Effects of Nonpoint Source Pollution on Water Environmental Quality at National Scale

Abstract

【Background and objective】 Non-point pollution from farmland (NPF) is the main source of pollutants in surface water in China and has received attention. the progress achievements of water pollution control effects and surface water environment obvious improvements had been carried out in recent years, which involve “Three Rivers” (the Huai River, Liao River and Hai River), “Three Lakes” (the Tai Lake, Dian Lake and Chao Lake), the Songhuajiang River, three Gorges Reservoir Region, the upper and middle Yellow River, the water resource and waterline basin of South to North water diversion project. The monitoring sections of Ⅰ-Ⅲ river quality had been improved by 18%, and that of interior class Ⅴ river quality had been reduced by 15% in the last 10 years, the total surface water quality has improved significantly. As President Xi Jinping pointed out, agricultural development should not only put an end to new accounts owed by the ecological environment, but also gradually repay the old accounts, and fight a tough battle against agricultural non-point source pollution. Prevention and control of agricultural non-point source pollution is an important way to realize high quality agricultural development and water environment quality assurance. 【Objective】 The fundamental status of China’s large agricultural country is to maintain a relatively high level of fertilizer application and a higher ratio of agricultural water for a long period of time, so national food and other agricultural products security could be guaranteed. However, the problems from NPF should be paid a close attention. 【Method】 Based on the data of fertilizer application amount, emission coefficient of nitrogen and phosphorus non-point source pollution, agricultural water consumption, and the quality of farmland tail water and the influence on surface water quality were analyzed. 【Result】 The ratio of fertilizer application was decreased after 2015, in which nitrogen fertilizer and phosphorus fertilizer were reduced 13.7% and 9.1% in 2019, respectively. Agricultural water use decreased after 2012, in which the ratio of agricultural water was reduced by 2.2% in 2019. From 2007 to 2017, the emission coefficient of farmland nitrogen pollution was reduced from 5.7% to 2.4%, and the emission coefficient of farmland phosphorus pollution was reduced from 0.9% to 0.4%. The environmental quality of surface water had been improved significantly, in which the ratio of class Ⅳ+Ⅴ of river water quality was reduced by 0.8% and interior class Ⅴ was reduced by 17.4% in 2018, compared to that in 2009. NPF control has achieved a great progress and crop yields continue to increase. Agricultural tail waters all belong to interior class Ⅴ, which have a potential effect on surface water quality, especially in some local areas or parts of basin. 【Conclusion】 On a national scale, effects on surface water quality of total nitrogen and total phosphorus pollution from NPF are limited and they showed a significant decreasing trend after 2017. The keys in NPF should pay attention to some local areas and river basins, so surface water environmental quality can gradually improve.

Keywords

• national scale
• non-point source pollution from farmland (npf)
• water environment quality