长江三角洲农灌区沉积物中重金属的污染特征及生态评价

Pollution Characteristics of Heavy Metals and Their Ecological Evaluations in Sediments from Agricultural Irrigation Area of the Yangtze River Delta Region,China

根据地质背景和人类活动方式,将整个长江三角洲地区划分为3个区域,探讨其区域特征和污染水平。利用多元统计学方法,分析不同区域重金属分布及污染特征;应用主成分分析,剖析了引起污染差异的原因;运用综合生态风险评价方法,探讨了沉积物的生态风险。结果表明,重金属的分布和区域特征既有相似性又存在差异:元素的富集程度以浙江区较高,太湖平原较低;浙江区不同元素变化最大,而太湖流域元素的变化则较为均匀。主成分分析表明,不同区域重金属的主要来源有所不同:长江两岸的Hg、Cu、Pb、As污染严重,与城市污水的排放和农业化肥的利用关系密切;太湖流域的主成分因子出现Zn、Cr、Cu组合,体现出电镀、化工行业污染排放的特征;浙江区主成分因子复杂,反映污染物质的多来源。采用Hakanson潜在生态风险指数法对沉积物中重金属进行风险评价,其单因子生态危害程度为Cd>Hg>Pb>As>Cu>Zn>Cr,综合潜在生态风险指数表明,长江三角洲农灌区的污染总体轻微,浙江区北部污染达到中等。

On account of the deteriorating environment in agricultural ecologic system of the Yangtze River Delta Region with rapid economic development,we need a comprehensive evaluation of environmental quality for the system. The research area was divided into three regions based on the geological setting and anthropogenic activities,in order to characterize heavy metals and pollution level of different regions. Distribution and characteristics of heavy metals in irrigation regions were expatiated by utilization of the multiple statistical method. Through principal component analysis,we elucidated the cause of diversities for components and pollutants of sediments. The ecological risks of heavy metals were further evaluated by composite risk index. The results showed that similarities and differences in distribution and characteristics existed in distinctive regions. The enrichment coefficients of heavy metals in sediments showed a higher level in Zhejiang plain,and a lower level in Taihu drainage. The changes of coefficients were largest in Zhejiang plain,while those of Taihu drainage were relatively small. Principal component analysis showed that the various sources of heavy metals presented in the research district. Mercury,Cu,Pb,As comprised main elements in the area along two sides of Yangtze River,which was related to the use of agricultural fertilizers and the discharge of municipal sewage. The principal components of Zn,Cr,Cu in the Taihu drainage reflected the pollution of industrial inputs such as electroplating,chemical plants. The principal component scores in Zhejiang plain had a wide range of factor plots,indicating the complexity of metal sources. The ecological risks of these samples were evaluated with the Hakanson ecological risk index,and results were exhibited in map. It was concluded that the single factors of the ecological ricks for irrigation regions metals declined with Cd〉Hg〉Pb〉As〉Cu〉Zn〉Cr. The potential ecological risks of sediments from different irrigation regions manifested a slight level in most areas of the Yangtze River,but manifested a moderate level in the northern area of Zhejiang plain in view of the comprehensive risk index.