[Spatial and Temporal Distribution Characteristics and Source Analysis of Agricultural Non-point Source Pollution in...

Henan Province is one of the major grain producing areas in China， and the irrational application of pesticides and chemical fertilizers during the grain production process has led to the continual accentuation of the problem of agricultural non-point source pollution. Agricultural non-point source pollution is the major source of pollutants in China's water bodies， which has become one of the main factors threatening the water environment and water ecological security. Inventory analysis was used to estimate the pollution load of chemical oxygen demand （COD）， total nitrogen （TN）， and total phosphorus （TP） from agricultural non-point source in Henan Province from 2001 to 2021. The study elucidated the spatial and temporal distribution characteristics of these pollution loads and their emission intensities. It also identified the main sources contributing to the pollution load. The results indicated that： ① In terms of temporal variation， from 2001 to 2021， the pollution load and emission intensity of COD and TN from agricultural non-point source in Henan Province showed a decreasing trend， while the pollution load and emission intensity of TP showed an increasing trend. ② The spatial distribution of COD， TN， and TP pollution loads exhibited spatial clustering characteristics， and the high value areas were mainly distributed in the southern part （Nanyang， Zhumadian， and Xinyang） and eastern part （Shangqiu and Zhoukou） of Henan Province. Nevertheless， there were substantial regional disparities in the spatial distribution of emission intensity. Generally， the eastern region had higher values than the western region， and the northern region had higher values than the southern region. Notably， the spatial distribution patterns of high value areas of pollution load and emission intensity revealed significant differences. ③ The main source of COD pollution load was livestock and poultry farming， and the main sources of TN and TP pollution loads were chemical fertilizer and livestock and poultry farming. The main contributing areas for COD， TN， and TP pollution loads were Nanyang， Zhumadian， and Zhoukou. In general， the agricultural non-point source pollution in Henan Province had staged changes in time and significant differences in spatial distribution. Dual control strategies of "load control-intensity constraint" should be implemented in pollution risk prevention and control， and pollution reduction paths such as fertilizer reduction and efficiency increase， manure organic fertilizer utilization， and straw resource utilization should be promoted.