Multi-methods to investigate spatiotemporal variations of nitrogen-nitrate and its risks to human health in China's largest fresh water lake (Poyang Lake)

Nitrogen-nitrate contamination has been recognized as the main threaten to the large lake surrounding with the inten-sive agriculture activities. However, there are still insufficient studies on the interannual evolution of nitrogen-nitrate, source and its impact on the environment and human health in the large fresh water lake. In this study, 248 samplings were collected in Poyang Lake from 2013 to 2018, multi-methods (mathematical statistics method, grey correlation analysis, person correlation analysis and human health risk assessment) to investigate the spatiotemporal variations, impact factors and potential health risks of NO2--N, NO3--N and NH4+-N. The results showed that the middle region had the highest NO2 - concentration (mean 0.04 mu g/l), the northern region had the highest NO3- concentration (mean 1.12 mg/l), and the southern region had the highest NH4+ concentration (mean 0.48 mg/l). For NO3- and NH4+ , the concentration was higher than in the wet season. While the concentration of NO2- had the reverse trend. Grey correlation analysis and person correlation analysis results indicate that nitrogen fertilizer, waste water, pH, CODMn and temperature were main factors affecting the nitrogen concentration in Poyang Lake. Health risk assess-ment results revealed that potential hazards in the study area were acceptable (HR < 1). NO3- provided the highest health risks, and oral ingestion is the major source of local nitrogen health risk. Those results can provide the reference for developing the treatment methods of the international large freshwater lake.