scholarly journals Simultaneous Measurements of Chemical Compositions of Fine Particles during Winter Haze Period in Urban Sites in China and Korea

Atmosphere ◽  
2020 ◽  
Vol 11 (3) ◽  
pp. 292 ◽  
Author(s):  
Minhan Park ◽  
Yujue Wang ◽  
Jihyo Chong ◽  
Haebum Lee ◽  
Jiho Jang ◽  
...  
Keyword(s):  
Biomass Burning ◽  
Fine Particles ◽  
Chemical Compositions ◽  
Aerosol Formation ◽  
Wind Speeds ◽  
Simultaneous Measurements ◽  
Dust Sources ◽  
Secondary Formation ◽  
Combustion Sources ◽  
Burning Coal

We performed simultaneous measurements of chemical compositions of fine particles in Beijing, China and Gwangju, Korea to better understand their sources during winter haze period. We identified PM2.5 events in Beijing, possibly caused by a combination of multiple primary combustion sources (biomass burning, coal burning, and vehicle emissions) and secondary aerosol formation under stagnant conditions and/or dust sources under high wind speeds. During the PM2.5 events in Gwangju, the contribution of biomass burning and secondary formation of nitrate and organics to the fine particles content significantly increased under stagnant conditions. We commonly observed the increases of nitrogen-containing organic compounds and biomass burning inorganic (K+) and organic (levoglucosan) markers, suggesting the importance of biomass burning sources during the winter haze events (except dust event cases) at both sites. Pb isotope ratios indicated that the fraction of Pb originated from possibly industry and coal combustion sources increased during the PM2.5 events in Gwangju, relative to nonevent days.

scholarly journals Seasonal variations in high time-resolved chemical compositions, sources, and evolution of atmospheric submicron aerosols in the megacity Beijing

2017 ◽  
Vol 17 (16) ◽  
pp. 9979-10000 ◽  
Author(s):  
Wei Hu ◽  
Min Hu ◽  
Wei-Wei Hu ◽  
Jing Zheng ◽  
Chen Chen ◽  
...  
Keyword(s):  
Biomass Burning ◽  
Coal Combustion ◽  
Fine Particles ◽  
Liquid Water Content ◽  
Urban Site ◽  
Chemical Components ◽  
Chemical Compositions ◽  
Average Mass ◽  
Four Seasons ◽  
Secondary Formation

Abstract. A severe regional haze problem in the megacity Beijing and surrounding areas, caused by fast formation and growth of fine particles, has attracted much attention in recent years. In order to investigate the secondary formation and aging process of urban aerosols, four intensive campaigns were conducted in four seasons between March 2012 and March 2013 at an urban site in Beijing (116.31° E, 37.99° N). An Aerodyne high-resolution time-of-flight aerosol mass spectrometry (HR-ToF-AMS) was deployed to measure non-refractory chemical components of submicron particulate matter (NR-PM1). The average mass concentrations of PM1 (NR-PM1+black carbon) were 45.1 ± 45.8, 37.5 ± 31.0, 41.3 ± 42.7, and 81.7 ± 72.4 µg m−3 in spring, summer, autumn, and winter, respectively. Organic aerosol (OA) was the most abundant component in PM1, accounting for 31, 33, 44, and 36 % seasonally, and secondary inorganic aerosol (SNA, sum of sulfate, nitrate, and ammonium) accounted for 59, 57, 43, and 55 % of PM1 correspondingly. Based on the application of positive matrix factorization (PMF), the sources of OA were obtained, including the primary ones of hydrocarbon-like (HOA), cooking (COA), biomass burning OA (BBOA) and coal combustion OA (CCOA), and secondary component oxygenated OA (OOA). OOA, which can be split into more-oxidized (MO-OOA) and less-oxidized OOA (LO-OOA), accounted for 49, 69, 47, and 50 % in four seasons, respectively. Totally, the fraction of secondary components (OOA+SNA) contributed about 60–80 % to PM1, suggesting that secondary formation played an important role in the PM pollution in Beijing, and primary sources were also non-negligible. The evolution process of OA in different seasons was investigated with multiple metrics and tools. The average carbon oxidation states and other metrics show that the oxidation state of OA was the highest in summer, probably due to both strong photochemical and aqueous-phase oxidations. It was indicated by the good correlations (r = 0.53–0.75, p < 0.01) between LO-OOA and odd oxygen (Ox =  O3 + NO2), and between MO-OOA and liquid water content in aerosols. BBOA was resolved in spring and autumn, influenced by agricultural biomass burning (e.g., field preparation burnings, straw burning after the harvest). CCOA was only identified in winter due to domestic heating. These results signified that the comprehensive management for biomass burning and coal combustion emissions is needed. High concentrations of chemical components in PM1 in Beijing, especially in winter or in adverse meteorological conditions, suggest that further strengthening the regional emission control of primary particulate and precursors of secondary species is expected.

scholarly journals Seasonal variations of high time-resolved chemical compositions, sources and evolution for atmospheric submicron aerosols in the megacity Beijing

2017 ◽  
Author(s):  
Wei Hu ◽  
Min Hu ◽  
Wei-Wei Hu ◽  
Jing Zheng ◽  
Chen Chen ◽  
...  
Keyword(s):  
Biomass Burning ◽  
Coal Combustion ◽  
Fine Particles ◽  
Urban Site ◽  
Chemical Components ◽  
Chemical Compositions ◽  
Average Mass ◽  
Four Seasons ◽  
Secondary Formation ◽  
Autumn And Winter

Abstract. Severe regional haze problem in the megacity Beijing and surrounding areas, caused by fast formation and growth of fine particles, has attracted much attention in recent years. In order to investigate the secondary formation and aging process of urban aerosols, four intensive campaigns were conducted in four seasons between March 2012 and March 2013 at an urban site in Beijing (116.31° E, 37.99° N). An Aerodyne high resolution time-of-flight aerosol mass spectrometry (HR-ToF-AMS) and other relevant instrumentations for gaseous and particulate pollutants were deployed. The average mass concentrations of submicron particulate matter (PM1) were 45.1±45.8, 37.5±31.0, 41.3±42.7, and 81.7±72.4 μg m−3 in spring, summer, autumn and winter, respectively. Organic aerosol (OA) was the most abundant component in PM1, accounting for 31, 33, 44 and 36 % seasonally, and secondary inorganic aerosol (SNA, sum of sulfate, nitrate and ammonium) accounted for 59, 57, 43, and 55 % of PM1 correspondingly. Based on the application of positive matrix factorization (PMF), the sources of OA were obtained, including the primary ones of hydrocarbon-like (HOA), cooking (COA), biomass burning OA (BBOA) and coal combustion OA (CCOA), and secondary component oxygenated OA (OOA). OOA, usually composed of more-oxidized (MO-OOA) and less-oxidized OOA (LO-OOA), accounted for 63, 69, 47 and 50 % in four seasons, respectively. Totally, the fraction of secondary components (OOA+SNA) contributed about 60–80 % to PM1, suggesting that secondary formation played an important role in the PM pollution in Beijing, and primary sources were also non-negligible. The evolution process of OA in different seasons was investigated with multiple metrics and tools. The average carbon oxidation states and other metrics show that the oxidation state of OA was the highest in summer, probably due to both strong photochemical and aqueous-phase oxidations. BBOA and CCOA were only resolved in autumn and winter, respectively, consistent with the agricultural activities (e.g., straw burning after the harvest in suburban areas) in autumn and domestic heating in winter, signifying that the comprehensive management for the emissions from biomass burning and coal combustion are needed. High concentrations of chemical components in PM1 in Beijing, especially in winter or in adverse meteorological conditions, suggest that further strengthening the regional emission control of primary particulate and precursors of secondary species is expected.

scholarly journals Source apportionment of fine organic aerosols in Beijing

2009 ◽  
Vol 9 (21) ◽  
pp. 8573-8585 ◽  
Author(s):  
Q. Wang ◽  
M. Shao ◽  
Y. Zhang ◽  
Y. Wei ◽  
M. Hu ◽  
...  
Keyword(s):  
Organic Matter ◽  
Particulate Organic Matter ◽  
Biomass Burning ◽  
Fine Particles ◽  
Organic Aerosols ◽  
Gas Chromatography Mass Spectrometry ◽  
Chemical Compositions ◽  
Vehicle Exhaust ◽  
Coal Burning ◽  
Alkanoic Acids

Abstract. Fine particles (PM2.5, i.e., particles with an aerodynamic diameter of ≤2.5 μm) were collected from the air in August 2005, August–September 2006, and January–February 2007, in Beijing, China. The chemical compositions of particulate organic matter in the ambient samples were quantified by gas chromatography/mass spectrometry. The dominant compounds identified in summertime were n-alkanoic acids, followed by dicarboxylic acids and sugars, while sugars became the most abundant species in winter, followed by polycyclic aromatic hydrocarbons, n-alkanes, and n-alkanoic acids. The contributions of seven emission sources (i.e., gasoline/diesel vehicles, coal burning, wood/straw burning, cooking, and vegetative detritus) to particulate organic matter in PM2.5 were estimated using a chemical mass balance receptor model. The model results present the seasonal trends of source contributions to organic aerosols. Biomass burning (straw and wood) had the highest contribution in winter, followed by coal burning, vehicle exhaust, and cooking. The contribution of cooking was the highest in summer, followed by vehicle exhaust and biomass burning, while coal smoke showed only a minor contribution to ambient organic carbon.

scholarly journals Characterization of submicron aerosols influenced by biomass burning at a site in the Sichuan Basin, southwestern China

2016 ◽  
Vol 16 (20) ◽  
pp. 13213-13230 ◽  
Author(s):  
Wei Hu ◽  
Min Hu ◽  
Wei-Wei Hu ◽  
Hongya Niu ◽  
Jing Zheng ◽  
...  
Keyword(s):  
High Resolution ◽  
Oxidation State ◽  
Biomass Burning ◽  
Sichuan Basin ◽  
Chemical Compositions ◽  
Aerosol Formation ◽  
Spectral Matrix ◽  
Synoptic Conditions ◽  
The Sichuan Basin ◽  
Primary Emissions

Abstract. Severe air pollution in Asia is often the consequence of a combination of large anthropogenic emissions and adverse synoptic conditions. However, limited studies on aerosols have been conducted under high emission intensity and under unique geographical and meteorological conditions. In this study, an Aerodyne high-resolution time-of-flight aerosol mass spectrometry (HR-ToF-AMS) and other state-of-the-art instruments were utilized at a suburban site, Ziyang, in the Sichuan Basin during December 2012 to January 2013. The chemical compositions of atmospheric submicron aerosols (PM1) were determined, the sources of organic aerosols (OA) were apportioned, and the aerosol secondary formation and aging process were explored as well. Due to high humidity and static air, PM1 maintained a relatively stable level during the whole campaign, with the mean concentration of 59.7 ± 24.1 µg m−3. OA was the most abundant component (36 %) in PM1, characterized by a relatively high oxidation state. Positive matrix factorization analysis was applied to the high-resolution organic mass spectral matrix, which deconvolved OA mass spectra into four factors: low-volatility (LV-OOA) and semivolatile oxygenated OA (SV-OOA), biomass burning (BBOA) and hydrocarbon-like OA (HOA). OOA (sum of LV-OOA and SV-OOA) dominated OA as high as 71 %. In total, secondary inorganic and organic formation contributed 76 % of PM1. Secondary inorganic species correlated well (Pearson r = 0.415–0.555, p < 0.01) with relative humidity (RH), suggesting the humid air can favor the formation of secondary inorganic aerosols. As the photochemical age of OA increased with higher oxidation state, secondary organic aerosol formation contributed more to OA. The slope of OOA against Ox( = O3+NO2) steepened with the increase of RH, implying that, besides the photochemical transformation, the aqueous-phase oxidation was also an important pathway of the OOA formation. Primary emissions, especially biomass burning, resulted in high concentration and proportion of black carbon (BC) in PM1. During the episode obviously influenced by primary emissions, the contributions of BBOA to OA (26 %) and PM1 (11 %) were much higher than those (10–17 %, 4–7 %) in the clean and other polluted episodes, highlighting the significant influence of biomass burning.

scholarly journals Substantial changes in gaseous pollutants and chemical compositions in fine particles in the North China Plain during the COVID-19 lockdown period: anthropogenic vs. meteorological influences

2021 ◽  
Vol 21 (11) ◽  
pp. 8677-8692
Author(s):  
Rui Li ◽  
Yilong Zhao ◽  
Hongbo Fu ◽  
Jianmin Chen ◽  
Meng Peng ◽  
...  
Keyword(s):  
Fine Particles ◽  
Industrial Process ◽  
Road Dust ◽  
Pollutant Emissions ◽  
Chemical Compositions ◽  
Economic Activities ◽  
Secondary Aerosol ◽  
The North ◽  
Secondary Formation ◽  
Meteorological Influences

Abstract. The rapid response to the COVID-19 pandemic led to unprecedented decreases in economic activities, thereby reducing the pollutant emissions. A random forest (RF) model was applied to determine the respective contributions of meteorology and anthropogenic emissions to the changes in air quality. The result suggested that the strict lockdown measures significantly decreased primary components such as Cr (−67 %) and Fe (−61 %) in PM2.5 (p<0.01), whereas the higher relative humidity (RH) and NH3 level and the lower air temperature (T) remarkably enhanced the production of secondary aerosol, including SO42- (29 %), NO3- (29 %), and NH4+ (21 %) (p<0.05). The positive matrix factorization (PMF) result suggested that the contribution ratios of secondary formation (SF), industrial process (IP), biomass burning (BB), coal combustion (CC), and road dust (RD) changed from 36 %, 27 %, 21 %, 12 %, and 4 % before the COVID-19 outbreak to 44 %, 20 %, 20 %, 9 %, and 7 %, respectively. The rapid increase in the contribution ratio derived from SF to PM2.5 implied that the intermittent haze events during the COVID-19 period were characterized by secondary aerosol pollution, which was mainly contributed by the unfavorable meteorological conditions and high NH3 level.

scholarly journals Characterization of submicron aerosols influenced by biomass burning at a site in the Sichuan Basin, southwestern China

2016 ◽  
Author(s):  
Wei Hu ◽  
Min Hu ◽  
Weiwei Hu ◽  
Hongya Niu ◽  
Jing Zheng ◽  
...  
Keyword(s):  
High Resolution ◽  
Oxidation State ◽  
Biomass Burning ◽  
Sichuan Basin ◽  
Chemical Compositions ◽  
Aerosol Formation ◽  
Spectral Matrix ◽  
Inorganic Species ◽  
The Sichuan Basin ◽  
Primary Emissions

Abstract. Severe air pollution caused by large amount of pollutants and adverse synoptic processes appears often in Asia. However, limited studies on aerosols have been conducted under high emission intensity, and unique geographical and meteorological conditions. In this study, an Aerodyne high resolution time-of-flight aerosol mass spectrometry (HR-ToF-AMS) and other state-of-the-art instruments were utilized at a suburban site, Ziyang, in the Sichuan Basin during December 2012 to January 2013. The chemical compositions of atmospheric submicron aerosols (PM1) were determined, the sources of organic aerosols (OA) were apportioned, and the aerosol secondary formation and aging process were explored as well. Due to high humidity and static air, PM1 was maintained at a relatively stable level during the whole campaign, with the mean concentration of 59.7 &amp;pm; 24.1 μg m−3. OA was the most abundant component (36 %) in PM1, characterized by a relatively high oxidation state. Positive matrix factorization analysis was applied to the high resolution organic mass spectral matrix, which deconvolved OA mass spectra into four factors: low volatility (LV-OOA) and semi-volatile oxygenated OA (SV-OOA), biomass burning (BBOA) and hydrocarbon-like OA (HOA). OOA (sum of LV-OOA and SV-OOA) dominated OA as high as 71 %. In total, secondary inorganic and organic formation contributed 76 % of PM. Secondary inorganic species correlated well with relative humidity (RH), indicating the humid air can favor the formation of secondary inorganic aerosols. With the increase of photochemical age, OA became more aged with higher oxidation state, and secondary organic aerosol formation contributed more significantly to OA. The slope of OOA against Ox (= O3 + NO2) steepened with the increase of RH, implying that besides the photochemical transformation, the aqueous-phase oxidation was also an important pathway of the OOA formation. Primary emissions, especially biomass burning, resulted in high concentration and proportion of black carbon (BC) in PM1. During the episode obviously influenced by primary emissions, the contributions of BBOA to OA (26 %) and PM1 (11 %) were much higher than those (10–17 %, 4–7 %) in the clean and other polluted episodes, highlighting the significant influence of biomass burning.

scholarly journals Substantial changes of gaseous pollutants and chemical compositions in fine particles in North China Plain during COVID-19 lockdown period: anthropogenic vs meteorological influences

2021 ◽  
Author(s):  
Rui Li ◽  
Yilong Zhao ◽  
Hongbo Fu
Keyword(s):  
Fine Particles ◽  
Industrial Process ◽  
Road Dust ◽  
Pollutant Emissions ◽  
Chemical Compositions ◽  
Economic Activities ◽  
Secondary Aerosol ◽  
Secondary Formation ◽  
Aerosol Pollution ◽  
Meteorological Influences

Abstract. The rapid response to COVID-19 pandemic led to the unprecedented decreases of economic activities, thereby reducing the pollutant emissions. A random forest (RF) model was applied to determine the respective contributions of meteorology and anthropogenic emissions to the changes of air quality. The result suggested the strict lockdown measures significantly decreased primary components such as Cr (−201 %) and Fe (−154 %) in PM2.5, whereas the higher relative humidity (RH) and NH3 level, and the lower air temperature (T) enhanced the production of secondary aerosol including SO42− (47.2 %), NO3− (38.6 %), and NH4+ (22.7 %). Positive matrix factorization (PMF) result suggested that the contribution ratios of secondary formation (SF), industrial process (IP), biomass burning (BB), coal combustion (CC), and road dust (RD) changed from 35.2 %, 28.9 %, 19.4 %, 11.8 %, and 4.75 % before COVID-19 outbreak to 42.7 %, 20.5 %, 19.45 %, 9.80 %, and 7.56 %, respectively. The rapid increase of the contribution ratio derived from SF to PM2.5 implied the intermittent haze events during COVID-19 period were characterized with secondary aerosol pollution, which was mainly contributed by the unfavorable meteorological conditions and high NH3 level.

scholarly journals Chemical and Optical Characteristics and Sources of PM2.5 Humic-Like Substances at Industrial and Suburban Sites in Changzhou, China

Atmosphere ◽  
2021 ◽  
Vol 12 (2) ◽  
pp. 276
Author(s):  
Ye Tao ◽  
Ning Sun ◽  
Xudong Li ◽  
Zhuzi Zhao ◽  
Shuaishuai Ma ◽  
...  
Keyword(s):  
Optical Properties ◽  
Biomass Burning ◽  
Inorganic Ions ◽  
Absorption Efficiency ◽  
Control Measures ◽  
Chemical Compositions ◽  
Air Pollution Control ◽  
Industrial Region ◽  
Secondary Sources ◽  
Secondary Formation

The chemical and optical properties and sources of atmospheric PM2.5 humic-like substances (HULIS) were investigated from October to December 2016 in both industrial and suburban areas in Changzhou, China, during polluted and fair days. The average PM2.5 concentration in the industrial region was 113.06 (±64.3) μg m−3, higher than 85.27 (±41.56) μg m−3 at the suburban site. The frequency of polluted days was significantly higher in the industrial region. In contrast, the chemical compositions of PM2.5 at the two sampling sites exhibited no statistically significant differences. Rapidly increased secondary inorganic ions (SNA = NH4+ + SO42− + NO3−) concentrations suggested secondary formation played an important role in haze formation. The daily mean concentration of humic-like substance (HULIS) was 1.8–1.9 times that of HULIS-C (the carbon content of HULIS). Our results showed that HULIS accounted for a considerable fraction of PM2.5 (industrial region: 6.3% vs. suburban region: 9.4%). There were no large differences in the mass ratios of HULIS-C/WSOC at the two sites (46% in the industrial region and 52% in the suburban region). On average, suburban HULIS-C constituted 35.1% of organic carbon (OC), higher than that (21.1%) in the industrial region. Based on different MAE (mass absorption efficiency) values under different pollution levels, we can infer that the optical properties of HULIS varied with PM levels. Moreover, our results showed no distinct difference in E2/E3 (the ratio of light absorbance at 250 nm to that at 365 nm) and AAE300–400 (Absorption Angstrom Exponent at 300–400 nm) for HULIS and WSOC. the MAE365 (MAE at 365 nm) value of HULIS-C was different under three PM2.5 levels (low: PM2.5 < 75 μg m−3, moderate: PM2.5 = 75–150 μg m−3, high: PM2.5 > 150 μg m−3), with the highest MAE365 value on polluted days in the industrial region. Strong correlations between HULIS-C and SNA revealed that HULIS might be contributed from secondary formation at both sites. In addition, good correlations between HULIS-C with K+ in the industrial region implied the importance of biomass burning to PM2.5-bound HULIS. Three common sources of HULIS-C (i.e., vehicle emissions, biomass burning, and secondary aerosols) were identified by positive matrix factorization (PMF) for both sites, but the contributions were different, with the largest contribution from biomass burning in the industrial region and secondary sources in the suburban region, respectively. The findings presented here are important in understanding PM2.5 HULIS chemistry and are valuable for future air pollution control measures.

scholarly journals SO<sub>2</sub> and NH<sub>3</sub> emissions enhance organosulfur compounds and fine particles formation from the photooxidation of a typical aromatic hydrocarbon

2021 ◽  
Author(s):  
Zhaomin Yang ◽  
Li Xu ◽  
Narcisse T. Tsona ◽  
Jianlong Li ◽  
Xin Luo ◽  
...  
Keyword(s):  
Fine Particles ◽  
Heterogeneous Reaction ◽  
Oxidation Mechanism ◽  
Unknown Origin ◽  
Formation Mechanisms ◽  
Chemical Compositions ◽  
Organosulfur Compounds ◽  
Aerosol Formation ◽  
Particle Volume ◽  
Secondary Aerosol

Abstract. Although atmospheric SO2 and NH3 levels can affect secondary aerosol formation, the influenced extent of their impact and their detailed driving mechanisms are not well understood. The focus of the present study is to examine the chemical compositions and formation mechanisms of secondary organic aerosols (SOA) from 1,2,4-trimethylbenzene (TMB) photooxidation influenced by SO2 and/or NH3. Here, we showed that SO2 emission could considerably enhance aerosol particle formation due to SO2-induced sulfates generation and acid-catalyzed heterogeneous reaction. Orbitrap mass spectrometry (MS) measurements revealed the generation of not only typical TMB products but also hitherto unidentified organosulfates (OSs) in SO2-added experiments. The OSs designated as unknown origin in earlier field measurements were also detected in TMB SOA, indicating that atmospheric OSs might be also originated from TMB photooxidation. For NH3-involved experiments, results demonstrated a positive correlation between NH3 levels and particle volume as well as number concentrations. The effects of NH3 on SOA composition was slight under SO2-free conditions but stronger in the presence of SO2. A series of multifunctional products with carbonyl, alcohols, and nitrate functional groups were tentatively characterized in NH3-involved experiments based on infrared spectra and HRMS analysis. Plausible formation pathways were proposed for detected products in the particle-phase. The volatility distributions of products, estimated using parameterization methods, suggested that the detected products gradually condense onto the nucleation particles to contribute to aerosol formation and growth. Our results suggest that strict control of SO2 and NH3 emissions might remarkably reduce organosulfates and secondary aerosol burden in the atmosphere. Updating the aromatic oxidation mechanism in models could result in more accurate treatment of particles formation for urban regions with considerable SO2, NH3, and aromatics emissions.

scholarly journals Secondary organic aerosol formation from biomass burning emissions

2019 ◽  
Author(s):  
Christopher Y. Lim ◽  
David H. Hagan ◽  
Matthew M. Coggon ◽  
Abigail R. Koss ◽  
Kanako Sekimoto ◽  
...  
Keyword(s):  
Biomass Burning ◽  
Secondary Organic Aerosol ◽  
Total Concentration ◽  
Organic Aerosol ◽  
Oh Radicals ◽  
Aerosol Formation ◽  
Atmospheric Aging ◽  
Aerosol Mass ◽  
Photochemical Aging ◽  
Organic Gases

Abstract. Biomass burning is an important source of aerosol and trace gases to the atmosphere, but how these emissions change chemically during their lifetimes is not fully understood. As part of the Fire Influence on Regional and Global Environments Experiment (FIREX 2016), we investigated the effect of photochemical aging on biomass burning organic aerosol (BBOA), with a focus on fuels from the western United States. Emissions were sampled into a small (150 L) environmental chamber and photochemically aged via the addition of ozone and irradiation by 254 nm light. While some fraction of species undergoes photolysis, the vast majority of aging occurs via reaction with OH radicals, with total OH exposures corresponding to the equivalent of up to 10 days of atmospheric oxidation. For all fuels burned, large and rapid changes are seen in the ensemble chemical composition of BBOA, as measured by an aerosol mass spectrometer (AMS). Secondary organic aerosol (SOA) formation is seen for all aging experiments and continues to grow with increasing OH exposure, but the magnitude of the SOA formation is highly variable between experiments. This variability can be explained well by a combination of experiment-to-experiment differences in OH exposure and the total concentration of non-methane organic gases (NMOGs) in the chamber before oxidation, measured by PTR-ToF-MS (r2 values from 0.64 to 0.83). From this relationship, we calculate the fraction of carbon from biomass burning NMOGs that is converted to SOA as a function of equivalent atmospheric aging time, with carbon yields ranging from 24 ± 4 % after 6 hours to 56 ± 9 % after 4 days.

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