Li-Ti Chou , Yan-Syuan Lin , Ta-Chih Hsiao , Pei-Ling Wang , Li-Hao Young , Kai-Hsien Chi , Stephen M. Griffith
{"title":"Source apportionment and mechanistic analysis of PM2.5 nitrate: interplay of OH and N2O5 in spatial and temporal variations","authors":"Li-Ti Chou , Yan-Syuan Lin , Ta-Chih Hsiao , Pei-Ling Wang , Li-Hao Young , Kai-Hsien Chi , Stephen M. Griffith","doi":"10.1016/j.scitotenv.2025.179813","DOIUrl":null,"url":null,"abstract":"<div><div>Particulate nitrate, a substantial component of PM<sub>2.5</sub> during pollution episodes, requires precise source apportionment for effective air quality management. This study investigated nitrate formation mechanisms through dual-isotope analysis at an urban ZongMing (ZM) and suburban TungHai (TH) site in Taichung City, Taiwan, with PM<sub>2.5</sub> samples collected during August and October 2020, including diurnal sampling at TH. Analysis of nitrate isotopic compositions (δ<sup>15</sup>N-NO<sub>3</sub><sup>−</sup> and δ<sup>18</sup>O-NO<sub>3</sub><sup>−</sup>) revealed spatial heterogeneity between the sampling sites, with TH exhibiting elevated mean δ<sup>15</sup>N-NO<sub>3</sub><sup>−</sup> values (2.6 ± 2.4 ‰) and distinct diurnal patterns in its 12-h measurements, while daily integrated samples at ZM showed mean values of 0.6 ± 2.1 ‰. Similar δ<sup>18</sup>O-NO<sub>3</sub><sup>−</sup> patterns at both sites indicated comparable oxidation mechanisms. OH-mediated oxidation and its products maintained substantial contributions to PM<sub>2.5</sub> nitrate during both day and night periods, dominating in summer (81–83 %) before declining in autumn (77 ± 13 %) as the N<sub>2</sub>O<sub>5</sub> pathway increased. The N<sub>2</sub>O<sub>5</sub> pathway showed enhanced effectiveness under elevated nocturnal humidity, correlating strongly with PM<sub>2.5</sub> concentrations (R<sup>2</sup> = 0.52). Source apportionment using MixSIAR identified biomass burning and coal combustion as primary NO<sub>x</sub> sources, with additional contributions from vehicular and biogenic soil emissions. These findings emphasize the importance of considering both diurnal and seasonal variations in formation mechanisms for developing targeted air quality control strategies.</div></div>","PeriodicalId":422,"journal":{"name":"Science of the Total Environment","volume":"989 ","pages":"Article 179813"},"PeriodicalIF":8.0000,"publicationDate":"2025-06-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Science of the Total Environment","FirstCategoryId":"93","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/S0048969725014548","RegionNum":1,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q1","JCRName":"ENVIRONMENTAL SCIENCES","Score":null,"Total":0}
引用次数: 0
Abstract
Particulate nitrate, a substantial component of PM2.5 during pollution episodes, requires precise source apportionment for effective air quality management. This study investigated nitrate formation mechanisms through dual-isotope analysis at an urban ZongMing (ZM) and suburban TungHai (TH) site in Taichung City, Taiwan, with PM2.5 samples collected during August and October 2020, including diurnal sampling at TH. Analysis of nitrate isotopic compositions (δ15N-NO3− and δ18O-NO3−) revealed spatial heterogeneity between the sampling sites, with TH exhibiting elevated mean δ15N-NO3− values (2.6 ± 2.4 ‰) and distinct diurnal patterns in its 12-h measurements, while daily integrated samples at ZM showed mean values of 0.6 ± 2.1 ‰. Similar δ18O-NO3− patterns at both sites indicated comparable oxidation mechanisms. OH-mediated oxidation and its products maintained substantial contributions to PM2.5 nitrate during both day and night periods, dominating in summer (81–83 %) before declining in autumn (77 ± 13 %) as the N2O5 pathway increased. The N2O5 pathway showed enhanced effectiveness under elevated nocturnal humidity, correlating strongly with PM2.5 concentrations (R2 = 0.52). Source apportionment using MixSIAR identified biomass burning and coal combustion as primary NOx sources, with additional contributions from vehicular and biogenic soil emissions. These findings emphasize the importance of considering both diurnal and seasonal variations in formation mechanisms for developing targeted air quality control strategies.
期刊介绍:
The Science of the Total Environment is an international journal dedicated to scientific research on the environment and its interaction with humanity. It covers a wide range of disciplines and seeks to publish innovative, hypothesis-driven, and impactful research that explores the entire environment, including the atmosphere, lithosphere, hydrosphere, biosphere, and anthroposphere.
The journal's updated Aims & Scope emphasizes the importance of interdisciplinary environmental research with broad impact. Priority is given to studies that advance fundamental understanding and explore the interconnectedness of multiple environmental spheres. Field studies are preferred, while laboratory experiments must demonstrate significant methodological advancements or mechanistic insights with direct relevance to the environment.