Atmospheric Ammonia in Beijing during the COVID-19 Outbreak: Concentrations, Sources, and Implications

Yangyang Zhang; Xuejun Liu; Yunting Fang; Duanyang Liu; Aohan Tang; Jeffrey L Collett Jr

doi:10.1021/acs.estlett.0c00756

Atmospheric Ammonia in Beijing during the COVID-19 Outbreak: Concentrations, Sources, and Implications

Environ Sci Technol Lett. 2020 Nov 2;8(1):32-38. doi: 10.1021/acs.estlett.0c00756. eCollection 2021 Jan 12.

Authors

Yangyang Zhang¹, Xuejun Liu¹, Yunting Fang², Duanyang Liu^{3

4}, Aohan Tang¹, Jeffrey L Collett Jr⁵

Affiliations

¹ Beijing Key Laboratory of Farmland Soil Pollution Prevention and Remediation, College of Resources and Environmental Sciences, China Agricultural University, Beijing 100193, China.
² Key Laboratory of Forest Ecology and Management, Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang 110164, China.
³ Key Laboratory of Transportation Meteorology, China Meteorological Administration, Nanjing 210008, China.
⁴ Nanjing Joint Institute for Atmospheric Sciences, Nanjing 210008, China.
⁵ Department of Atmospheric Science, Colorado State University, Fort Collins, Colorado 80523, United States.

PMID: 37566379
DOI: 10.1021/acs.estlett.0c00756

Abstract

This study investigates the concentrations and δ¹⁵N values of NH₃ in Beijing during and after the 2020 COVID-19 lockdown. Higher NH₃ concentrations and lower δ¹⁵N-NH_3(measured) were observed at most sites in 2020 compared to 2017. Except for a site inside a tunnel, NH₃ concentrations did not increase significantly after the lockdown had ended compared to those during the lockdown, while δ¹⁵N-NH_3(measured) increased by 2.1-9.9‰. Nonagricultural sources (fossil fuel and urban waste) overall contributed 81% and 62% of NH₃ at on-road (tunnel interior) and nonroad (CAU) sites in 2020, respectively, comparable to those in 2017 (without significant difference). The contribution of nonagricultural sources slightly increased after the lockdown compared to the contribution during the lockdown at the nonroad site and hardly changed at the tunnel interior site. Our results suggest that (1) unfavorable meteorological conditions, especially lower boundary layer heights and changes in regional transport patterns, might play a more important role than reduced anthropogenic emissions in the temporal variations of Beijing NH₃ and (2) the effect of reduced anthropogenic emissions, during the COVID-19 outbreak or with the future implementation of emission control strategies, on atmospheric NH₃ can be better demonstrated by isotope-based source apportionment of NH₃, rather than only by changes in NH₃ concentrations.