Distribution and Pollution Evaluation of Nitrogen and Phosphorus of Sediments in Zhangze Reservoir

Abstract

The nitrogen and phosphorus pollution of sediments has increasingly become the main cause of eutrophication in reservoir. The temporal-spatial distribution features and pollution level of nitrogen and phosphorus of sediments were revealed in Zhangze Reservoir. The nitrogen and phosphorus content of 16 sediment samples were detected, as well as sediment oxygen demand. The temporal-spatial changing rules of nitrogen and phosphorus of sediments were analyzed. The pollution level of sediments was evaluated. The results showed that the total nitrogen content of sediments varied from 506 mg/kg to 4411 mg/kg, the total phosphorus content of sediments varied from 160 mg/kg to 961 mg/kg, and the sediment oxygen demand varied from 1295.7 mg/(m2•d) to 2957.6 mg/(m2•d). The nitrogen and phosphorus content of sediments in north and south section was larger than that in middle section. The temporal variation rule of nitrogen and phosphorus content was that it increased obviously in flood season and decreased obviously in freezing stage. The nitrogen pollution level of most of the sediments was severe pollution, with the most serious pollution near the dam and at the end of the reservoir. The phosphorus pollution level of most of the sediments was mild pollution, with moderate and severe pollution near the dam and at the end of the reservoir.