Nitrogen Species and Vertical Distribution Characteristics in the Sediment of the Tuo River

BACKGROUND The serious water pollution accident that occurred in the Tuo River in February 2004 caused serious harm to the ecological environment. In recent years, the ecological environment of the Tuo River has suffered from some degrees of pollution through industrial, agricultural and the life of coastal residents, but the geochemical study of nitrogen in the Tuo River is scarce. BAOBJECTIVES To reveal the vertical distribution and temporal and spatial variation characteristics of nitrogen in river sediments and assess the ecological restoration in the area by analyzing the total nitrogen (TN), exchangeable ammonia nitrogen (AN) and organic nitrogen (ON) in the winter sediments of the Jintang Section of the Tuo River and to compare the results with the records of nitrogen species in the same sediments 10 years ago. METHODS Based on the method of Mackin's extraction method of adsorbed ammonia nitrogen in sediments and Smart's method for total nitrogen extraction in sediments, spectrophotometry is used to analyze the occurrence of TN, AN and ON in winter sediments in the Jintang area of the Lancang River Basin. RESULTS [JP3]The concentrations of TN range from 518.913 to 4386.899 mg/kg, whereas ON range from 101.531 to 3793.683 mg/kg. The concentrations of TN and ON were above -3 cm, and ON was the main form of TN. With the increased depth, the concentrations of TN and ON decreased rapidly, and the concentrations of AN decreased slightly. A comparison between the results of nitrogen species in sediments and the records of 10 years ago shows that the concentration of AN increased significantly and the concentrations of ON and TN increased significantly above -3 cm. CONCLUSIONS The nitrogen in the sediments of the Tuo River had been released upward to the porewaters and even overlying waters as endogenous nitrogen. Combined with external pollution in this area, the concentrations of ON and TN in the surface of the sediment have increased significantly.