黄河干流甘肃白银-宁夏沙坡头段水体污染现状评价及源解析

Water Pollution Assessment and Pollutant Source Analysis in the Mainstream Section from Baiyin in Gansu to Shapotou in Ningxia of the Yellow River

为查明黄河干流甘肃白银-宁夏沙坡头段水体污染现状,系统采集代表性水体样品69组,测定As、Cu、Cd、Zn、Pb和Mn浓度,分别采用重金属污染指数、内梅罗综合指数和潜在生态风险评估模型对6种元素污染特征和潜在生态风险进行评价,并结合研究区工农业分布现状,基于皮尔逊相关性分析和主成分分析法解析主要污染源。结果表明,研究区水体中Mn超标,As、Cu、Cd、Zn和Pb达Ⅱ类水质标准;在空间分布上,各元素浓度从上游至下游呈逐渐上升趋势,且高浓度点位大都位于入河交汇处及下游邻近河段。重金属污染指数评价结果表明研究区水体属非常轻微污染水平,内梅罗综合指数评价结果表明水体介于尚清洁状态到重度污染状态之间;潜在生态风险评价结果表明,单元素潜在生态风险指数和多元素综合潜在生态风险指数均属于轻微生态风险。As、Cu和Mn主要为工业源和自然源的复合污染源,Cd和Pb主要受农业源和工业源的复合影响,Zn主要来源于交通污染,人类活动是影响研究区水质的关键因素。

69 groups of water samples were collected for investigation on concentration of As,Cu,Cd,Zn,Pb and Mn to expose the pollution status in the mainstream of the Yellow River,from Baiyin City in Gansu Province to Shapotou City in Ningxia Hui Autonomous Region.Heavy metal pollution index,Nemero index and potential ecological risk assessment model were employed to evaluate the pollution characteristics and potential ecological risk in this stream section,and pollutant sources were also analyzed based on the distribution of industrial and agricultural activities by Pearson correlation analysis and principal component analysis.The results show that Class II criteria of national surface water quality standard was matched by As,Cu,Cd,Zn and Pb but exceeded by Mn component with increasing tendency of all heavy metal content along the river,and high content samples were mostly found in or near the tributaries confluence.The assessment results demonstrate that pollution level of this river section is very slight pollution level by heavy metal pollution index,relatively clean to heavy pollution level by Nemero index and slight ecological risk level by both single and multi-element comprehensive potential ecological risk index.As,Cu and Mn pollutants are recognized as mainly composite pollutants from industrial and natural sources,Cd and Pb are mainly influenced by the combination of agricultural and industrial activities,and Zn is mainly from traffic source.Human activity is the key factor affecting the water quality in the study area.