Distribution characteristics of organic matter, nitrogen and phosphorus in sediments of Xiao River

Given the scarcity of fresh water resources in Haihe Basin, an increasing amount of wastewater has been used for irrigation in the area, posing a major threat to the environmental health. The contents and distribution of organic matter (OM), nitrogen and phosphorus in different forms in the sediments of the Xiao River, a typical sewage river, were analyzed, and the release mechanism of pollutants from the sediments and their impacts on the local environment were investigated. The results show that the release mechanism of total nitrogen (TN) in the sediments is similar to that of the OM, the distributions of OM and TN in the sediments have no relations to the content of OM and TN in the river water. This may be due to the fact that the OM and TN of sediments in different river section are governed by different factors; in the river section without sediments dredging, OM and TN are mainly caused by the diffusion and release of deep sediments to surface sediments, and in the river section with sediment dredging, the contents of OM and TN are associated with the water project condition, microbial activities and other factors. The total phosphorus (TP) in the sediments has no relation to the TP in water, primarily due to the fact that the Ca-P and Fe/Al-P can be combined to form a kind of insoluble phosphate. The TP in the sediments has no relation to TN and OM, as the phosphate adsorption of sediments is significantly related to the contents of Ca ²⁺, Al ³⁺, and Fe ²⁺(or Fe ³⁺) in the water.