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Emissions, Chemistry, and the Environmental Impacts of Wildland Fire

2024; American Chemical Society; Volume: 11; Issue: 9 Linguagem: Inglês

10.1021/acs.estlett.4c00612

2328-8930

Amara L. Holder, Amy P. Sullivan,

Fire dynamics and safety research

InfoMetricsFiguresRef. Environmental Science & Technology LettersASAPArticle This publication is free to access through this site. Learn More CiteCitationCitation and abstractCitation and referencesMore citation options ShareShare onFacebookX (Twitter)WeChatLinkedInRedditEmailJump toExpandCollapse EditorialAugust 14, 2024Emissions, Chemistry, and the Environmental Impacts of Wildland FireClick to copy article linkArticle link copied!Amara L. Holder*Amara L. Holder*[email protected]More by Amara L. HolderView Biographyhttps://orcid.org/0000-0001-6443-5298Amy P. Sullivan*Amy P. Sullivan*[email protected]More by Amy P. SullivanView BiographyOpen PDFEnvironmental Science & Technology LettersCite this: Environ. Sci. Technol. Lett. 2024, XXXX, XXX, XXX-XXXClick to copy citationCitation copied!https://pubs.acs.org/doi/10.1021/acs.estlett.4c00612https://doi.org/10.1021/acs.estlett.4c00612Published August 14, 2024 Publication History Received 25 July 2024Accepted 25 July 2024Published online 14 August 2024editorialPublished 2024 by American Chemical Society. This publication is available under these Terms of Use. Request reuse permissionsThis publication is licensed for personal use by The American Chemical Society. ACS PublicationsPublished 2024 by American Chemical SocietySubjectswhat are subjectsArticle subjects are automatically applied from the ACS Subject Taxonomy and describe the scientific concepts and themes of the article.Atmospheric chemistryContaminationEnvironmental chemistryParticulate matterRedox reactionsSpecial IssuePublished as part of Environmental Science & Technology Letters virtual special issue "Wildland Fires: Emissions, Chemistry, Contamination, Climate, and Human Health".Wildland fires pose an environmental challenge that has been growing in recent years, as wildfires increase in magnitude and the use of prescribed fire has expanded to reduce the risk of catastrophic wildfire. Fire is also used throughout the world for reducing agricultural waste and clearing land. Wildland fires are one of the largest sources of pollutants to the global atmosphere with major impacts on air quality and climate. Fire also disturbs terrestrial and aquatic systems and poses numerous environmental impacts in areas near the fire and downwind ecosystems. With climate change increasingly driving higher fire activity, understanding the environmental impacts of wildland fires will continue to become more important.As the research community strives to understand the full complexity of fire and its environmental impacts, the research questions continue to expand. To capture the latest scientific developments in this area, the Environmental Science & Technology (ES&T) portfolio of journals (ES&T, ACS ES&T Air, and ES&T Letters) recently launched a new special issue call for papers entitled "Wildland Fires: Chemistry, Contamination, Climate and Human Health", with a submission deadline of September 2, 2024. To complement this, we have collated previously published research on this topic from ES&T, ES&T Letters, and ACS ES&T Water from 2020 to present as a virtual collection that highlights nascent wildfire research topics. The papers chosen are grouped by topic and introduced below.Wildland Fire EmissionsClick to copy section linkSection link copied!Nearly half a century of wildland fire emissions research exists. However, due to the complex emissions chemistry of wildland fires, key data gaps remain alongside challenges representing this complexity in emissions inventories and air quality models. Measurements by Peng et al. (1) during the WE-CAN (Western Wildfire Experiment for Cloud chemistry, Aerosol absorption and Nitrogen) Campaign found emitted HONO (nitrous acid) to be the dominant contributor to oxidant radicals during the first few hours of plume age along with ozone (O3) as the dominant radical source downwind. Sekimoto et al. (2) describe a novel approach using VOC (volatile organic compounds) emission profiles from low- and high-temperature pyrolysis integrated into satellite fire radiative power to estimate speciated VOC emissions from western wildfires sampled during the FIREX-AQ (Fire Influence on Regional and Global Environments and Air Quality) Campaign. Pagonis et al. (3) addressed another area of emissions complexity, by accounting for the organic aerosol volatility information to better constrain the estimated particulate matter (PM) emissions in a smoke forecasting model.Wildland Urban Interface FiresClick to copy section linkSection link copied!Increasing fire activity combined with population growth in areas intermixed or adjacent to wildlands, also known as the wildland urban interface (WUI), has led to an increase in the number of wildfires that move into urban areas and burn buildings and vehicles. Petersen et al. (4) have shown that the risk of urban wildfire exposure has increased as climate-driven fire danger has increased. These WUI fires can cause mass destruction and loss of life and pose serious environmental challenges such as emissions of toxic compounds to the air, contamination of water systems, and contaminated soil that can further impact air through wind-blown dust and waterways through runoff. Boaggio et al. (5) identified an increase in the levels of toxic metals in WUI fire smoke, such as copper and lead, that increased with the increasing scale of destruction pointing to the urban materials as the likely source of these compounds. Villarruel et al. (6) identified some of these same toxic metals in the ashes of WUI fires and found them to be in a more bioavailable form than those compounds naturally found in soil.Brown CarbonClick to copy section linkSection link copied!Wildland fires may be the largest source of primary brown carbon (BrC) and BrC precursors to the atmosphere. The concentration, optical properties, and lifetime of BrC remain active research areas. Hettiyadura et al. (7) provided a comprehensive characterization on the composition, volatility, viscosity, and optical properties of laboratory-generated BrC. They used this rich data set to call attention to how BrC fractions with different polarity have different optical and physical properties, suggesting that measurement methods that subject BrC to low-pressure conditions could volatilize the weaker chromophores leaving a darker more viscous particle. Gregson et al. (8) found that BrC viscosity impacted rates of reaction with O3, which may impact atmospheric bleaching rates. Multiple studies examined the variation of optical properties during reaction with oxidants. These studies found that oxygenated hydrocarbons can react with NO3 (nitrate radicals) formed overnight (or HONO in dark plume cores) forming secondary BrC and increasing BrC light absorption, (9−11) in addition to generating more toxic nitroaromatics. (12)The combination of complex chemistry, physical properties, and the propensity to bleach and darken in the atmosphere means it remains challenging to represent BrC in climate models (7) and to monitor for BrC in the atmosphere. Chen et al. (13) developed a novel method for assigning brownness to organic carbon measurements at routine monitoring locations and were able to use this data set to identify BrC trends at a national scale. They observed heightened wintertime brownness and increased urban versus rural brownness, and only moderate brownness of wildfire plumes. These results demonstrate that while wildland fires may be a major source of atmospheric BrC there may be other significant sources and atmospheric processes that are contributing.Atmospheric Evolution of Wildland Fire SmokeClick to copy section linkSection link copied!A major objective of wildland fire research is to differentiate the impact of wildland fire smoke on air quality and health from the impact of other pollution sources. This has proved to be complex because wildfire smoke undergoes numerous changes as it cools, dilutes, and reacts in the atmosphere while simultaneously mixing with atmospheric emissions from other pollutant sources during its atmospheric lifetime. During this process, other harmful pollutants, like O3, can form, further degrading air quality and posing challenges for downwind areas to meet air quality regulations.Recent research has measured plume evolution by different approaches to better understand the key factors controlling O3 formation, including remote sensing, (14) aircraft studies, (15) and ground-based studies. (16) Other important factors determining O3 formation rates include the time of day of emission, (15) the location in the plume, (17) and plume history, including mixing with urban air and other pollutants. (16) In addition, O3 formation can be highly variable depending on the conditions. For example, wildfire plumes are often NOx (nitrous oxides) limited and may have shaded areas with limited photolysis rates, resulting in straightforward O3 formation only at the edges of the plume where sunlight and precursors are abundant. Ozone formation may also be impacted by external factors (e.g., nearby urban NOx sources) as the plume ages and is transported downwind, which results in variable O3 formation as observed in numerous wildland fire plumes. (14)Decker et al. (18) highlighted how radical chemistry differs between daytime and nighttime plume evolution and the importance of the NO3 radicals in driving nighttime chemistry based on observations from the SENEX (Southeast Nexus) Campaign in conjunction with a detailed chemical box model. This was also seen in plumes emitted later in the day (15) as well as in the dark cores of fresh plumes (17) observed during FIREX-AQ. The importance of these other reaction pathways is now being investigated in the laboratory to better understand the NO3-dependent formation pathways for BrC and degradation of BrC from photolysis or O3 oxidation. Atmospheric plume evolution is also important for determining the volatilization of primary organic aerosol (3) and the formation of secondary organic carbon as well as the addition of and eventual loss of organic coatings on black carbon. (19)Air Quality ModelingClick to copy section linkSection link copied!Over the past decade, a proliferation of observational data has emerged with new satellite products, a rapid expansion of lower-cost PM sensors, and the continued advancement of air quality models and modeling approaches. Multiple research groups have taken advantage of these big data sets and statistical methods (e.g., machine learning) to generate air quality data that are impacted by smoke versus air quality data that are not impacted by smoke at high spatial and temporal resolution over extended periods of time. (20−22) Schneider et al. (20) used back trajectory models to identify pollution from satellite fire detects to elucidate a clear increase in the level of PM2.5 from wildfires but a minimal increase in the levels of CO (carbon monoxide) and NO2 (nitrogen dioxide) and mixed effects on the level of O3, once again demonstrating the complex relationship between wildfire smoke and O3 formation.Despite major advances in smoke modeling, Considine et al. (23) show that some commonly used machine learning-based models are not able to predict the very high ground-level concentrations near wildfires. Cleland et al. (24) found that increasing the number of ground-level observations near fires can greatly improve model performance and points to the need for more monitoring data near fires to support statistical model approaches that rely on ambient data as input. Furthermore, Zhang et al. (22) used lower-cost sensor data to show that areas not covered by air quality monitoring stations have higher smoke impacts, meaning that smoke exposures are underestimated by most models and the full extent of public health impacts from smoke is not known.Source ApportionmentClick to copy section linkSection link copied!Source apportionment studies are used to identify the impact of wildfires on air quality or ecosystems. Levoglucosan has long been used as a tracer for biomass burning activities, but recent research in China has reported there are numerous other minor sources of levoglucosan (25) and that the degradation of levoglucosan in the atmosphere (26) can result in an underestimation of the attribution of wildland fire smoke to ambient pollutant concentrations. An alternative approach is to use carbon isotope measurements such as those of Liu et al. (27) that underscored the inaccuracy of levoglucosan as a tracer for wildland fire. Liu et al. (27) also demonstrated the importance of wildland fire as a source of dissolved organic carbon in the Tibetan Plateau just as Kirago et al. (28) identified savanna burning as a major source of background aerosols in sub-Saharan Africa.HealthClick to copy section linkSection link copied!Understanding the relative contribution of wildland fire smoke to ambient air pollution can help to answer another key research question, which is whether wildland fire smoke is more harmful than other types of pollution sources. Additionally, is smoke from some fires more harmful if inhaled than others, such as smoke from wildfires versus prescribed fires, vegetative fires versus WUI fires, high- versus low-intensity fires, etc.? Researchers have probed the complex chemistry of wildland fire emissions in laboratory experiments to better understand the factors that may result in health effects. For example, Koval et al. (29) found that flaming peat emissions were most biologically active as evidenced by changes in the transcriptome of exposed mice, while smoldering peat was least active. Other researchers have found that aged smoke caused increased oxidative potential and inflammation. (30,31) Xu et al. (32) developed a national scale model of PM2.5 oxidative potential (i.e., the ability to cause oxidative damage, which may be related to increased health impacts) in Canada, finding an association between oxidative potential and wildfire smoke. More attention is also being paid to the hazards from the gas phase components of wildfire smoke, with studies by O'Dell et al. (33) and Navarro et al. (34) both showing that some gas phase smoke constituents may pose substantial health risks in addition to that from PM2.5. This risk has important implications for common exposure reduction methods like air cleaners that may be effective in removing only PM.EcosystemsClick to copy section linkSection link copied!The impacts of wildfires on ecosystems has become increasingly important as the scale and severity of wildfires have increased. Paul and co-workers (35) reported clear deficiencies in our understanding of wildfire effects on downwind ecosystems with more information needed on how wildfires impacted endangered species and protected lands. Bhattarai et al. (36) attributed nitrogen deposition in the Tibetan Plateau to wildland fires in South Asia, resulting in levels above the critical load threshold, potentially resulting in adverse ecosystem impacts.Water QualityClick to copy section linkSection link copied!Wildland fires can also have an impact on water quality, including contamination of drinking water systems. This was observed in California following the 2018 Camp Fire, where VOCs in contaminated service lines were studied. Contaminants associated with pyrolysis of PVC (polyvinyl chloride) and polyethylene as well as uncontrolled burning of biomass and waste materials were detected, providing evidence that wildfires can cause contamination by both thermal damage to plastic pipes and intrusion of smoke. (37) Benzene contamination was found to be more abundant in service connections to destroyed structures versus standing homes, likely arising from chemical pyrolysis products being pulled into these lines due to loss of system pressure. Therefore, the ability to quickly shut off sections of water systems that depressurize, coupled with backflow prevention, may help reduce contamination from smoke. (38) In addition, a study by Schulze et al. (39) found that burn severity, as measured by the density of damaged structures, was correlated with the probability of VOC contamination in a water sample exceeding California maximum contamination levels. This could also provide useful information for WUI water utilities regarding the implementation of mitigation strategies and location of vulnerabilities to minimize potential damage from future wildland fires.This Collection of previously published papers across the journals ES&T, ES&T Letters, and ACS ES&T Water highlights the wide range of environmental challenges posed by wildland fire and the progress that has been made in better understanding the impacts of fire on human health, ecosystems, and the climate.We hope you enjoy this curated collection as a useful reference point summarizing recent advances in this important field of research.Author InformationClick to copy section linkSection link copied!Corresponding AuthorsAmara L. Holder, https://orcid.org/0000-0001-6443-5298, Email: [email protected]Amy P. Sullivan, Email: [email protected]NotesViews expressed in this editorial are those of the authors and do not necessarily represent the views or policies of the U.S. Environmental Protection Agency and the ACS.BiographiesClick to copy section linkSection link copied!Amara L. HolderHigh Resolution ImageDownload MS PowerPoint SlideAmara Holder is a research mechanical engineer with the U.S. Environmental Protection Agency's Office of Research and Development. Her research focuses broadly on pollutant emissions from combustion processes and their impacts on human health and the environment, with a special focus on wildland fires. Her research has advanced the understanding of the emissions of toxic compounds from fires, including those that burn in the wildland urban interface (10.1093/pnasnexus/pgad186). She has evaluated low-cost sensor technology (10.3390/s20174796) and developed mobile monitoring approaches to measure the impacts of wildfire smoke on air quality (10.1039/D3EA00170A). She has received EPA's highest honor, the Gold Medal for Exceptional Service, for contributing to the science to support the AirNow Fire and Smoke map, which provides real-time information about smoke impacts on air quality to millions of Americans each year (10.3390/s22249669). She has also helped to identify and promote cost-effective and accessible approaches to reduce exposure to wildfire smoke, such as the do-it-yourself air cleaner (10.1111/ina.13163).Amy P. SullivanHigh Resolution ImageDownload MS PowerPoint SlideAmy Sullivan is a Research Scientist in the Atmospheric Science Department at Colorado State University. She received her Ph.D. in atmospheric chemistry at Georgia Institute of Technology in 2006. She has worked closely with aerosol instrumentation and developing methods to better understand the composition of aerosols, including developing real-time measurements of water-soluble organic carbon using the Particle-into-Liquid Sampler (PILS). Her research focuses in particular on aqueous SOA (secondary organic aerosols) and biomass burning aerosols. She has participated in more than 40 field studies, including the FLAME (Fire Lab at Missoula Experiments) Studies conducted at the Fire Science Laboratory in Missoula, MT (10.1029/2008JD010216), and the WE-CAN Campaign. She made the first airborne measurements of levoglucosan from the sampling of prescribed burning (10.5194/acp-14-10535-2014), residential burning (10.1029/2017JD028153), and wildfires as well as water-soluble BrC absorption from wildfires (10.5194/acp-22-13389-2022) using the PILS.ReferencesClick to copy section linkSection link copied! This article references 39 other publications. 1Peng, Q.; Palm, B. B.; Melander, K. E.; Lee, B. H.; Hall, S. R.; Ullmann, K.; Campos, T.; Weinheimer, A. J.; Apel, E. C.; Hornbrook, R. S.; Hills, A. J.; Montzka, D. D.; Flocke, F.; Hu, L.; Permar, W.; Wielgasz, C.; Lindaas, J.; Pollack, I. B.; Fischer, E. V.; Bertram, T. H.; Thornton, J. A. HONO Emissions from Western U.S. Wildfires Provide Dominant Radical Source in Fresh Wildfire Smoke. Environ. Sci. Technol. 2020, 54 (10), 5954– 5963, DOI: 10.1021/acs.est.0c00126 Google Scholar1HONO Emissions from Western U.S. Wildfires Provide Dominant Radical Source in Fresh Wildfire SmokePeng, Qiaoyun; Palm, Brett B.; Melander, Kira E.; Lee, Ben H.; Hall, Samuel R.; Ullmann, Kirk; Campos, Teresa; Weinheimer, Andrew J.; Apel, Eric C.; Hornbrook, Rebecca S.; Hills, Alan J.; Montzka, Denise D.; Flocke, Frank; Hu, Lu; Permar, Wade; Wielgasz, Catherine; Lindaas, Jakob; Pollack, Ilana B.; Fischer, Emily V.; Bertram, Timothy H.; Thornton, Joel A.Environmental Science & Technology (2020), 54 (10), 5954-5963CODEN: ESTHAG; ISSN:0013-936X. (American Chemical Society) Wildfires are an important source of HONO, a photo-labile radical precursor, yet in-situ measurements and quantification of primary HONO emissions from open wildfires are scarce. Airborne observations of HONO within wildfire plumes sampled during the Western Wildfire Expt. for Cloud Chem., Aerosol Absorption and Nitrogen (WE-CAN) campaign were obsd. ΔHONO:ΔCO ratios close to fire locations were 0.7-17 pptv/ppbv, using a max. enhancement method, with a median similar to previous observations of temperate forest fire plumes. Measured HONO:NOx enhancement ratios were generally factors of 2 or higher at early plume ages vs. previous studies. Enhancement ratios scaled with modified combustion efficiency and certain nitrogenous trace gases, which may be useful to est. HONO release when HONO observations are lacking or plumes have photochem. exposures >1 h, since emitted HONO is rapidly photolyzed. HONO photolysis was the dominant contributor to hydrogen oxide radicals (HOx = OH- + HO2) in the early stage ( > More from SciFinder ®https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3cXntFCnsLk%253D&md5=3999adcaa94203bb3f6c6466d5bac9292Sekimoto, K.; Coggon, M. M.; Gkatzelis, G. I.; Stockwell, C. E.; Peischl, J.; Soja, A. J.; Warneke, C. Fuel-Type Independent Parameterization of Volatile Organic Compound Emissions from Western US Wildfires. Environ. Sci. Technol. 2023, 57 (35), 13193– 13204, DOI: 10.1021/acs.est.3c00537 Google ScholarThere is no corresponding record for this reference.3Pagonis, D.; Selimovic, V.; Campuzano-Jost, P.; Guo, H.; Day, D. A.; Schueneman, M. K.; Nault, B. A.; Coggon, M. M.; DiGangi, J. P.; Diskin, G. S.; Fortner, E. C.; Gargulinski, E. M.; Gkatzelis, G. I.; Hair, J. W.; Herndon, S. C.; Holmes, C. D.; Katich, J. M.; Nowak, J. B.; Perring, A. E.; Saide, P.; Shingler, T. J.; Soja, A. J.; Thapa, L. H.; Warneke, C.; Wiggins, E. B.; Wisthaler, A.; Yacovitch, T. I.; Yokelson, R. J.; Jimenez, J. L. Impact of Biomass Burning Organic Aerosol Volatility on Smoke Concentrations Downwind of Fires. Environ. Sci. Technol. 2023, 57 (44), 17011– 17021, DOI: 10.1021/acs.est.3c05017 Google ScholarThere is no corresponding record for this reference.4Peterson, G. C. L.; Prince, S. E.; Rappold, A. G. Trends in Fire Danger and Population Exposure along the Wildland–Urban Interface. Environ. Sci. Technol. 2021, 55 (23), 16257– 16265, DOI: 10.1021/acs.est.1c03835 Google ScholarThere is no corresponding record for this reference.5Boaggio, K.; LeDuc, S. D.; Rice, R. B.; Duffney, P. F.; Foley, K. M.; Holder, A. L.; McDow, S.; Weaver, C. P. Beyond Particulate Matter Mass: Heightened Levels of Lead and Other Pollutants Associated with Destructive Fire Events in California. Environ. Sci. Technol. 2022, 56 (20), 14272– 14283, DOI: 10.1021/acs.est.2c02099 Google Scholar5Beyond Particulate Matter Mass: Heightened Levels of Lead and Other Pollutants Associated with Destructive Fire Events in CaliforniaBoaggio Katie; LeDuc Stephen D; Rice R Byron; Duffney Parker F; Foley Kristen M; Holder Amara L; McDow Stephen; Weaver Christopher PEnvironmental science & technology (2022), 56 (20), 14272-14283 ISSN:. As the climate warms, wildfire activity is increasing, posing a risk to human health. Studies have reported on particulate matter (PM) in wildfire smoke, yet the chemicals associated with PM have received considerably less attention. Here, we analyzed 13 years (2006-2018) of PM2.5 chemical composition data from monitors in California on smoke-impacted days. Select chemicals (e.g., aluminum and sulfate) were statistically elevated on smoke-impacted days in over half of the years studied. Other chemicals, mostly trace metals harmful to human health (e.g., copper and lead), were elevated during particular fires only. For instance, in 2018, lead was more than 40 times higher on smoke days on average at the Point Reyes monitoring station, due mostly to the Camp Fire, burning approximately 200 km away. There was an association between these metals and the combustion of anthropogenic material (e.g., the burning of houses and vehicles). Although still currently rare, these infrastructure fires are likely becoming more common and can mobilize trace metals in smoke far downwind, at levels generally unseen except in the most polluted areas of the country. We hope a better understanding of the chemicals in wildfire smoke will assist in the communication and reduction of public health risks. >> More from SciFinder ®https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A280%3ADC%252BB283kt1Cksg%253D%253D&md5=725b335e7ccdfa2ecea3de248bfd9e406Villarruel, C. M.; Figueroa, L. A.; Ranville, J. F. Quantification of Bioaccessible and Environmentally Relevant Trace Metals in Structure Ash from a Wildland–Urban Interface Fire. Environ. Sci. Technol. 2024, 58 (5), 2502– 2513, DOI: 10.1021/acs.est.3c08446 Google ScholarThere is no corresponding record for this reference.7Hettiyadura, A. P. S.; Garcia, V.; Li, C.; West, C. P.; Tomlin, J.; He, Q.; Rudich, Y.; Laskin, A. Chemical Composition and Molecular-Specific Optical Properties of Atmospheric Brown Carbon Associated with Biomass Burning. Environ. Sci. Technol. 2021, 55 (4), 2511– 2521, DOI: 10.1021/acs.est.0c05883 Google Scholar7Chemical composition and molecular-specific optical properties of atmospheric brown carbon associated with biomass burningHettiyadura, Anusha Priyadarshani Silva; Garcia, Valeria; Li, Chunlin; West, Christopher P.; Tomlin, Jay; He, Quanfu; Rudich, Yinon; Laskin, AlexanderEnvironmental Science & Technology (2021), 55 (4), 2511-2521CODEN: ESTHAG; ISSN:0013-936X. (American Chemical Society) This study provides mol. insights into the light absorption properties of biomass burning (BB) brown carbon (BrC) through the chem. characterization of tar condensates generated from heated wood pellets at oxidative and pyrolysis conditions. Both liq. tar condensates sepd. into "darker oily" and "lighter aq." immiscible phases. The mol. compn. of these samples was investigated using reversed-phase liq. chromatog. coupled with a photodiode array detector and a high-resoln. mass spectrometer. The results revealed two sets of BrC chromophores: common to all four samples and specific to the "oily" fractions. The common BrC chromophores consist of polar, monoarom. species. The oil-specific BrC chromophores include less-polar and nonpolar polyarom. compds. The most-light-absorbing pyrolysis oily phase (PO) was aerosolized and size-sepd. using a cascade impactor to compare the compn. and optical properties of the bulk vs. the aerosolized BrC. The mass absorption coeff. (MAC300-500 nm) of aerosolized PO increased compared to that of the bulk, due to gas-phase partitioning of more volatile and less absorbing chromophores. The optical properties of the aerosolized PO were consistent with previously reported ambient BB BrC measurements. These results suggest the darkening of atm. BrC following non-reactive evapn. that transforms the optical properties and compn. of aged BrC aerosols. >> More from SciFinder ®https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3MXitVWjtrk%253D&md5=71ea42aa31d0f43b955c40912f7b5ea48Gregson, F. K. A.; Gerrebos, N. G. A.; Schervish, M.; Nikkho, S.; Schnitzler, E. G.; Schwartz, C.; Carlsten, C.; Abbatt, J. P. D.; Kamal, S.; Shiraiwa, M.; Bertram, A. K. Phase Behavior and Viscosity in Biomass Burning Organic Aerosol and Climatic Impacts. Environ. Sci. Technol. 2023, 57 (39), 14548– 14557, DOI: 10.1021/acs.est.3c03231 Google ScholarThere is no corresponding record for this reference.9Rana, Md. S.; Guzman, M. I. Oxidation of Catechols at the Air–Water Interface by Nitrate Radicals. Environ. Sci. Technol. 2022, 56 (22), 15437– 15448, DOI: 10.1021/acs.est.2c05640 Google ScholarThere is no corresponding record for this reference.10Mayorga, R.; Chen, K.; Raeofy, N.; Woods, M.; Lum, M.; Zhao, Z.; Zhang, W.; Bahreini, R.; Lin, Y.-H.; Zhang, H. Chemical Structure Regulates the Formation of Secondary Organic Aerosol and Brown Carbon in Nitrate Radical Oxidation of Pyrroles and Methylpyrroles. Environ. Sci. Technol. 2022, 56 (12), 7761– 7770, DOI: 10.1021/acs.est.2c02345 Google Scholar10Chemical Structur