Concurrent measurements of nitrate at urban and suburban sites identify local nitrate formation as a driver for urban episodic PM 2.5 pollution.

Autor: Li J; Department of Chemistry, Hong Kong University of Science and Technology, Kowloon, Hong Kong SAR., Ho SCH; Division of Environment and Sustainability, Hong Kong University of Science and Technology, Kowloon, Hong Kong SAR., Griffith SM; Department of Chemistry, Hong Kong University of Science and Technology, Kowloon, Hong Kong SAR; Department of Atmospheric Sciences, National Taiwan University, Taipei, Taiwan. Electronic address: stegriff@ntu.edu.tw., Huang Y; Division of Environment and Sustainability, Hong Kong University of Science and Technology, Kowloon, Hong Kong SAR., Cheung RKY; Division of Environment and Sustainability, Hong Kong University of Science and Technology, Kowloon, Hong Kong SAR., Hallquist M; Department of Chemistry and Molecular Biology, University of Gothenburg, Gothenburg, Sweden., Hallquist ÅM; IVL Swedish Environmental Research Institute, Gothenburg, Sweden., Louie PKK; Hong Kong Environmental Protection Department, 47/F, Revenue Tower, 5 Gloucester Road, Wan Chai, Hong Kong SAR., Fung JCH; Division of Environment and Sustainability, Hong Kong University of Science and Technology, Kowloon, Hong Kong SAR., Lau AKH; Division of Environment and Sustainability, Hong Kong University of Science and Technology, Kowloon, Hong Kong SAR., Yu JZ; Department of Chemistry, Hong Kong University of Science and Technology, Kowloon, Hong Kong SAR; Division of Environment and Sustainability, Hong Kong University of Science and Technology, Kowloon, Hong Kong SAR. Electronic address: jian.yu@ust.hk.
Jazyk: angličtina
Zdroj: The Science of the total environment [Sci Total Environ] 2023 Nov 01; Vol. 897, pp. 165351. Date of Electronic Publication: 2023 Jul 06.
DOI: 10.1016/j.scitotenv.2023.165351
Abstrakt: Nitrate (NO 3 - ) is often among the leading components of urban particulate matter (PM) during PM pollution episodes. However, the factors controlling its prevalence remain inadequately understood. In this work, we analyzed concurrent hourly monitoring data of NO 3 - in PM 2.5 at a pair of urban and suburban locations (28 km apart) in Hong Kong for a period of two months. The concentration gradient in PM 2.5 NO 3 - was 3.0 ± 2.9 (urban) vs. 1.3 ± 0.9 μg m -3 (suburban) while that for its precursors nitrogen oxides (NO x ) was 38.1 vs 4.1 ppb. NO 3 - accounted for 45 % of the difference in PM 2.5 between the sites. Both sites were characterized to have more available NH 3 than HNO 3 . Urban nitrate episodes, defined as periods of urban-suburban NO 3 - difference exceeding 2 μg m -3 , constituted 21 % of the total measurement hours, with an hourly NO 3 - average gradient of 4.2 and a peak value of 23.6 μg m -3 . Our comparative analysis, together with 3-D air quality model simulations, indicates that the high NO x levels largely explain the excessive NO 3 - concentrations in our urban site, with the gas phase HNO 3 formation reaction contributing significantly during the daytime and the N 2 O 5 hydrolysis pathway playing a prominent role during nighttime. This study presents a first quantitative analysis that unambiguously shows local formation of NO 3 - in urban environments as a driver for urban episodic PM 2.5 pollution, suggesting effective benefits of lowering urban NO x .
Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
(Copyright © 2023 Elsevier B.V. All rights reserved.)
Databáze: MEDLINE
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