Potential Ecological Risk And Speciation Analysis Of Heavy Metals In Sediments From Jialu River

The Jialu River is an important branch of the Huaihe River, the main flood and waterlogging drainage channel of Zhengzhou City, China. It is 256 km long with a basin area of 5896 km2, originating from Xinmi County, Henan Province, flowing via Zhengzhou, Zhongmou, Weishi and Xihua, and then down into the Shaying River near Zhoukou City. Unfortunately, it has been seriously polluted due to the rapid economic growth and urbanization.In order to evaluate ecological risks and existing forms of heavy metals in Jialu River, sediments samples were collected from 22 sites along this river. A BCR-sequential extraction procedure was applied to analyze the chemical speciation of heavy metals (Cr, Mn, Co, Ni, Zn, Cu and Cd) in sediments. And supernatants were used to analyse metal contents by using inductively coupled plasma optical emission spectrometer. Pearson correlation and principal components analysis were used to evaluate the metal source. The Geo-accumulation Index and risk assessment code were used to evaluate the polluted situation of heavy metals in sediments of Jialu River. The main results of this research are as follows:1. The heavy metals exist in different combination states in the sediments of Jialu River. Mn and Zn mainly exist in reducible fraction and average account for 42.72% and 37.71% of the total, respectively. While, Cr、Co、Ni、Cu and Cd exist in residual fraction and average accounted for 77.90%,58.75%, 59.02%,43.93% and 48.21% of their total, respectively.2. Among the heavy metals of the sediment of Jialu River, there is a significant correlation between mutual Cr, Ni, Zn, Cu, Cd. While, no correlation between Mn with other heavy metals, so does Co. Zhengzhou City was the main releasing source for these heavy metals and had major effect on the pollution of the Jialu River.3. The GAIs of all samples were less than 1. All of the sampling sites are subject to varying degrees of different heavy metals pollution. The sample site S15 and S16 polluted seriously with Mn, Co, Zn, Cu and Cd compared with other sampling sites. All of the sampling sites were unpolluted with Cr and Ni, and lots of sampling sites were moderately polluted with Mn, Co, Zn, Cu and Cd.4. The concentrations of Cr, Co and Ni are posing a low risk (1-10%) to the environment of all the sampling sites in Jialu River. Cu and Mn fall in medium risk category in all of the sampling sites. The concentration of Cd is posing a high risk (31-50%) in the sampling site 11. And besides this site, Cd is posing a medium risk in other sites. The concentrations of the studied metals decreased in the order:Mn> Zn> Cr> Ni> Cu> Co> Cd. However, the order of risk levels was as follow:Zn> Cd> Mn> Cu> Ni> Co> Cr.