Research progress of agricultural non-point source pollution migration process and model in basins

Agricultural non-point source pollution is still the main source of water pollution in China. It involves multi-disciplinary intersection of agriculture, water conservancy, environment and ecology, etc., and is one of the key issues of both national and international environmental pollution academic research and watershed pollution control and management. Different disciplines usually use different methods to study the generation and migration of agricultural non-point source pollution at different time and space scales. For example, agriculture focuses on processes such as water irrigation on fields-hillsides-watershed scale, fertilization for different crops at different life stages, nutrient transformation and absorption, soil pool budget, and the effect of microorganisms on nutrients. However, it is often overlooked the internal relationship between different scales or systems, and there are few studies on the integrated simulation of the transportation process. The agricultural non-point source pollution transportation process and its influencing factors from different typical spatial scales (from fields to hillsides, and then to watershed scales), as well as the agricultural non-point source pollution modeling methods in watershed, were summarized. It was proposed that in addition to deeply considering local hydrological processes and the yield, accumulation, release and transportation of pollutants at the typical scales of field and hillside in the model system, the hydrological and pollutant migration processes and the development of an integrated non-point source model, which covered fields-hillsides-watershed system, should be highlighted. Meantime, the existing research problems related to the scale transformation, modeling methods and model uncertainty research of agricultural non-point source pollution migration process were analyzed, and the future research directions were prospected.