Interannual variation of reactive nitrogen emissions and their impacts on PM2.5 air pollution in China during 2005–2015

Youfan Chen,Zhang Wen,Yu Song,Lin Zhang,Daven K Henze,Xiao Lu,Yuepeng Pan,Yixin Guo,Xuejun Liu,Yuanhong Zhao,Wilfried Winiwarter

doi:10.1088/1748-9326/ac3695

Abstract

Emissions of reactive nitrogen as ammonia (NH3) and nitrogen oxides (NO x ), together with sulfur dioxide (SO2), contribute to formation of secondary PM2.5 in the atmosphere. Satellite observations of atmospheric NH3, NO2, and SO2 levels since the 2000s provide valuable information to constrain the spatial and temporal variability of their emissions. Here we present a bottom-up Chinese NH3 emission inventory combined with top-down estimates of Chinese NO x and SO2 emissions using ozone monitoring instrument satellite observations, aiming to quantify the interannual variations of reactive nitrogen emissions in China and their contributions to PM2.5 air pollution over 2005–2015. We find small interannual changes in the total Chinese anthropogenic NH3 emissions during 2005–2016 (12.0–13.3 Tg with over 85% from agricultural sources), but large interannual change in top-down Chinese NO x and SO2 emissions. Chinese NO x emissions peaked around 2011 and declined by 22% during 2011–2015, and Chinese SO2 emissions declined by 55% in 2015 relative to that in 2007. Using the GEOS-Chem chemical transport model simulations, we find that rising atmospheric NH3 levels in eastern China since 2011 as observed by infrared atmospheric sounding interferometer and atmospheric infrared sounder satellites are mainly driven by rapid reductions in SO2 emissions. The 2011–2015 Chinese NO x emission reductions have decreased regional annual mean PM2.5 by 2.3–3.8 μg m−3. Interannual PM2.5 changes due to NH3 emission changes are relatively small, but further control of agricultural NH3 emissions can be effective for PM2.5 pollution mitigation in eastern China.

Highlights

Nitrogen (N) is an essential element for life, but most N in the Earth cannot be used directly by ecosystems
Estimates of Chinese NH3 emissions over 2005–2016 Previously we have developed a bottom-up inventory of Chinese agricultural NH3 emissions for the year 2008 (Zhang et al 2018)
We scale the baseline cropland area to match those observed by moderate resolution imaging spectroradiometer (MODIS) as described in the section above to account for their interannual changes in China

Summary

Introduction

Nitrogen (N) is an essential element for life, but most N in the Earth cannot be used directly by ecosystems. The productivity of the ecosystem depends on the abundance of reactive N (Nr or fixed N) (Vitousek et al 2002). China is one of the regions with the most intensive reactive nitrogen emissions in the globe due to its rapid industrialization, urbanization, as well as high demand for food production (Liu et al 2013). Recent satellite observations have recorded significant changes in atmospheric ammonia (NH3) and nitrogen dioxide (NO2) levels over China since the 2000s (Qu et al 2017, van der A et al 2017, Warner et al 2017, Liu et al 2018a). We will use these satellite observations to constrain Nr emissions in China over 2005–2015 and to assess their impacts on the PM2.5 air quality

Objectives

Results

Conclusion