Evaluation of Agricultural Non-point Source Pollution: a Review

Non-point source pollution in agriculture was a global environmental concern. It is an important measure for preventing and controlling targeted agricultural non-point source (ANPS) pollution to determine the critical source areas and key factors by evaluation. This paper reviewed the evaluation indexes and methods of ANPS pollution and their selection at different scales, highlighting the evaluation indexes and their weights involved in the pollution sources, mitigation strategies, and environmental impacts of ANPS. It also explored load estimation of different scales from ANPS pollution. Estimation methods mainly include regional pollution load balance, unit pollution load, and simulation model. Field monitoring can provide an accurate estimation of ANPS pollution loads. Still, it is costly, and it requires intensive labor, leading to scarce monitoring data. Most empirical models in calculating ANPS pollution at watershed scales lacked the process of ANPS pollution entering the water body. The mechanism model was limited by available monitoring data, which was difficult to be applied on a large scale. Quantifying nutrient loads at regional or national scales was challenging, mainly due to model shortcomings and a lack of high-resolution data on agricultural management practices. Therefore, the evaluation of ANPS pollution should formulate systematic technical standards and develop the evaluation model based on information technology. Further implemented measures to prevent and control ANPS pollution should be according to local conditions.