Nitrogen isotope characteristics and source apportionment of atmospheric ammonium in urban cities during a haze event in Northern China Plain. (15th January 2022)

• Record Type: Journal Article
• Authors: Xiang, Yan-Kun; Dao, Xu; Gao, Meng; Lin, Yu-Chi; Cao, Fang; Yang, Xiao-Ying; Zhang, Yan-Lin
• Is Part Of: Atmospheric environment. Volume 269(2022)
• Publication Date: 2022-01-15
• Subjects: Particulate ammonium -- Urban ammonia -- δ15N–NH4+ -- δ15N–NH3; Air -- Pollution -- Periodicals; Air -- Pollution -- Meteorological aspects -- Periodicals; 551.51
• DOI: 10.1016/j.atmosenv.2021.118800
• Languages: English
• ISSNs: 1352-2310

Abstract

Abstract: Ammonium (NH4 + ) is a well-known alkaline species for haze formation and possesses potential impacts on human health and biological diversity. To date, regional source apportionments of NH4 + have been poorly understood in Northern China Plain (NCP). In this study, daily PM2.5 samples were synchronously collected in eight cities over the NCP region. In addition to water-soluble ions, the nitrogen isotopic composition of NH4 + (δ 15 N–NH4 + ) was also analyzed. The average concentrations of NH4 +, a targeted species, varied from 0.9 μg/m³ to 42.5 μg/m³. Note that the significant enhancements of NH4 + coincided with increasing PM2.5 masses, suggesting that NH4 + was one of the contributing species for haze formation. The δ 15 N–NH4 + averaged 12.4 ± 6.9‰ and the average δ 15 N–NH3 were further calculated to be −9.0 ± 6.7‰ over the NCP region. Both δ 15 N–NH4 + and δ 15 N–NH3 showed negative correlations with PM2.5 mass and there were no obvious differences among those 8 cities. Combining air-mass backward trajectories and quantifying contributions of potential sources, we pointed out that non-agricultural sources (fossil fuel related and NH3 slip) were dominant sources (totally contributed 42%–85%) not only on extreme haze phase but also on haze accumulation/dissipation phase in all 8 cities of NCP region in winter, the heating season in North China. However, the contribution of fossil fuel related source reduced to only 20%–35% while livestock breeding source rose to about 15%–32% and NH3 slip source kept contributing about 30% on the extreme haze phase. Thus, we considered that volatilization-related agricultural sources (especially livestock breeding) could discharge considerable NH3 to form SIA-led haze event in urban cities of the NCP region, even though non-agricultural sources were the foremost sources. Graphical abstract: Image 1 Highlights: Regional transmission and source apportionments of atmospheric NHx during a haze event over the NCP were investigated. Non-agricultural sources were the dominant sources (42%–85%). Agricultural sources increased over 26% on extreme haze phase than others.