Study on heavy metals and ecological risk assessment from Gansu, Ningxia and Inner Mongolia sections of the Yellow River, China.

The Yellow River is the most important resource of water supply in northern China. The purpose of this work are to investigate the concentrations and potential ecological risk of heavy metals in the upper reaches of the Yellow River, the concentrations of eight heavy metals including As, Hg, Cd, Pb, Cr, Ni, Cu and Zn in filtered water and suspended particles from 12 sampling sites of Gansu, Ningxia and Inner Mongolia sections of the Yellow River of China were studied by atomic fluorescence spectrometry (AFS) and high resolution inductively coupled plasma mass spectrometer (HR-ICP-MS) in this paper. The results implied that all heavy metals in filtered water were lower than the limit standards for drinking water except for Cr (56.9 approximately 71. 5 microg L-1 ). Water quality parameters such as total nitrogen (TN), total phosphorus (TP) and pH were also determined and the contents were low along the river except for TN at S1 (2.48) and S9 (2.38), which exceeded the maximum permitted concentration of Class V for the protection of surface water. In suspended particles, the concentrations of Hg, Cd, Pb and Zn were much higher than those in the background value of soil from local section. Cluster analysis (CA) indicated that same sources for Ni, Cu, Cr, Zn and Pb could be stainless steel and petrochemical industrial activities, while As, Cd and Hg derived from agrochemicals, fertilizers, mining, fuel and coal combustion, respectively. Ecological risk assessment was undertaken using risk index (RI) for sampling sites and ecological risk factor (Er) for heavy metals. Eleven suspension samples existed considerable ecological risk (300.6< RI< 508. 6), while S1 was moderate ecological risk (RI, 299.3). According to Er, Hg had considerable or high ecological risk in Inner Mongolia section, while very high ecological risk for Cd at S11 (396.0), S9 (384. 0) and S5 (373. 3), respectively, implied a high pollution in these sampling sites. The results could provide reliable experimental data and theoretical basis for the relevant departments.