Water Sources Upstream Tributaries Of Heavy Metal Contamination And Potential Ecological Risk Assessment Of The Situation In Bridge Reservoir

Yuqiao Reservoir, an important adjusting reservoir in the project of diverting water from the Luan River to Tianjin City, is the water resource for drinking of Tianjin City. In recently years, with the rapidly development of society, there were many point source pollutions and non-point pollutions reservoir around the reservoir were mainly brought into Yuqiao Reservoir by rainfall runoff and soil erosion, which increasingly led to be an increasing number of pollution in Yuqiao’ Reservoir. Therefore, it is a great threat on the water resource for drinking of Tianjin City.In this Paper, concentrations and distribution characteristics of six kinds of heavy metals-cadmium (Cd), lead (Pb), chromium (Cr), copper (Cu), zinc (Zn), manganese (Mn), and nickel (Ni)-in sediments from the upper reaches of Yuqiao reservoir were analyzed by ICP-MS, then each specie of heavy metal was extracted by Tessier sequential extracting method and measured by ICP-MS, and the potential ecological risk of heavy metals were analyzed and assessed by using Hankanson ecological risk index methods. What more, the sources of heavy metal were analyzed by Principal component analysis (PCA) and correlation analysis.(1) The sediments samples from three tributaries of Yuqiao reservoir were collected and the concentrations and distribution characteristics of heavy metals such as Cd, Pb, Cr, Cu, Zn, Mn and Ni were analyzed by ICP-MS. The results show that sediments of the upper reaches of Yuqiao reservoir are uncontaminated with Cr, Pb, lightly contaminated with Ni, Cu, Zn, moderately contaminated with Cd, and the most obvious manifestation of heavy metal contamination in the no.2sampling site and no.6.(2) For the three rivers of the upper reaches of Yuqiao reservoir, heavy metal pollution ofahe river was the most serious, and at the highest level ecological risk.(3) The results of Tessier’s method of sequential extracting indicate that Cr, Ni, Zn, Cd and Cu mainly existed as residual forms, while Pb mainly existed as Fe-Mn oxide forms. The contents for organic forms of Cu were high than residual forms and the contents for Fe-Mn oxide forms of Pb were high than organic forms, excepting Cu and Pb, concentrations of Fe-Mn oxide forms and organic forms of the rest heavy metals are close. The contents for exchange forms and carbohydrate forms of Cd were higher than the rest heavy metals.(4) The results of potential ecological risk factors reveals that cadmium (Cd) was at the highest level ecological risk, copper (Cu) and lead (Pb) next to it. The results of the potential ecological risk index demonstrate that most sampling sites of sediments in the upper reaches of Yuqiao reservoir were at low level ecological risk, the downstream of Bahuzhuang sampling site was at medium level ecological risk, the upstream of Zunhua city was at the intensity level and the downstream of Zunhua city reaching high intensity level.(5)From the perspective of pollution sources, the results of Principal component analysis (PCA) demonstrate that comparing with the natural, the industrial is the main sources of heavy metal contamination.(6) From the perspective of position characteristics of Yuqiao reservoir, the results of correlation analysis and current situation information analysis reveal that Zn and Cd are positively correlated with each other, and seriously contaminated from the same source and heavy metal pollution in the sediments of Yuqiao Reservoir is mainly due to characteristics of mining area and riverway shape.