.17 ± 41.92 ng g. About 89% of samples had THg content above the background value in Chongqing, showing specific enrichment of Hg in WLFZ due to contamination in the TGR. The surface soils have low SOC, with an average value of 8.10 ± 3.90 g kg. Moreover, THg content showed consistent distribution with the SOC in WLFZ, with a significantly positive correlation ( = 0.52, < 0.01, = 242). THg storage (201.82 ± 103.46 g ha) in the surface soils was also significantly positively correlated with the SOC storage ( = 0.47, < 0.01, = 242). The reduced SOC sequestration, due to the periodical alternative "flooding-draining" and frequent reclamation and utilization of WLFZ, decreased the Hg adsorption in soil. Those might result in the re-release of Hg into waters when WLFZ is flooded. Therefore, more attention should be directed towards Hg cycling and the consequent environmental risks in the TGR region.
三峡水库（TGR）是中国最大的水力发电水库，其水位波动区（WLFZ）的特殊条件引起了人们对汞（Hg）污染和生态风险的极大关注。此外，先前的研究发现，土壤有机碳（SOC）在控制 Hg 分布和形态方面起着至关重要的作用。然而，关于 TGR 中 WLFZ 的 Hg 储量分布及其与 SOC 的关系，信息很少。本研究调查了 WLFZ 表层土壤中 Hg 的分布、储量及其与 SOC 的关系。结果表明，表层土壤中总汞（THg）含量范围为 18.40-218.50ng g，平均值为 78.17±41.92ng g。约 89%的样品的 THg 含量高于重庆的背景值，表明由于 TGR 的污染，WLFZ 中 Hg 存在特定的富集。表层土壤中 SOC 含量较低，平均值为 8.10±3.90g kg。此外，THg 含量与 WLFZ 中的 SOC 呈一致分布，呈显著正相关（ = 0.52， < 0.01， = 242）。表层土壤中 THg 的储量（201.82±103.46g ha）也与 SOC 的储量呈显著正相关（ = 0.47， < 0.01， = 242）。由于周期性的“涨水-退水”和 WLFZ 的频繁开垦利用，SOC 的封存减少，导致土壤中 Hg 的吸附减少。当 WLFZ 被淹没时，这可能导致 Hg 重新释放到水中。因此，应更加关注 TGR 地区的 Hg 循环及其带来的环境风险。
