Pollution Source Analysis of Heavy Metal and Ecological Risk Assessment in Urban Fringe

Abstract

With the rapid development of modern urbanization, the unreasonable industrial structure has impacted urban environment, which greatly restricts the use of land resources safely. Especially in some cities with rapid urbanization, on the one hand, urban development requires a large amount of lands; on the other hand, the urban environment exceeds its bearing capacity, and human settlements environment have been negatively affected. Taking the typical urban fringe of Xi’an as the research area, this study detected Cd, Cr, Cu, Ni, Pb and Zn combined with GIS, RS and GPS technologies. Totally 26 sample points were collected. The pollution index method (single pollution index, Nemerow comprehensive pollution index method), geo-accumulation index method and potential ecological risk index method were used to evaluate the results, and the pollution sources were analysed. According to the analysis results, Cd, Pb and Zn existed obviously ecological risks. The Pb pollution of each sample point was quite different. Sample points 1-13 were located in the east of the research area, mainly distributed on both sides of the traffic road. Pb pollution was relatively serious. The average value of Igeo (Pb) reached 4.20, which belongs to strong pollution - extremely strong pollution. The heavy metal pollution of Zn was universal, however, the toxicity response parameter of Zn is low, Tr i=1, so the ecological risk was not significant. The detection rate of Cd was only 11.5%, but the value was much higher than background value, which should be paid attention to. The results showed that there are different degrees of heavy metal pollution and potential ecological risks in the research area, which supported the safe use of land in urban fringe areas.