Spatiotemporal Distribution of Nonpoint Source Pollution from Agriculture in the Huangshui River Basin

Abstract

【Objective】 Huangshui River is a tributary of the Yellow River in China, located in Qinghai. Agricultural production has resulted in pollution to it. The purpose of this paper is to analyze the spatiotemporal evolution of nonpoint source pollution due to agriculture in this basin. 【Method】 The studied area is located at the upstream in the Xiaoxiaqiao section in the mainstream of the river. Data measured from 2010—2018 from16 sub-units in the section were used for analysis. Pollutant discharge coefficient method was used to estimate the discharge amount and intensity of total nitrogen (TN), total phosphorus (TP), chemical oxygen demand (COD) and ammonia nitrogen (NH3-N). Spatiotemporal analysis and cold-hot spot analysis were used to analyze the spatiotemporal evolution of these pollutants. 【Result】 Temporally, pollutant discharge from livestock and poultry breeding and rural areas had showed an increasing trend, while those from crop farming had exhibited a decreasing trend. The discharge and intensity of TN, COD and NH3-N had increased, while TP had decreased slightly. Spatially, discharge of the four pollutants was less in Xiameng Bridge and Jintan cross-section areas, and more in the Xinning Bridge section. The contribution from different sectors to the pollution was ranked in the following order based on their significance: livestock and poultry breeding source > rural areas > farmland, with COD being the primary pollutant. Cold-hot spot analysis showed that the hot spots are mainly in Qiaotou Bridge, Xinning Datong Bridge, Xigang Bridge and the east of Xining, while the cold spots are mainly in Jintan and Sanqi Bridge. Overall, pollutant discharge had increased slightly in the basin, despite some areas having seen a decrease in pollution. Prevention and control of the pollutants should focus on reducing discharge from livestock and poultry breeding industry, especially COD, and reducing discharge of the pollutants into the Xinningqiao Section. 【Conclusion】 Nonpoint source pollution from agriculture in Huangshui basin varied spatiotemporally, and the main contributors to the pollution are livestock and poultry breeding sector. Reducing and mitigating their discharge is hence essential to ameliorate pollution of the basin.

Keywords

• huangshui river basin
• agricultural non-point source pollution
• temporal and spatial evolution
• cold and hot spot analysis
• prevention and control countermeasures