Evaluation of nutrients and heavy metals of surface soil in the upper watershed of Xiashan Reservoir in Shandong Province, China.

Reservoir is easy to be polluted by nutrients and heavy metals in the surrounding soil. There is a close relationship between heavy metals and nutrients in soil. Nutrient salts will affect the activity of heavy metals, and heavy metal pollution will affect plant growth and nutrient salt absorption, thus affecting ecosystem health. This study was performed to evaluate nutrients (TN, TP) and heavy metals (As, Cd, Cr, Cu, Hg, Ni, Pb, Zn) in the upper watershed of Xiashan Reservoir by the enrichment factor, the geoaccumulation index, the enrichment factor and leaching experiments. The results showed that the average enrichment of TN and TP reached the level of moderate pollution. The nutrient enrichment of different sampling sites increased gradually from south to north, which may be affected by the topography of the study area. The comprehensive trophic level exceeds the criteria for a state of severe eutrophication of water bodies, which may lead to the enrichment of nitrogen and phosphorus in the water body through processes such as runoff. Evaluation of the geoaccumulation index and potential ecological risk index revealed that the soil was primarily contaminated by Cd and Hg, which are in the level of considerable potential ecological risk and high potential ecological risk. So most attention should be paid to Cd and Hg pollution. Pollution control of heavy metals in soil is a priority because they are more difficult to leach than nutrients. This study provided an insight into the nitrogen and phosphorus control and heavy metal pollution management in the upper watershed of Xiashan Reservoir.