[Characteristics of Nitrogen Variation and Its Response to Rainfall:A Case Study in Wuxi Port at Taihu Lake Basin].

Based on monitoring data of the water quality in the Wuxi port estuary of Taihu Lake from 2010 to 2015, we studied the temporal variation characteristics of nitrogen and its response to rainfall in Wuxi port. The results showed that the pollution level in Wuxi port is serious, with an average annual total nitrogen (TN) concentration of (4.41-5.92 mg·L), worse than the water environment quality grade Ⅴ standard (2 mg·L). The ammonia nitrogen (NH-N) concentration was 1.09-1.72 mg·L. The concentrations of TN and NH-N showed obvious seasonal variations, with the concentration of TN and NH-N in summer and autumn higher than in spring and winter. The concentration of TN in 2015, 2012, and 2011 was 5.92, 5.82, and 5.47 mg·L, respectively, which was significantly higher than in 2013 and 2014. The concentration of NH-N in 2011 (1.72 mg·L) was higher than in 2013 and 2015. With the increase of rainfall intensity, the TN concentration showed an increase after the first downward trend and then a decrease, while the NH-N concentration increased first and then decreased. In addition, the nitrogen concentration in the non-flood season was higher than in the flood season.