长江下游干流沉积物重金属特征及生态风险评价

金阳; 姜月华; 周权平; 王晓龙; 张鸿; 梅世嘉; 陈孜; 杨海; 吕劲松; 侯莉莉; 齐秋菊; 贾正阳; 杨辉

doi:10.12029/gc20220331001

长江下游干流沉积物重金属特征及生态风险评价

Characteristics and ecological risk assessment of sedimentary heavy metals from the Lower Mainstream of Yangtze River

摘要

摘要:
研究目的 长江下游干流沿岸分布众多取水口，为保障用水安全和生态环境健康，亟需了解近岸沉积物中重金属相关现状。
研究方法 调查过程中自上而下分左右岸共采集沉积物样品85组，利用描述统计分析重金属含量特征，综合相关性分析和主成分分析探讨重金属来源，采用地累积指数法、污染负荷法分析重金属污染程度，并评估其潜在生态风险。
研究结果 平均含量由高至低为Zn＞Cr＞Cu＞Ni＞Pb＞As＞Cd；上游至下游，Cu、Zn、Cr、Ni呈小幅波动增加趋势，As、Pb呈小幅波动下降趋势，Cd呈较大波动下降趋势；Cd的污染程度最重，主要来源于农业生产等人类活动，1~4级污染分别占比1.18%、1.18%、18.82%和34.12%，Cr和Ni为无污染，主要是工业生产源和地球化学自然源；中等污染程度（1≤PLI_point＜2）的样点占比34.18%，潜在生态风险指数（RI）为19.48~388.62，轻微潜在生态风险、中等潜在生态风险、强潜在生态风险和极强潜在生态风险占比分别为38.82%、42.35%、17.65%和1.18%。
结论长江下游干流沉积物中重金属含量较低，流域整体处于轻微—中等风险的无污染状态（PLI_area＜1），右岸重金属平均含量、污染程度和潜在生态风险均普遍高于左岸。

Abstract:
This paper is the result of hydrogeological survey engineering.
Objective There are numerous water−intakes along the mainstream of the Yangtze River downstream, in order to ensure water safety and eco−environmental health, relevant situation of heavy metals in the nearshore sediment need to be studied urgently.
Methods A total of 85 sediment samples were collected on both left and right banks from the upstream to the downstream with the investigation. Descriptive statistics analysis was used to show the characteristics of heavy metals. Correlational analysis and principal component analysis (PCA) were applied to study the sources of heavy metals. Geoaccumulation index and pollution load index were used to analyze the pollution levels, and the potential ecological risk of heavy metals were evaluated by the methods of potential ecological risk assessment index.
Results The order of average content from high to low is Zn＞Cr＞Cu＞Ni＞Pb＞As＞Cd. From the upstream to the downstream, Cu、Zn、Cr、Ni had a small fluctuating but increasing trend, while As and Pb had a small fluctuating but decreasing trend, Cd showed decreasing trend with an obvious fluctuation. The most polluted one is Cd among seven heavy metals, which were mainly from human activities, such as agriculture. Cd accounted for 1.18%, 1.18%, 18.82% and 34.12% from polluted Class 1 to 4, respectively. Cr and Ni were non−pollution class, which mainly from industries and geochemical natural source. 34.18% of all sampling sites were in moderate pollution (1≤PLI_point＜2). RI was ranged from 19.48 to 388.62, and the proportions of slight potential ecological risk, medium potential ecological risk, strong potential ecological risk and extremely strong potential ecological risk were 38.82 %, 42.35 %, 17.65 % and 1.18 %, respectively.
Conclusions Contents of all heavy metals in mainstream sediment of the Yangtze River downstream were at a lower level. The catchment were overall at non-pollution sate (PLI _area＜1 )with slight to moderate ecological risk. The average contents, pollution levels and potential ecological risks of heavy metals on the right bank were all higher than those on the left bank.

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