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The Earth's atmosphere is composed of an enormous variety of chemical species associated with trace gases and aerosol particles whose composition and chemistry have critical impacts on the Earth's climate, air quality, and human health. Mass spectrometry analysis as a powerful and popular analytical technique has been widely developed and applied in atmospheric chemistry for decades. Mass spectrometry allows for effective detection, identification, and quantification of a broad range of organic and inorganic chemical species with high sensitivity and resolution. In this review, we summarize recently developed mass spectrometry techniques, methods, and applications in atmospheric chemistry research in the past several years on molecular‐level. Specifically, new developments of ion‐molecule reactors, various soft ionization methods, and unique coupling with separation techniques are highlighted. The new mass spectrometry applications in laboratory studies and field measurements focused on improving the detection limits for traditional and emerging volatile organic compounds, characterizing multiphase highly oxygenated molecules, and monitoring particle bulk and surface compositions. [ABSTRACT FROM AUTHOR]

• The chemical composition of PM 2.5 in a country in the East Mediterranean - Middle East region is investigated in the hot season, including organic markers. • Long-range transport was an important contributor to V, Ni, and sulfate in the region with a characteristic ratio based on the air mass origin. • Main local sources determined through the chemical speciation including organics are road transport, resuspension of dust and diesel private generators. • A health risk assessment of airborne metals was performed and the carcinogenic risk for all the metals exceeded by 14 and 42 times the acceptable risk level in the US (10−6). The chemical composition of PM 2.5 at two sites in Lebanon, a country in the East Mediterranean - Middle East region, is investigated in the spring and summer seasons. The average PM 2.5 concentrations were of (29 ± 16) µg/m3 for Beirut urban site and (32 ± 14) µg/m3 for Beirut suburban site. This study showed that the geographic location of the East Mediterranean region, such as its proximity to the Mediterranean Sea and the dust storm intrusion are a significant contributor to the high PM levels from natural sources, which cannot be mitigated, rendering the PM 2.5 WHO annual Air Quality guideline unattainable due to high natural background, which also applies to the entire Middle East region. Turkey and Eastern Europe are the dominant origin of air masses throughout our sampling days, suggesting the long-range transport as an important potential contributor to the high observed concentrations of V, Ni, and sulfate in this region most probably in other East Mediterranean countries than Lebanon too. Main local sources determined through the chemical speciation including organics are road transport, resuspension of dust and diesel private generators. A health risk assessment of airborne metals was performed and the carcinogenic risk for all the metals exceeded by 42 (adults) and 14 (children) times the acceptable risk level (10−6) at both sites. Vanadium was the predominant carcinogenic metal, emphasizing the need to replace energy production with cleaner energy on a regional level and highlighting the severe impact of air pollution on the health of inhabitants in this region's main cities. [ABSTRACT FROM AUTHOR]

The widespread presence of organic aerosols (OA) in the atmosphere and their dominant role in climate forcing are increasingly recognized. Measurements from the high‐altitude region provide insights into the natural processes and long‐range transport of aerosols. We studied water‐soluble organic compounds in PM1.1 during January‐March 2020 and February‐April 2021 at Ponmudi (8.8°N and 77.1°E), a tropical hill station (960 m a.s.l.) located on the Western Ghats of India. The 5‐day backward trajectories of air masses presented that continental and marine sources impacted the site during the campaign, and thus we classified samples as mixed and marine air masses. Their molecular fingerprints revealed the prevalence of oxalic acid (C2), followed by terephthalic acid in mixed air mass and malonic (C3) or succinic (C4) acid in maritime air mass aerosol samples. This feature and the phthalic to azelaic acid ratio, as well as the C3 to C4 and fumaric to maleic acid ratios, evidenced that water‐soluble OA were of anthropogenic origin and less photochemically aged in mixed air mass samples, whereas they derived from biogenic sources and more photochemical aging in marine air mass samples. However, we found their comparable contributions in water‐soluble organic carbon under mixed and marine air masses. Linear correlations between C2 relative abundance and its ratios with the precursor compounds implied that the oxidation of precursors to oxalic acid occurs during atmospheric transport. The results revealed that the input of anthropogenic and biogenic precursors followed by atmospheric processing controlled the burden of water‐soluble OA across the Western Ghats. Plain Language Summary: Dicarboxylic acids (DCAs), oxocarboxylic acids and dicarbonyls are ubiquitous water‐soluble components of organic aerosol (OA) that can serve as cloud condensation nuclei and affect the climate of the Earth. We reveal for the first time the molecular fingerprints and sources as well as formation processes of water‐soluble OA in PM1.1 at a tropical hill station in Western Ghats of India. Significant differences in the molecular fingerprints and atmospheric processes of water‐soluble OA were found due to the influence of different air masses. DCAs and related compounds in mixed air mass aerosols originated from anthropogenic sources and produced in the atmosphere by photooxidation during long‐range transport whereas they were of biogenic origin followed by intense photochemical aging of biogenic volatile organic compounds such as isoprene and unsaturated fatty acids during atmospheric transport in marine air mass aerosols. The results revealed that DCAs substantially contribute to water‐soluble OA not only in mixed air mass aerosols but also in marine air mass aerosols at the tropical hill station in the Western Ghats. These findings have implications for assessing climate‐forcing feedback of secondary OA over the Western Ghats that is driven by anthropogenic and biogenic sources followed by photochemical processes. Key Points: Mixed and marine air masses drive the molecular fingerprints of atmospheric water‐soluble organic compounds over the Western GhatsAerosols of mixed air masses comprised dicarboxylic acids (DCAs) of anthropogenic origin and less photochemically processedDCAs were produced from biogenic sources followed by intense photochemical aging in marine air mass aerosols [ABSTRACT FROM AUTHOR]

Complex organic aerosols in the upper atmosphere of Saturn's moon Titan reach the troposphere and surface, where a methane (CH4)‐based hydrological cycle occur. Previous studies have assumed no interactions between organic aerosols and liquid CH4, although the dissolution of low‐molecular‐weight photochemical products in liquid CH4 has been considered. Here we report experimental results of soaking a laboratory analog (so‐called tholin) of Titan's organic aerosols in liquid CH4 at 93–98 K for several hours and then evaporating the liquid, simulating wet–dry cycling on Titan. After wet–dry cycling, residual tholin particles form aggregates through cementation. Solid evaporitic deposits formed by evaporation of interacted liquid contain nitrogen‐bearing aromatics, suggesting selective dissolution of aromatics. Our results suggest that organic aerosols or high‐molecular‐weight compounds adsorbed on them partly dissolve in liquid CH4 on Titan, even during short‐term wetting events, promoting the growth of aerosols to dune particles via aggregation and providing aromatics to evaporites. Plain Language Summary: Saturn's largest moon, Titan has a dense atmosphere composed of nitrogen and methane. Active organic chemistry induced by sunlight occurs in the atmosphere to form complex organic aerosols. These organic aerosols eventually settle on the surface, where rivers, lakes, and seas of liquid methane are present. Upon seasonal changes in precipitation and evaporation, wet–dry cycling of liquid methane is believed to occur on Titan, similar to Earth's water cycles. Can organic aerosols settled on the surface be dissolved into liquid methane? If so, what components of aerosol can be dissolved, and how could this affect Titan's geology? Here we perform laboratory experiments to address these questions. Unlike predictions by previous studies, we find that organic aerosols or aromatics adsorbed on them would partly dissolve into liquid methane efficiently. These processes could play key roles in the formation of unique landforms, such as dunes and evaporites, on Titan. Key Points: We experimentally simulate interactions between laboratory analogs (tholin) of Titan's aerosols and liquid methane at low temperaturesComplex aromatics are dissolved from tholin, forming evaporites after drying; while, residual tholin form aggregatesWet–dry cycling of aerosols on Titan may provide aromatics to evaporites and could explain size growth of aerosols to dune particles [ABSTRACT FROM AUTHOR]

A hygroscopic tandem differential mobility analyser (H-TDMA) was used to observe the size-resolved hygroscopic characteristics of submicron particles in January and April 2018 in urban Beijing. The probability distribution of the hygroscopic growth factor (HGF-PDF) in winter and spring usually showed a bimodal pattern, with more hygroscopic mode (MH) being more dominant. The seasonal variation in particle hygroscopicity was related to the origin of air mass, which received polluted southerly air masses in spring and clean northwesterly air masses in winter. Particles showed stronger hygroscopic behaviour during heavy pollution episodes (HPEs) with elevated concentrations of secondary aerosols, especially higher mass fraction of nitrate, which were indicated using the PM 2.5 (particulate matter with diameter below 2.5 µm) mass concentration normalised by CO mass concentration. The hygroscopic parameter (κ) values were calculated using H-TDMA (κ htdma) and chemical composition (κ chem). The closure study showed that κ chem was overestimated in winter afternoon when compared with κ htdma , because the organic particle hygroscopic parameter (κ org) was overestimated in the calculations. It was influenced by the presence of a high concentration of hydrocarbon-like organic aerosol (HOA) with a weak water uptake ability. A positive relationship was observed between κ org and the ratio of oxygenated organic aerosol (OOA) and HOA, thereby indicating that the strong oxidation state enhanced the hygroscopicity of the particles. This study revealed the effect of local emission sources and secondary aerosol formation processes on particle hygroscopicity, which is of great significance for understanding the pollution formation mechanism in the North China Plain. [Display omitted] [ABSTRACT FROM AUTHOR]

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]

Organic aerosols (OAs) are key components of atmospheric PM 2.5, which impose an important influence on citizens' health and atmospheric chemistry. However, the vertical distribution and evolutionary mechanisms of OAs have remained unclear, posing challenges for accurate model simulations. To compare the difference in molecular distribution and sources at different altitudes and explore the impact of vertical transport of mountain-valley breezes on OAs in mountainous regions, PM 2.5 samples were simultaneously collected at both the summit (SM: 1840 m a.s.l) and the foot Mt. Huang (FM: 480 m a.s.l.) in winter. All the 128 detected organic species presented higher concentrations at FM (237 ± 118 ng m−3) than at SM (89.3 ± 40.9 ng m−3), indicating that the influence of anthropogenic emissions on OAs became more significant as elevation decreased. Levoglucosan was the dominant single organic species and displayed robust correlations with most organic components at both sites, suggesting the notable effect of biomass burning on OAs in the alpine atmosphere. Molecular composition, characteristic ratios, and positive matrix factorization analysis suggested that OAs at SM were more aged and mostly derived from secondary oxidation and biomass burning from long-range transport. However, anthropogenic sources (e.g., biomass burning and fossil fuel combustion) contributed more to OAs at FM. Potential source contribution function results revealed that the northeastern part of Jiangxi Province and the nearby regions of the observation point are the potential source regions for OAs at FM, while long-range transport from northwestern Anhui Province and northern Jiangxi Province played a key role in OAs at SM. This study proved that OAs at FM could influence the mountaintop aerosols through the vertical transport of valley breeze in the day at Mt. Huang. These findings enhance our understanding of the vertical distribution of OAs and provide a scientific foundation for cross-regional atmospheric pollution control. [Display omitted] • The concentrations of all the 128 organic species decreased as elevation increased. • The effect of anthropogenic pollutants became more significant as elevation decreased. • The mountaintop organic aerosols (OAs) were more aged than those at the foot. • The mountaintop OAs in the day were strongly impacted by the valley wind in winter. [ABSTRACT FROM AUTHOR]

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. [Display omitted] • A GC×GC-TOFMS method is developed for aerosols using flow type modulation. • The PM organic constituents at a high-mountain site in March 2015 were analyzed. • PAEs and TPP were detected presumably from transboundary sources. [ABSTRACT FROM AUTHOR]

As a part of the Integrated Campaign for Aerosols, gases and Radiation Budget (ICARB-2018), shipborne measurements of aerosol properties were carried out to study the influence of South Asian outflow on cloud condensation nuclei (CCN) characteristics over the South East Arabian Sea (SEAS) and equatorial Indian Ocean (EIO) during winter, 2018. The poor association between CCN concentration and mass concentrations of the major aerosol species (organic matter, sulfate, and elemental carbon) is observed over SEAS, where airmass is mostly continental. In comparison, the CCN is well-correlated with aerosol mass concentrations over remote EIO. The dependence of CCN activation (at lower supersaturations) on the ultrafine particle fraction differs between SEAS and EIO depending on the mass concentration of organic aerosols. The coexistence of small and hydrophobic aerosols (organics) decreased the CCN activation ratio during ultrafine particle events. The hygroscopicity estimated using the chemical composition of aerosols is comparable to that estimated from CCN measurements over the Indian Ocean, except for the SEAS, where organic aerosols dominate. The effect of outflow aerosols on cloud droplet number concentration (CDNC) is simulated using a parcel model, which showed a good association (R ∼0.96) with CCN measurements over the EIO; however, the estimated CDNC did not follow the CCN variation over the SEAS region. This study highlights the importance of aerosol chemical composition, especially organics, in CCN activation and cloud droplet formation in the South Asian outflow over the Indian Ocean. • Hygroscopicity (κ) of continental aerosols over the Indian Ocean is examined. • Ultrafine particles and organics decrease the CCN activation of South Asian outflow. • CCN at 0.2% SS estimated from measured κ has positive bias over the Arabian Sea. • Estimated CDNC over near-coastal regions is mostly invariant with CCN concentration. [ABSTRACT FROM AUTHOR]

Organic aerosols (OA) represent a significant fraction of total submicron particulate matter (PM1) concentrations globally, including densely populated megacities such as Seoul. However, scientific understanding of the atmospheric formation and removal processes of OA, especially for secondary organic aerosols (SOA), is still highly uncertain. In this study, we examine the characteristics of SOA formation in Seoul during spring‐summer 2016 and fall‐winter 2017/2018, using airborne and ground observations along with a 3‐D global chemical transport model, GEOS‐Chem. We use four different SOA schemes in the model, including simplified and complex volatility‐based frameworks, and evaluate them by comparing the simulations with the observations to examine how our scientific understanding embedded in each SOA scheme affects the observed biases. Our analysis of the model performance of each scheme also provides the most suitable approach in simulating SOA in a typical urban environment. Comparisons of the simulated versus observed OA concentrations show that model biases range from −72% to +118%, with considerable variability among different schemes and seasons. We find that the inclusion of semi/intermediate volatile precursors, in addition to the traditional precursors, and chemical aging (functionalization) are important factors to simulate surface SOA concentrations in Seoul. However, a comparison of observed and simulated SOA/∆CO enhancement ratios suggests that most schemes underpredict SOA aging in upper levels in the boundary layer. We also find that the simplified SOA scheme can reproduce observed OA but often shows overestimation in surface air, indicating that uncertainties exist in bottom‐up emissions and precursor parameterization in Seoul. Plain Language Summary: We compare four different modeling approaches for simulating secondary organic aerosol (SOA) formation, accounting for a significant fraction of total fine particulate matter concentrations in Seoul, Korea. Using GEOS‐Chem, a chemical transport model, we find that current SOA schemes show large variabilities. Including an additional precursor species and further oxidation (i.e., chemical aging) of simulated SOA improves model performance. We also find that a simplified scheme with less computational cost can reproduce observed values but generally shows an overestimation in Seoul, indicating uncertainties in parameterization. Key Points: Model evaluation of simulated organic aerosols (OA) using different secondary organic aerosols (SOA) schemes in Seoul shows large variabilityThe inclusion of semi/intermediate volatile precursors and chemical aging are important factors in reducing model biasesThe simplified SOA scheme can reproduce observed OA, but uncertainties exist in precursor parameterization in Seoul [ABSTRACT FROM AUTHOR]

Brown carbon is a type of carbonaceous aerosol with strong light absorption in the ultraviolet and visible wavelengths that leads to radiative forcing. However, it is difficult to correlate the chemical composition of brown carbon with its atmospheric light absorption properties, which translates into significant uncertainty. Thus, a time-dependent density functional theory (TD-DFT) approach was used to model the real-world absorption properties of 14 polycyclic aromatic hydrocarbons (PAHs) over three regions of the Basque Country (Spain): Bilbao, Urretxu, and Azpeitia. The data were corrected for atmospheric concentration. The results show that the absorption spectra over each region are qualitatively identical, with the absorption intensities being significantly higher over Bilbao than over Azpeitia and Urretxu. Furthermore, it was found that the light absorption by PAHs should be more relevant for radiative forcing when it occurs at UVA and (sub)visible wavelengths. Finally, among the 14 studied PAHs, benzo[b]fluoranthene, pyrene, fluoranthene, benzo[a]pyrene, and benzo[k]fluoranthene and benzoperylene were identified as the molecules with larger contributions to radiative forcing. [ABSTRACT FROM AUTHOR]

The North China Plain (NCP) is a region that experiences serious aerosol pollution. A number of studies have focused on aerosol pollution in urban areas in the NCP region; however, research on characterizing aerosols in rural NCP areas is comparatively limited. In this study, we deployed a TD-HR-AMS (thermodenuder high-resolution aerosol mass spectrometer) system at a rural site in the NCP region in summer 2013 to characterize the chemical compositions and volatility of submicron aerosols (PM1). The average PM1 mass concentration was 51.2 ± 48.0 µg m−3 and organic aerosol (OA) contributed most (35.4%) to PM1. Positive matrix factorization (PMF) analysis of OA measurements identified four OA factors, including hydrocarbon-like OA (HOA, accounting for 18.4%), biomass burning OA (BBOA, 29.4%), less-oxidized oxygenated OA (LO-OOA, 30.8%) and more-oxidized oxygenated OA (MO-OOA, 21.4%). The volatility sequence of the OA factors was HOA > BBOA > LO-OOA > MO-OOA, consistent with their oxygen-to-carbon (O:C) ratios. Additionally, the mean concentration of organonitrates (ON) was 1.48–3.39 µg m−3, contributing 8.1%–19% of OA based on cross validation of two estimation methods with the high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS) measurement. Correlation analysis shows that ON were more correlated with BBOA and black carbon emitted from biomass burning but poorly correlated with LO-OOA. Also, volatility analysis for ON further confirmed that particulate ON formation might be closely associated with primary emissions in rural NCP areas. [ABSTRACT FROM AUTHOR]

A method using ultra‐high performance liquid chromatography coupled to a high resolution Orbitrap mass spectrometer was developed to identify and quantify imidazoles in aqueous extracts of aerosol particles. The aqueous particle extract was used without further enrichment or sample clean‐up. Five columns were tested for efficient separation of ten imidazoles and the Acquity HSS T3 column was chosen for further optimization. Low limits of detection (<25 nM) and good intraday and interday repeatability (<1.6 and <6%, respectively) were achieved. Investigation of matrix effects showed that external calibration is applicable when the loading of organic carbon in the sample is below 10 µg m−3. The developed method was applied to ten real samples, and six out of the ten test imidazoles were successfully quantified, while six further imidazoles were qualitatively identified, among them 4‐imidazolecarboxaldehyde and 4‐methyl‐5‐imidazolecarboxaldehyde. Advantages of the method are the minimal sample preparation, the short run time for each sample, and the low detection limits. These allow for a fast and reliable quantification of imidazoles even in a large number of aqueous particle extract samples. [ABSTRACT FROM AUTHOR]

The Community Earth System Model version 2 (CESM2) includes three main atmospheric configurations: the Community Atmosphere Model version 6 (CAM6) with simplified chemistry and a simplified organic aerosol (OA) scheme, CAM6 with comprehensive tropospheric and stratospheric chemistry representation (CAM6‐chem), and the Whole Atmosphere Community Climate Model version 6 (WACCM6). Both, CAM6‐chem and WACCM6 include a more comprehensive secondary organic aerosols (SOA) approach using the Volatility Basis Set (VBS) scheme and prognostic stratospheric aerosols. This paper describes the different OA schemes available in the different atmospheric configurations of CESM2 and discusses differences in aerosol burden and resulting climate forcings. Derived OA burden and trends differ due to differences in OA formation using the different approaches. Regional differences in Aerosol Optical Depth with larger values using the comprehensive approach occur over SOA source regions. Stronger increasing SOA trends between 1960 and 2015 in WACCM6 compared to CAM6 are due to increasing biogenic emissions aligned with increasing surface temperatures. Using the comprehensive SOA approach further leads to improved comparisons to aircraft observations and SOA formation of ≈143 Tg/yr. We further use WACCM6 to identify source contributions of OA from biogenic, fossil fuel, and biomass burning emissions, to quantify SOA amounts and trends from these sources. Increasing SOA trends between 1960 and 2015 are the result of increasing biogenic emissions aligned with increasing surface temperatures. Biogenic emissions are at least two thirds of the total SOA burden. In addition, SOA source contributions from fossil fuel emissions become more important, with largest values over Southeast Asia. The estimated total anthropogenic forcing of OA in WACCM6 for 1995–2010 conditions is −0.43 W/m2, mostly from the aerosol direct effect. Key Points: CESM2 (WACCM6) includes an updated secondary aerosol scheme using the volatility basis set approachThe new SOA parameterization results in regional changes in radiative forcings and aerosol optical depthPositive SOA trends between 1960 and 2015 are caused by both increasing biogenic and anthropogenic sources [ABSTRACT FROM AUTHOR]

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 14C‐PS aerosol of 3·105 ultrafine particles per 1 cm3 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. [ABSTRACT FROM AUTHOR]

Abstract A high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS) was deployed during wintertime (5 February to 15 March 2016) at a suburban site in Douai, northern France, in order to investigate the characteristics and sources of the organic matter (OM). The campaign average concentration of non-refractory submicron particulate matter (NR-PM 1) was 11.1 ± 9.3 μg m−3, and composed of 38% OM, 36% nitrate, 16% ammonium and 9% sulfate. The average values for the OM:OC, O:C and H:C ratios were 1.60 ± 0.15, 0.32 ± 0.11 and 1.55 ± 0.14, respectively, indicating a moderate level of aerosol oxidation. The positive matrix factorization (PMF) source apportionment method was applied to the high-resolution organic aerosol (OA) mass spectra, resulting in four factors: a hydrocarbon-like (HOA) factor; one associated with oxidized biomass burning (oBBOA); and two oxygenated factors (OOA) denoted as less oxidized (LO-OOA) and more oxidized (MO-OOA), with average contributions to OA of 20%, 28%, 17% and 35%, respectively. The oBBOA factor was found to be mainly local as shown by non-parametric wind regression (NWR) analysis, and to correlate well with relative humidity (RH), suggesting fast aqueous processing of locally emitted primary biomass burning emissions. During most part of the campaign, the sampling site was affected by different air masses. However, during the last period of the campaign (5–16 March 2016) the site was heavily impacted by air masses from Eastern Europe which were rich in secondary inorganic and organic aerosols. The H:C versus O:C (Van Krevelen, VK) diagram highlighted that the aerosol followed an oxidation process throughout the whole campaign, with an average slope of −1.05. The impact of continental air masses towards the end of the campaign confined the aerosol towards a narrower space in the VK diagram, suggesting a homogenization of the different aerosol sources due to OA ageing during transport. Several nocturnal NPF (new particle formation)-like events were observed and associated to the fast processing of BBOA emissions and the formation of ammonium nitrate. Graphical abstract Image 1 Highlights • Organic matter at a suburban site in winter investigated at high time resolution. • Aerosols were moderately oxidized with four sources of organic aerosol identified. • Oxidized biomass burning organic aerosols (BBOA) mostly local represented 28% of OA. • Several nocturnal NPF (new particle formation)-like events were observed. • It suggests a fast processing of BBOA and the possible role of ammonium nitrate. [ABSTRACT FROM AUTHOR]

This study reports for the first-time the ambient concentrations of HULIS mass (HULIS-OM, Humic-like substances) and HULIS-C (carbon) in PM10 (particulate matter with aerodynamic diameter ≤ 10 μm) from the Indo-Gangetic Plain (IGP at Kanpur, wintertime). HULIS extraction followed by purification and isolation protocol with methanol: acetonitrile (1:1 v/v) on HLB (Hydrophilic-Lipophilic Balanced) cartridge has been established. Quantification of HULIS-C was achieved on a total organic carbon (TOC) analyser whereas HULIS-OM was determined gravimetrically. Consistently high recovery (> 90%) of HULIS-C based on analysis of Humic standard (sodium salt of Humic acid) suggested suitability of our established analytical protocol involving solvent extraction, purification and accurate quantification of HULIS. HULIS-OM varied from 17.3-38 μg m−3 during daytime and from 19.8-40.6 μg m−3 during night in this study. During daytime the HULIS-OM constituted 20-30% mass fraction of OMTotal and 10-15% of PM10 mass. However, a relatively low contribution of HULIS-OM has been observed during the night. This observation has been attributed to higher concentrations of OM and PM10 in night owing to nighttime chemical reactivity and condensation of organics in conjunction with shallower planetary boundary layer height. Strong correlation of HULIS-C with K+BB (R2 > 0.80) and significant day-night variability of HULIS-C/WSOC ratio in conjunction with air-mass back trajectories (showing transport of pollutants from upwind IGP) suggest biomass burning emission and secondary transformations as important sources of HULIS over IGP. High-loading of atmospheric PM10 (as high as 440 μg m−3) with significant contribution of water-soluble organic aerosols (WSOC/OC: ~ 0.40-0.80) during wintertime highlights their plausible potential role in fog and haze formation and their impact on regional-scale atmospheric radiative forcing over the IGP. [ABSTRACT FROM AUTHOR]

The characteristics of non-refractory submicron aerosols (NR-PM 1), focusing on organic aerosols, are examined over a tropical coastal location, Thumba, in southern peninsular India. The measurements were carried out using an aerosol chemical speciation monitor during 2017–2021. The results indicated organic aerosols as the major component (67–85%) in the NR-PM 1 mass loading during all seasons. Positive matrix factorization (PMF) analysis on the OA mass spectra yielded two factors resolving Hydrocarbon-like organic aerosols (HOA) and Oxygenated organic aerosols (OOA), with the major contribution to OA coming from OOA (mass fraction >50%) during all the seasons. Examination of the diurnal variations revealed the daytime enhancement in OOA and sulfate mass fractions, indicating photochemical production overwhelming the dilution at the surface due to local atmospheric boundary layer expansion. The OOA mass concentration showed a good correlation (R > 0.5) with odd oxygen (O 3 +NO 2) and with an increase in oxygen-to-carbon ratio (ΔO:C = 0.11 to 0.35 with Δodd oxygen = 60 μg m−3 for different seasons) (i.e., increased oxidation degree of OA) signifying the dominance of photochemistry and subsequent enhanced atmospheric oxidative capacity in OOA formation. Interestingly, the aerosol liquid water content (ALWC) doubled during the nighttime (>40 μg m−3) compared to the daytime (<20 μg m−3) in different seasons, indicating the combined impact of varying submicron aerosol composition and ambient relative humidity. Since highly humid (relative humidity >85%) conditions prevail over this tropical coastal station, especially during the nighttime, the role of aqueous-phase formation of OA is also examined. It was found that less oxidized/less-hygroscopic OA were prevalent during the nighttime, resulting in lower aqueous-phase OA processing. During all the seasons, the hygroscopicity of organics (к organics) reached as high as > 0.22 and was mainly driven by photochemical processing rather than aqueous-phase chemistry. These results highlight the importance of the OA formation pathways in affecting their hygroscopic properties over the tropical atmosphere. • Organics are the dominant NR-PM 1 species in all seasons. • Oxygenated species dominated (>50%) the overall OA. • Photochemical reactions dominated OOA production. • The hygroscopicity of organics is mainly driven by photochemical processing. [ABSTRACT FROM AUTHOR]

Organic aerosols (OAs) account typically for 20–90% of fine particles (PM 2.5 ) in the lower troposphere. They contribute to a wide range of environmental problems, from local issues (e.g., urban haze) to global problems (e.g., climate change). Huge efforts have been dedicated to studying the composition, abundance, spatial and temporal distribution and sources of organic aerosols in China. This review aims to summarize recent studies on characteristics and sources of OAs and assesses the current state of understanding of the organic aerosol pollution in China. The OA constitutes ∼20–45% of the PM 2.5 with an annual mean value of 5.2–44.5 μg/m 3 at sites across China, which is about five times higher than that reported in North America and Europe. There are thousands of different organic compounds in atmospheric aerosols, but only about 5–10% of them have been identified and quantified. OAs show pronounced spatial variations with much higher concentrations in Northern than Southern China. Seasonally, the highest OA concentrations are observed in the winter, whereas the lowest are in the summer. This is due to higher emission rates from anthropogenic sources (e.g., biomass and coal combustion) and poorer dispersion conditions in the winter. Approximately 60–80% of total OA is apportioned by receptor modeling (such as Chemical Mass Balance, CMB) and tracer-yield method, based on the source profiles of primary organic aerosols (POA) and secondary OA (SOA) derived from local emission sources. A number of OA sources are identified, including motor vehicles, industrial emissions, biomass combustion, food cooking, and coal combustion for POA and anthropogenic and biogenic emissions for SOA. Industrial emissions and motor vehicular exhaust are the dominant sources of organic aerosols in the industrialized areas of Northern China, as well as the Pearl River Delta and Eastern China, whereas in other urban areas, residential coal combustion and motor vehicular exhaust are the dominant sources in winter and summer respectively. [ABSTRACT FROM AUTHOR]

Fifteen hydrolyzed amino acids (THAA) were quantified in urban aerosols (TSP samples) collected during April 2012 to May 2013 in Beijing, China using high-performance liquid chromatography (HPLC) after their derivatization with o -phthalaldehyde (OPA), to investigate their molecular distributions and seasonal variation. Total concentrations of amino acids ranged from 1.73–25.7 nmol m − 3 with a peak in spring (13.7 nmol m − 3 ), followed by winter (11.5 nmol m − 3 ), fall (9.51 nmol m − 3 ) and summer (7.45 nmol m − 3 ). Glycine (Gly), alanine (Ala) and valine (Val) are found to be the most abundant species, which account for 46% of the total THAA. Compared with those recorded in previous studies, the atmospheric levels of amino acids in Beijing were higher than those from other regions. Enhanced amounts of methionine, tyrosine, histidine, aspartic acid and glutamic acid were found during the rainfall events. The factor analysis further suggests that amino acids in urban Beijing originated from multiple sources including biological emission, biomass burning, as well as anthropogenic activities. [ABSTRACT FROM AUTHOR]

Atmospheric aerosol optical, physical, and chemical properties play a fundamental role in the Earth's climate system. A better understanding of the processes involved in their formation, evolution, and interaction with radiation and the water cycle is critical. We report the analysis of atmospheric molecules/particles collected with a new sampling system that flew under regular weather balloons for the first time. The flight took place on January 18, 2022 from Reims (France). The samples were subsequently analyzed by high-resolution mass spectrometry (Orbitrap) to specifically infer hundreds of organic components present in 4 different layers from the troposphere to the stratosphere (up to 20 km). Additional measurements of O 3 , CO, and aerosol concentrations a few hours before this flight took place to contextualize the sampling. After separating common species found on each filter that might be common to atmospheric layers or residuals for contaminations, we found that each sample yields significant differences in the number and size of organic species detected that should reflect the unique composition of atmospheric layers. While tropospheric samples yield significantly oxidized and saturated components, with carbon numbers below 30 that might be explained by complex organics chemistry from local and distant source emissions, the upper tropospheric and stratospheric samples were associated with increased carbon numbers (C > 30), with a significantly reduced unsaturation number for the stratosphere, that might be induced by strong UV radiations. The multimodal distributions of carbon numbers in chemical formulas observed between 15 and 20 km suggest that oligomerization and growth of organic molecules may take place in aged air masses of tropical origin that are known to carry organic compounds even several km above the tropopause where their lifetime significantly increases. In addition, the presence of organics may also reflect the extended influence of wildfires smoke injected during the spring and summer in the NH hemisphere before the in situ observations and their long-lifetime in the upper troposphere and stratosphere. Photographic credit: Marc Fourmentin - Laboratoire de PhysicoChimie de l'Atmosphère. [Display omitted] • Unique launching infrastructure in Europe (Reims/France) to operate state-of-the art atmospheric instruments • New balloon-borne sampling device to characterize the chemical composition of organics (troposphere to stratosphere) • Offline analysis reveals the growth of organics aerosol in the stratosphere • Organics aerosol could derive from oligomerization processes along transport from the tropics and/or influenced by wildfires [ABSTRACT FROM AUTHOR]

Polycyclic aromatic hydrocarbons (PAHs) have toxic impacts on humans and ecosystems. One of the most carcinogenic PAHs, benzo(a)pyrene (BaP), is efficiently bound to and transported with atmospheric particles. Laboratory measurements show that particle-bound BaP degrades in a few hours by heterogeneous reaction with ozone, yet field observations indicate BaP persists much longer in the atmosphere, and some previous chemical transport modeling studies have ignored heterogeneous oxidation of BaP to bring model predictions into better agreement with field observations. We attribute this unexplained discrepancy to the shielding of BaP from oxidation by coatings of viscous organic aerosol (OA). Accounting for this OA viscosity-dependent shielding, which varies with temperature and humidity, in a global climate/chemistrymodel brings model predictions into much better agreement with BaP measurements, and demonstrates stronger long-range transport, greater deposition fluxes, and substantially elevated lung cancer risk from PAHs. Model results indicate that the OA coating is more effective in shielding BaP in the middle/high latitudes compared with the tropics because of differences in OA properties (semisolid when cool/dry vs. liquid-like when warm/humid). Faster chemical degradation of BaP in the tropics leads to higher concentrations of BaP oxidation products over the tropics compared with higher latitudes. This study has profound implications demonstrating that OA strongly modulates the atmospheric persistence of PAHs and their cancer risks. [ABSTRACT FROM AUTHOR]

Chemical characterization of ambient non-refractory submicron aerosols (NR-PM 1 ) was carried out in real time at Kanpur, India. The measurements were performed during the winter (December 2014 to February 2015), and comprised of two very distinct high and low aerosol loading periods coupled with prevalent foggy conditions. The average non-refractory submicron aerosol loading varied significantly from high (HL, ~ 240 μg/m 3 ) to low loading (LL, ~ 100 μg/m 3 ) period and was dominated by organic aerosols (OA) which contributed more than half (~ 60%) of the measured aerosol mass. OA source apportionment via positive matrix factorization (PMF) showed drastic changes in the composition of OA from HL to LL period. Overall, O/C (oxygen to carbon) ratios also varied significantly from HL (= 0.59) to LL (= 0.69) period. Fog episodes (n = 17) studied here seem to be reducing the magnitude of the negative impact of OA loading on O/C ratio (OA loading and O/C ratio are anti-correlated, as higher OA loading allows gas to particle partitioning of relatively less oxidized organics) by 60% via aqueous processing. This study provided new insights into the combined effects of OA loading and fog aqueous processing on the evolution of ambient organic aerosols (OA) for the first time. [ABSTRACT FROM AUTHOR]

Accelerator mass spectrometry (AMS) was shown to be applicable for studying the penetration of organic aerosols, inhaled by laboratory mice at ultra-low concentration ca. 10 3 cm −3 . We synthesized polystyrene (PS) beads, composed of radiocarbon-labeled styrene, for testing them as model organic aerosols. As a source of radiocarbon we used methyl alcohol with radioactivity. Radiolabeled polystyrene beads were obtained by emulsifier-free emulsion polymerization of synthesized 14 C-styrene initiated by K 2 S 2 O 8 in aqueous media. Aerosol particles were produced by pneumatic spraying of diluted 14 C-PS latex. Mice inhaled 14 C-PS aerosol consisting of the mix of 10 3 225-nm particles per 1 cm 3 and 5·10 3 25-nm particles per 1 cm 3 for 30 min every day during five days. Several millions of 225-nm particles deposited in the lungs and slowly excreted from them during two weeks of postexposure. Penetration of particles matter was also observed for liver, kidneys and brain, but not for a heart. [ABSTRACT FROM AUTHOR]

Aerosol samples collected over a tropical location, Thumba, southernmost West Coast of India were analyzed for the abundance of homologous dicarboxylic acids (C to C), oxocarboxylic acids (ωC to ωC, pyruvic acid), α-dicarbonyls (glyoxal and methylglyoxal), organic and elemental carbon. Among the measured organics, oxalic acid was found to be the most abundant species followed by succinic and/or malonic acids. As oxoacid and α-carbonyl groups, glyoxylic acid and glyoxal, respectively, were observed to be dominant. On average, dicarboxylic acids accounted almost 2.1 ± 0.7 % of the aerosol total organic carbon. Among the aerosols over Thumba, two types of formation pathways were noticed for oxalic acid. During the post-monsoon and winter periods, the photo-oxidation of biogenic and anthropogenic volatile organic compounds lead to the formation of oxalic acid through a chain reaction involving glyoxal, methylglyoxal, pyruvic and glyoxylic acids. In contrast, during the pre-monsoon, the oxidative degradation of the biogenic unsaturated fatty acids give rise to succinic acid, which can be decomposed to malonic acid and then to oxalic acid. The observed seasonal variations in acid concentrations are consistent with photochemical production and the subsequent accumulation under favourable meteorological conditions prevailing over the region. [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]

Seventy three individual organic compounds in the atmospheric particulate matter with an aerodynamic diameter of less than or equal to a nominal 10 μm (PM 10 ) 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. [ABSTRACT FROM AUTHOR]

The effects of aromatic carbonyls (ACs), polycyclic aromatic hydrocarbons (PAHs) and phenols (PHs) on the photolysis of nitroaromatic compounds (ArNO 2) in the solid phase were explored. The reactive nitrogen gas formation by the photolysis process was investigated in a cylindrical reactor coupled to a NO x analyzer. These organics had an enhanced or inhibited influence on the nitrous acid (HONO) and NO formations by the photolysis of 1-nitropyrene (NPy) and 5-nitrosalicylic acid (NSA), depending on the hydrogen abstraction and donation abilities of organics. Based on the high-performance liquid chromatography (HPLC) results, methyl-2-benzoylbenzoate (MBB), fluoranthene (FLA) and syringaldehyde (SG) showed a promoted effect on the photodegradation of NPy and NSA, as shown by an increase in the photolysis frequency of ArNO 2 (J ArNO 2) by a factor of 1.19–2.76. Based on experimental results, the HONO source strength by the photolysis of ArNO 2 in organic aerosols was estimated to be lower than 1 ppt h−1. • Organics enhanced or impeded the HONO generation by the nitroaromatics photolysis. • The nitroaromatics photolysis frequency increased by 0.19–1.76 times with organics. • The HONO source strength of nitroaromatics photolysis was lower than 1 ppt h−1. [ABSTRACT FROM AUTHOR]

Organic aerosols are ubiquitous in the atmosphere and oxygenated organics are a major driver of aerosol growth. The volatility basis set (VBS) as introduced by Donahue et al. (2006, 2011) is often used to simplify the partitioning behavior of the huge variety of atmospheric organics. Recently, the VBS was used to dynamically model aerosol growth from the smallest sizes onwards. This tutorial is intended to equip the reader with the necessary tools to facilitate organic growth modelling based on gas-phase measurements of oxygenated organics using a 2-dimensional VBS. We start with a contextualization of the VBS in partitioning theory and point out the need for dynamic modeling. We provide an overview on the most common methods to estimate the volatility of oxygenated organics and give detailed instruction on how to construct the binned VBS. We then explain the dynamic condensation model including solution and curvature effects. Furthermore, we provide a python package for VBS growth calculations and show with two examples from ambient and chamber measurements how growth rates can be calculated. Last, we summarize the limitation of this approach and outline necessary future developments. • Provides a contextualization of the VBS in partitioning theory and dynamic modeling. • Gives instructions on the most common methods to estimate the volatility of oxygenated organics and construction of the VBS. • Explains the dynamic condensation model including solution and curvature effects. • Provides freely accessible code to facilitate growth modeling. [ABSTRACT FROM AUTHOR]

Organic aerosol (OA) is one of the major components of fine atmospheric aerosol particles. Recent field campaigns and modeling studies in Colombia have demonstrated the presence of a large OA fraction in urban and rural aerosols. In this work we focus on constraining the sources associated with OA and its precursors over the city of Bogotá, Colombia. We used PM 2.5 chemical speciation data from field campaigns carried out during 2018 to evaluate the ability of a regional transport model to reproduce and explain the observed OA. The samples were collected at three sites during high- and low-aerosol concentration seasons in the region. We used The Weather Research and Forecasting Model coupled with Chemistry (WRF-Chem) with two different chemical mechanisms and aerosol schemes, RACM/MADE-VBS and MOZART/MOSAIC, in conjunction with the detailed in-situ aerosol chemical speciation observations to analyze the seasonality of OA in the city of Bogotá, and to establish the most relevant sources. Simulations were carried out for the same periods for which data is available, spanning a high biomass burning (BB) season (February 2018) and a low biomass burning season (September 2018). We demonstrated that long-range transport of BB emissions from Northern Amazonia can episodically increase aerosol loading during September, while BB activity in the Grasslands of the Orinoco River Basin are the main source during February. The two aerosol schemes utilized in this work reproduce the observed seasonal variations in total fine aerosol concentration, with a difference between February and September of 10 μ g m−3. The comparison between aerosol schemes demonstrated that MOZART/MOSAIC consistently predicted more OA with a larger SOA:OA ratio than in the RACM/MADE-VBS experiment. SOA dominates the OA fraction by 66% for RACM/MADE-VBS and 74% for MOZART/MOSAIC during February and 69% for RACM/MADE-VBS and 71% for MOZART/MOSAIC during September. These differences between organic aerosol burden between the mechanisms used in this study may be attributed to the different treatment of SOA gas/particle partitioning in the schemes. • WRF-Chem simulations and in-situ PM 2.5 chemical composition data were used to understand the contribution of OA over Bogotá. • Biomass burning plumes from Northern Amazonia and from the Orinoco River Grassland can severely impact the region. • Field data shows that OA contributes over 40% to PM 2.5 in the city. • The model underpredicts organic aerosols, with the MOZART/MOSAIC scheme predicting higher POA and SOA than RACM/MADE-VBS. [ABSTRACT FROM AUTHOR]

The air quality in the outflow from Fort Worth, TX was studied in June 2011 at a location surrounded by oil and gas development in the Barnett Shale. The objectives of this study were to understand the major sources of volatile organic compounds (VOCs) and organic aerosols and explore the potential influence each VOC source had on ozone and secondary organic aerosol formation. Measurements of VOCs were apportioned between six factors using Positive Matrix Factorization (PMF): Natural Gas (25 ± 2%; ±99% CL); Fugitive Emissions (15 ± 2%); Internal Combustion Engines (15 ± 2%); Biogenic Emissions (7 ± 1%); Industrial Emissions/Oxidation 1(8 ± 1%); and Oxidation 2 (18 ± 2%). Reactivity calculations suggest the Biogenic and Oxidation 2 factors were the most likely VOC sources to influence local ozone. However, enough OH reactivity was calculated for factors related to the oil and gas development that they could incrementally increase O 3 . Three organic aerosol (OA) types were identified with PMF applied to high-resolution time-of-flight aerosol mass spectrometry measurements: hydrocarbon-like OA (HOA; 11% of mass) and two classes of oxidized OA (semi- and less-volatile OOA, SV and LV; 45% and 44%, respectively). The HOA correlated with the Internal Combustion Engine VOC factor indicating that a large fraction of the HOA was emitted by gasoline and diesel motors. The SV-OOA correlated with the oxidized VOC factors during most of the study, whereas a correlation between LV-OOA and the oxidized VOC factors was only observed during part of the study. It is hypothesized that SV-OOA and the oxidized VOC factors correlated reasonably well because these factors likely were separated by at most only a few oxidation generations on the oxidation pathway of organic compounds. [ABSTRACT FROM AUTHOR]

In this study the long-term trends of non-refractory submicrometer aerosol (NR-PM 1 ) composition and mass concentration measured by an Aerosol Chemical Speciation Monitor (ACSM) at the Atmospheric Radiation Measurement (ARM) program's Southern Great Plains (SGP) site are discussed. NR-PM 1 data was recorded at ∼30 min intervals over a period of 19 months between November 2010 and June 2012. Positive Matrix Factorization (PMF) was performed on the measured organic mass spectral matrix using a rolling window technique to derive factors associated with distinct sources, evolution processes, and physiochemical properties. The rolling window approach also allows us to capture the dynamic variations of the chemical properties in the organic aerosol (OA) factors over time. Three OA factors were obtained including two oxygenated OA (OOA) factors, differing in degrees of oxidation, and a biomass burning OA (BBOA) factor. Back trajectory analyses were performed to investigate possible sources of major NR-PM 1 species at the SGP site. Organics dominated NR-PM 1 mass concentration for the majority of the study with the exception of winter, when ammonium nitrate increases due to transport of precursor species from surrounding urban and agricultural areas and also due to cooler temperatures. Sulfate mass concentrations have little seasonal variation with mixed regional and local sources. In the spring BBOA emissions increase and are mainly associated with local fires. Isoprene and carbon monoxide emission rates were obtained by the Model of Emissions of Gases and Aerosols from Nature (MEGAN) and the 2011 U.S. National Emissions Inventory to represent the spatial distribution of biogenic and anthropogenic sources, respectively. The combined spatial distribution of isoprene emissions and air mass trajectories suggest that biogenic emissions from the southeast contribute to SOA formation at the SGP site during the summer. [ABSTRACT FROM AUTHOR]

Residential cooking in China's urban areas could be a more significant contributor to organic aerosols when compared to restaurant cooking, yet no source profiles are available for Chinese residential cooking. In this study, a typical nine-floor residential apartment building in urban Guangzhou was selected to investigate the particulate mass emissions and chemical compositions of organic aerosols from Chinese residential cooking. During dinner cooking period, the average of total suspended particle (TSP) mass concentrations increased by a factor of 4.40 compared with that during non-cooking period. Organic matter (OM) was the major component of aerosols from cooking, and accounted for 66.9 % of the TSP mass. Over 90 organic species were identified and quantified, and could explain 14.5 % of OC in cooking emissions. Fatty acids alone shared 75.7 % of the total mass of quantified organic compounds, with palmitic acid as the predominant one. Sterols, monosaccharide anhydrides and polyols were also significant compositions and they together contributed 14.3 % in the total mass of the quantified organic compounds. While cholesterol was detected from western-style cooking, phytosterols were additionally observed from Chinese-style cooking, and campesterol and polyols were only reported in the present study. Chinese residential cooking emission showed small differences in composition patterns of organic compounds when compared to previously report Chinese restaurant cooking emissions, however, large differences existed when compared to western style cooking. Using cholesterol as a tracer for cooking emissions, in Guangzhou we found cooking emissions contributed 3.9-8.2 % of OC in PM. Spatial distributions of cooking emission contribution were consistent with the distributions of population. [ABSTRACT FROM AUTHOR]

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 (1H 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 1H NMR analysis corroborated that the WSOC and MSOC fractions hold similar 1H 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/m3. 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 1H 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. [Display omitted] • Aerosols of traffic exhaust origin show more hydrophobic nature functional groups. • Ar–H largely primary in origin and correlates positively with EC, WSOC and H–C at urban sites. • WSOC fraction fits the established 1H NMR source apportionment regions of urban aerosols. • Biomass cooking aerosols depict distinct character and with new source boundaries. [ABSTRACT FROM AUTHOR]

Aerosol samples were collected in autumn 2007 on day- and nighttime basis in the northern receptor site of Beijing, China. The samples were analyzed for total carbon (TC) and water-soluble dicarboxylic acids (C 2 –C 12 ), oxocarboxylic acids (C 2 –C 9 ), glyoxal and methylglyoxal to better understand the photochemical aging of organic aerosols in the vicinity of Beijing. Concentrations of TC are 50% greater in daytime when winds come from Beijing than in nighttime when winds come from the northern forest areas. Most diacids showed higher concentrations in daytime, suggesting that the organics emitted from the urban Beijing and delivered to the northern vicinity in daytime are subjected to photo-oxidation to result in diacids. However, oxalic acid (C 2 ), which is the most abundant diacid followed by C 3 or C 4 , became on average 30% more abundant in nighttime together with azelaic, ω-oxooctanoic and ω-oxononanoic acids, which are specific oxidation products of biogenic unsaturated fatty acids. Methylglyoxal, an oxidation product of isoprene and a precursor of oxalic acid, also became 29% more abundant in nighttime. Based on a positive correlation between C 2 and glyoxylic acid (ωC 2 ) in nighttime when relative humidity significantly enhanced, we propose a nighttime aqueous phase production of C 2 via the oxidation of ωC 2 . We found an increase in the contribution of diacids to TC by 3 folds during consecutive clear days. This study demonstrates that diacids and related compounds are largely produced in the northern vicinity of Beijing via photochemical processing of organic precursors emitted from urban center and forest areas. [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: Wintertime TSP samples collected in the two megacities of Xi'an, China and New Delhi, India were analyzed for elements, inorganic ions, carbonaceous species and organic compounds to investigate the differences in chemical compositions and sources of organic aerosols. The current work is the first time comparing the composition of urban organic aerosols from China and India and discussing their sources in a single study. Our results showed that the concentrations of Ca, Fe, Ti, inorganic ions, EC, PAHs and hopanes in Xi'an are 1.3–2.9 times of those in New Delhi, which is ascribed to the higher emissions of dust and coal burning in Xi'an. In contrast, Cl−, levoglucosan, n-alkanes, fatty alcohols, fatty acids, phthalates and bisphenol A are 0.4–3.0 times higher in New Delhi than in Xi'an, which is attributed to strong emissions from biomass burning and solid waste incineration. PAHs are carcinogenic while phthalates and bisphenol A are endocrine disrupting. Thus, the significant difference in chemical compositions of the above TSP samples may suggest that residents in Xi'an and New Delhi are exposed to environmental hazards that pose different health risks. Lower mass ratios of octadecenoic acid/octadecanoic acid (C18:1/C18:0) and benzo(a)pyrene/benzo(e)pyrene (BaP/BeP) demonstrate that aerosol particles in New Delhi are photochemically more aged. Mass closure reconstructions of the wintertime TSP indicate that crustal material is the most abundant component of ambient particles in Xi'an and New Delhi, accounting for 52% and 48% of the particle masses, respectively, followed by organic matter (24% and 23% in Xi'an and New Delhi, respectively) and secondary inorganic ions (sulfate, nitrate plus ammonium, 16% and 12% in Xi'an and New Delhi, respectively). [Copyright &y& Elsevier]

Tropical aerosols of PM2.5 and PM10 were collected at a rural site in Morogoro, Tanzania (East Africa), and analysed for stable carbon isotopic composition (d13C) of dicarboxylic acids (C2-C9), glyoxylic acid (?C2) and glyoxal (Gly) using gas chromatography/isotope ratio mass spectrometer. PM2.5 samples showed that d13C of oxalic (C2) acid are largest (mean, -18.3±1.7‰) followed by malonic (C3, -19.6±1.0‰) and succinic (C4, -21.8±2.2‰) acids, whereas those in PM10 are a little smaller: -19.9±3.1‰ (C2), -20.2±2.7‰ (C3) and -23.3±3.2‰ (C4). The d13C of C2-C4 diacids showed a decreasing trend with an increase in carbon numbers. The higher d13C values of oxalic acid can be explained by isotopic enrichment of 13C in the remaining C2 due to the atmospheric decomposition of oxalic acid or its precursors. d13C of ?C2 and Gly that are precursors of oxalic acid also showed larger values (mean, -22.5‰ and -20.2‰, respectively) in PM2.5 than those (-26.7‰ and -23.7‰) in PM10. The d13C values of ?C2 and Gly are smaller than those of C2 in both PM2.5 and PM10. On the other hand, azelaic acid (C9; mean, -28.5‰) is more depleted in 13C, which is consistent with the previous knowledge; that is, C9 is produced by the oxidation of unsaturated fatty acids emitted from terrestrial higher plants. A significant enrichment of 13C in oxalic acid together with its negative correlations with relative abundance of C2 in total diacids and ratios of water-soluble organic carbon and organic carbon further support that a photochemical degradation of oxalic acid occurs during long-range transport from source regions. [ABSTRACT FROM AUTHOR]

An intensive field campaign was carried out in Hefei, a city in the Yangtze River Delta in eastern China, in the summer of 2020 to examine the composition and sources of organic aerosols (OA). Time-resolved filter samples were collected and quantified to obtain the concentrations for organic functional groups (OFGs), including alkane, hydroxyl, carboxylic acid, non-acid carbonyl, amine, and aromatic groups using Fourier transform infrared (FTIR). Inorganic aerosol components and gas-phase pollutants were also measured to facilitate the data analysis. The OA concentration ranged from 2.8 to 41.8 μg m−3, with a mean value (±standard deviation) of 12.5 (±5.8) μg m−3, which accounted for 53.6% of the PM 2.5 mass. The most abundant OFG in OA was the hydroxyl group (35.2%), followed by alkane (24.0%) and carboxylic (22.4%) groups. The positive matrix factorization (PMF) was applied to the IR spectra of OA that identified three major sources, i.e., aged fossil fuel combustion, biomass burning, and vegetative detritus/dust. Their campaign-average contributions to OA were 38.3%, 28.3%, and 33.4%, respectively. The OFG composition of the aged fossil fuel combustion component was similar to the OFG composition of oxidized alkane products, indicating that alkanes may be important precursors of OA at the sampling site. Cluster and air mass trajectory analyses showed that the OFG concentration was highest when the air masses originated from the eastern Yangtze River Delta, suggesting the influence of the transported industrial emissions on the particulate pollution at the sampling site. • Organic functional group composition of PM 2.5 was quantified using FTIR in eastern China for the first time. • PMF identified aged fossil fuel combustion, biomass burning, and vegetative detritus/dust as sources of organic aerosols. • High particulate pollution was associated with air masses originating from the industrial areas of the Yangtze River Delta. [ABSTRACT FROM AUTHOR]