Environmental impacts of nitrogen emissions in China and the role of policies in emission reduction

Abstract

Atmospheric reactive nitrogen (N_r) has been a cause of serious environmental pollution in China. Historically, China used too little N_r in its agriculture to feed its population. However, with the rapid increase in N fertilizer use for food production and fossil fuel consumption for energy supply over the last four decades, increasing gaseous N_r species (e.g. NH₃ and NO_x) have been emitted to the atmosphere and then deposited as wet and dry deposition, with adverse impacts on air, water and soil quality as well as plant biodiversity and human health. This paper reviews the issues associated with this in a holistic way. The emissions, deposition, impacts, actions and regulations for the mitigation of atmospheric N_r are discussed systematically. Both NH₃ and NO_x make major contributions to environmental pollution but especially to the formation of secondary fine particulate matter (PM_2.5), which impacts human health and light scattering (haze). In addition, atmospheric deposition of NH₃ and NO_x causes adverse impacts on terrestrial and aquatic ecosystems due to acidification and eutrophication. Regulations and practices introduced by China that meet the urgent need to reduce N_r emissions are explained and resulting effects on emissions are discussed. Recommendations for improving future N management for achieving 'win-win' outcomes for Chinese agricultural production and food supply, and human and environmental health, are described. This article is part of a discussion meeting issue 'Air quality, past present and future'.

Keywords: China; ammonia; eutrophication; integrated nitrogen management; nitrogen oxides; particulate pollution.

Figure 1.

Nitrogen emissions, deposition, impacts and regulation in China. (Online version in colour.)

Figure 2.

Annual NH₃ and NO_x emissions averaged for the years 2008–2012. The numbers are annual emission totals for China (From Zhao et al. [21], © 2017 Elsevier Ltd.). (Online version in colour.)

Figure 3.

Trends in anthropogenic emissions of NO_x (a) and NH₃ (b) over the period of 1980-2017 in China and emissions of NO_x (c) and NH₃ (d) by sectors during 2008–2016. NO_x emission data were averaged from the China Statistical Yearbook (http://www.stats.gov.cn/), EDGAR (https://edgar.jrc.ec.europa.eu/) and Zheng et al. [30]. NH₃ emission data were averaged from EDGAR, Kang et al. [31] and Zheng et al. [30]. Sectors emission data were adapted from MEIC (http://meicmodel.org/index.html). (Online version in colour.)

Figure 4.

Spatial patterns of atmospheric total (wet plus dry) deposition of various N species (NH_x and NO_y) over China, averaged for 2011–2015 (From Yu et al. [85], © 2019, Springer Nature). (Online version in colour.)

Figure 5.

Temporal trends of wet (a), dry (b) and total (c) N deposition across China. Error bars denote standard errors (s.e., the variation among the 31 provinces in mainland China) (From Yu et al. [85], © 2019, Springer Nature). (Online version in colour.)

Figure 6.

Implementation steps of China's atmospheric environmental protection policies and measures particularly related to atmospheric N_r emission control and air quality improvement (Modified from Wen et al. [95]). (Online version in colour.)