The study looked at the nitrogen content in rivers around Lake Taihu in China to understand pollution sources. They compared nitrogen levels from rivers affected by industry, agriculture, and sewage during different flow periods. Results showed that dissolved nitrogen was the main type found in these rivers. Agriculture-polluted rivers had a big impact on the lake's nitrogen levels, especially nitrate. Industry-polluted rivers increased ammonium levels in the lake. All river types increased particulate nitrogen concentration in Lake Taihu. Nitrogen levels in the lake were higher than in the rivers during certain flow periods. This suggests the need to focus on reducing nitrogen from agriculture and industry to tackle lake pollution.