Abstract
Abstract. Although nitrogen oxide (NOx) emission controls have been implemented for several years, northern China is still facing high particulate nitrate (NO3-) pollution during severe haze events in winter. In this study, the thermodynamic equilibrium model (ISORROPIA-II) and the Weather Research and Forecast model coupled with chemistry (WRF-Chem) were used to study the efficiency of NH3 emission controls on alleviating particulate NO3- during a severe winter haze episode. We found that particulate-NO3- formation is almost NH3-limited in extremely high pollution but HNO3-limited on the other days. The improvements in manure management of livestock husbandry could reduce 40 % of total NH3 emissions (currently 100 kt month−1) in northern China in winter. Consequently, particulate NO3- was reduced by approximately 40 % (on average from 40.8 to 25.7 µg m−3). Our results indicate that reducing livestock NH3 emissions would be highly effective in reducing particulate NO3- during severe winter haze events.
Highlights
In northern China, severe haze pollution events occur frequently during wintertime, with the concentration of PM2.5 reaching hundreds of micrograms per cubic meter and SIA accounting for more than 50 % of PM2.5 (Zheng et al, 2016; Tan et al, 2018)
nitrogen oxide (NOx) emissions in 48 Chinese cities decreased by 21 % from 2011 to 2015 (Liu et al, 2017a), no obvious decreasing trend for particulate NO−3 has been observed in northern China during recent years (Zhang et al, 2015)
Livestock husbandry accounts for the largest proportion of NH3 emissions in northern China in winter, which is mainly caused by poor manure management
Summary
In northern China (including Beijing, Tianjin, Hebei, Shandong, Shanxi and Henan), severe haze pollution events occur frequently during wintertime, with the concentration of PM2.5 (particles with an aerodynamic diameter less than 2.5 μm) reaching hundreds of micrograms per cubic meter and SIA (secondary inorganic aerosol) accounting for more than 50 % of PM2.5 (Zheng et al, 2016; Tan et al, 2018). To mitigate fine-particle pollution, the Chinese government has been taking strong measures to control SO2 emissions (http: //www.gov.cn/zwgk/2011-12/20/content_2024895.htm, last access: 5 January 2019). NOx emissions in 48 Chinese cities decreased by 21 % from 2011 to 2015 (Liu et al, 2017a), no obvious decreasing trend for particulate NO−3 has been observed in northern China during recent years (Zhang et al, 2015). In October 2015, a severe haze episode was reported in the North China Plain
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