Nanjing University, School of Atmospheric Sciences, 163 Xianlin Road, Qixia Distinct, Nanjing 210023, China; Nanjing University, School of Geography and Ocean Science, Ministry of Education Key Laboratory for Coast and Island Development, 163 Xianlin Road, Qixia Distinct, Nanjing 210023, China.
Nanjing University, School of Geography and Ocean Science, Ministry of Education Key Laboratory for Coast and Island Development, 163 Xianlin Road, Qixia Distinct, Nanjing 210023, China.
Water Res. 2023 Sep 1;243:120390. doi: 10.1016/j.watres.2023.120390. Epub 2023 Jul 22.
Riverine processes are crucial for the biogeochemical cycle of mercury (Hg). The Yangtze River, the largest river in East Asia, discharges a substantial amount of Hg into the East China Sea. However, the influencing factors of the Hg budget and its recent trends remain unclear. This study quantitatively analyzed the total Hg concentration (THg) in suspended particulate matter (SPM) in the Yangtze River and calculated the Hg budget in 2018 and 2021. The results showed that the total Hg concentrations varied substantially along the river, with concentrations ranging from 23 to 883 μg/kg in 2018 and 47 to 146 μg/kg in 2021. The average Hg flux to China Sea in 2018 and 2021 were approximately 10 Mg/yr, lower than in 2016 (48 Mg/yr). Over 70% of the SPM was trapped in the Three Gorges Dam (TGD), and 22 Mg/yr of Hg settled in the TGD in 2018 and 10 Mg/yr in 2021. Hg fluxes in the Yangtze River watershed were driven by various factors, including decreased industrial emissions, increased agriculture emissions, and decreased soil erosion flux. We found that in the upper reach of the Yangtze River changed from sink to source of Hg possibly due to the resuspension of sediments, which implies that the settled sediments could be a potential source of Hg for downstream. Overall, emission control policies may have had a positive impact on reducing Hg flux to the East China Sea from 2016 to 2021, but more efforts are needed to further reduce Hg emissions.
河流过程对于汞（Hg）的生物地球化学循环至关重要。长江是东亚最大的河流，向东海排放大量汞。然而，Hg 收支及其近期趋势的影响因素仍不清楚。本研究定量分析了长江悬浮物中总汞（THg）的浓度，并计算了 2018 年和 2021 年的 Hg 收支。结果表明，Hg 浓度沿河流变化很大，2018 年浓度范围为 23-883μg/kg，2021 年为 47-146μg/kg。2018 年和 2021 年向中国海输送的 Hg 通量约为 10 Mg/yr，低于 2016 年（48 Mg/yr）。超过 70%的 SPM 被三峡大坝（TGD）截留，2018 年 TGD 中沉淀了 22 Mg/yr 的 Hg，2021 年为 10 Mg/yr。长江流域 Hg 通量受多种因素驱动，包括工业排放量减少、农业排放量增加和土壤侵蚀通量减少。我们发现，由于沉积物的再悬浮，长江上游可能已经从 Hg 的汇变成了源，这意味着沉降的沉积物可能是下游 Hg 的潜在来源。总体而言，排放控制政策可能对减少 2016 年至 2021 年向东海输送的 Hg 通量产生了积极影响，但仍需进一步努力减少 Hg 排放。
