Ministry of Education Laboratory of Earth Surface Processes, College of Urban and Environmental Sciences, Peking University, Beijing 100871, China; Department of Marine Sciences, University of Connecticut, 1080 Shennecossett Rd., Groton, CT 06340, United States; School of the Environment, Yale University, New Haven, CT 06511, United States.
Ministry of Education Laboratory of Earth Surface Processes, College of Urban and Environmental Sciences, Peking University, Beijing 100871, China; Department of Marine Sciences, University of Connecticut, 1080 Shennecossett Rd., Groton, CT 06340, United States.
Water Res. 2020 Oct 15;185:116295. doi: 10.1016/j.watres.2020.116295. Epub 2020 Aug 13.
The Three Gorges Dam (TGD) is the world's largest hydropower construction. It can significantly impact contaminant transport in the Yangtze River-East China Sea Continuum (YR-ECSC). In addition to evaluating the impact of the TGD on the deposition of contaminants in the reservoir, we also address their cycles in the river below the dam and in the coastal East China Sea. A comprehensive study of metal contaminant transport along the YR-ECSC has not been previously attempted. We quantified the fates of mercury (Hg), arsenic (As), lead (Pb), cadmium (Cd) and chromium (Cr) within the YR-ECSC, and the impacts of the TGD, by sampling water and suspended particles along the Yangtze River during spring, summer, fall, and winter and by modeling. We found that the Yangtze River transports substantial amounts of heavy metals into the coastal ocean. In 2016, riverine transport amounted to 48, 5900, 11,000, 230, and 15,000 megagrams (Mg) for Hg, As, Pb, Cd, and Cr, respectively, while other terrestrial contributions were negligible. Metal flux into the coastal ocean was primarily derived from the downstream portion of the river (84-97%), while metals transported from upstream were largely trapped in the Three Gorges Reservoir (TGR, 72%-96%). For example, 34 Mg of Hg accumulated in the TGR owing to river damming, large-scale soil erosion, and anthropogenic point source releases, while 21 Mg of Hg was depleted from the riverbed downstream owing to the altered river hydrology caused by the TGD. Overall the construction of TGD resulted in a 6.9% net decrease in the Hg burden of the East China Sea, compared to the pre-TGD period.
三峡大坝（TGD）是世界上最大的水电工程。它会对长江-东海连续体（YR-ECSC）中的污染物输运产生重大影响。除了评估 TGD 对水库中污染物沉积的影响外，我们还研究了大坝下游河流和东海沿海地区污染物的循环情况。此前，人们尚未对 YR-ECSC 沿线的金属污染物输运进行全面研究。我们通过在春季、夏季、秋季和冬季沿长江采集水样和悬浮颗粒物，并进行模拟，定量研究了 YR-ECSC 内汞（Hg）、砷（As）、铅（Pb）、镉（Cd）和铬（Cr）的命运及其受 TGD 的影响。结果表明，长江向沿海海洋输送了大量重金属。2016 年，Hg、As、Pb、Cd 和 Cr 分别有 48000、59000、11000、230 和 15000 吨通过河流输送至沿海，而其他陆地来源可以忽略不计。金属向沿海海洋的通量主要来自河流的下游部分（84-97%），而来自上游的金属则主要被三峡水库（TGR）截留（72%-96%）。例如，由于筑坝、大规模土壤侵蚀和人为点源释放，TGR 中累积了 34 吨 Hg，而由于 TGD 改变了河流水文，下游河床损失了 21 吨 Hg。总体而言，与 TGD 之前相比，TGD 的建设导致东海 Hg 负荷净减少了 6.9%。
