Potentially Toxic Element Pollution Levels and Risk Assessment of Soils and Sediments in the Upstream River, Miyun Reservoir, China

This study focused on the Chao River and Baimaguan River located upstream of the Miyun Reservoir in Miyun District (Beijing, China). Soil and sediment samples were collected from the river and drainage basin. Total nitrogen, total phosphorus, and six potentially toxic elements including cadmium, zinc, lead, chromium, arsenic, and copper, were analyzed in terms of concentration, potential ecological risk, and human health risk. The average concentrations of the six potentially toxic elements were all below the soil environmental quality standards for China. Cadmium was the most serious pollutant in both soils and sediments, at 2.58 and 3.40 times its background values. The contents of Cd and Pb were very closely related (p < 0.01) to total nitrogen concentrations in both soil and sediment samples. The potential ecological risks posed by Cd in the Chao and Baimaguan River soils were considerable and moderate, respectively. The historical iron ore mining and agricultural activity were identified as the primary sources of potentially toxic element pollution of soil and sediment in the Chao-Bai River in Miyun District. Human health risk assessment indicated that non-carcinogenic risks all fell below threshold values. The total carcinogenic risks due to Cr and As were within the acceptable range for both adults and children. This conclusion provides a scientific basis for the control of potentially toxic element pollution and environmental protection of the Miyun Reservoir in Beijing.