Spatio-Temporal Distribution Characteristics of Nitrogen and Phosphorus in the Typical Inflow River of Taihu Lake

Liangxi River, one tributary of Taihu Lake, was selected as study region in order to explore the water environmental situation of the typical inflow water. The temporal and spatial distribution characteristics of nitrogen and phosphorus of the water was investigated based on the data of water quality from December 2017 to December 2018. The results show that the pollution status of the tributaries of the Liangxi River was more serious than that of the main stream and their water quality was mostly worse than Grade V. In details, the concentrations of TN, NH₄⁺-N, NO₃^--N and TP in the main stream ranged from 0.57-2.86, 0.10-0.75, 0.02-0.53 and 0.05-0.39 mg·L^-1, respectively. The concentrations of TN, NH₄⁺-N, NO₃^--N and TP in tributaries ranged from 2.42-5.63, 1.12-3.35, 0.32-2.33 and 0.07-0.52 mg·L^-1, respectively. Correlation analysis indicate that the form of inputs and pathways of nitrogen and phosphorus in Liangxi River were consistent. Peak values of TN were observed in spring and summer, while concentrations of TP were lower in winter and higher than those in summer. Concentrations of nitrogen and phosphorus in summer presented an upward trend toward the downstream along the main stream. The pollution of nitrogen and phosphorus was more serious in some tributaries, thus imposing an impact on main stream. In future river restoration and improvement, a comprehensive restoration strategy of joint regulation of the main stream and tributaries should be followed.