Source identification of heavy metals in surface sediments from a river in Anhui, China

Abstract

Mineral resources (such as sulphur, iron, lead, and zinc) are abundant in one of the watersheds in Anhui Province, China. Unfortunately, excessive mining has negatively impacted the surrounding ecosystems and human health. To facilitate planning of the dredging project for the main river in the watershed, identification of the contaminant source(s) of sediments in the river course is critical. This study focuses on the investigation of seven mines and related businesses. Soil samples were collected from tailings piles and sewage outlets from the mines, sediments in the river course, surrounding croplands, and background areas. The concentrations of eight heavy metals (cadmium, mercury, lead, arsenic, chromium, copper, zinc, and nickel) were analysed. Multivariate statistical analyses, combined with the specific site information, were conducted to evaluate the potential sources of heavy metals in river sediments. The results indicated that the concentrations of copper, cadmium, and arsenic exceeded the thresholds in most parts of the river course. The degree of pollution was highest for copper, moderate for cadmium and arsenic, and lowest for lead, zinc, mercury, nickel, and chromium. Based on pollutant characteristics of different samples, the hydrology and hydrogeology in the watershed, and the operational history of the businesses, the primary source(s) of the contamination of heavy metals in river sediments was determined to be the effluents discharged from mine operations. When the effluents containing large amounts of heavy metals-laden suspensions entered the watershed, the suspensions precipitated gradually, leading to the high concentrations of heavy metals in the river sediments.