Evaluating Nationwide Non-Point Source Pollution of Crop Farming and Related Environmental Risk in China

The increase in non-point source (NPS) pollution from agricultural cultivation and production sources has been cited as one of the main reasons for water eutrophication. This study built a national NPS database and estimated the nutrient (including both nitrogen (N) and phosphorus (P)) balance and NPS pollution of crop farming at the county level in 2015. Finally, the NPS pollution risks were assessed, and relative policy suggestions were provided. The results indicated that (1) in 2015, the total amounts of N and P surpluses in China were 7.95 and 7.39 million tons, respectively. The south of the Yangtze River had a relatively higher nutrient surplus compared to that in northern China. (2) The NPS emissions for N and P in China were 168.84 x 10(4) tons and 8.93 x 10(4) tons, respectively, with the highest NPS loads occurring in the eastern part of the Sichuan Basin, southern China and southwestern China, while the lowest loads occurred in northeast China. (3) The potential risk assessment results showed that a broad division emerged at the Yangtze River basin, with the northern area under lower risk than the southern area. This estimation work can provide guidance and technical support for local government and policy makers to control NPS pollution.