Basin Water Environmental Research Department, Changjiang River Scientific Research Institute, Wuhan 430010, China; Key Lab of Basin Water Resource and Eco-Environmental Science in Hubei Province, Wuhan 430010, China.
Basin Water Environmental Research Department, Changjiang River Scientific Research Institute, Wuhan 430010, China; Key Lab of Basin Water Resource and Eco-Environmental Science in Hubei Province, Wuhan 430010, China.
Sci Total Environ. 2020 Apr 20;714:136779. doi: 10.1016/j.scitotenv.2020.136779. Epub 2020 Jan 18.
Water, sediment, and zoobenthos are crucial carriers and storage media for heavy metal migration and transformation. The distribution characteristics of heavy metals in water, sediment, and zoobenthos can reflect their pollution status and potential influences on the health of aquatic ecosystems. On the basis of monitoring data related to Cu, Zn, Pb, Cd, Ni, Mn, Hg, and As in mainstream water, surface sediment, and zoobenthos at eight sections-from Wuhan to Shanghai-of the Changjiang River (also known as the Yangtze River) and historical monitoring data on heavy metal distributions in different environmental media of the Changjiang River since the 1980s, this study undertook systematically analyzed the spatiotemporal distribution dynamics, pollution levels, and corresponding environmental risks related to heavy metals in water, sediment, and biota, and examined the effects of pollution source variations and water and sediment regimes on heavy metal distribution. Heavy metal concentrations in the waters were much lower than the water quality threshold of Grade III of the Chinese Surface Water Environmental Quality Standard (GB3838-2002); the concentrations of different heavy metals were irregularly distributed and varied significantly along the river mainstream; Cu, Cd, Zn, and Pb concentrations in sediment all exceeded their respective critical effect concentrations and exposed the ecosystem to pollution risks; the pollution levels of and ecosystem health risks posed by Zn and Cu in zoobenthos were high, with pollution concentrations ranked as shrimp > snails > crabs. In general, heavy metal concentrations in the three environmental mediums were ranked as sediment > zoobenthos > water. Finally, comparison with historical monitoring data revealed increasing Cd and Hg concentrations, with the average heavy metal concentration in sediment reaching its maximum value in the 2000s in the middle and lower reaches of the Changjiang River, which are subjected to the combined effect of pollutant emissions and changing water and sediment regimes.
水、沉积物和底栖生物是重金属迁移和转化的重要载体和储存介质。水中、沉积物中和底栖生物中重金属的分布特征可以反映其污染状况及其对水生生态系统健康的潜在影响。本研究基于长江干流武汉至上海段 8 个断面的 Cu、Zn、Pb、Cd、Ni、Mn、Hg 和 As 等重金属的水质监测数据、沉积物和底栖生物监测数据，以及 20 世纪 80 年代以来长江流域不同环境介质重金属分布的历史监测数据，系统分析了重金属在水、沉积物和生物中的时空分布动态、污染水平及相应的环境风险，探讨了污染源变化和水沙条件对重金属分布的影响。水体中重金属浓度远低于《地表水环境质量标准》（GB3838-2002）Ⅲ类水质标准限值；不同重金属浓度沿长江干流呈不规则分布且变化较大；Cu、Cd、Zn 和 Pb 等重金属在沉积物中的浓度均超过各自的临界效应浓度，使生态系统受到污染风险；底栖生物中 Zn 和 Cu 的污染水平和生态系统健康风险较高，污染浓度表现为虾＞螺＞蟹；总体上，三种环境介质中重金属浓度的排序为沉积物＞底栖生物＞水。最后，与历史监测数据的对比结果表明，Cd 和 Hg 的浓度呈上升趋势，在长江中下游，沉积物中重金属的平均浓度在 21 世纪达到最大值，这是污染物排放和水沙条件变化的综合作用所致。
