scholarly journals Offline analysis of the chemical composition and hygroscopicity of sub-micrometer aerosol at an Asian outflow receptor site and comparison with online measurements

2021 ◽  
Author(s):  
Yange Deng ◽  
Hiroaki Fujinari ◽  
Hikari Yai ◽  
Kojiro Shimada ◽  
Yuzo Miyazaki ◽  
...  
Keyword(s):  
Organic Matter ◽  
Chemical Composition ◽  
East Asian ◽  
Receptor Site ◽  
Water Soluble ◽  
Inorganic Salts ◽  
Chemical Compositions ◽  
Online Analysis ◽  
Offline Analysis ◽  
Aerosol Hygroscopicity

Abstract. Filter-based offline analysis of atmospheric aerosol hygroscopicity coupled to composition analysis provides information complementary to that obtained from online analysis. However, its application itself and comparison to online analysis have remained limited to date. In this study, daily submicrometer aerosol particles (PM0.95, 50 % cutoff diameter: 0.95 μm) were collected onto quartz fiber filters in Okinawa Island, a receptor of East Asian outflow, in the autumn of 2015. The chemical composition of water-soluble matter (WSM) in PM0.95 and PM0.95 itself, and their respective hygroscopicities were characterized through the offline use of an aerosol mass spectrometer and a hygroscopicity tandem differential mobility analyzer. Thereafter, results were compared with those obtained from online analyses. Sulfate dominated the WSM mass (60 %), followed by water-soluble organic matter (WSOM, 20 %) and ammonium (13 %). WSOM accounted for most (93 %) of the mass of extracted organic matter (EOM) and the atomic O to C ratios (O : C) of WSOM and EOM were high (mean ± standard deviation were, respectively, 0.84 ± 0.08 and 0.79 ± 0.08), both of which indicate highly aged characteristics of the observed aerosol. The hygroscopic growth curves showed clear hysteresis for most samples. At 85 % RH, the calculated hygroscopicity parameter κ of the WSM (κWSM), WSOM, EOM, and PM0.95 (κPM0.95) were, respectively, 0.50 ± 0.03, 0.22 ± 0.12, 0.20 ± 0.11, and 0.47 ± 0.03. An analysis using the thermodynamic E-AIM model shows, on average, that inorganic salts and WSOM respectively contributed 88 % and 12 % of the κWSM (or κPM0.95). High similarities were found between offline and online analysis for chemical compositions that are related to particle hygroscopicity (the mass fractions and O : C of organics, and the degree of neutralization), and also for aerosol hygroscopicity. As possible factors governing the variation of κWSM, the influences of WSOM abundance and the neutralization of inorganic salts were assessed. At high RH (70–90 %), the hygroscopicity of WSM and PM0.95 was affected considerably by the presence of organic components; at low RH (20–50 %), the degree of neutralization could be important. This study not only characterized aerosol hygroscopicity at the receptor site of East Asian outflow, but also shows that the offline hygroscopicity analysis is an appropriate method, at least for aerosols of the studied type. The results encourage further applications to other environments and to more in-depth hygroscopicity analysis, in particular for organic fractions.

scholarly journals First insights into northern Africa high-altitude background aerosol chemical composition and source influences

2021 ◽  
Vol 21 (24) ◽  
pp. 18147-18174
Author(s):  
Nabil Deabji ◽  
Khanneh Wadinga Fomba ◽  
Souad El Hajjaji ◽  
Abdelwahid Mellouki ◽  
Laurent Poulain ◽  
...  
Keyword(s):  
Organic Matter ◽  
Chemical Composition ◽  
High Altitude ◽  
North Africa ◽  
Mineral Dust ◽  
Water Soluble ◽  
Atmospheric Composition ◽  
Chemical Compositions ◽  
Aerosol Composition ◽  
Aerosol Chemical Composition

Abstract. Field measurements were conducted to determine aerosol chemical composition at a newly established remote high-altitude site in North Africa at the Atlas Mohammed V (AMV) atmospheric observatory located in the Middle Atlas Mountains. The main objectives of the present work are to investigate the variations in the aerosol composition and better assess global and regional changes in atmospheric composition in North Africa. A total of 200 particulate matter (PM10) filter samples were collected at the site using a high-volume (HV) collector in a 12 h sampling interval from August to December 2017. The chemical composition of the samples was analyzed for trace metals, water-soluble ions, organic carbon (OC/EC), aliphatic hydrocarbons, and polycyclic aromatic hydrocarbon (PAH) contents. The results indicate that high-altitude aerosol composition is influenced by both regional and transregional transport of emissions. However, local sources play an important role, especially during low wind speed periods, as observed for November and December. During background conditions characterized by low wind speeds (avg. 3 m s-1) and mass concentrations in the range from 9.8 to 12 μg m-3, the chemical composition is found to be dominated by inorganic elements, mainly suspended dust (61 %) and ionic species (7 %), followed by organic matter (7 %), water content (12 %), and unidentified mass (11 %). Despite the proximity of the site to the Sahara, its influence on the atmospheric composition at this high-altitude site was mainly seasonal and accounted for only 22 % of the sampling duration. Biogenic organics contributed up to 7 % of the organic matter with high contributions from compounds such as heneicosane, hentriacontane, and nonacosane. The AMV site is dominated by four main air mass inflows, which often leads to different aerosol chemical compositions. Mineral dust influence was seasonal and ranged between 21 % and 74 % of the PM mass, with peaks observed during the summer, and was accompanied by high concentrations of SO42- of up to 3.0 μg m-3. During winter, PM10 concentrations are low (<30 μg m-3), the influence of the desert is weaker, and the marine air masses (64 %) are more dominant with a mixture of sea salt and polluted aerosol from the coastal regions (Rabat and Casablanca). During the daytime, mineral dust contribution to PM increased by about 42 % because of road dust resuspension. In contrast, during nighttime, an increase in the concentrations of alkanes, PAHs, alkane-2-ones, and anthropogenic metals such as Pb, Ni, and Cu was found due to variations in the boundary layer height. The results provide the first detailed seasonal and diurnal variation of the aerosol chemical composition, which is valuable for long-term assessment of climate and regional influence of air pollution in North Africa.

scholarly journals A molecular-level approach for characterizing water-insoluble components of ambient organic aerosol particulates using ultra-high resolution mass spectrometry

2014 ◽  
Vol 14 (7) ◽  
pp. 10393-10427
Author(s):  
A. S. Willoughby ◽  
A. S. Wozniak ◽  
P. G. Hatcher
Keyword(s):  
Organic Matter ◽  
Chemical Composition ◽  
High Resolution Mass Spectrometry ◽  
Organic Aerosols ◽  
Organic Aerosol ◽  
Water Soluble ◽  
Proton Nuclear Magnetic Resonance ◽  
Aerosol Sample ◽  
Resonance Spectroscopy ◽  
Ion Cyclotron Resonance

Abstract. The chemical composition of organic aerosols in the atmosphere is strongly influenced by human emissions, and the effect these have on the environment, human health, and climate change is determined by the molecular nature of these chemical species. The complexity of organic aerosol samples limits the ability to study the chemical composition, and, therefore, the associated properties and the impacts they have. Many studies address the water-soluble fraction of organic aerosols, and have had much success in identifying specific molecular formulas for thousands of compounds present. However, little attention is given to the water-insoluble portion, which can contain most of the fossil material that is emitted through human activity. Here we compare the organic aerosols present in water extracts and organic solvent extracts (pyridine and acetonitrile) of an ambient aerosol sample collected in a rural location that is impacted by natural and anthropogenic emission sources. A semi-quantitative method was developed using proton nuclear magnetic resonance spectroscopy to determine that the amount of organic matter extracted by pyridine is comparable to that of water. Electrospray ionization Fourier transform ion cyclotron resonance mass spectra show that pyridine extracts a molecularly unique fraction of organic matter compared to water or acetonitrile, which extract chemically similar organic matter components. The molecular formulas unique to pyridine were less polar, more aliphatic, and reveal formulas containing sulfur to be an important component of insoluble aerosol organic matter.

scholarly journals First insights into Northern Africa high-altitude background aerosol chemical composition and source influences

2021 ◽  
Author(s):  
Nabil Deabji ◽  
Khanneh Wadinga Fomba ◽  
Souad El Hajjaji ◽  
Abdelwahid Mellouki ◽  
Hartmut Herrmann
Keyword(s):  
Organic Matter ◽  
Chemical Composition ◽  
High Altitude ◽  
Field Measurements ◽  
High Volume ◽  
Ionic Species ◽  
Atmospheric Composition ◽  
Chemical Compositions ◽  
Aerosol Composition ◽  
Aerosol Chemical Composition

Abstract. Field measurements were conducted to determine aerosol chemical composition in a newly established remote high-altitude site in North Africa to investigate the variations in aerosol composition useful in assessing global and regional changes in atmospheric composition. Particulate matter (PM10) filter samples (200) were collected at the Atlas Mohammed V atmospheric observatory (AM5) located in the Middle-Atlas Mountains in Morocco using a high-volume (HV) collector in a 12 h sampling interval from August to December 2017. The chemical composition of the samples was analyzed for trace metals, ions, elemental carbon, organic carbon, aliphatic hydrocarbons, and polycyclic aromatic hydrocarbon (PAHs) content. The results indicate that high-altitudes aerosol composition is influenced by both regional as well as trans-regional transport of emissions. However, local sources play an important role, especially during low wind speed periods, as observed for November and December. Despite the proximity of the site to the Sahara Desert, its influence on the atmospheric composition at this high-altitude site was mainly seasonal and accounted for only 14 % of the sampling duration. Background conditions at this remote site are characterized by low wind speeds (Av. 2.5 m/s) and mass concentrations in the range of 9.8 and 20 µg/m3. The chemical composition is found to be dominated by inorganic elements, mainly suspended dust (47 %) and ionic species (16 %), followed by organic matter (15 %), water content (12 %), and indeterminate mass (9 %). Biogenic organics contributed up to 7 % of the organic matter with high contributions from compounds such as Nonacosane, Heptacosane, and 2-Pentadecanone. The AM5 site is dominated by four main air mass inflow, which often leads to different aerosol chemical compositions. Mineral dust influenced was seasonal and ranged between 20 and 70 % of the PM mass with peaks observed during the summer and was accompanied by high concentrations of SO42− of up to 1.3 µg/m3. During winter, PM10 concentrations are low (

scholarly journals Hygroscopic properties of water-soluble matter and humic-like organics in atmospheric fine aerosol

2004 ◽  
Vol 4 (1) ◽  
pp. 35-50 ◽  
Author(s):  
M. Gysel ◽  
E. Weingartner ◽  
S. Nyeki ◽  
D. Paulsen ◽  
U. Baltensperger ◽  
...  
Keyword(s):  
Organic Matter ◽  
Growth Factors ◽  
Humic Acids ◽  
Solid Phase ◽  
Water Soluble ◽  
Inorganic Salts ◽  
Hygroscopic Growth ◽  
Average Molecular Mass ◽  
Hygroscopic Properties ◽  
Fine Aerosol

Abstract. Ambient continental-rural fine aerosol (K-puszta, Hungary, PM1.5) was sampled on quartz fibre filters in winter and summer 2001. Water-soluble matter (WSM) was extracted in MilliQ-water, and, in a second step, solid phase extraction was used to isolate the less hydrophilic fraction (ISOM) of the water-soluble organic matter (WSOM) from remaining inorganic salts and "most" hydrophilic organic matter (MHOM). This approach allowed ISOM, which constitutes the major fraction of WSOM, to be isolated from ambient aerosols and investigated in pure form. Hygroscopic properties of both WSM and ISOM extracts as well as of aquatic reference fulvic and humic acids were investigated using a Hygroscopicity Tandem Differential Mobility Analyser (H-TDMA). ISOM deliquesced between 30% and 60% relative humidity (RH), and hygroscopic growth factors at 90% RH ranged from 1.08 to 1.17. The hygroscopicity of ISOM is comparable to secondary organic aerosols obtained in smog chamber experiments, but lower than the hygroscopicity of highly soluble organic acids. The hygroscopic behaviour of investigated fulvic and humic acids had similarities to ISOM, but hygroscopic growth factors were slightly smaller and deliquescence was observed at higher RH (75-85% and 85-95% RH for fulvic acid and humic acid, respectively). These differences probably originate from larger average molecular mass and lower solubility of fulvic and humic acids. Inorganic composition data, measured ISOM hygroscopicity, and a presumed value for the hygroscopicity of the small remaining MHOM fraction were used to predict hygroscopic growth of WSM extracts. Good agreement between model prediction and measured water uptake was observed with differences (by volume) ranging from +1% to -18%. While deliquescence properties of WSM extracts were mainly determined by the inorganic salts (42-53 wt % of WSM), the WSOM accounted for a significant fraction of particulate water. At 90% RH, according to model predictions and measurements, about 80-62% of particulate water in the samples are associated with inorganic salts and about 20-38% with WSOM. The relative contributions of both distinguished WSOM fractions, ISOM and MHOM, remains uncertain since MHOM was not available in isolated form, but the results suggest that the less abundant MHOM is also important due to its presumably larger hygroscopicity.

scholarly journals Hygroscopic properties of water-soluble matter and humic-like organics in atmospheric fine aerosol

2003 ◽  
Vol 3 (5) ◽  
pp. 4879-4925 ◽  
Author(s):  
M. Gysel ◽  
E. Weingartner ◽  
S. Nyeki ◽  
D. Paulsen ◽  
U. Baltensperger ◽  
...  
Keyword(s):  
Organic Matter ◽  
Growth Factors ◽  
Humic Acids ◽  
Solid Phase ◽  
Average Molecular Weight ◽  
Water Soluble ◽  
Inorganic Salts ◽  
Hygroscopic Growth ◽  
Hygroscopic Properties ◽  
Fine Aerosol

Abstract. Ambient continental-rural fine aerosol (K-puszta, Hungary, PM1.5) was sampled on quartz fibre filters in winter and summer 2001. Water-soluble matter (WSM) was extracted in MilliQ-water, and, in a second step, solid phase extraction was used to isolate the less hydrophilic fraction (ISOM) of the water-soluble organic matter (WSOM) from inorganic salts and remaining most hydrophilic organic matter (MHOM). This approach allowed to investigate a major fraction of WSOM isolated in pure form from ambient aerosols. Hygroscopic properties of both WSM and ISOM extracts as well as of aquatic reference fulvic and humic acids were investigated using a Hygroscopicity Tandem Differential Mobility Analyser (H-TDMA). ISOM deliquesced between 40–60% and 30–55% relative humidity (RH), in winter and summer, respectively, and hygroscopic growth factors at 90% RH were 1.08–1.11 and 1.16–1.17. The hygroscopicity of ISOM is comparable to secondary organic aerosols obtained in smog chamber experiments, but lower than the hygroscopicity of highly soluble organic acids. Hygroscopic behaviour of investigated fulvic and humic acids had similarities to ISOM, but hygroscopic growth factors were slightly smaller and deliquescence was observed at higher RH (75–85% and 85–95% RH for fulvic acid and humic acid, respectively). These differences probably originate from larger average molecular weight and lower solubility of fulvic and humic acids. Inorganic composition data, measured ISOM hygroscopicity, and a presumable value for the hygroscopicity of the small remaining MHOM fraction were used to predict hygroscopic growth of WSM extracts. Good agreement between model prediction and measured water uptake was observed with differences (by volume) of +1% and −5% in winter, and −18% and −12% in summer. While deliquescence properties of WSM extracts were mainly determined by the inorganic salts (42–53 wt \\% of WSM), the WSOM accounted for a significant fraction of particulate water. At 90% RH, according to model predictions and measurements, about 80% (62%) of particulate water in winter (summer) samples are associated with inorganic salts and about 20% (38%) with WSOM. The relative contributions of both distinguished WSOM fractions, ISOM and MHOM, remains uncertain since MHOM was not available in isolated form, but the results suggest that the less abundant MHOM is also important due to its presumably larger hygroscopicity.

scholarly journals The impacts of firework burning at the Chinese Spring Festival on air quality: insights of tracers, source evolution and aging processes

2015 ◽  
Vol 15 (4) ◽  
pp. 2167-2184 ◽  
Author(s):  
S. F. Kong ◽  
L. Li ◽  
X. X. Li ◽  
Y. Yin ◽  
K. Chen ◽  
...  
Keyword(s):  
Organic Matter ◽  
Air Quality ◽  
Human Health ◽  
Chinese Spring ◽  
Soot Formation ◽  
Water Soluble ◽  
Chemical Compositions ◽  
Spring Festival ◽  
Haze Pollution ◽  
The Impact

Abstract. To understand the impact of firework-burning (FW) particles on air quality and human health during the winter haze period, 39 elements, 10 water-soluble ions and 8 fractions of carbonaceous species in atmospheric PM2.5 in Nanjing were investigated during the 2014 Chinese Spring Festival (SF). Serious regional haze pollution persisted throughout the entire sampling period, with PM2.5 averaging at 113 ± 69 μg m−3 and visibility at 4.8 ± 3.2 km. The holiday effect led to almost all the chemical species decreasing during the SF, except for Al, K, Ba and Sr which were related to FW. The source contributions of coal combustion, vehicle emission and road dust decreased dramatically, whereas FW contributed to about half of the PM2.5 during the SF period. The intensive emission of FW particles on New Year's Eve accounted for 60.1% of the PM2.5. Fireworks also obviously modified the chemical compositions of PM2.5, with 39.3% contributed by increased organic matter, followed by steadily increased loadings of secondary inorganic ions. The aging processes of the FW particles lasted for about 4 days reflected by the variations of Ba, Sr, NH4+, NO3−, SO42− and K+, characterized by heterogeneous reactions of SO2 and NOx on crustal materials directly from FW, the replacement of Cl− by NO3− and SO42−, coating of NO3− and SO42− on soot, formation of secondary organic aerosols and metal-catalyzed formation of NO3− and SO42− at higher relative humidity. During aging, the main contributors to the extinction coefficient shifted from elemental carbon and organic matter to ammonium sulfate. The particles raised higher cancer risk of 1.62 × 10−6 by heavy metals (especially for Cd and As). This study provided detailed composition data and first comprehensive analysis of the aging processes of FW particles during the serious haze pollution period and their potential impact on human health.

scholarly journals Estimation of aerosol water and chemical composition from AERONET Sun–sky radiometer measurements at Cabauw, the Netherlands

2014 ◽  
Vol 14 (12) ◽  
pp. 5969-5987 ◽  
Author(s):  
A. J. van Beelen ◽  
G. J. H. Roelofs ◽  
O. P. Hasekamp ◽  
J. S. Henzing ◽  
T. Röckmann
Keyword(s):  
Refractive Index ◽  
Organic Matter ◽  
Chemical Composition ◽  
Relative Humidity ◽  
Volume Fraction ◽  
Inorganic Salts ◽  
Water Volume ◽  
Aerosol Composition ◽  
Water Volume Fraction ◽  
The Individual

Abstract. Remote sensing of aerosols provides important information on atmospheric aerosol abundance. However, due to the hygroscopic nature of aerosol particles observed aerosol optical properties are influenced by atmospheric humidity, and the measurements do not unambiguously characterize the aerosol dry mass and composition, which complicates the comparison with aerosol models. In this study we derive aerosol water and chemical composition by a modeling approach that combines individual measurements of remotely sensed aerosol properties (e.g., optical thickness, single-scattering albedo, refractive index and size distribution) from an AERONET (Aerosol Robotic Network) Sun–sky radiometer with radiosonde measurements of relative humidity. The model simulates water uptake by aerosols based on the chemical composition (e.g., sulfates, ammonium, nitrate, organic matter and black carbon) and size distribution. A minimization method is used to calculate aerosol composition and concentration, which are then compared to in situ measurements from the Intensive Measurement Campaign At the Cabauw Tower (IMPACT, May 2008, the Netherlands). Computed concentrations show good agreement with campaign-average (i.e., 1–14 May) surface observations (mean bias is 3% for PM10 and 4–25% for the individual compounds). They follow the day-to-day (synoptic) variability in the observations and are in reasonable agreement for daily average concentrations (i.e., mean bias is 5% for PM10 and black carbon, 10% for the inorganic salts and 18% for organic matter; root-mean-squared deviations are 26% for PM10 and 35–45% for the individual compounds). The modeled water volume fraction is highly variable and strongly dependent on composition. During this campaign we find that it is >0.5 at approximately 80% relative humidity (RH) when the aerosol composition is dominated by hygroscopic inorganic salts, and <0.1 when RH is below 40%, especially when the composition is dominated by less hygroscopic compounds such as organic matter. The scattering enhancement factor (f(RH), the ratio of the scattering coefficient at 85% RH and its dry value at 676 nm) during 1–14 May is 2.6 ± 0.5. The uncertainty in AERONET (real) refractive index (0.025–0.05) is the largest source of uncertainty in the modeled aerosol composition and leads to an uncertainty of 0.1–0.25 (50–100%) in aerosol water volume fraction. Our methodology performs relatively well at Cabauw, but a better performance may be expected for regions with higher aerosol loading where the uncertainties in the AERONET inversions are smaller.

scholarly journals The impacts of fireworks burning at Chinese Spring Festival on air quality and human health: insights of tracers, source evolution and aging processes

2014 ◽  
Vol 14 (21) ◽  
pp. 28609-28655 ◽  
Author(s):  
S. Kong ◽  
L. Li ◽  
X. Li ◽  
Y. Yin ◽  
K. Chen ◽  
...  
Keyword(s):  
Organic Matter ◽  
Air Quality ◽  
Human Health ◽  
Chinese Spring ◽  
Soot Formation ◽  
Water Soluble ◽  
Chemical Compositions ◽  
Spring Festival ◽  
Haze Pollution ◽  
The Impact

Abstract. To understand the impact of fireworks burning (FW) particles on air quality and human health during winter haze period, thirty-nine elements, ten water-soluble ions and eight fractions of carbonaceous species in atmospheric PM2.5 at Nanjing were investigated during 2014 Chinese Spring Festival (SF). Serious regional haze pollution persisted throughout the entire sampling period, PM2.5 averaging at 113 ± 69 μg m−3 and visibility at 4.8 ± 3.2 km. The holiday effect led to almost all the chemical species decreasing during the SF, except for Al, K, Ba and Sr which were related to FW. The source contributions of coal combustion, vehicle emission and road dust descreased dramatically, whereas FW contributed to about half of the PM2.5 during SF period. The intensive emission of FW particles at New Year's Eve accounted for 60.1% of the PM2.5. They also significnatly modified the chemical compositions of PM2.5, with 39.3% contributed by increased organic matter, followed by steadly increased loadings of secondary inorganic ions. The aging processes of the FW particles lasted for at least six days reflected by the variation of SO42−, characterized by heterogeneous reactions of SO2 and NOx on crustal materials directly from FW, the replacement of Cl− by NO3− and SO42− coating of NO3− and SO42− on soot, formation of secondary organic aerosols and metal-catalyzed formation of NO3− and SO42− at higher relative humidity. During aging, the main contributors to the extinction coefficient shifted from elemental carbon and organic matter to sulfate ammonium. The particles raised higher cancer risks by heavy metals (especially for Cd and As) as 1.62 ×10−6. This study provided detailed composition data and first comprehensive analysis of the aging processes of FW particles at serious haze pollution period and their potential impact on human health.

scholarly journals A molecular-level approach for characterizing water-insoluble components of ambient organic aerosol particulates using ultrahigh-resolution mass spectrometry

2014 ◽  
Vol 14 (18) ◽  
pp. 10299-10314 ◽  
Author(s):  
A. S. Willoughby ◽  
A. S. Wozniak ◽  
P. G. Hatcher
Keyword(s):  
Organic Matter ◽  
Chemical Composition ◽  
Organic Aerosols ◽  
Chemical Species ◽  
Organic Aerosol ◽  
Water Soluble ◽  
Proton Nuclear Magnetic Resonance ◽  
Aerosol Sample ◽  
Resonance Spectroscopy ◽  
Ion Cyclotron Resonance

Abstract. The chemical composition of organic aerosols in the atmosphere is strongly influenced by human emissions. The effect these have on the environment, human health, and climate change is determined by the molecular nature of these chemical species. The complexity of organic aerosol samples limits the ability to study the chemical composition, and therefore the associated properties and the impacts they have. Many studies have addressed the water-soluble fraction of organic aerosols and have had much success in identifying specific molecular formulas for thousands of compounds present. However, little attention is given to the water-insoluble portion, which can contain most of the fossil material that is emitted through human activity. Here we compare the organic aerosols present in water extracts and organic solvent extracts (pyridine and acetonitrile) of an ambient aerosol sample collected in a rural location that is impacted by natural and anthropogenic emission sources. A semiquantitative method was developed using proton nuclear magnetic resonance spectroscopy to determine that the amount of organic matter extracted by pyridine is comparable to that of water. Electrospray ionization Fourier transform ion cyclotron resonance mass spectra show that pyridine extracts a molecularly unique fraction of organic matter compared to water or acetonitrile, which extract chemically similar organic matter components. The molecular formulas unique to pyridine were less polar, more aliphatic, and reveal formulas containing sulfur to be an important component of insoluble aerosol organic matter.

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