Distribution and pollution risk assessment of nitrogen, phosphorus and organic matter in inlet rivers of Erhai Basin

Abstract

The estuarine wetland of Luoshi River, which flowed into Lake Erhai in Yunnan Plateau, is used to be studied as a typical research object. Sediment samples in the estuarine wetland of Luoshi River were collected by the cylindrical sediment sampler and taken from the surface layer (0-10 cm). The spatial distributions of the total nitrogen, total phosphorus and total organic matter were analyzed, and did the pollution risk assessment of sediments. The results showed that: The contents of total phosphorus (TP) in the surface sediments ranged from 0.04 to 1.28 g/kg, and the TP spatial distribution characteristics were lower in area I than area II, but higher in channel I than channel II. The content of total nitrogen (TN) in the surface sediments ranged from 0.33 to 2.96 g/kg, and the TN spatial distribution characteristics were higher in area I than area II, and higher in channel I than channel II. The content of OM in the surface sediments ranged from 32.43 to 233.03 g/kg, and the OM spatial distribution characteristics were lower in area I than area II, and lower in channel I than channel II. Combined evaluation methods with the comprehensive pollution index and organic index to analyze the pollution of the total nitrogen and the total phosphorus in the surface sediments at the estuarine wetland of Luoshi River, results show that the pollution in area I and channel I was medium level, and the pollution in area II and channel II was mild level. The pollution of organic contaminants in channel I and channel II was heavy level, and the area I and area II was medium level. The spatial distribution of surface sediment at the estuarine wetland of Luoshi River was influenced by the external pollutant, the culture activity and the aquatic plant. Pollution in channel I was mainly sourced by input of nitrogen and phosphorus, and pollution in channel II was mainly dominated by organic matter.