气候变化领域集成服务门户(CCPortal): Stable nitrogen isotopic signatures reveal the NH4+ evolution processes in pollution episodes in urban southwestern China

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DOI	10.1016/j.atmosres.2021.105474
	Stable nitrogen isotopic signatures reveal the NH4+ evolution processes in pollution episodes in urban southwestern China
	Guo W.; Zheng N.; Zhang Z.
发表日期	2021
ISSN	0169-8095
卷号	253
英文摘要	In most of the urban atmosphere, the formation of ammonium (NH4+) is mainly controlled by the initial isotope value of ammonia (δ15N-NH3 values) and the corresponding ammonia (NH3) conversion ratio (NH4+/(NH4+ + NH3)), as N isotope fractionation may occur under an NH3-sufficient environment. The significant influence of δ15N-NH3 values on the formation of NH4+ in the urban atmosphere has been demonstrated by many previous studies; however, exploration of the effect of the NH3 conversion ratios on NH4+ formation has been limited, especially during pollution episodes. To better understand the NH3 sources and the effect of the NH3 conversion ratios on the formation of NH4+ in the urban environment, NH4+ concentrations (0.2 to 13.4 μg·m−3, average 3.9 ± 2.8 μg·m−3) and their δ15N values (−4.0‰ to 29.2‰, average 20.6‰ ± 6.1‰) in PM2.5 were determined in the urban area of Nanning from September 1 to December 31, 2017. Based on the measured δ15N-NH4+ values and the isotope fractionation that occurred during gas-to-particle partitioning, we estimated that the initial δ15N-NH3 values were − 22.8‰ to 3.1‰ (average − 8.8‰ ± 5.5‰). These initial δ15N-NH3 values were influenced by agricultural emission sources (−31.0‰ to −4.4‰), fossil fuel-related NH3 emission sources (−14.6‰ to 10.1‰) and biomass combustion sources (12‰ and 23‰). Source apportionment indicated that these three potential NH3 emission sources contributed 43%, 33% and 24% to the ambient NH3, respectively. On clean days, similar trends in initial δ15N-NH3 and δ15N-NH4+ values were observed, and there was an apparent positive linear correlation between these values (R2 = 0.70, p < 0.01). This suggested that the δ15N-NH4+ signatures recorded changes in the NH3 sources and that NH4+ formation was controlled by the NH3 sources on clean days. However, during different pollution episodes the variations in δ15N-NH4+ values were consistent with the NH4+ concentrations and the NH4+/(NH4+ + NH3) values, and there were negative linear correlation between these values (R2 > 0.6, p < 0.01). This suggested that the δ15N-NH4+ signatures recorded NH4+ evolution processes and that the increased NH3 conversion ratios was the main reason for the development of NH4+ and PM2.5 in pollution episodes. We inferred that the decreased air temperature in cold months may stimulate the increased NH3 conversion ratios, based on the negative correlation of NH4+/(NH4+ + NH3) values with air temperature (r = −0.63, p < 0.01). © 2021 Elsevier B.V.
英文关键词	Ammonia; Ammonium; NH3 conversion ratios; PM2.5; δ15N-NHx
来源期刊	Atmospheric Research
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/236843
作者单位	Jiangxi Province Key Laboratory of the Causes and Control of Atmospheric Pollution, East China University of Technology, Nanchang, 330013, China; College of Water Resources and environmental Engineering, East China University of Technology, Nanchang, 330013, China
推荐引用方式 GB/T 7714	Guo W.,Zheng N.,Zhang Z.. Stable nitrogen isotopic signatures reveal the NH4+ evolution processes in pollution episodes in urban southwestern China[J],2021,253.
APA	Guo W.,Zheng N.,&Zhang Z..(2021).Stable nitrogen isotopic signatures reveal the NH4+ evolution processes in pollution episodes in urban southwestern China.Atmospheric Research,253.
MLA	Guo W.,et al."Stable nitrogen isotopic signatures reveal the NH4+ evolution processes in pollution episodes in urban southwestern China".Atmospheric Research 253(2021).