鄱阳湖地区多尺度流域水体重金属输送特征及其污染风险评价

Transport characteristics and risk assessment of heavy metals in multi-scale watersheds in the Poyang Lake area, China

鄱阳湖流域的生态健康是维系长江下游区域生态安全的重要保障,而流域内丰富的重金属矿排放的工业废水会对流域生态健康产生巨大威胁。通过对不同级别河流水体中8种重金属(As、Cr、Fe、Mn、Mo、Pb、Se和V)的浓度进行监测,分析和探讨鄱阳湖流域河流重金属污染状况、来源及迁移输出特征,评估通江河流重金属迁移运输对鄱阳湖流域生态健康的影响。研究结果表明:鄱阳湖流域内梅罗综合污染指数平均值为2.67,属于中度污染,丰水期污染情况较为严重,污染指数在4.14—4.74之间,处于重度污染水平,水体主要污染元素是V和Se,V的最大浓度达331.90μg/L,超过国家水质标准(50μg/L)6.64倍。重金属浓度和由季节差异造成的水文特征变化是控制流域重金属输出通量的主要原因,而小流域的重金属输出通量对丰枯水期的响应更为敏感。香溪对架竹河、架竹河对赣江以及赣江对鄱阳湖的重金属输出通量分别为7.30 kg/km2、4.06 kg/km2和28.10 kg/km2。不同尺度流域对下游的重金属输出贡献率与径流量相关,丰水期,香溪流域对下游架竹河流域重金属输出的贡献率为1.10%,架竹河对赣江的贡献率为0.02%,而在枯水期,上述贡献率分别为1.61%和0.02%。主成分分析表明鄱阳湖流域水体溶解态重金属的主要污染来源为工业采矿,因此,在预防和治理鄱阳湖流域水体重金属污染问题时,应重点控制工业污染来源。

The ecological health of the Poyang Lake watershed is an important guarantee for maintaining ecological security in the downstream region of the Yangtze River,while the discharge of industrial wastewater from heavy metal minerals in the Poyang Lake watershed will pose a great threat to the ecological health.The aims of this study were to determine and discuss the pollutant source and transport characteristics of heavy metals in Poyang Lake by monitoring the concentration of eight elements(As,Cr,Fe,Mn,Mo,Pb,Se,and V)in rivers of different scales and evaluate the adverse effects of heavy metals on the ecological health of the Poyang Lake watershed.The results showed that the average Nemero comprehensive pollution index in the Poyang Lake watershed was 2.67,belonging to moderate pollution,and that its pollution indexes were between 4.14 to 4.74 during the high flow period,belonging to severe pollution,which was more serious than during the low flow period.The main polluted elements for the Poyang Lake watershed were V and Se,wherein the maximum concentration of V was 331.90μg/L,which was 6.64 times higher than the national water quality standard(50μg/L).The concentrations of heavy metals and the changes in the hydrological characteristics due to seasonal differences were the main factors for controlling the transport flux of heavy metals from the watershed,while the response of transport flux from small scale watershed to the change of flow was more sensitive.The heavy metals transport fluxes from Xiang River to Jiazhu River,Jiazhu River to the Gan River,and the Gan River to the Poyang Lake were 7.30 kg/km2,4.06 kg/km2,and 28.10 kg/km2,respectively.The output contribution rate of heavy metals downstream in watersheds of different scales was related to runoff.During the high flow period,the contribution rate of Xiang River watershed to the output of heavy metals in Jiazhu River watershed was 1.10%,and that of Jiazhu River watershed to the Gan River watershed was 0.02%.In contrast,during the low flow period,the contribution rate of Xiang River watershed to the output of heavy metals in Jiazhu River watershed and that of Jiazhu River watershed to the Gan River watershed were 1.61%and 0.02%,respectively.Principal component analysis indicated that the main source of dissolved heavy metals in Poyang Lake was industrial mining activities.Thus,the industrial pollution sources should be given priority when preventing and controlling heavy metals pollution of the water body in the Poyang Lake watershed.