The Distribution Characteristics And Environmental Evalution Of Heavy Metals In Water-sediments Of Nanfei River

In order to systematically study the state of heavy metal pollution in Nanfei River,the surface water and sediments are sampled during the wet season,level period and dry season,the temporal and spatial distribution of heavy metals are analyzed.This paper discusses the total amounts and characteristics of occurrence speciations of heavy metals in environmental media such as water and sediment.To evaluate the state of heavy metal pollution in Nanfei River,the single factor water quality identification index method and improved fuzzy comprehensive evaluation method are applied for pollution assessment of heavy metals in the surface water,and geo-accumulation index method and potential ecological risk assessment method are used for pollution evaluation of total amounts of heavy metals in sediments,while P value ecological risk assessment method and risk assessment code method are used to evaluate the risk of characteristics of occurrence speciations of heavy metals in sediments.Based on the mathematical method,the SPSS software is emplied to analyze the sources of heavy metal pollution in Nanfei River.The results show that:(1)The variations of contents of elements in surface water are basically the same during different hydrological periods,but the degree of heavy metal pollution is lowest during wet period and highest during dry period.(2)The contents of five kinds of elements are different,but there is a little difference of the contents of same element at different time.And the contents of five metallic elements exceed the standards,of which Cd is worst.All the metallic elements are dominated by residual form.According to the proportion of residual form,the reactivity of As is the lowest,while Cd is the highest.(3)Evaluation results from single factor water quality identification index method and improved fuzzy comprehensive evaluation method show that the pollution level of Cd is the highest,and the second highest is Pb.The results of geo-accumulation index method show that the pollution degree of each sampling points are either clean or mild,and the highest pollution degree of the five metallic element is Cd.The results of potential ecological risk assessment method show that all sampling sites are in the situation of moderate ecological risk level.Among the five metallic elements,the risk of Cd is the highest.According to P value risk assessment and risk assessment index method,only Cd is in the state of high risk level.As a consequence,Cd is the main pollution factor of the five metallic elements.(4)Combining the principal components analysis results of heavy metal in overlying water with in sediments,the heavy metals are mainly derived from pesticides and chemical fertilizers,wastewater of machinery manufacturing and electroplating industry and sailing activity.