Seasonal variations in nitrogen and phosphorus levels were studied in Hanfeng Lake. The researchers found that nitrogen and phosphorus concentrations were highest in winter and lowest in summer. Nitrate was the main form of nitrogen in the lake, while ammonia and nitrite levels were low. Phosphorus levels increased in spring and summer, then decreased in autumn and winter. The lake was mostly suitable for algae growth, with occasional nitrogen limitations and rare phosphorus limitations. Factors like rainfall, fertilizer use, and sewage discharge influenced the nitrogen-to-phosphorus ratio in the lake. Protection strategies were suggested to improve water quality in Hanfeng Lake.