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The presence of organic compounds on the particulate matter (PM) or aerosols can arise from the condensation of gaseous organic compounds on the existing aerosols, or from organic precursors to form secondary organic aerosols (SOA) through photochemistry. The objective of this study is to characterize organic constituents on aerosols relevant to their emission sources and the key compounds revealing the evolution of aerosols with the use of a novel analytical technique. A time-of-flight mass spectrometry (TOFMS) coupled with comprehensive two-dimensional gas chromatography (GC×GC) was developed using a flow type of modulator instead of a thermal type as a prelude to field applications without the need for cryogen. The methodology of GC×GC-TOFMS is discussed in this study in detail. Since the coarse PM (PM 10-2.5 ) may exhibit with a relatively high OC content compared to PM 2.5 , the GC×GC results have been obtained by analyzing PM 10 samples collected in parallel with OC/EC analysis of PM 2.5 samples at the Lulin Atmospheric Background Station (LABS, 23.47°N, 120.87°E, 2862 m ASL) as the high-mountain background site in East Asia. We found that the organic analytes were in a majority in the range of 12-30 carbon numbers falling in the category of semi-volatile organic compounds (SVOCs) with 43 compounds of alcohol, aldehyde, ketone, and ester varieties if excluding alkanes. Intriguingly, trace amounts of plasticizers and phosphorus flame retardants such as phthalates (PAEs) and triphenyl phosphate (TPP) were also found, likely originating from regions involved in open burning of household solid waste in Southeast Asia or e-waste recycling in southern China and along the long-range transport route. Compounds such as these are unique to the specific sources, demonstrating the wide spread of these hazardous compounds in the environment., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests:Jia-Lin Wang reports financial support was provided by Ministry of Science and Technology, Taiwan. Chang-Feng Ou-Yang reports statistical analysis was provided by NOAA Air Resources Laboratory. If there are other authors, they declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

The first excited state of molecular oxygen is singlet-state oxygen ( 1 O 2 ), formed by indirect photochemistry of chromophoric organic matter. To determine whether 1 O 2 can be a competitive atmospheric oxidant, we must first quantify its production in organic aerosols (OA). Here, we report the spatiotemporal distribution of 1 O 2 over a 1-year dataset of PM 10 extracts at two locations in Switzerland, representing a rural and suburban site. Using a chemical probe technique, we measured 1 O 2 steady-state concentrations with a seasonality over an order of magnitude peaking in wintertime at 4.59 ± 0.01 × 10 -13 M and with a quantum yield of up to 2%. Next, we identified biomass burning and anthropogenic secondary OA (SOA) as the drivers for 1 O 2 formation in the PM 10 aqueous extracts using source apportionment data. Importantly, the quantity, the amount of brown carbon present in PM 10 , and the quality, the chemical composition of the brown carbon present, influence the concentration of 1 O 2 sensitized in each extract. Anthropogenic SOA in the extracts were 4 times more efficient in sensitizing 1 O 2 than primary biomass burning aerosols. Last, we developed an empirical fit to estimate 1 O 2 concentrations based on PM 10 components, unlocking the ability to estimate 1 O 2 from existing source apportionment data. Overall, 1 O 2 is likely a competitive photo-oxidant in PM 10 since 1 O 2 is sensitized by ubiquitous biomass burning OA and anthropogenic SOA.

The formation processes of particulate amines are closely related to their emission sources and secondary reactions, which can be revealed through the investigation of their real-time mixing states in individual particles. The mixing states of methylamine (MA)-, trimethylamine (TMA)-, and diethylamine (DEA)-containing particles were studied using a high-performance single particle aerosol mass spectrometer (HP-SPAMS) in Guangzhou, China, in January 2020. The sharp increase in TMA particles was found to be closely associated with the increase in the ambient relative humidity (RH), while the MA- and DEA-containing particles were not similarly influenced by the changes in the RH. The prominent enrichment of secondary oxygenated organics in DEA particles during the daytime was consistent with the active period of photochemistry, implying that the sharp decrease in DEA particles in the afternoon was likely due to photo-oxidation of the DEA. The number fraction (N f ) of DEA particles, the N f of the nitrate in the DEA particles, and the abundance of nitrate increased as the NO x content all increased during the nighttime, suggesting that the formation of DEA·HNO 3 salt was the dominant pathway of particulate DEA production. These results are consistent with our previous measurements in Nanjing, confirming the general and distinct mixing states of TMA and DEA particles. Positive matrix factorization analysis revealed that the total fraction of the more oxidized organics factor and the less oxidized organics factor were much higher in the DEA particles (26.9 %) than in the TMA particles (9 %), confirming the significant enrichment of oxygenated species in the DEA particles. The different mixing states of the amines revealed the unique response of each type of amine to the same atmospheric environment, and the prominent mixing states of the DEA with secondary oxygenated species suggest the potential role of DEA in tracing the evolution of organic aerosols., Competing Interests: Declaration of competing interest The authors declare that they have no conflict of interest., (Copyright © 2022 Elsevier B.V. All rights reserved.)

Organic aerosols (OA) play significant roles in several atmospheric processes and adversely impact human health. This study examines the key structural units present in water- and methanol-soluble organic carbon (WSOC, MSOC) fraction of OA from emission sources (traffic and biomass cooking) and an urban background location in India. Proton nuclear magnetic resonance ( 1 H NMR) spectroscopy was employed to assess the distribution of non-exchangeable proton structural groups of the OAs. Organic carbon, elemental carbon, black carbon, and water-soluble organic carbon (WSOC) analyses were also conducted. The 1 H NMR analysis corroborated that the WSOC and MSOC fractions hold similar 1 H structural groups; however, they differ in their relative distribution and absolute concentrations across the ambient locations and source emissions. The relative contribution of the proton structural groups to OA was in the order C-H > H-C-C=> H-C-O > Ar-H. The aliphatic concentration was lower in the morning tunnel entry aerosols when compared to other tunnel aerosols, whereas the unsaturated structures (H-C-C= ) were present in all the tunnel aerosols within a range of 47.2-62.3 μmol/m 3 . The aromatic groups were the maximum in the firewood aerosols, about 1.4 and 3.7 times higher than the crop residue and the mixed fuel aerosols, respectively. The total functional groups, i.e., the sum of all the observed groups, significantly correlated with C-H (r = 0.96) and WSOC (r = 0.7), suggesting the higher contribution of aliphatic groups in the WSOC fraction. WSOC examined in this study fits well in the established 1 H NMR source identification fingerprints of urban aerosols. However, biomass cooking aerosols do not fit the established biomass burning organic aerosols (BBOAs) boundaries, exhibiting a smaller relative contribution of carbon-oxygen double bonds and a less oxidised character than open-field burning. Our results provide essential insights into the nature of urban atmospheric, near-traffic and biomass cooking OAs in India., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

Lipids are important biogenic markers to indicate the sources and chemical process of aerosol particles in the atmosphere. To better understand the influences of biogenic and anthropogenic sources on forest aerosols, total suspended particles (TSP) were collected at Mt. Changbai, Shennongjia, and Xishuangbanna that are located at different climatic zones in northeastern, central and southwestern China. n-Alkanes, fatty acids and n-alcohols were detected in the forest aerosols based on gas chromatography-mass spectrometry. The total concentrations of aliphatic compounds ranged from 15.3 ng m -3 to 566 ng m -3 , and fatty acids were the most abundant (44-95%) followed by n-alkanes and n-alcohols. Low molecular weight- (LFAs) and unsaturated fatty acids (UnFAs) showed diurnal variation with higher concentrations during the nighttime in summer, indicating the potential impact from microbial activities on forest aerosols. The differences of oleic acid (C 18:1 ) and linoleic acid (C 18:2 ) concentrations between daytime and nighttime increased at lower latitude, indicating more intense photochemical degradation occurred at lower latitude regions. High levels of n-alkanes during daytime in summer with higher values of carbon preference indexes, combining the strong odd carbon number predominance with a maximum at C 27 or C 29 , implied the high contributions of biogenic sources, e.g., higher plant waxes. In contrast, higher concentrations of low molecular weight n-alkanes were detected in winter forest aerosols. Levoglucosan showed a positive correlation (R 2  > 0.57) with high- and low molecular weight aliphatic compounds in Mt. Changbai, but such a correlation was not observed in Shennongjia and Xishuangbanna. These results suggest the significant influence of biomass burning in Mt. Changbai, and fossil fuel combustion might be another important anthropogenic source of forest aerosols. This study adds useful information to the current understanding of forest organic aerosols at different geographical locations in China., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

This study was designed to investigate the seasonal characteristics and apportion the sources of organic carbon during non-haze days (<75 μg m -3 ) and haze (≥75 μg m -3 ) events at Pinggu, a rural Beijing site. Time-resolved concentrations of carbonaceous aerosols and organic molecular tracers were measured during the winter of 2016 and summer 2017, and a Chemical Mass Balance (CMB) model was applied to estimate the average source contributions. The concentration of OC in winter is comparable with previous studies, but relatively low during the summer. The CMB model apportioned seven separate primary sources, which explained on average 73.8% on haze days and 81.2% on non-haze days of the organic carbon in winter, including vegetative detritus, biomass burning, gasoline vehicles, diesel vehicles, industrial coal combustion, residential coal combustion and cooking. A slightly lower percentage of OC was apportioned in the summer campaign with 64.5% and 78.7% accounted for. The other unapportioned OC is considered to consist of secondary organic carbon (SOC). During haze episodes in winter, coal combustion and SOC were the dominant sources of organic carbon with 23.3% and 26.2%, respectively, followed by biomass burning emissions (20%), whereas in summer, industrial coal combustion and SOC were important contributors. Diurnal contribution cycles for coal combustion and biomass burning OC showed a peak at 6-9 pm, suggesting domestic heating and cooking were the main sources of organic aerosols in this rural area. Backward trajectory analysis showed that high OC concentrations were measured when the air mass was from the south, suggesting that the organic aerosols in Pinggu were affected by both local emissions and regional transport from central Beijing and Hebei province during haze episodes. The source apportionment by CMB is compared with the results of a Positive Matrix Factorization (PMF) analysis of ACSM data for non-refractory PM 1 , showing generally good agreement., Competing Interests: Declaration of competing interest The authors have no actual or potential conflict of interest including any financial, personal or other relationships with other people or organizations within three years of beginning the submitted work that could inappropriately influence, or be perceived to influence, their work., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Particulate n-alkanes are major constituents of organic aerosols (OA). Being primary in origin, chemically stable and thus long-lived, n-alkanes retains source signatures and along with diagnostic parameters have extensively been used to identify source(s) of OA. Systematic, yearlong study was carried out in the Dhauladhar region of North-Western Himalaya (NWH) to investigate dynamics in the composition and concentration of aerosol-associated n-alkanes. PM 10 samples were collected for 24 h, once every week, at an urban mid-altitude location (Dharamshala) and a rural low-altitude site (Pohara). Particulate bound n-alkanes were identified and quantified using thermal desorption gas chromatography mass spectrometry (TD-GCMS). Annual mean concentrations of total n-alkanes (TNA) were 211 ± 99 ng m -3 and 223 ± 83 ng m -3 , while mass fractions of TNA in PM 10 were 4410 ± 1759 ppm and 3622 ± 1243 ppm at Dharamshala and Pohara, respectively. At both sites, a slight dominance of odd carbon-numbered n-alkanes was noticed. The TNA concentration and associated diagnostic parameters indicated unique source profiles at rural and urban locations. Significant seasonal variations were attributed to the contrasting land-use settings and meteorological variations. Influence of petrogenic contributions at urban location and predominance of biogenic contributions at rural location were observed in spring and autumn seasons. Preliminary insights on sources of organic aerosols are presented here. The diagnostic parameters allowed apportionment of biogenic and petrogenic sources. Biogenic emissions from agricultural practices viz. harvesting and threshing were predominant in the rural settings, while tourism-led anthropogenic contributions significantly add to petrogenic contributions in urban environment of the NWH region.

Experimental results of the second series of experiments on the penetration of monodisperse polymeric particles, inhaled at low dose by mice, to different organs using direct way of particle registration, based on the ultra-sensitive accelerator mass spectrometer (AMS), are presented. Polystyrene (PS) beads, composed of radiocarbon-labeled styrene, were produced for testing them as model organic aerosols. Mice inhaled 14 C-PS aerosol of 3·10 5 ultrafine particles per 1 cm 3 for 30 minutes every day during 5 days. Long-term investigation showed that PS ultrafine particles have been effectively accumulated in lungs with the maximum content in the fifth day of postexposure, and have also appeared in liver on the fifth day of exposure and in the brain on the 30th day of experiments. No particles have been detected in kidneys, spleen, and excrements. Thirty-five millions of particles remained in the lungs after half a year of postexposure showing extremely slow removal of such particles from the organ., (© 2019 John Wiley & Sons, Ltd.)

The cell-free dithiothreitol (DTT) assay is widely used and the DTT consumption rate is interpreted to assess the oxidative potential (OP). Most researchers use an experimental procedure developed by Cho et al. (2005) while some adopt a procedure by Li et al. (2009). The key difference between the two procedures is the initial DTT concentration, 100 μM used in the former and 20 μM in the latter, raising an unaddressed issue of comparability. We examine in this work this issue using metal-free humic-like substance (HULIS) samples isolated from ambient aerosol and two metals (i.e. copper and manganese). We found that higher initial DTT concentrations led to higher DTT consumption rates for both HULIS and metals. For HULIS, the increase in DTT consumption rate was proportional to the initial DTT concentration (i.e., roughly by 5-fold), allowing correction of the concentration effect and direct comparison of results from the two protocols. However, the proportionality did not hold for the metals or metal-organic mixtures. The increase was much lower than the proportionality of 5 and metal concentration-dependent, specifically, 1.2-1.3 for Cu and from negligible to 2.0 for Mn. For six water extracts of ambient aerosol samples, in which HULIS and metals co-exist, the proportionality ranged from 1.3 to 2.2. This deviation from a linear dependence on initial DTT concentration, plausibly due to metal-DTT binding, impedes assessing and comparing OP of metals and metal-organic mixtures using different implementations of the DTT assay. Considering the different antioxidants concentrations in real human lung fluid, this work raises caution about using the DTT assay to assess metal-containing mixtures, such as ambient aerosol samples., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Seventy three individual organic compounds in the atmospheric particulate matter with an aerodynamic diameter of less than or equal to a nominal 10 μm (PM10) over Seoul were identified and quantified from April 2010 to April 2011 using gas chromatography/mass spectrometry (GC/MS). These organic compounds were classified into five groups, n-alkanes, polycyclic aromatic hydrocarbons (PAHs), mono-carboxylic acids, di-carboxylic acids (DCAs), and sugars based on their chemical structures and properties. The organic compounds showed higher seasonal average concentrations from fall to winter than from spring to summer due to source strength, except some organic compounds among mono-carboxylic acids, DCAs, sugars such as undecanoic acid, methylmalonic acid, and fructose. Through qualitative data analysis using seasonal concentration variations and relevant diagnostic parameters, it was found that (1) anthropogenic sources such as combustion of fossil fuel and biomass burning attributed more to the formation of the organic aerosols than biogenic sources, and (2) the ambient level of n-alkanes, PAHs, and some compounds of DCAs and sugars was elevated in winter due to the increased primary emissions and larger transport from outside of the organic compounds in winter., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

Brown carbon is a type of strong light-absorbing carbonaceous aerosol associated with radiative forcing. Nevertheless, the difficulty in correlating the chemical composition of brown carbon with its light absorption properties impairs the proper elucidation of its role in radiative forcing. Here, we have used a time-dependent density functional theory (TD-DFT)-based procedure to revisit the "real-world" absorption spectra of polycyclic aromatic hydrocarbons (PAHs) over the city of Porto, in Portugal, while correcting the spectra for their quantity in PM10 particulate matter. Our aim is to, by comparing these new results with those obtained previously regarding PM2.5 data, evaluate the role of different groupings of particulate matter in the light absorption of brown carbon. The results indicate that irrespective of the absorption spectra corresponding to their PM10 or PM2.5 data, the studied PAHs should contribute to radiative forcing by light absorption at UVA and (sub)visible wavelengths. However, the identity of the individual PAH species that contribute the most for the considered wavelengths can be quite different. Thus, different groupings of particulate matter appear to provide distinct contributions to light absorption and radiative forcing over the same location, even when considering the same class of molecular compounds. [ABSTRACT FROM AUTHOR]

Secondary particulate matter exerts adverse effects on air quality and human health. The production or reaction rate of secondary aerosols in polluted environments remains uncertain and is complicated by diverse emissions and meteorological conditions. By concurrently measuring the mass spectra of compounds in both particulate (using an aerosol mass spectrometer) and gas phases (using proton‐transfer‐reaction mass spectrometry) in suburban Beijing, we linked the secondary organic aerosol (OA) and volatile organic compounds (VOCs) to photochemical age (tage) and obtained their reaction or production rates. Factorization analysis of the mass spectra of OA and the 108 VOC species resolved three oxygenated OAs (OOA) and three secondary VOC factors at different oxidation levels. Primary organic aerosols and VOCs from traffic sources were determined to be important sources for secondary aerosol formation. At high pollution levels under the conditions of weaker solar radiation and higher relative humidity, moderately oxygenated OA (O/C = 0.61) and secondary inorganics were coproduced in combination with rapid consumption of all VOCs. At lower pollution levels, the intense solar radiation caused substantial and rapid production of OOA (O/C = 0.81) and intermediate VOCs (both in a high oxidation state) at a rate of 15.0% h−1 and 14.0% h−1, respectively. These results highlight the feedback effects between radiation and moisture in terms of altering the formation mechanism of secondary aerosols. In particular, highly oxygenated secondary airborne products under strong radiation should be considered in regard to their environmental impact. Plain Language Summary: In this study, the compositions of submicron aerosols and volatile organic compounds (VOCs) in suburban Beijing were concurrently characterized for their detailed mass spectra, and based on these spectra, the primary and secondary sources were apportioned to investigate their evolution and conversion. Our results demonstrate the contrasting phenomena of chemical evolution under the influence of solar radiation and moisture. Photo‐oxidation was observed to rapidly produce organic aerosol (OA) and secondary VOCs in a considerably high oxidation state, while higher relative humidity induced overall moderately oxygenated OA and secondary inorganic aerosols but resulted in more rapid consumption of all VOCs. Key Points: Mass spectra of organic compounds in both aerosols and gases were concurrently characterized in suburban BeijingThe production and consumption rates of organic aerosols (OAs) and gases were obtained under high radiation or moist conditionsHighly oxidized OAs and intermediate volatile gases are rapidly produced through photo oxidation under strong solar radiation [ABSTRACT FROM AUTHOR]

The current understanding of water-soluble organic aerosol (OA) composition, sources, transformations, and effects is still limited to outdoor scenarios. However, the OA is also an important component of particulate matter indoors, whose complexity impairs a full structural and molecular identification. The current limited knowledge on indoor OA, and particularly on its water-soluble organic matter (WSOM) fraction is the basis of this feature paper. Inspired by studies on outdoor OA, this paper discusses and prioritizes issues related to indoor water-soluble OA and their effects on human health, providing a basis for future research in the field. The following three main topics are addressed: (1) what is known about the origin, mass contribution, and health effects of WSOM in outdoor air particles; (2) the current state-of-the-art on the WSOM in indoor air particles, the main challenges and opportunities for its chemical characterization and cytotoxicity evaluation; and (3) why the aerosol WSOM should be considered in future indoor air quality studies. While challenging, studies on the WSOM fraction in air particles are highly necessary to fully understand its origin, fate, toxicity, and long-term risks indoors. [ABSTRACT FROM AUTHOR]

As part of the ChArMEx project (Chemistry-Aerosol Mediterranean Experiment, http://charmex.lsce.ipsl.fr), one year of continuous filter sampling was conducted from August 2012 to August 2013 at a rural (coastal) site in Algeria aiming to better document fine aerosol seasonal variability and chemical composition in the Southern part of the Mediterranean. Over 350 filters have been collected, weighted, and analyzed for the main ions and organic and elemental carbon. The obtained mass concentrations varied between 2.5 and 50.6 μg/m3 for PM2.5. The annual modulations of PM2.5 showed higher concentrations in the end summer 2012 and the early summer 2013 (28.50 μg/m3 in August 2012, 20.23 μg/m3 in September 2012, 20.19 μg/m3 in July 2013, and 17.88 μg/m3in August 2013). The particulate organic matter (POM) presented the greatest contribution (50%), followed by the secondary inorganic aerosols (SIA, 27%). The average organic carbon OC concentrations ranged from 1.66 to 6.05 μgC/m3. The average elemental carbon EC concentrations ranged from 0.92 to 3.49 μgC/m3 and contributed 7% of the PM2.5 mass to Bou-Ismail. The average value of the OC /EC ratio was close to 5.1 in Bou-Ismail, and was close to that found in Finokalia 4 (Greece 2004, 2006) but was lower than that of Montseny 11 (Spain 2002–2007) Western Mediterranean Basin (WMB). The concentrations of water-soluble organic carbon WSOC in the PM2.5 ranging from 0.66 to 3.70 μg/m3 recorded the minimum level in March 2013, and the maximum level in August 2012, with an average of 2.02 μg/m3. [ABSTRACT FROM AUTHOR]

Organic aerosols (OA) are universally regarded as an important component of the atmosphere that have far-ranging impacts on climate forcing and human health. Many of these impacts are related to OA molecular characteristics. Despite the acknowledged importance, current uncertainties related to the source apportionment of molecular properties and environmental impacts make it difficult to confidently predict the net impacts of OA. Here we evaluate the specific molecular compounds as well as bulk structural properties of total suspended particulates in ambient OA collected from key emission sources (marine, biomass burning, and urban) using ultrahigh resolution mass spectrometry (UHR-MS) and proton nuclear magnetic resonance spectroscopy (¹H NMR). UHR-MS and ¹H NMR show that OA within each source is structurally diverse, and the molecular characteristics are described in detail. Principal component analysis (PCA) revealed that (1) aromatic nitrogen species are distinguishing components for these biomass burning aerosols; (2) these urban aerosols are distinguished by having formulas with high O/C ratios and lesser aromatic and condensed aromatic formulas; and (3) these marine aerosols are distinguished by lipid-like compounds of likely marine biological origin. This study provides a unique qualitative approach for enhancing the chemical characterization of OA necessary for molecular source apportionment. [ABSTRACT FROM AUTHOR]

This study evaluated one-year performance of the community multiscale air quality (CMAQ) model v5.0.1 and the comprehensive air quality model with extensions (CAMx) v6.00. One-year air quality simulations were conducted with common input meteorology, emission and boundary concentration data in the Kinki region of Japan. CAMx-simulated ground-level concentrations were generally higher by 10%-20% than CMAQ-simulated values. Despite the systematical difference, the overall one-year performances of the two models for simulating ground-level concentrations were similar to each other according to comparisons with observed data. The two models approximately reproduced mass concentrations of fine particulate matter (PM2.5), but shared common difficulties in simulating PM2.5 components. The models substantially underestimated organic aerosol, which was compensated by overestimate of dust transported from the Asian continent. In addition, the systematical difference between the CMAQ- and CAMx-simulated ground-level PM2.5 concentrations was mainly attributed to the treatment of the vertical diffusivity and the below-cloud scavenging. [ABSTRACT FROM AUTHOR]

A measurement campaign was conducted at a semi-urban site located in the suburbs of the city of Beirut (Lebanon) during summertime (2–18 July 2011). The molecular composition of organic PM2.5 was investigated following a chemical derivatization gas chromatography/mass spectrometry technique. Accordingly, several classes of compounds represented by 18 individual organic tracers were determined. These tracers include levoglucosan, a tracer for biomass combustion, dicarboxylic acids, and several tracers for the photo-oxidation of isoprene, α-pinene and β-caryophyllene. The sum of the mean concentrations of the isoprene oxidation products was 4ng/m3, that of α-pinene was 124ng/m3 and that of β-caryophyllene was 11ng/m3. For other tracers of organic aerosols, the highest concentrations were obtained for carboxylic acids with an average value of 939ng/m3. An average value of 49ng/m3 was obtained for levoglucosan. Organic and elemental carbon concentrations were measured by a thermo-optical analyzer. Average values were 5.6 and 1.8μg/m3, respectively. A reconstruction of organic PM2.5 composition suggests that cooking, fossil-fuel combustion, biomass burning, sesquiterpenes, monoterpenes, and isoprene contribute on average about 27±13, 16±7, 5±3, 26±5, 26±13 and <1±0.3% of PM2.5 organic carbon, respectively. [ABSTRACT FROM AUTHOR]

Abstract: Long-term exposure to vehicle emissions has been associated with detrimental health effects. Children are amongst the most susceptible group and schools represent an environment where they can experience significant exposure to vehicle emissions. However, there are limited studies on children's exposure to vehicle emissions in schools. The aim of this study was to quantify the concentration of organic aerosol (OA) and in particular, vehicle emissions that children are exposed to during school hours. Therefore an Aerodyne compact time-of-flight aerosol mass spectrometer (TOF-AMS) was deployed at five urban schools in Brisbane, Australia. TOF-AMS enabled the chemical composition of the non-refractory (NR-PM1) to be analysed with a high temporal resolution to assess the concentration of vehicle emissions and other OA components during school hours. The organic fraction at each school comprised the majority of NR-PM1. Primary emissions were found to dominate the OA at only one school which had an O:C ratio of 0.17, due to fuel powered gardening equipment used near the TOF-AMS. A significant source of the OA at two of the schools was aged vehicle emissions from nearby highways. More oxidised OA was observed at the remaining two schools, which also recorded strong biomass burning influences. In general, the diurnal cycle of the total OA concentration varied between schools and was found to be at a minimum during school hours. The major organic component that school children were exposed to during school hours was secondary OA at all schools. Peak exposure of school children to vehicle emissions occurred during school drop-off and pick-up times. Unless a school is located near major roads, children are exposed predominately to regional secondary OA as opposed to local emissions during school hours in urban environments. [Copyright &y& Elsevier]

Abstract: Sugars are important water-soluble organic constituents of atmospheric particulate matter (PM). In order to better understand the sources and seasonal variations of sugars in aerosols, primary saccharides (fructose, glucose, sucrose, and trehalose) and sugar alcohols (arabitol and mannitol), together with levoglucosan, have been studied in ambient aerosols at Gosan, Jeju Island in the western North Pacific, the downwind region of the Asian outflow, using gas chromatography–mass spectrometry. The results showed that the sugar composition varied seasonally with a total concentration range of 6.8–1760 ng m−3 (mean 246 ng m−3). The total identified sugars had the highest concentration in April, the spring bloom season at Jeju Island, when sucrose contributed up to 80% of the total sugars. The dominance of sucrose was also detected in pollen samples, suggesting that pollen can contribute significantly to sucrose in aerosols during the spring bloom. The seasonal variation of trehalose is consistent with those of non-sea-salt Ca2+ and δ13C of total carbon with elevated levels during the Asian dust storm events. This study indicates that sugar compounds in atmospheric PM over East Asia can be derived from biomass burning, Asian dust, and primary biological aerosols such as fungal spores and pollen. Furthermore, this study supports the idea that sucrose could be used as a tracer for airborne pollen grains, and trehalose as a tracer for Asian dust outflow. [Copyright &y& Elsevier]

To better understand the current physical and chemical properties of East Asian aerosols, an intensive observation of atmospheric particles was conducted at Gosan site, Jeju Island, South Korea during 2005 spring. Total suspended particle (TSP) samples were collected using pre-combusted quartz filters and a high-volume air sampler with the time intervals ranging from 3h to 48h. The kinds and amount of various organic compounds were measured in the samples using gas chromatography–mass spectrometry. Among the 99 target compounds detected, saccharides (average, 130±14ngm−3), fatty acids (73±7ngm−3), alcohols (41±4ngm−3), n-alkanes (32±3ngm−3), and phthalates (21±2ngm−3) were found to be major compound classes with polyols/polyacids, lignin and resin products, PAHs, sterols and aromatic acids being minor. Compared to the previous results reported for 2001 late spring samples, no significant changes were found in the levels of their concentrations and compositions for 4 years, although the economy in East Asia, especially in China, has sharply expanded from 2001 to 2005. During the campaign at Gosan site, we encountered two distinct dust storm episodes with high TSP concentrations. The first dust event occurred on March 28, which was characterized by a predominance of secondary organic aerosols. The second event that occurred on the next day (March 29) was found to be characterized by primary organic aerosols associated with forest fires in Siberia/northeastern China. A significant variation in the molecular compositions, which was found within a day, suggests that the compositions of East Asian aerosols are heterogeneous due to multi-contributions from different source regions together with different pathways of long-range atmospheric transport of particles. [Copyright &y& Elsevier]

Real-time analyzers of selected chemical components (sulfate, nitrate, Black Carbon) and integrative aerosol parameters (particulate matter and light scattering coefficient) were implemented for a 2-week campaign (November–December 2005) in a suburban area of Clermont-Ferrand (France) in order to document fast changes in the chemical composition of submicron aerosols. Measurements of particulate organic matter (POM) were not available in the field but were indirectly estimated from time-resolved (3-min) reconstruction of the light scattering coefficient. This methodology offered the opportunity to investigate almost real-time and artifact-free POM concentrations even at low concentrations (typically below 0.1μgm−3). The overall uncertainties associated with this POM calculation were of the order of 20%, which are comparable to those commonly referred in literature for POM calculation or measurements. A chemical mass balance (CMB) of PM1 was performed using the derived POM concentrations and showed a very good correlation (slope=0.93; r 2=0.91, N=663) with real-time PM1 measurements obtained from R&P TEOM-FDMS, demonstrating the consistency of our approach. Important diurnal variations were observed in POM concentrations, with a dominant contribution of POM from fossil fuel origin during daytime and a dominant contribution of POM from residential wood burning at night. POM was calculated to contribute as much as 70% of PM1 during our study, pointing out the major role of carbonaceous aerosols at this period of the year at our residential area. [Copyright &y& Elsevier]

Organic materials make up a significant fraction of ambient particulate mass. It is important to quantify their contributions to the total aerosol mass for the identification of aerosol sources and subsequently formulating effective control measures. The organic carbon (OC) mass can be determined by an aerosol carbon analyzer; however, there is no direct method for the determination of the mass of organic compounds, which also contain N, H, and O atoms in addition to C. The often-adopted approach is to estimate the organic mass (OM) from OC multiplying by a factor. However, this OC-to-OM multiplier was rarely measured for a lack of appropriate methods for OM. We report here a top-down approach to determine OM by coupling thermal gravimetric and chemical analyses. OM is taken to be the mass difference of a filter before and after heating at 550°C in air for 4h minus mass losses due to elemental carbon (EC), volatile inorganic compounds (e.g., NH4NO3), and loss of aerosol-associated water that arise from the heating treatment. The losses of EC and inorganic compounds are determined through chemical analysis of the filter before and after the heating treatment. We analyzed 37 ambient aerosol samples collected in Hong Kong during the winter of 2003, spring of 2004, and summer of 2005. A value of 2.1±0.3 was found to be the appropriate factor to convert OC to OM in these Hong Kong aerosol samples. If the dominant air mass is classified into two categories, then an OM-to-OC ratio of 2.2 was applicable to aerosols dominated by continent-originated air mass, and 1.9 was applicable to aerosols dominated by marine air mass. [Copyright &y& Elsevier]

Abstract: A practical analytical methodology based on coupling microwave-assisted extraction–stir bar sorptive extraction–thermal desorption-gas chromatography–mass spectrometry (MAE–SBSE–TD–GC–MS) was developed and validated for the characterization of several SVOC in atmospheric particulate matter (PM). The high enrichment capacity of SBSE makes it a powerful tool for improving detection limits and MAE has been useful for overcoming the long extraction times and high volumes of extraction solvent used in traditional methodologies. Relative to Soxhlet extraction followed by GC–MS analysis (EPA Methods 3540 and 8270C), the MAE–SBSE–TD–GC–MS methodology resulted with approximately 104 times better detection limits. Detection limits ranged from 0.3 to 8.3pgm−3 for pp′-DDD and decachlorobyphenyl, respectively in PM2.5, 24m3 air sample. The performance of the optimized methodology gave good precisions, with R.S.D. less than 30% for most of the standards, and linearity within the range tested of 0.1–15μgL−1. Analysis of real PM samples resulted in the identification of compounds in the ngL−1 range. [Copyright &y& Elsevier]

The Interagency Monitoring of Protected Visual Environments (IMPROVE) protocols for reconstructing the ambient light extinction coefficient (b ext) from measured aerosol species are the basis for evaluating compliance under the Regional Haze Rule. Aerosol mass composition and optical properties have been measured as part of the IMPROVE program since 1988, providing a long-term data set of aerosol properties at 38 sites around the US. This data set is used to evaluate assumptions made in calculating reconstructed mass and b ext by applying statistical analysis techniques. In particular, the molecular weight to carbon weight ratio used to compute particulate organic matter is investigated. An annual average value of 1. 7±0. 2 for the IMPROVE sites, compared to the value of 1. 4 currently assumed in the IMPROVE algorithm, is derived. Regression analysis also indicates that fine soil mass concentrations are underestimated by roughly 20% on average. Finally, aerosol mass scattering and extinction efficiencies assumed in the IMPROVE reconstructed b ext protocol are examined. Fine mode (D p<2. 5μm) mass scattering efficiencies have a functional dependence on mass concentrations at many sites, and use of a mass-concentration-dependent adjustment factor to refine the assumed efficiencies provides for closer agreement between measured and reconstructed b ext. [Copyright &y& Elsevier]

Abstract: The Pacific 2001 Air Quality Study was undertaken to characterize the physical and chemical properties of particulate matter in the Lower Fraser Valley (LFV) airshed of British Columbia. Aerosol transport in the LFV was observed to occur through several regional scale mechanisms, including seabreeze–landbreeze flows, upslope–downslope flows and north–south valley flows. Enhanced aerosol concentrations were observed in the eastern portion of the LFV, the north–south tributary valleys and the Gulf/San Juan islands convergence zone. Particle composition was found to vary according to proximity to emission sources relative to surface flows. Approximately half of the particle mass was comprised of organic carbon, with the rest being inorganic species. Sodium nitrate was an important component of the coarse particle fraction, while ammonium sulphate was concentrated in the fine fraction. A broad suite of organic substances were detected, and both anthropogenic and biogenic sources were found to contribute to secondary organic aerosol formation. Particle formation and growth was observed to occur via nucleation, condensation and coagulation. In general, the western part of the LFV airshed was dominated by combustion-related compounds, sea salt chemistry and organics (both anthropogenic and biogenic), while the eastern part of the airshed was dominated by NH3 chemistry and biogenic organics. The extent of processing of air masses was found to increase in a west to east direction, although the occasional accumulation of photochemically aged pollutants in the Gulf/San Juan islands convergence zone was observed to reverse this gradient. NH3 was found not to be a limiting species in the formation of fine mode inorganic aerosols, suggesting that NH3 emission reductions would have to be substantial in order to confer a significant improvement in PM and visibility. This coupled with the non-linear relationships between NO x , VOC and secondary particulates, suggests that PM and visibility improvement in the LFV would most likely require concurrent reductions in NH3, SO x , NO x and VOC emissions. [Copyright &y& Elsevier]

Marine atmospheric aerosols play important roles in the global radiation balance and climate change. Hence, measuring physiochemical aerosol properties is essential to better understand their formation, aging processes, and source origins. However, high temporal resolution measurements of submicron particles are currently scarce in the northern South China Sea (SCS). In this study, we conducted a ship-based cruise campaign with a scanning mobility particle sizer and an online time of flight aerosol chemical speciation monitor to measure the particle number size distribution (PNSD) and the chemical composition of submicron particles over the northern SCS during summer 2018. The mean concentration of non-refractory submicron particulate matter (NR-PM 1) was generally 9.11 ± 4.86 μg m−3; sulfate was the most abundant component, followed by organics, ammonium, nitrate, and chloride. Positive matrix factorization (PMF) analysis was applied to the PNSD (size PMF) and organic aerosols (OA PMF) and further investigated the source apportionment of the submicron particles. The size PMF identified four factors, including ship exhaust, ship influencing marine primary, continent affected marine secondary, and mixed accumulation aerosols. The most abundant particles in the number concentration were associated with ship emissions, which accounted for approximately 44 %. The submicron organic aerosols were highly oxidized and composed of low-volatility oxygenated OA (LV-OOA, 68 %), semi-volatile OOA (SV-OOA, 21 %), and hydrocarbon-like OA (HOA, 11 %). The backward trajectory of air masses showed that the northern SCS was most frequently (64.7 %) influenced by air masses from the Indo-Chinese Peninsula (ICP) during the campaign, implying that pollutants from ICP have a significant impact on the atmosphere of the northern SCS during summer. Thus, in situ ship-based cruise measurements can provide valuable data on the physiochemical characteristics of marine atmospheric aerosols to better understand their source origins. [Display omitted] • Ship emissions contribute significantly to aerosol numbers in South China Sea (SCS). • Pollutants from Indo-Chinese Peninsula affect most frequently SCS during summer. • Submicron particle concentration in SCS resembles Mediterranean, but exceeds others. • Organic aerosol in SCS is highly oxidized in comparison to North Pacific and Arctic. [ABSTRACT FROM AUTHOR]

Understanding the drivers for high ozone (O 3) and atmospheric particulate matter (PM) concentrations is a pressing issue in urban air quality, as this understanding informs decisions for control and mitigation of these key pollutants. The Houston, TX metropolitan area is an ideal location for studying the intersection between O 3 and atmospheric secondary organic carbon (SOC) production due to the diversity of source types (urban, industrial, and biogenic) and the on- and off-shore cycling of air masses over Galveston Bay, TX. Detailed characterization of filter-based samples collected during Deriving Information on Surface Conditions from Column and VERtically Resolved Observations Relevant to Air Quality (DISCOVER-AQ) Houston field experiment in September 2013 were used to investigate sources and composition of organic carbon (OC) and potential relationships between daily maximum 8 h average O 3 and PM. The current study employed a novel combination of chemical mass balance modeling defining primary (i.e. POC) versus secondary (i.e. SOC) organic carbon and radiocarbon (14C) for apportionment of contemporary and fossil carbon. The apportioned sources include contemporary POC (biomass burning [BB], vegetative detritus), fossil POC (motor vehicle exhaust), biogenic SOC and fossil SOC. The filter-based results were then compared with real-time measurements by aerosol mass spectrometry. With these methods, a consistent urban background of contemporary carbon and motor vehicle exhaust was observed in the Houston metropolitan area. Real-time and filter-based characterization both showed that carbonaceous aerosols in Houston was highly impacted by SOC or oxidized OC, with much higher contributions from biogenic than fossil sources. However, fossil SOC concentration and fractional contribution had a stronger correlation with daily maximum 8 h average O 3 , peaking during high PM and O 3 events. The results indicate that point source emissions processed by on- and off-shore wind cycles likely contribute to peak events for both PM and O 3 in the greater Houston metropolitan area. • Contemporary carbon was largest contributor to total organic carbon in Houston. • Secondary organic carbon contributed an average of 67% of total organic carbon. • Secondary fossil carbon was variable ranging from 3 to 27% of total organic carbon. • During peak ozone event, secondary fossil carbon was well correlated with ozone. • Houston was impacted by sea breeze re-circulation during high pollutant day. [ABSTRACT FROM AUTHOR]