Non-agricultural source dominates the ammonium aerosol in the largest city of South China based on the vertical δ15N measurements

Zixi Chen; Chenglei Pei; Junwen Liu; Xiangyun Zhang; Ping Ding; Lan Dang; Zheng Zong; Fan Jiang; Lili Wu; Xi Sun; Shengzhen Zhou; Yanlin Zhang; Zhisheng Zhang; Junyu Zheng; Chongguo Tian; Jun Li; Gan Zhang

doi:10.1016/j.scitotenv.2022.157750

Non-agricultural source dominates the ammonium aerosol in the largest city of South China based on the vertical δ¹⁵N measurements

Sci Total Environ. 2022 Nov 20:848:157750. doi: 10.1016/j.scitotenv.2022.157750. Epub 2022 Aug 1.

Authors

Zixi Chen¹, Chenglei Pei², Junwen Liu³, Xiangyun Zhang⁴, Ping Ding⁵, Lan Dang⁶, Zheng Zong⁶, Fan Jiang¹, Lili Wu¹, Xi Sun⁷, Shengzhen Zhou⁷, Yanlin Zhang⁸, Zhisheng Zhang⁹, Junyu Zheng¹, Chongguo Tian⁶, Jun Li¹⁰, Gan Zhang¹⁰

Affiliations

¹ Institute for Environmental and Climate Research, Jinan University, Guangzhou, China; Guangdong-Hongkong-Macau Joint Laboratory of Collaborative Innovation for Environmental Quality, Guangzhou, China.
² State Key Laboratory of Organic Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou, China; Guangzhou Sub-branch of Guangdong Ecological and Environmental Monitoring Center, Guangzhou, China; Guangdong Key Laboratory of Environmental Protection and Resources Utilization, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou, China; CAS Center for Excellence in Deep Earth Science, Guangzhou, China; University of Chinese Academy of Sciences, Beijing, China.
³ Institute for Environmental and Climate Research, Jinan University, Guangzhou, China; Guangdong-Hongkong-Macau Joint Laboratory of Collaborative Innovation for Environmental Quality, Guangzhou, China. Electronic address: liu.junwen@jnu.edu.cn.
⁴ State Key Laboratory of Organic Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou, China.
⁵ State Key Laboratory of Isotope Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou, China.
⁶ CAS Key Laboratory of Coastal Environmental Processes and Ecological Remediation, Yantai Institute of Coastal Zone Research, Chinese Academy of Sciences, Yantai, China.
⁷ School of Atmospheric Sciences, Sun Yat-sen University, Guangzhou, China; Guangdong Provincial Observation and Research Station for Climate Environment and Air Quality Change in the Pearl River Estuary, Guangzhou, China.
⁸ Yale-NUIST Center on Atmospheric Environment, International Joint Laboratory on Climate and Environment Change, Nanjing University of Information Science and Technology, Nanjing, China.
⁹ South China Institute of Environmental Sciences, Ministry of Environmental Protection, Guangzhou, China.
¹⁰ State Key Laboratory of Organic Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou, China; CAS Center for Excellence in Deep Earth Science, Guangzhou, China.

PMID: 35926604
DOI: 10.1016/j.scitotenv.2022.157750

Abstract

Ammonia (NH₃) is the most prevalent alkaline gas in the atmosphere and plays a critical role in air pollution and public health. However, scientific debate remains over whether agricultural emissions (e.g., livestock and fertilizer application) dominate NH₃ in urban atmosphere in China, which is one of the largest NH₃ emitters in the world. In this study, we first simultaneously collected the fine atmospheric particles (PM_2.5) at two heights (ground and 488 m) using the atmospheric observatories in Canton Tower, Guangzhou city, China for the measurements of stable nitrogen isotope composition in ammonium (δ¹⁵N-NH₄⁺). Our results showed that the average δ¹⁵N-NH₄⁺ value at the ground and the 488 m observatory were 16.9 ‰ and 3.8 ‰, respectively, implying that NH₄⁺ aerosols between the two heights probably have different sources. Moreover, we found that the δ¹⁵N-NH₄⁺ value would sharply decrease to -16.7 ‰ when the air masses came from western Guangzhou, where the urbanization is limited compared to other surrounding areas. The Bayesian mixing model indicated that NH₄⁺ aerosol at the ground observatory was mainly derived from non-agricultural activities (76 %, e.g., vehicular exhaust), with the rest from agricultural sources (24 %). As for the 488 m observatory, the contribution of non-agricultural sources was 53 %, which is lower than the ground observatory. This is expected as the lower air receives more impacts from the local urban emission. However, the current "bottom-up" emission inventory illustrates that only ~20 % NH₃ in Guangzhou is associated with non-agricultural emissions, which is significantly lower than our δ¹⁵N-based results. Overall, our findings strongly imply that non-agricultural sources dominate the urban NH₃ in Guangzhou or maybe in adjacent cities of the Pearl River Delta region as well, suggesting that the emission inventory of NH₃ in this region probably is urgently needed to be revisited in future studies.

Keywords: Ammonia; Ammonium; Canton tower; Guangzhou; Stable nitrogen isotope.

MeSH terms

Aerosols / analysis
Air Pollutants* / analysis
Ammonia / analysis
Ammonium Compounds* / analysis
Bayes Theorem
China
Cities
Environmental Monitoring
Fertilizers
Nitrogen Isotopes / analysis
Particulate Matter / analysis

Substances

Aerosols
Air Pollutants
Ammonium Compounds
Fertilizers
Nitrogen Isotopes
Particulate Matter
Ammonia