Regional Transport Increases Ammonia Concentration in Beijing, China

Qingmei Wang,Ligang Wang,Yucong Miao

doi:10.3390/atmos11060563

Abstract

To elucidate the critical factors influencing the ammonia (NH3) concentration in Beijing, this study combined observational analyses, backward trajectory calculations, and meteorology–chemistry coupled simulations to investigate the variations in the NH3 concentration from 11 May to 24 June, 2015. A significant positive correlation was found between the NH3 and PM2.5 concentrations in Beijing. By examining the relationships between meteorological parameters and the NH3 concentration, both near-surface temperature and relative humidity showed positive correlations with the NH3 concentration. The higher NH3 concentrations were usually associated with the warming of the upper atmosphere. Distinct wind directions were noted during the days of the top and bottom 33.3% NH3 concentrations. The top 33.3% concentrations were primarily related to southwesterly winds, while the bottom ones were associated with westerly and northerly winds. Since there are strong NH3 emissions in the southern plains adjacent to Beijing, the regional transport induced by the southerly prevailing winds would increase the NH3 concentration in Beijing significantly. From 23 to 25 May, more than one third of NH3 in Beijing was contributed by the southerly transport processes. Thus, joint efforts to reduce NH3 emissions in the whole Beijing–Tianjin–Hebei region are necessary to regulate the NH3 concentration in Beijing.

Highlights

Being the most abundant basic/alkaline gas species in the atmosphere, ammonia (NH3 ) plays an important role in determining the overall acidity of precipitation, cloud water, and airborne particulate matter [1,2]
It was found that the daily NH3 concentration was positively correlated with the near-surface T and relative humidity (RH), with correlation coefficients of 0.49 and 0.65, respectively
May, 15.0 μg m−3 on May, and 15.7 μg m−3 on May (Figure 8), and the southern plains could contribute 5.4 μg m−3 (36%), 6.1 μg m−3 (41%), and 5.3 μg m−3 (34%), respectively. These results indicate that when the Beijing–Tianjin–Hebei region is influenced by the southerly prevailing winds, the regional transport plays an important role in the

Summary

Introduction

Being the most abundant basic/alkaline gas species in the atmosphere, ammonia (NH3 ) plays an important role in determining the overall acidity of precipitation, cloud water, and airborne particulate matter [1,2]. Several studies have pointed out the importance of NH3 [6,7,8,9], which acts as a limiting species in the formation of secondary inorganic aerosols (SIA). NH3 can neutralize ambient acidic species, such as sulfuric acid (H2 SO4 ) and nitric acid (HNO3 ), to form ammonium salts, which are the dominant inorganic compounds in the ambient PM2.5 [2,10]. These reaction pathways link NH3 to aerosol pollution and its subsequent impacts on human health and climate change [11,12]. It was found that the mass of secondary sulfate, nitrate, and ammonium

Methods

Results

Conclusion