兰州市城区河道表层沉积物地球化学元素分布特征

Element Characters of River Sediment of Urban Area in Lanzhou City

通过对兰州市河道表层沉积物地球化学元素分析发现,兰州市河道表层沉积物41种地球化学元素富集因子多小于1,Cl、S、P、Bi、Cr、Cu、Pb、Sn、U、W、Zn富集因子值均大于2,显示了较高的污染水平。对单个采样点总富集因子的分析研究发现,R值均大于2,显示出较多的富集。其中水磨沟下游和鱼儿沟下游富集因子出现高值,显示出严重污染。元素来源研究结果显示,兰州市河道表层沉积物地球化学元素的来源可分为3类:①生活污水排放以及雨水对地面或街道的冲刷作用;②工业污染,包括冶金、电镀、农药和化肥等污水的排放;③本地土壤类型灰钙土中元素的贡献。通过粒度与元素相关性分析可知,元素P、Cl主要分布于细颗粒物质中,反映了兰州市河道表层沉积物污染物质在细颗粒中有较大量的富集。

In this study,element concentrations were investigated for 23 deposit samples collected from 8 rivers in Lanzhou urban area.Results indicate that enrichment factor values of Cl,S,P,Bi,Cr,Cu,Pb,Sn,U,W,Zn are all bigger than 2.Analysis of sediment enrichment factor shows a high pollution statue at downstream of Shuimo River and Yuer River.At certain extent,these elements come from artificial factors.The contribution of anthropogenic activities can be divided into 3 types： first is domestic sewage discharge and rain erosion on the ground or the street,and second is industrial pollution such as metallurgical industry,electro-deposition,and third is contribution of elements in soil of sierozem which is a major soil type in local area.Pearson correlation analysis between elements and grain size of river sediment indicates that pollutant always is rich in fine particles.