ACS ES&T Air最新文献

{"title":"Air Quality Sensor Experts Convene: Current Quality Assurance Considerations for Credible Data.","authors":"Karoline K Barkjohn, Andrea Clements, Corey Mocka, Colin Barrette, Ashley Bittner, Wyatt Champion, Brett Gantt, Elizabeth Good, Amara Holder, Berkley Hillis, Matthew S Landis, Menaka Kumar, Megan MacDonald, Eben Thoma, Tim Dye, Jan-Michael Archer, Michael Bergin, Wilton Mui, Brandon Feenstra, Michael Ogletree, Christi Chester-Schroeder, Naomi Zimmerman","doi":"10.1021/acsestair.4c00125","DOIUrl":"10.1021/acsestair.4c00125","url":null,"abstract":"<p><p>Air sensors can provide valuable non-regulatory and supplemental data as they can be affordably deployed in large numbers and stationed in remote areas far away from regulatory air monitoring stations. Air sensors have inherent limitations that are critical to understand before collecting and interpreting the data. Many of these limitations are mechanistic in nature, which will require technological advances. However, there are documented quality assurance (QA) methods to promote data quality. These include laboratory and field evaluation to quantitatively assess performance, the application of corrections to improve precision and accuracy, and active management of the condition or state of health of deployed air quality sensors. This paper summarizes perspectives presented at the U.S. Environmental Protection Agency's 2023 Air Sensors Quality Assurance Workshop (https://www.epa.gov/air-sensor-toolbox/quality-assurance-air-sensors#QAworkshop) by stakeholders (e.g., manufacturers, researchers, air agencies) and identifies the most pressing needs. These include QA protocols, streamlined data processing, improved total volatile organic compound (TVOC) data interpretation, development of speciated VOC sensors, and increased documentation of hardware and data handling. Community members using air sensors need training and resources, timely data, accessible QA approaches, and shared responsibility with other stakeholders. In addition to identifying the vital next steps, this work provides a set of common QA and QC actions aimed at improving and homogenizing air sensor QA that will allow stakeholders with varying fields and levels of expertise to effectively leverage air sensor data to protect human health.</p>","PeriodicalId":100014,"journal":{"name":"ACS ES&T Air","volume":"1 10","pages":"1203-1214"},"PeriodicalIF":0.0,"publicationDate":"2024-09-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11534011/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142585311","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Factors Affecting Chlorinated Product Formation from Sodium Hypochlorite Bleach and Limonene Reactions in the Gas Phase","authors":"Callee M. Walsh*,&nbsp;Notashia N. Baughman,&nbsp;Jason E. Ham and J. R. Wells,&nbsp;","doi":"10.1021/acsestair.4c0015010.1021/acsestair.4c00150","DOIUrl":"https://doi.org/10.1021/acsestair.4c00150https://doi.org/10.1021/acsestair.4c00150","url":null,"abstract":"<p >During use of sodium hypochlorite bleach, gas-phase hypochlorous acid (HOCl) and chlorine (Cl₂) are released, which can react with organic compounds present in indoor air. Reactivity between HOCl/Cl₂ and limonene, a common constituent of indoor air, has been observed. The purpose of this study was to characterize the chemical species generated from gas-phase reactions between HOCl/Cl₂ and limonene. Gas-phase reactions were prepared in Teflon chambers housing HOCl, Cl₂, and limonene. The resulting chemical products were analyzed using gas-phase preconcentration, followed by gas chromatography and high-resolution mass spectrometry. Several chlorinated products were detected, including limonene species containing one, two, and three chlorines and limonene chlorohydrin. Product concentrations and yields were estimated for the most abundant products, and greater than 80% of transformed limonene was represented in the detected products. Temporal sampling of the reactions allowed time courses to be plotted for limonene decay and chlorinated limonene product generation under different conditions, including the treatments of HOCl/Cl₂, Cl₂ only, high vs low relative humidity, and ± ozone. These experiments add product speciation, yield estimates, and an understanding of environmental factors affecting product formation to previous studies, further highlighting the chemical transformations initiated by sodium hypochlorite bleach in indoor air.</p>","PeriodicalId":100014,"journal":{"name":"ACS ES&T Air","volume":"1 10","pages":"1317–1328 1317–1328"},"PeriodicalIF":0.0,"publicationDate":"2024-09-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142430702","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Factors Affecting Chlorinated Product Formation from Sodium Hypochlorite Bleach and Limonene Reactions in the Gas Phase.","authors":"Callee M Walsh, Notashia N Baughman, Jason E Ham, J R Wells","doi":"10.1021/acsestair.4c00150","DOIUrl":"https://doi.org/10.1021/acsestair.4c00150","url":null,"abstract":"<p><p>During use of sodium hypochlorite bleach, gas-phase hypochlorous acid (HOCl) and chlorine (Cl₂) are released, which can react with organic compounds present in indoor air. Reactivity between HOCl/Cl₂ and limonene, a common constituent of indoor air, has been observed. The purpose of this study was to characterize the chemical species generated from gas-phase reactions between HOCl/Cl₂ and limonene. Gas-phase reactions were prepared in Teflon chambers housing HOCl, Cl₂, and limonene. The resulting chemical products were analyzed using gas-phase preconcentration, followed by gas chromatography and high-resolution mass spectrometry. Several chlorinated products were detected, including limonene species containing one, two, and three chlorines and limonene chlorohydrin. Product concentrations and yields were estimated for the most abundant products, and greater than 80% of transformed limonene was represented in the detected products. Temporal sampling of the reactions allowed time courses to be plotted for limonene decay and chlorinated limonene product generation under different conditions, including the treatments of HOCl/Cl₂, Cl₂ only, high vs low relative humidity, and ± ozone. These experiments add product speciation, yield estimates, and an understanding of environmental factors affecting product formation to previous studies, further highlighting the chemical transformations initiated by sodium hypochlorite bleach in indoor air.</p>","PeriodicalId":100014,"journal":{"name":"ACS ES&T Air","volume":"1 10","pages":"1317-1328"},"PeriodicalIF":0.0,"publicationDate":"2024-09-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11708576/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142961076","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Spatiotemporally Detailed Quantification of Air Quality Benefits of Emissions Reductions-Part I: Benefit-per-Ton Estimates for Canada and the U.S.","authors":"Shunliu Zhao, Petros Vasilakos, Anas Alhusban, Yasar Burak Oztaner, Alan Krupnick, Howard Chang, Armistead Russell, Amir Hakami","doi":"10.1021/acsestair.4c00127","DOIUrl":"https://doi.org/10.1021/acsestair.4c00127","url":null,"abstract":"<p><p>The U.S. EPA's Community Multiscale Air Quality (CMAQ)-adjoint model is used to map monetized health benefits (defined here as benefits of reduced mortality from chronic PM_2.5 exposure) in the form of benefits per ton (of emissions reduced) for the U.S. and Canada for NOx, SO₂, ammonia, and primary PM_2.5 emissions. The adjoint model provides benefits per ton (BPTs) that are location-specific and applicable to various sectors. BPTs show significant variability across locations, such that only 20% of primary PM_2.5 emissions in each country makes up more than half of its burden. The greatest benefits in terms of BPTs are for primary PM_2.5 reductions, followed by ammonia. Seasonal differences in benefits vary by pollutant: while PM_2.5 benefits remain high across seasons, BPTs for reducing ammonia are much higher in the winter due to the increased ammonium nitrate formation efficiency. Based on our location-specific BPTs, we estimate a total of 91,000 U.S. premature mortalities attributable to natural and anthropogenic emissions.</p>","PeriodicalId":100014,"journal":{"name":"ACS ES&T Air","volume":"1 10","pages":"1215-1226"},"PeriodicalIF":0.0,"publicationDate":"2024-09-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11474827/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142485105","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Modeling Indoor Inorganic Aerosol Concentrations During the ATHLETIC Campaign with IMAGES.","authors":"Bryan Berman, Bryan Cummings, Hongyu Guo, Pedro Campuzano-Jost, Jose Jimenez, Demetrios Pagonis, Douglas Day, Zachary Finewax, Anne Handschy, Benjamin A Nault, Peter DeCarlo, Shannon Capps, Michael Waring","doi":"10.1021/acsestair.4c00060","DOIUrl":"https://doi.org/10.1021/acsestair.4c00060","url":null,"abstract":"<p><p>In 2018, the ATHLETIC campaign was conducted at the University of Colorado Dal Ward Athletic Center and characterized dynamic indoor air composition in a gym environment. Among other parameters, inorganic particle and gas-phase species were alternatingly measured in the gym's supply duct and weight room. The Indoor Model of Aerosols, Gases, Emissions, and Surfaces (IMAGES) uses the inorganic aerosol thermodynamic equilibrium model, ISORROPIA, to estimate the partitioning of inorganic aerosols and corresponding gases. In this study herein, measurements from the ATHLETIC campaign were used to evaluate IMAGES' performance. Ammonia emission rates, nitric acid deposition, and particle deposition velocities were related to observed occupancy, which informed these rates in IMAGES runs. Initially, modeled indoor inorganic aerosol concentrations were not in good agreement with measurements. A parametric investigation revealed that lowering the temperature or raising the relative humidity used in the ISORROPIA model drove the semivolatile species more toward the particle phase, substantially improving modeled-measured agreement. One speculated reason for these solutions is that aerosol water was enhanced by increasing the RH or decreasing the temperature. Another is that thermodynamic equilibrium was not established in this indoor setting or that the thermodynamic parametrizations in ISORROPIA are less accurate for typical indoor settings. This result suggests that applying ISORROPIA indoors requires further careful experimental validation.</p>","PeriodicalId":100014,"journal":{"name":"ACS ES&T Air","volume":"1 9","pages":"1084-1095"},"PeriodicalIF":0.0,"publicationDate":"2024-09-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11406535/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142305501","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Modeling Indoor Inorganic Aerosol Concentrations During the ATHLETIC Campaign with IMAGES","authors":"Bryan Berman,&nbsp;Bryan Cummings,&nbsp;Hongyu Guo,&nbsp;Pedro Campuzano-Jost,&nbsp;Jose Jimenez,&nbsp;Demetrios Pagonis,&nbsp;Douglas Day,&nbsp;Zachary Finewax,&nbsp;Anne Handschy,&nbsp;Benjamin A. Nault,&nbsp;Peter DeCarlo,&nbsp;Shannon Capps and Michael Waring*,&nbsp;","doi":"10.1021/acsestair.4c0006010.1021/acsestair.4c00060","DOIUrl":"https://doi.org/10.1021/acsestair.4c00060https://doi.org/10.1021/acsestair.4c00060","url":null,"abstract":"<p >In 2018, the ATHLETIC campaign was conducted at the University of Colorado Dal Ward Athletic Center and characterized dynamic indoor air composition in a gym environment. Among other parameters, inorganic particle and gas-phase species were alternatingly measured in the gym’s supply duct and weight room. The Indoor Model of Aerosols, Gases, Emissions, and Surfaces (IMAGES) uses the inorganic aerosol thermodynamic equilibrium model, ISORROPIA, to estimate the partitioning of inorganic aerosols and corresponding gases. In this study herein, measurements from the ATHLETIC campaign were used to evaluate IMAGES’ performance. Ammonia emission rates, nitric acid deposition, and particle deposition velocities were related to observed occupancy, which informed these rates in IMAGES runs. Initially, modeled indoor inorganic aerosol concentrations were not in good agreement with measurements. A parametric investigation revealed that lowering the temperature or raising the relative humidity used in the ISORROPIA model drove the semivolatile species more toward the particle phase, substantially improving modeled-measured agreement. One speculated reason for these solutions is that aerosol water was enhanced by increasing the RH or decreasing the temperature. Another is that thermodynamic equilibrium was not established in this indoor setting or that the thermodynamic parametrizations in ISORROPIA are less accurate for typical indoor settings. This result suggests that applying ISORROPIA indoors requires further careful experimental validation.</p><p >This work applies an indoor aerosol model, IMAGES, that estimates the partitioning of inorganic aerosol components and their corresponding gas-phase species with ISORROPIA by leveraging measurements from a university athletic center and derived relationships between occupancy and nitric acid deposition, particle deposition, and ammonia emissions. This study highlights that applying ISORROPIA indoors can sometimes result in inaccurate gas-particle partitioning. However, forcing the model to predict increased particle water by either adjusting relative humidity up or temperature down will result in accurate gas-particle partitioning.</p>","PeriodicalId":100014,"journal":{"name":"ACS ES&T Air","volume":"1 9","pages":"1084–1095 1084–1095"},"PeriodicalIF":0.0,"publicationDate":"2024-09-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://pubs.acs.org/doi/epdf/10.1021/acsestair.4c00060","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142228354","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Spatiotemporally Detailed Quantification of Air Quality Benefits of Emissions Reductions–Part I: Benefit-per-Ton Estimates for Canada and the U.S.","authors":"Shunliu Zhao,&nbsp;Petros Vasilakos,&nbsp;Anas Alhusban,&nbsp;Yasar Burak Oztaner,&nbsp;Alan Krupnick,&nbsp;Howard Chang,&nbsp;Armistead Russell and Amir Hakami*,&nbsp;","doi":"10.1021/acsestair.4c0012710.1021/acsestair.4c00127","DOIUrl":"https://doi.org/10.1021/acsestair.4c00127https://doi.org/10.1021/acsestair.4c00127","url":null,"abstract":"<p >The U.S. EPA’s Community Multiscale Air Quality (CMAQ)-adjoint model is used to map monetized health benefits (defined here as benefits of reduced mortality from chronic PM_2.5 exposure) in the form of benefits per ton (of emissions reduced) for the U.S. and Canada for NOx, SO₂, ammonia, and primary PM_2.5 emissions. The adjoint model provides benefits per ton (BPTs) that are location-specific and applicable to various sectors. BPTs show significant variability across locations, such that only 20% of primary PM_2.5 emissions in each country makes up more than half of its burden. The greatest benefits in terms of BPTs are for primary PM_2.5 reductions, followed by ammonia. Seasonal differences in benefits vary by pollutant: while PM_2.5 benefits remain high across seasons, BPTs for reducing ammonia are much higher in the winter due to the increased ammonium nitrate formation efficiency. Based on our location-specific BPTs, we estimate a total of 91,000 U.S. premature mortalities attributable to natural and anthropogenic emissions.</p><p >Due to the spatiotemporal variabilities in benefit per ton of emission reductions, reducing 20% of the primary emissions would result in over half the societal health benefits in both the U.S. and Canada.</p>","PeriodicalId":100014,"journal":{"name":"ACS ES&T Air","volume":"1 10","pages":"1215–1226 1215–1226"},"PeriodicalIF":0.0,"publicationDate":"2024-09-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://pubs.acs.org/doi/epdf/10.1021/acsestair.4c00127","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142430616","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Seasonal Changes in the Oxidative Potential of Urban Air Pollutants: The Influence of Emission Sources and Proton- and Ligand-Mediated Dissolution of Transition Metals.","authors":"Pourya Shahpoury, Steven Lelieveld, Deepchandra Srivastava, Andrea Baccarini, Jacob Mastin, Thomas Berkemeier, Valbona Celo, Ewa Dabek-Zlotorzynska, Tom Harner, Gerhard Lammel, Athanasios Nenes","doi":"10.1021/acsestair.4c00093","DOIUrl":"https://doi.org/10.1021/acsestair.4c00093","url":null,"abstract":"<p><p>The inhalation of fine particulate matter (PM_2.5) is a major contributor to adverse health effects from air pollution worldwide. An important toxicity pathway is thought to follow oxidative stress from the formation of exogenous reactive oxygen species (ROS) in the body, a proxy of which is oxidative potential (OP). As redox-active transition metals and organic species are important drivers of OP in urban environments, we investigate how seasonal changes in emission sources, aerosol chemical composition, acidity, and metal dissolution influence OP dynamics. Using a kinetic model of the lung redox chemistry, we predicted ROS (O₂ ^•-, H₂O₂, ^•OH) formation with input parameters comprising the ambient concentrations of PM_2.5, water-soluble Fe and Cu, secondary organic matter, nitrogen dioxide, and ozone across two years and two urban sites in Canada. Particulate species were the largest contributors to ROS production. Soluble Fe and Cu had their highest and lowest values in summer and winter, and changes in Fe solubility were closely linked to seasonal variations in chemical aging, the acidity of aerosol, and organic ligand levels. The results indicate three conditions that influence OP across various seasons: (a) low aerosol pH and high organic ligand levels leading to the highest OP in summer, (b) opposite trends leading to the lowest OP in winter, and (c) intermediate conditions corresponding to moderate OP in spring and fall. This study highlights how atmospheric chemical aging modifies the oxidative burden of urban air pollutants, resulting in a seasonal cycle with a potential effect on population health.</p>","PeriodicalId":100014,"journal":{"name":"ACS ES&T Air","volume":"1 10","pages":"1262-1275"},"PeriodicalIF":0.0,"publicationDate":"2024-08-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11474821/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142485104","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Seasonal Changes in the Oxidative Potential of Urban Air Pollutants: The Influence of Emission Sources and Proton- and Ligand-Mediated Dissolution of Transition Metals","authors":"Pourya Shahpoury*,&nbsp;Steven Lelieveld,&nbsp;Deepchandra Srivastava,&nbsp;Andrea Baccarini,&nbsp;Jacob Mastin,&nbsp;Thomas Berkemeier,&nbsp;Valbona Celo,&nbsp;Ewa Dabek-Zlotorzynska,&nbsp;Tom Harner*,&nbsp;Gerhard Lammel and Athanasios Nenes,&nbsp;","doi":"10.1021/acsestair.4c0009310.1021/acsestair.4c00093","DOIUrl":"https://doi.org/10.1021/acsestair.4c00093https://doi.org/10.1021/acsestair.4c00093","url":null,"abstract":"<p >The inhalation of fine particulate matter (PM_2.5) is a major contributor to adverse health effects from air pollution worldwide. An important toxicity pathway is thought to follow oxidative stress from the formation of exogenous reactive oxygen species (ROS) in the body, a proxy of which is oxidative potential (OP). As redox-active transition metals and organic species are important drivers of OP in urban environments, we investigate how seasonal changes in emission sources, aerosol chemical composition, acidity, and metal dissolution influence OP dynamics. Using a kinetic model of the lung redox chemistry, we predicted ROS (O₂^•–, H₂O₂, ^•OH) formation with input parameters comprising the ambient concentrations of PM_2.5, water-soluble Fe and Cu, secondary organic matter, nitrogen dioxide, and ozone across two years and two urban sites in Canada. Particulate species were the largest contributors to ROS production. Soluble Fe and Cu had their highest and lowest values in summer and winter, and changes in Fe solubility were closely linked to seasonal variations in chemical aging, the acidity of aerosol, and organic ligand levels. The results indicate three conditions that influence OP across various seasons: (a) low aerosol pH and high organic ligand levels leading to the highest OP in summer, (b) opposite trends leading to the lowest OP in winter, and (c) intermediate conditions corresponding to moderate OP in spring and fall. This study highlights how atmospheric chemical aging modifies the oxidative burden of urban air pollutants, resulting in a seasonal cycle with a potential effect on population health.</p><p >Using field measurements and model simulations, this work investigates if seasonal changes in emission sources, aerosol acidity and composition, and metal dissolution influence the oxidative potential of urban air.</p>","PeriodicalId":100014,"journal":{"name":"ACS ES&T Air","volume":"1 10","pages":"1262–1275 1262–1275"},"PeriodicalIF":0.0,"publicationDate":"2024-08-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://pubs.acs.org/doi/epdf/10.1021/acsestair.4c00093","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142430572","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Explainable Machine Learning Reveals the Unknown Sources of Atmospheric HONO during COVID-19","authors":"Zhiwei Gao,&nbsp;Yue Wang,&nbsp;Sasho Gligorovski,&nbsp;Chaoyang Xue,&nbsp;LingLing Deng,&nbsp;Rui Li,&nbsp;Yusen Duan,&nbsp;Shan Yin,&nbsp;Lin Zhang,&nbsp;Qianqian Zhang and Dianming Wu*,&nbsp;","doi":"10.1021/acsestair.4c0008710.1021/acsestair.4c00087","DOIUrl":"https://doi.org/10.1021/acsestair.4c00087https://doi.org/10.1021/acsestair.4c00087","url":null,"abstract":"<p >Nitrous acid (HONO) is a key precursor of the hydroxyl radical (•OH), playing an important role in atmospheric oxidation capacity. However, unknown sources of HONO (<i>P</i>_unknown) are frequently reported and the potential sources are controversial. Here, we explored <i>P</i>_unknown during COVID-19 in different seasons and epidemic control phases in Shanghai by eXtreme Gradient Boosting (XGBoost) and Shapley Additive Explanations (SHAP) for the first time. They demonstrated that the decrease of anthropogenic activity would inhibit secondary formation of HONO, as epidemic control policies turned strict. The explainable machine learning revealed that nitrogen dioxide (NO₂) had significant impacts on the <i>P</i>_unknown during spring 2020 (P1), where <i>P</i>_unknown could be fully explained by including light-induced heterogeneous conversion of NO₂ on ground, building, and aerosol surfaces. With the untightening of epidemic control in spring 2021 (P3), the HONO budget came to balance after further addition of the photolysis of particulate nitrate (NO₃^–) and soil HONO emission. As for P2 (summer), <i>P</i>_unknown decreased by 54% with all new sources added. These results provide new insights into HONO chemistry in response to reduced anthropogenic emissions, improving the predictions of atmospheric oxidation capacity.</p>","PeriodicalId":100014,"journal":{"name":"ACS ES&T Air","volume":"1 10","pages":"1252–1261 1252–1261"},"PeriodicalIF":0.0,"publicationDate":"2024-08-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142407536","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}