Temporal variation trend and influencing factors of water quality in the Nanchong section of the Jialing River mainstream

In this study, three sampling points located in the Nanchong section of the Jialing River were selected as research objects, and the temporal distribution characteristics and influencing factors of water pol-lutants in the Nanchong section of the Jialing River mainstream were discussed through monthly sampling analysis of nine monitoring indicators from 2017 to 2021. Gray correlation analysis, Mann- Kendall test, Spearman's correlation analysis, and multivariate statistical analysis were used to ana-lyze the variation trend, time distribution, and differences in water pollutants in different periods. Results show that the water quality in the Nanchong section of the Jialing River mainstream was lightly polluted, and total nitrogen (TN) was the main water pollutant. Except for the concentra-tions of NH3-N and TN, the concentrations of pollutants (TP and CODMn) in the Nanchong section of the Jialing River mainstream decreased. The water quality of the Jialing River was different in time, and the water quality in the rainy season (May-November) was better than that in the dry season (December-April). The concentrations of CODMn, NH3-N, TP, and TN in water were lower in the rainy season than in the dry season. The contents of organic matter, nitrogen, and phosphorus nutrients in water in the Jialing River were affected by climate change, rainfall dilution, and other environmental factors. The main sources of pollution were agricultural and rural nonpoint source pollution.