Framework for quantifying rural NPS pollution of a humid lowland catchment in Taihu Basin, Eastern China

Controlling of rural non-point sources (NPS) pollution has been a major priority of Chinese government in an initiative to improve the rural living environment. However, quantifying NPS pollution remains a considerable challenge in the humid lowland rural areas of Eastern China, which are characterized by complicated hydrological and nutrient processes and exhibits intensified artificial interference. In this study, a new and feasible framework was developed to estimate different NPSs specifically for this area by combing hydrological modelling, export coefficient, and sediment release experiment. Then the framework was applied to a typical lowland area (Zongjiaqiao River catchment) in Eastern China. The results showed that annual total nitrogen (TN), total phosphorus (TP), chemical oxygen demand (COD), and ammonia-nitrogen (NH₃-N) in the area were 8.49 t, 0.63 t, 83.71 t, and 4.22 t, respectively. Rainfall-runoff contributed more NPS (except for TP) loads to the river than other sources and had a substantial spatiotemporal difference in contrast to other sources. Rural living was the largest source for TP, with a total TP load of 58%. The majority of this TP was derived from toilets and laundry areas. Sediment was another important source, particularly for TN and NH₃-N pollution. Nevertheless, the livestock here contributed the least to water pollution. The proposed method has extensive application potential in critical source identification and policy drafting for rural NPS pollution control of lowland area.