Seasonal variation and spatial distribution characteristics of total nitrogen,total phosphorus and chlorophyll-a in Sihe river and eutrophication evaluation

ZHAO Wanyu; LI pan; HU Qingjing; WEI Yuqiu; SHU Fengyue

doi:10.13984/j.cnki.cn37-1141.2025.02.003

Abstract：The seasonal variation and spatial distribution characteristics of TN,TP and Chl.a in 20 sec-tions of the Sihe river from 2016 to 2017 were analyzed.The water nutritional status was evaluated by using the universal index formula in the form of a logarithmic power function,and the factors affecting the distribution of nitrogen and phosphorus nutrients,and their environmental effects were discussed.The results showed that the average mass concentration of TN,TP and Chl.a in Sihe river from 2016 to 2017 were 5.52±2.83 mg·L-1,0.24±0.25 mg·L-1 and 36.56±26.98 μg·L-1.The seasonal difference of nitrogen nutrients in water was not obvious;the seasonal variation of phosphorus nutrients was significant(p＜0.01),and the TP concentration in autumn was about twice of that in summer.The nitrogen and phosphorus nutrients in the Sihe river had obvious spatial distribution characteristic.The two areas with higher content were the confluence of the Jihe river,the Pushan river,and the Yihe river.Overall,the main pollutant in Sihe river was TN,which was in the state of severe eutrophica-tion.The point source pollution of industrial wastewater and domestic sewage was the main source of the Sihe river pollution,and the non-point source pollution of livestock and poultry breeding and agri-culture also made an important contribution.Based on the analysis of the annual variation data of TN and TP from 2011 to 2021,it was found that the TN concentration reached peak in 2016-2017 and then decreases gradually.The TN concentration in 2021 was about 70％lower than that in 2016.In re-cent years,the water quality of the Sihe river has been significantly improved through the treatment of ecological environment and the control of pollution discharge.