Quantification of urban organic aerosols at a molecular level: Identification, abundance and seasonal variation

Characteristics of typical intermediate and semi volatile organic compounds in Shanghai during China International Import Expo event

To ensure good air quality during the China International Import Expo (CIIE) event, stringent emission-reduction measures were implemented in Shanghai. To assess the efficacy of these measures, this study measured typical categories of intermediate/semi volatile organic compounds (I/SVOCs), including alkanes (C10-C26 n-alkanes and pristane), EPA-priority polycyclic aromatic hydrocarbons (PAHs), alkylnaphthalenes, benzothiazole (BTH) and chlorobenzenes (CBs), at an urban site of Shanghai before and during two CIIE events (2019 and 2020; non-CIIE versus CIIE). The average concentrations of alkanes and PAHs during both 2019 and 2020 CIIE events decreased by approximately 41% and 17%, respectively, compared to non-CIIE periods. However, the decline in BTH and CBs was only observed during CIIE-2019. Secondary organic aerosol (SOA) formation from alkanes, PAHs and BTH was evaluated under atmospheric conditions, revealing considerable SOA contributions from dimethylnaphthalenes and BTH. Positive matrix factorization (PMF) analysis further revealed that life-related sources, such as cooking and residential emissions, make a noticeable contribution (21.6%) in addition to the commonly concerned gasoline-vehicle sources (31.5%), diesel-related emissions (20.8%), industrial emissions (18.6%) and ship emissions (7.5%). These findings provide valuable insights into the efficacy of the implemented measures in reducing atmospheric I/SVOCs levels. Moreover, our results highlight the significance of exploring additional individual species of I/SVOCs and life-related sources for further research and policy development.

Implications of PM2.5 chemical composition in modulating microbial community dynamics during spring in Seoul

Particulate matter with an aerodynamic diameter of 2.5 μm or less (PM2.5) harbors a diverse microbial community. To assess the ecological dynamics and potential health risks associated with airborne microorganisms, it is crucial to understand the factors influencing microbial communities within PM2.5. This study investigated the influence of abiotic parameters, including air pollutants, PM2.5 chemical composition (water-soluble ions and organics), and meteorological variables, on microbial communities in PM2.5 samples collected in Seoul during the spring season. Results revealed a significant correlation between air pollutants and water-soluble ions of PM2.5 with microbial α-diversity indices. Additionally, air pollutants exerted a dominant effect on the microbial community structure, with stronger correlations observed for fungi than bacteria, whereas meteorological variables including temperature, pressure, wind speed, and humidity exerted a limited influence on fungal α-diversity. Furthermore, the results revealed specific water-soluble ions, such as SO42-, NO3-, and NH4+, as important factors influencing fungal α-diversity, whereas K+ negatively correlated with both microbial α-diversity. Moreover, PM2.5 microbial diversity was affected by organic compounds within PM2.5, with fatty acids exhibited a positive correlation with fungal diversity, while dicarboxylic acids exhibited a negative correlation with it. Furthermore, network analysis revealed direct links between air pollutants and dominant bacterial and fungal genera. The air pollutants exhibited a strong correlation with bacterial genera, such as Arthrospira and Clostridium, and fungal genera, including Aureobasidium and Cladosporium. These results will contribute to our understanding of the ecological dynamics of airborne microorganisms and provide insights into the potential risks associated with PM2.5 exposure.

Quantifying functional group compositions of household fuel-burning emissions

Globally, billions of people burn fuels indoors for cooking and heating, which contributes to millions of chronic illnesses and premature deaths annually. Additionally, residential burning contributes significantly to black carbon emissions, which have the highest global warming impacts after carbon dioxide and methane. In this study, we use Fourier transform infrared spectroscopy (FTIR) to analyze fine-particulate emissions collected on Teflon membrane filters from 15 cookstove types and 5 fuel types. Emissions from three fuel types (charcoal, kerosene, and red oak wood) were found to have enough FTIR spectral response for functional group (FG) analysis. We present distinct spectral profiles for particulate emissions of these three fuel types. We highlight the influential FGs constituting organic carbon (OC) using a multivariate statistical method and show that OC estimates by collocated FTIR and thermal-optical transmittance (TOT) are highly correlated, with a coefficient determination of 82.5 %. As FTIR analysis is fast and non-destructive and provides complementary FG information, the analysis method demonstrated herein can substantially reduce the need for thermal-optical measurements for source emissions.

Sources and influences of atmospheric nonpolar organic compounds in Nanchang, central China: Full-year monitoring with a focus on winter pollution episodes

Nonpolar organic compounds (NPOCs) are found in atmospheric aerosols and have significant implications for environmental and human health. Although many studies have quantitatively estimated the sources of NPOCs in different cities, few have evaluated their main influencing factors (e.g., emissions and meteorological conditions) at relatively long (e.g., different seasons) and short timescales (e.g., several days during pollution episodes). A better understanding of this issue could optimise strategies for dealing with organic contamination in atmospheric particulate matter. NPOCs (including n-alkanes, PAHs and hopanes) in fine particulate matter (PM2.5) were sampled daily at Nanchang, China, from 1 November 2020 to 31 October 2021. Analyses of specific biomarkers and diagnostic ratios indicate that the NPOCs mainly had anthropogenic sources. The quantitative estimates of a positive matrix factorization model show that fossil fuel and biomass combustion were the main sources of n-alkanes (contributing 64.8 %), while vehicle exhaust was the main source of PAHs (47.0 %) and hopanes (52.3 %). Seasonally, the contributions from coal and/or biomass combustion were higher in autumn and winter (40.2-56.3 %) than in spring and summer (25.7-44.3 %), while contributions from natural plants, petroleum volatilization and vehicle exhaust were higher in spring and summer (14.7-63.5 %) than in autumn and winter (8.1-48.9 %). Redundancy analysis shows that increased emissions, especially from coal and/or biomass combustion, are the main cause of increases in NPOCs, during both annual sampling periods and winter pollution episodes. Over the year, higher temperature and longer sunshine hours correspond to lower NPOC concentrations. In winter pollution episodes, increases in temperature and relative humidity correspond to increases in NPOC concentrations. Our results suggest that controlling primary emissions, especially from coal and biomass combustion, may be an effective way to prevent increases in NPOC concentrations.

Anthropogenic emission controls organic aerosols at Gosan background site in the outflow from northeast Asia

Anthropogenic activities release substantial amounts of organic components into the atmosphere. In this study, eight groups of organic compounds such as polycyclic aromatic hydrocarbons (PAHs), hopanes, steranes, n-alkanes, fatty acids, fatty alcohols, phthalate esters, and lignin and resin acids were identified in the ambient aerosol samples collected from a regional background site in the Korean Climate Observatory at Gosan (KCOG), South Korea. The total identified organics were most abundant in winter (220 ± 60.3 ng m-3), followed by spring, autumn, and summer, with the predominance of n-fatty acids. All classes of aliphatic lipid components showed a significant positive correlation with fossil fuel-derived organic carbon (OC-FF) and biomass burning-derived organic carbon (OC-BB), indicating that they were abundantly emitted from anthropogenic sources such as fossil fuel combustion and biomass burning. The composition profiles and diagnostic ratios of PAHs indicate that they were largely derived from coal and/or biomass combustion in the continent. In contrast, hopanes are predominantly emitted from gasoline or diesel engines, particularly in the summer, from commercial ships. The high concentration of phthalates in the summer suggested that plastic emissions from the open ocean substantially contributed to the Gosan aerosols. The low ratios of unsaturated/saturated fatty acids indicate that Gosan organic aerosols were photochemically aged during atmospheric transport. The temporal and seasonal variations of organic species over KCOG provide crucial information on the emission strengths of different contributing sources in the East Asian outflow. Positive Matrix Factorization (PMF) results and 14C-based source apportionment studies demonstrated that anthropogenically derived organic aerosols largely contributed to the aerosol mass over KCOG. Thus, the East Asian continent might be the major source region for organic aerosols over the western North Pacific, except in the summer.

Hydroxy fatty acids in the surface Earth system

Lipids are ubiquitous and highly abundant in a wide range of organisms and have been found in various types of environmental media. These molecules play a crucial role as organic tracers by providing a chemical perspective on viewing the material world, as well as offering a wealth of information on metabolic activities. Among the diverse lipid compounds, hydroxy fatty acids (HFAs) with one to multiple hydroxyl groups attached to the carbon chain stand out as important biomarkers for different sources of organic matter. HFAs are widespread in nature and are involved in biotransformation and oxidation processes in living organisms. The unique chemical and physical properties attributed to the hydroxyl group make HFAs ideal biomarkers in biomedicine and environmental toxicology, as well as organic geochemistry. The molecular distribution patterns of HFAs can be unique and diagnostic for a given class of organisms, including animals, plants, and microorganisms. Thus, HFAs can act as a valuable proxy for understanding the ecological relationships between different organisms and their environment. Furthermore, HFAs have numerous industrial applications due to their higher reactivity, viscosity, and solvent miscibility. This review paper integrates the latest research on the sources and chemical analyses of HFAs, as well as their applications in industrial/medicinal production and as biomarkers in environmental studies. This review article also provides insights into the biogeochemical cycles of HFAs in the surface Earth system, highlighting the importance of these compounds in understanding the complex interactions between living organisms and the environment.

Emission factors for a biofuel impacted fleet in south America's largest metropolitan area

The Metropolitan Area of São Paulo (MASP) is among the largest urban areas in the Southern Hemisphere. Vehicular emissions are of great concern in metropolitan areas and MASP is unique due to the use of biofuels on a large scale (sugar-cane ethanol and biodiesel). In this work, tunnel measurements were employed to assess vehicle emissions and to calculate emission factors (EFs) for heavy-duty and light-duty vehicles (HDVs and LDVs). The EFs were determined for particulate matter (PM) and its chemical compounds. The EFs obtained for 2018 were compared with previous tunnel experiments performed in the same area. An overall trend of reduction of fine and coarse PM, organic carbon (OC), and elemental carbon (EC) EFs for both LDVs and HDVs was observed if compared to those observed in past years, suggesting the effectiveness of vehicular emissions control policies implemented in Brazil. A predominance of Fe, Cu, Al, and Ba metals emission was observed for the LDV fleet in the fine fraction. Cu presented higher emissions than two decades ago, which was associated with the increased use of ethanol fuel in the region. For HDVs, Zn and Pb were mostly emitted in the fine mode and were linked with lubricating oil emissions from diesel vehicles. A predominance in the emission of three- and four-ring polycyclic aromatic hydrocarbons (PAHs) for HDVs and five-ring PAHs for LDVs agreed with what was observed in previous studies. The use of biofuels may explain the lower PAH emissions for LDVs (including carcinogenic BaP) compared to those observed in other countries. The tendency observed was that LDVs emit higher amounts of carcinogenic species. The use of these real EFs in air quality modeling resulted in more accurate simulations of PM concentrations, showing the importance of updating data with real-world measurements.

Comparison of the sources and oxidative potential of PM2.5 during winter time in large cities in China and South Korea

Regional air pollution is rising in Northeast Asia due to increasing energy consumption resulting from a growing population and intensifying industrialization. This study analyzes the sources of air pollution using fine particulate matter (PM_2.5) sampling from the atmosphere over Korea and China. We then use this analysis to further investigate the relationship between organic compounds (source tracers) and the oxidative potential of PM_2.5. The PM_2.5 concentration during winter measured at a measurement stations in Korea showed no significant variation year-to-year. The PM_2.5 concentrations measured during winter at a site near Beijing, China were 62.45 μg/m³ in 2018 and 33.07 μg/m³ in 2020. The sources, as determined from PMF, were analyzed at a site in Korea, the sources as secondary nitrate (34.10 %), secondary sulfate (20.20 %), coal combustion (4.01 %), vehicle emission (8.55 %), cooking and biomass burning (18.39 %), dust (8.45 %), and SOA (6.29 %) were identified. At a site in China, secondary nitrate (17.54 %), secondary sulfate (12.03 %), coal combustion (15.53 %), vehicle emission (12.43 %), cooking and biomass burning (9.25 %), dust (26.40 %), secondary organic aerosol (6.82 %) were identified. Our results show secondary organic carbon had a positive association with oxidative potential in Korea while primary organic carbon presented higher correlation with oxidative potential in China. Further, the ECMWF Reanalysis v5 (ERA5) wind field during the high PM_2.5 events demonstrated airflow from the west coast of China resulting in high polar organic compounds at the Korean monitoring site. The results further support that aged PM_2.5, which contains secondary products, leads to increased oxidative potential. The results presented explain the high concentrations of secondary products and the impact on the biological activities of PM_2.5, supporting additional actions to address the impacts of long-range transport of PM_2.5.

Approaches to the source evaluation of chlorinated polycyclic aromatic hydrocarbons in fine particles

Chlorinated polycyclic aromatic hydrocarbons (ClPAHs) have been recognized as novel hazardous pollutants; however, the dominant sources remain unclear. This study investigates the occurrences of ClPAHs in five stages of size-segregated particles collected from an urban site and evaluates the sources and factors affecting the concentrations using organic and inorganic source tracers. ClPAHs are the most frequently detected in the finest particle fraction (less than 1.1 µm; PM1.1), similar to polycyclic aromatic hydrocarbons (PAHs), hopanes, and levoglucosan (LEV). The concentrations of total ClPAHs in PM1.1 shows a significant correlation (p < 0.05) with those of total PAHs and specific hopanes but not to LEV and biogenic fatty acids; this suggests that ClPAHs dominantly originate from industrial activities and vehicular emissions. Heatmap analysis, including source tracers, is used to categorize the possible sources of ClPAHs into three types: ClPAH-specific sources, local industrial activities and vehicular emissions, and remote industrial activities. Furthermore, correlation network analysis is used to clarify the relationships between the pollutants.

An extensive assessment on the distribution pattern of organic contaminants in the aerosols samples in the Middle East

Nowadays, in spite of a significant progress in indoor air quality (IAQ), an assessable and predictive understanding of atmospheric aerosol sources, chemical composition, transformation processes, and environmental effects are still rather incomplete and therefore signifies a key research challenge in the atmospheric science. Thus, the current comprehensive review is concerned with the dominant sources, organic compositions, and potential health impacts of the organic contaminants in the atmospheric particle matters (PMs) in the Middle East (ME). The ME contributes a major impact of organic contaminants on the atmosphere along with other Asian and African countries. In the Gulf Cooperation Council (GCC) countries, the communities are noted for being the center of the great majority of the world’s oil reserves and infrastructure for producing crude oil. The review starts with a historical outlook on the scientific queries regarding major source of organic contaminants to the atmospheric aerosols over the past centuries, followed by an explanation of the distribution, sources, transformation processes, and chemical and physical properties as they are formerly assumed. Natural product chemicals from biota, manufactured organic compounds including pesticides, chlorinated hydrocarbons, and lubricants, as well as organic compounds from the use and combustion of fossil fuels make up the aerosol contamination. Thus, in the recent years, IAQ may be seen as a significant health issue because of the increase in industrial activity. Fugitive emissions from industrial processes, as well as natural and anthropogenic emissions from other sources such as forest fires, volcanic eruptions, incomplete combustion of fossil fuels, wood, agricultural waste, or leaves, are typical sources of organic pollutants to the aerosol. In the spring and early summer in the GCC countries, aerosol concentration increases because of dust storms; however, in winter, there are fewer dust storms and higher precipitation rates, and aerosol concentrations are lower. Significances of future research and major suggestions are also outlined to narrow the gap between the present understanding of the contribution of both anthropogenic and biogenic aerosols to radiative forcing, resulting from the spatial nonuniformity, intermittency of sources, unresolved composition, and reactivity.

Physical and chemical characterization of urban grime: An impact on the NO2 uptake coefficients and N-containing product compounds

Urban grime represents an important environmental surface for heterogeneous reactions in urban environment. Here, we assess the physical and chemical properties of urban grime collected during six consecutive months in downtown of Guangzhou, China. There is a significant variation of the uptake coefficients of NO₂ on the urban grime as a function of the relative humidity (RH). In absence of water molecules (0% RH), the light-induced uptake coefficients of NO₂ on urban grime samples collected during six months are very similar in order of ≈10^-6. At 80% RH, depending on the sampling month the light-induced uptake coefficient of NO₂ can reach one order of magnitude higher values (1.5 × 10^-5, at 80% RH) compared to those uptakes at 0% RH. In presence of 80% RH, there are strong correlations between the measured NO₂ uptakes and the concentrations of the water soluble carbon, soluble anions, polycyclic aromatic hydrocarbons and n-alkanes depicted in the urban grime. These correlations, demonstrate that surface adsorbed water on urban grime play an important role for the uptakes of NO₂. The heterogeneous conversion of NO₂ on two-month old urban grime under sunlight irradiation (68 W m^-2, 300 nm < λ < 400 nm) at 60% RH leads to the formation of unprecedented HONO surface flux of 4.7 × 10¹⁰ molecules cm^-2 s^-1 which is higher than all previously observed HONO fluxes, thereby affecting the oxidation capacity of the urban atmosphere. During the heterogeneous chemistry of NO₂ with urban grime, the unsaturated and N-containing organic compounds are released in the gas phase which can affect the air quality in the urban environment.

Primary and secondary organic winter aerosols in Mediterranean cities under different mixing layer conditions (Barcelona and Granada)

PM₁₀ was collected during an EMEP winter campaign of 2017-2018 in two urban background sites in Barcelona (BCN) and Granada (GRA), two Mediterranean cities in the coast and inland, respectively. The concentrations of PM₁₀, organic carbon (OC), elemental carbon (EC), and organic molecular tracer compounds such as hopanes, anhydro-saccharides, polycyclic aromatic hydrocarbon, and several biogenic and anthropogenic markers of secondary organic aerosols (SOA) were two times higher in GRA compared to BCN and related to the atmospheric mixing heights in the areas. Multivariate curve resolution (MCR-ALS) source apportionment analysis identified primary emissions sources (traffic + biomass burning) that were responsible for the 50% and 20% of the organic aerosol contributions in Granada and Barcelona, respectively. The contribution of biomass burning was higher in the holidays than in the working days in GRA while all primary combustion emissions decreased in holidays in BCN. The MCR-ALS identified that oxidative species and SOA formation processes contributed to 40% and 80% in Granada and Barcelona, respectively. Aged SOA was dominant in Granada and Barcelona under stagnant atmospheric conditions and in presence of air pollution. On the other hand, fresh SOA contributions from α-pinene oxidation (cis-pinonic acid) were three times higher in Barcelona than Granada and could be related to new particle formation, essentially due to overall cleaner air conditions and elevated air temperatures.

Phase Behavior of Internal Mixtures of Hydrocarbon-like Primary Organic Aerosol and Secondary Aerosol Based on Their Differences in Oxygen-to-Carbon Ratios

The phase behavior, the number and type of phases, in atmospheric particles containing mixtures of hydrocarbon-like organic aerosol (HOA) and secondary organic aerosol (SOA) is important for predicting their impacts on air pollution, human health, and climate. Using a solvatochromic dye and fluorescence microscopy, we determined the phase behavior of 11 HOA proxies (O/C = 0-0.29) each mixed with 7 different SOA materials generated in environmental chambers (O/C 0.4-1.08), where O/C represents the average oxygen-to-carbon atomic ratio. Out of the 77 different HOA + SOA mixtures studied, we observed two phases in 88% of the cases. The phase behavior was independent of relative humidity over the range between 90% and <5%. A clear trend was observed between the number of phases and the difference between the average O/C ratios of the HOA and SOA components (ΔO/C). Using a threshold ΔO/C of 0.265, we were able to predict the phase behavior of 92% of the HOA + SOA mixtures studied here, with one-phase particles predicted for ΔO/C < 0.265 and two-phase particles predicted for ΔO/C ≥ 0.265. The threshold ΔO/C value provides a relatively simple and computationally inexpensive framework for predicting the number of phases in internal SOA and HOA mixtures in atmospheric models.

Oxidative potential of solvent-extractable organic matter of ambient total suspended particulate in Bangkok, Thailand

Oxidative stress is a key mechanism by which ambient particulate matter induces adverse health effects. Most studies have focused on the oxidative potential (OP) of water-soluble constituents, while there has been limited work on the OP of solvent-extractable organic matter (EOM OP). In this study, the EOM OP of ambient total suspended particulate (TSP) from Bangkok, Thailand, was determined using the dithiothreitol (DTT) assay. Positive matrix factorization (PMF), combined with chemical analysis of molecular markers, was employed to apportion the contributions of various emission sources to EOM OP. The volume-normalized OP initially increased with organic carbon (OC) concentration and plateaued gradually, while the mass-normalized OP fitted well with OC concentration using a power function. Fossil fuel combustion (62%) and plastic waste burning (23%) were the major contributors to EOM OP, while biomass burning demonstrated only a limited contribution. EOM OP correlated well with each group of polycyclic aromatic hydrocarbons (PAHs), suggesting that secondary formation of quinones associated with fossil fuel combustion and plastic waste burning could be an important pathway of TSP toxicity. This study underscores the importance of considering different emission sources when evaluating potential health impacts and the implementation of air pollution regulations.

Occurrences and Potential Sources of Halogenated Polycyclic Aromatic Hydrocarbons Associated with PM2.5 in Mumbai, India

Occurrences of chlorinated and brominated polycyclic aromatic hydrocarbons (ClPAHs and BrPAHs, respectively) in fine aerosol particulate matter <2.5 μm in diameter were investigated in urban and suburban sites in Mumbai, India; and the possible sources from association with indicators, such as hopanes, steranes, and trace elements are discussed. The mean concentrations of total ClPAHs and BrPAHs were 0.54 and 0.25 ng/m³ in the urban site and 0.16 and 0.02 ng/m³ in the suburban site during the campaign, respectively. The variations in total Cl-/BrPAH concentrations showed a similar trend between the urban and suburban sites, whereas the composition profiles varied in each air sample. The relationships between the concentrations among individual compounds in the urban site suggest that dominant sources of Cl-/BrPAHs could be common to PAHs but not in the suburban site. Principal component analysis using the data set of certain compounds showed that Cl-/BrPAH concentrations in urban and suburban sites are occasionally driven by specific sources of either coal combustion or traffic emissions. In contrast, most air samples during the campaign could be attributed to a mix of those sources. Environ Toxicol Chem 2022;41:312-320. © 2021 SETAC.

Phase Behavior of Hydrocarbon-like Primary Organic Aerosol and Secondary Organic Aerosol Proxies Based on Their Elemental Oxygen-to-Carbon Ratio

A large fraction of atmospheric aerosols can be characterized as primary organic aerosol (POA) and secondary organic aerosol (SOA). Knowledge of the phase behavior, that is, the number and type of phases within internal POA + SOA mixtures, is crucial to predict their effect on climate and air quality. For example, if POA and SOA form a single phase, POA will enhance the formation of SOA by providing organic mass to absorb SOA precursors. Using microscopy, we studied the phase behavior of mixtures of SOA proxies and hydrocarbon-like POA proxies at relative humidity (RH) values of 90%, 45%, and below 5%. Internal mixtures of POA and SOA almost always formed two phases if the elemental oxygen-to-carbon ratio (O/C) of the POA was less than 0.11, which encompasses a large fraction of atmospheric hydrocarbon-like POA from fossil fuel combustion. SOA proxies mixed with POA proxies having 0.11 ≤ O/C ≤ 0.29 mostly resulted in particles with one liquid phase. However, two liquid phases were also observed, depending on the type of SOA and POA surrogates, and an increase in phase-separated particles was observed when increasing the RH in this O/C range. The results have implications for predicting atmospheric SOA formation and policy strategies to reduce SOA in urban environments.

Predicting carbonaceous aerosols and identifying their source contribution with advanced approaches

Organic carbon (OC) and elemental carbon (EC) play important roles in various atmospheric processes and health effects. Predicting carbonaceous aerosols and identifying source contributions are important steps for further epidemiological study and formulating effective emission control policies. However, we are not aware of any study that examined predictions of OC and EC, and this work is also the first study that attempted to use machine learning and hyperparameter optimization method to predict concentrations of specific aerosol contaminants. This paper describes an investigation of the characteristics and sources of OC and EC in fine particulate matter (PM_2.5) from 2005 to 2010 in the City of Taipei. Respective hourly average concentrations of OC and EC were 5.2 μg/m³ and 1.6 μg/m³. We observed obvious seasonal variation in OC but not in EC. Hourly and daily OC and EC concentrations were predicted using generalized additive model and grey wolf optimized multilayer perceptron model, which could explain up to about 80% of the total variation. Subsequent clustering suggests that traffic emission was the major contribution to OC, accounting for about 80% in the spring, 65% in the summer, and 90% in the fall and winter. In the Taipei area, local emissions were the dominant sources of OC and EC in all seasons, and long-range transport had a significant contribution to OC and in PM_2.5 in spring.

Nuclear Magnetic Resonance Aerosolomics: A Tool for Analysis of Polar Compounds in Atmospheric Aerosols

Nuclear magnetic resonance aerosolomics was proposed as a new approach to the analysis of the water-soluble organic compound fraction in aerosol particulate matter. The identification of individual compounds is based on a comparison of precise chemical shifts in the 1H NMR spectrum with the signals in the standards library. For this purpose, Chenomx metabolomics software and a comprehensive spectra library of 150 compounds known from chemistry of aerosols were used. This approach enabled the identification of 60 compounds in real aerosol samples collected at a suburban site in Prague. Using the metabolomic spectra library, three new compounds were identified in aerosols for the first time, and an association of four other compounds to the atmospheric particulate matter was confirmed. The obtained concentration profiles of all identified chemical individuals were subsequently subjected to advanced statistical analysis. NMR aerosolomics clearly differentiates between summer and winter aerosol samples via multivariate statistical analysis and revealed some interesting trends in composition, according to aerosol particle size. Furthermore, the univariate statistical analysis was applied to highlight compounds responsible for the group separation, and possible sources of these compounds were suggested.

Aerosol-associated n-alkanes over Dhauladhar region of North-Western Himalaya: seasonal variations in sources and processes

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. PM₁₀ 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 PM₁₀ 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.

Indoor acids and bases

Numerous acids and bases influence indoor air quality. The most abundant of these species are CO₂ (acidic) and NH₃ (basic), both emitted by building occupants. Other prominent inorganic acids are HNO₃ , HONO, SO₂ , H₂ SO₄ , HCl, and HOCl. Prominent organic acids include formic, acetic, and lactic; nicotine is a noteworthy organic base. Sources of N-, S-, and Cl-containing acids can include ventilation from outdoors, indoor combustion, consumer product use, and chemical reactions. Organic acids are commonly more abundant indoors than outdoors, with indoor sources including occupants, wood, and cooking. Beyond NH₃ and nicotine, other noteworthy bases include inorganic and organic amines. Acids and bases partition indoors among the gas-phase, airborne particles, bulk water, and surfaces; relevant thermodynamic parameters governing the partitioning are the acid-dissociation constant (K_a ), Henry's law constant (K_H ), and the octanol-air partition coefficient (K_oa ). Condensed-phase water strongly influences the fate of indoor acids and bases and is also a medium for chemical interactions. Indoor surfaces can be large reservoirs of acids and bases. This extensive review of the state of knowledge establishes a foundation for future inquiry to better understand how acids and bases influence the suitability of indoor environments for occupants, cultural artifacts, and sensitive equipment.

Organic molecular markers and source contributions in a polluted municipality of north-east Italy: Extended PCA-PMF statistical approach

Exceeding the maximum levels for environmental pollutants creates public and scientific interest for the environmental and human health impact it may have. In Northern Italy, the Po Valley, and in particular the Veneto region, is still a hotspot for air quality improvement. Several monitoring campaigns were carried out in this area to acquire information about sources of pollutants which are considered critical. For the first time, a deep study of the aerosol organic fraction was performed in the town Sernaglia della Battaglia, nearby Treviso. During three seasons of 2017, PM₁ and PM_2.5 samples were collected simultaneously. Organic molecular markers have been analyzed by in-situ derivatization thermal desorption gas chromatography time-of-flight mass spectrometry (IDTD-GC-TOFMS). Alkanes, polycyclic aromatic hydrocarbons, oxi-polycyclic aromatic hydrocarbons, anhydrous sugars, resins acids, triterpenoids, and acids were considered. The organic chemical composition has been analyzed based on seasonal variation and source contributions. Principal Component Analysis (PCA) and Positive Matrix Factorization (PMF) have been combined to deeply investigate the main sources of particulate organic matter. On the one hand, PCA evaluates the correlations between the organic markers and their seasonal distribution. On the other hand, the source contributions to aerosol composition are estimated by PMF. Four main emission sources were found by PMF: solid fuel combustion (coal, wood), combustion of petroleum distillates (gas and fuel oil) and exhaust gases of vehicles, industrial combustion processes, home heating, and forest fires are evaluated as the most important sources for the air quality and pollution in this municipality of Northern Italy.

Review of Gravimetric Sensing of Volatile Organic Compounds

Volatile organic compounds (VOCs) are pervasive in the environment. Since the early 1980s, substantial work has examined the detection of these materials, as they can indicate environmental changes that can affect human health. VOCs and similar compounds present a very specific sensing problem in that they are not reactive and often nonpolar, so it is difficult to find materials that selectively bind or adsorb them. A number of techniques are applied to vapor sensing. High resolution molecular separation approaches such as gas chromatography and mass spectrometry are well-characterized and offer high sensitivity, but are difficult to implement in portable, real-time monitors, whereas approaches such as chemiresistors are promising, but still in development. Gravimetric approaches, in which the mass of an adsorbed vapor is directly measured, have several potential advantages over other techniques but have so far lagged behind other approaches in performance and market penetration. This review aims to offer a comprehensive background on gravimetric sensing including underlying resonators and sensitizers, as well as a picture of applications and commercialization in the field.

Impacts of Sources on PM2.5 Oxidation Potential during and after the Asia-Pacific Economic Cooperation Conference in Huairou, Beijing

To illustrate the major sources responsible for the redox activity of ambient fine particles during the 2014 Asia-Pacific Economic Cooperation (APEC) conference in Beijing, 3 months of daytime (8:00-19:30 LST) and nighttime (20:00-7:30 LST) particulate kmatter (PM_2.5) was collected in Huairou, Beijing from November 3, 2014 through January 31, 2015. PM_2.5 compositions were analyzed, including elements, organic carbon, elemental carbon, water-soluble ions, organics, and redox activities measured by both the dithiothreitol and the macrophage reactive oxygen species (ROS) assays. The mass-normalized redox activity was approximately constant during the noncontrol period (NCP) and control period (CP). The absolute value of the volume-normalized redox activity was about 4 times higher during NCP than that during CP, indicating the effectiveness of the control measures. The statistical analysis results showed that an interquartile range increase in PM_2.5 mass, chemicals, and sources (μg/m³) was associated with the 1-3% increase in redox activity, indicating that the successful control did make a significant reduction in redox activity but did not elucidate that some source controls (i.e., vehicle emissions) could be more effective at reducing redox activity than other control programs (i.e., dust source). This study demonstrated that combustion particles from both solid fuels and liquid fuels could contribute to ROS generation. Furthermore, ROS could be formed in the atmosphere via photochemical reactions, which highlights the need to further research on their formation pathways. A better understanding of the relevant mechanistic pathways and different source contributors to ROS will help to guide strategies for targeted mitigation of the atmospheric oxidation potential and will also help to reduce the great disease stress caused by exposure to air pollution.

Seasonal effects of ambient PM2.5 on the cardiovascular system of hyperlipidemic mice

People in polluted communities are often exposed to both PM and ozone (O₃), albeit not always simultaneously; an important question is whether exposure to particles with seasonal compositional differences can influence biological outcomes. We addressed this question using a mouse model of cardiovascular disease by contrasting the health outcomes of exposures to particles formed or aged during periods of relatively high photochemical activity (i.e. spring/summer), which has increased ambient O₃ concentrations, with outcomes of exposures to fall/winter particles which are associated with lower O₃ concentrations. Electrocardiographs (ECGs) and blood pressures (BPs) were acquired following exposures to concentrated ambient particles (CAPs). ECGs were analyzed to changes in specific waveform parameters and changes in heart rate variability (HRV). Exposures elicited several types of waveform abnormalities that were associated with seasonal differences in particle constituents. Alterations in R-R interval and P-R interval were seen following exposure to summer CAPs but not fall CAPs and differential responses were seen in the corrected Q-T interval following the two seasonal exposures. Measures of HRV increased after exposure to summer CAPs compared to air-exposed controls but not following the winter CAPs exposure. There were chemical differences with respect to the organic constituents in ambient particles between summer and fall aerosol. The oxygen to carbon ratios (O:C) were generally higher in the spring and summer than in the fall, consistent with seasonal differences in atmospheric photochemical activity. Seasonal differences in atmospheric photochemical activity can modify ambient aerosol composition and can alter biological responses in the cardiovascular system. The results from this study confirm that ambient photochemical activity can alter the toxicity of ambient PM. Regional and seasonal differences in PM_2.5 composition should be important considerations when evaluating the effects of PM exposure on cardiovascular health.Implications: Particles formed during periods of high photochemical activity (e.g. spring/summer) elicit more adverse cardiovascular health effects than particles formed during periods of low photochemical activity (e.g. fall/winter). Seasonal differences in atmospheric photochemical activity modified ambient aerosol composition and worsened cardiovascular responses. These results can inform regulatory agencies and may help design air quality regulations for PM2.5 that consider seasonal and regional variations.

The effects of particle-induced oxidative damage from exposure to airborne fine particulate matter components in the vicinity of landfill sites on Hong Kong

The physical, chemical and bioreactivity characteristics of fine particulate matter (PM_2.5) collected near (<1 km) two landfill sites and downwind urban sites were investigated. The PM_2.5 concentrations were significantly higher in winter than summer. Diurnal variations of PM_2.5 were recorded at both landfill sites. Soot aggregate particles were identified near the landfill sites, which indicated that combustion pollution due to landfill activities was a significant source. High correlation coefficients (r) implied several inorganic elements and water-soluble inorganic ions (vanadium (V), copper (Cu), chloride (Cl^-), nitrate (NO₃^-), sodium (Na) and potassium (K)) were positively associated with wind flow from the landfill sites. Nevertheless, no significant correlations were also identified between these components against DNA damage. Significant associations were observed between DNA damage and some heavy metals such as cadmium (Cd) and lead (Pb), and total Polycyclic Aromatic Hydrocarbons (PAHs) during the summer. The insignificant associations of DNA damage under increased wind frequency from landfills suggested that the PM_2.5 loading from sources such as regional sources was possibly an important contributing factor for DNA damage. This outcome warrants the further development of effective and source-specific landfill management regulations for particulate matter production control to the city.

Polycyclic aromatic hydrocarbon (PAHs) geographical distribution in China and their source, risk assessment analysis

In China, the huge amounts of energy consumption caused severe carcinogenic polycyclic aromatic hydrocarbon (PAHs) concentration in the soil and ambient air. This paper summarized that the references published in 2008-2018 and suggested that biomass, coal and vehicular emissions were categorized as major sources of PAHs in China. In 2016, the emitted PAHs in China due to the incomplete combustion of fuel was about 32720 tonnes, and the contribution of the emission sources was the sequence: biomass combustion > residential coal combustion > vehicle > coke production > refine oil > power plant > natural gas combustion. The total amount of PAHs emission in China at 2016 was significantly decreased due to the decrease of the proportion of crop resides burning (indoor and open burning). The geographical distribution of PAHs concentration demonstrated that PAHs concentration in the urban soil is 0.092-4.733 μg/g. At 2008-2012, the serious PAHs concentration in the urban soil occurred in the eastern China, which was shifted to western China after 2012. The concentration of particulate and gaseous PAHs in China is 1-151 ng/m3 and 1.08-217 ng/m3, respectively. The concentration of particle-bound PAHs in the southwest and eastern region are lower than that in north and central region of China. The incremental lifetime cancer risk (ILCR) analysis demonstrates that ILCR in the soil and ambient air in China is below the acceptable cancer risk level of 10-6 recommended by US Environmental Protection Agency (EPA), which mean that there is a low potential PAHs carcinogenic risk for the soil and ambient air in China.

Molecular Characterization of Atmospheric Organic Aerosol by Mass Spectrometry

Atmospheric aerosol, particulate matter suspended in the air we breathe, exerts a strong impact on our health and the environment. Controlling the amount of particulate matter in air is difficult, as there are many ways particles can form by both natural and anthropogenic processes. We gain insight into the sources of particulate matter through chemical composition measurements. A substantial portion of atmospheric aerosol is organic, and this organic matter is exceedingly complex on a molecular scale, encompassing hundreds to thousands of individual compounds that distribute between the gas and particle phases. Because of this complexity, no single analytical technique is sufficient. However, mass spectrometry plays a crucial role owing to its combination of high sensitivity and molecular specificity. This review surveys the various ways mass spectrometry is used to characterize atmospheric organic aerosol at a molecular level, tracing these methods from inception to current practice, with emphasis on current and emerging areas of research. Both offline and online approaches are covered, and molecular measurements with them are discussed in the context of identifying sources and elucidating the underlying chemical mechanisms of particle formation. There is an ongoing need to improve existing techniques and develop new ones if we are to further advance our knowledge of how to mitigate the unwanted health and environmental impacts of particles.

Assessment of forest fire impacts on carbonaceous aerosols using complementary molecular marker receptor models at two urban locations in California's San Joaquin Valley

Two hundred sixty-three fine particulate matter (PM_2.5) samples were collected over fourteen months in Fresno and Bakersfield, California. Samples were analyzed for organic carbon (OC), elemental carbon (EC), water soluble organic carbon (WSOC), and 160 organic molecular markers. Chemical Mass Balance (CMB) and Positive Matrix Factorization (PMF) source apportionment models were applied to the results in order to understand monthly and seasonal source contributions to PM_2.5 OC. Similar source categories were found from the results of the CMB and PMF models to PM_2.5 OC across the sites. Six source categories with reasonably stable profiles, including biomass burning, mobile, food cooking, two different secondary organic aerosols (SOAs) (i.e., winter and summer), and forest fires were investigated. Both the CMB and the PMF models showed a strong seasonality in contributions of some sources, as well as dependence on wind transport for both sites. The overall relative source contributions to OC were 24% CMB wood smoke, 19% CMB mobile sources, 5% PMF food cooking, 2% CMB vegetative detritus, 17% PMF SOA summer, 22% PMF SOA winter, and 12% PMF forest fire. Back-trajectories using the Weather Research and Forecasting model combined with the FLEXible PARTicle dispersion model (WRF-FLEXPART) were used to further characterize wind transport. Clustering of the trajectories revealed dominant wind patterns associated with varying concentrations of the different source categories. The Comprehensive Air Quality Model with eXtensions (CAMx) was used to simulate aerosol transport from forest fires and thus confirm the impacts of individual fires, such as the Rough Fire, at the measurement sites.

Ionization of carboxylic acid clusters in the gas phase and on free ArN and (H2O)N nanoparticles: valeric acid as a model for small carboxylic acids

In ionized valeric acid clusters, not only the expected proton transfer reaction, but also anhydride formation is observed. Could this be a common motif in the ionization chemistry of small carboxylic acid clusters?

Levels and sources of organic compounds in fine ambient aerosols over National Capital Region of India

The study presents the spatial and temporal variation of fine ambient aerosols (PM_2.5) over National Capital Region (NCR), India, during January to June 2016. The investigation includes three sampling sites, one in Delhi and two in the adjoining states of Delhi (Uttar Pradesh and Haryana), across NCR, India. The average PM_2.5 concentration was highest for Delhi (128.5 ± 51.5 μg m^-3) and lowest for Mahendragarh, Haryana (74.5 ± 28.7 μg m^-3), during the study period. Seasonal variation was similar for all the sites with highest concentration during winter and lowest in summer. PM_2.5 samples were analysed for organic compounds using gas chromatograph (GC). The concentration of three organic compound classes, n-alkanes (C11-C35), polycyclic aromatic hydrocarbons (PAHs), and phthalates, present in PM_2.5 samples has been reported. Diagnostic ratios for n-alkanes demonstrated that biogenic emissions were dominant over Mahendragarh while major contributions were observed from petrogenic emissions over Delhi and Modinagar, Uttar Pradesh. Molecular diagnostic ratios were calculated to distinguish between different sources of PAHs, which revealed that the fossil fuel combustion (diesel and gasoline emissions), traffic emissions, and biomass burning are the major source contributors. Health risk associated with human exposure of phthalates and PAHs was also assessed as daily intake (DI, ng kg^-1 day^-1) and lung cancer risk, respectively. Backward trajectory analysis explained the local, regional, and long-range transport routes of PM_2.5 for all sites. Principal component analysis (PCA) results summarized that the vehicular emissions, biomass burning, and plastic burning were the major sources of the PAHs and phthalates over the sampling sites.

Levels and risk assessment of hydrocarbons and organochlorines in aerosols from a North African coastal city (Bizerte, Tunisia)

The aim of this study was to assess, for the first time, the concentrations, sources, dry deposition and human health risks of polycyclic aromatic hydrocarbons (PAHs), aliphatic hydrocarbons (AHs), polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs) in total suspended particle (TSP) samples collected in Bizerte city, Tunisia (North Africa), during one year (March 2015-January 2016). Concentrations of PAHs, AHs, PCBs and OCPs ranged 0.5-17.8 ng m^-3, 6.7-126.5 ng m^-3, 0.3-11 pg m^-3 and 0.2-3.6 pg m^-3, respectively, with higher levels of all contaminants measured in winter. A combined analysis revealed AHs originating from both biogenic and petrogenic sources, while diesel vehicle emissions were identified as dominant sources for PAHs. PCB potential sources included electronic, iron, cement, lubricant factories located within or outside Bizerte city. The dominant OCP congeners were p,p'-DDT and p,p'-DDE, reflecting a current or past use in agriculture. Health risk assessment showed that the lifetime excess cancer risk from exposure to airborne BaP was negligible in Bizerte, except in winter, where a potential risk to the local population may occur.

Impacts of springtime biomass burning in the northern Southeast Asia on marine organic aerosols over the Gulf of Tonkin, China

Fine particles (PM_2.5) samples, collected at Weizhou Island over the Gulf of Tonkin on a daytime and nighttime basis in the spring of 2015, were analyzed for primary and secondary organic tracers, together with organic carbon (OC), elemental carbon (EC), and stable carbon isotopic composition (δ¹³C) of total carbon (TC). Five organic compound classes, including saccharides, lignin/resin products, fatty acids, biogenic SOA tracers and phthalic acids, were quantified by gas chromatography/mass spectrometry (GC/MS). Levoglucosan was the most abundant organic species, indicating that the sampling site was under strong influence of biomass burning. Based on the tracer-based methods, the biomass-burning-derived fraction was estimated to be the dominant contributor to aerosol OC, accounting for 15.7% ± 11.1% and 22.2% ± 17.4% of OC in daytime and nighttime samples, respectively. In two episodes E1 and E2, organic aerosols characterized by elevated concentrations of levoglucosan as well as its isomers, sugar compounds, lignin products, high molecular weight (HMW) fatty acids and β-caryophyllinic acid, were attributed to the influence of intensive biomass burning in the northern Southeast Asia (SEA). However, the discrepancies in the ratios of levoglucosan to mannosan (L/M) and OC (L/OC) as well as the δ¹³C values suggest the type of biomass burning and the sources of organic aerosols in E1 and E2 were different. Hardwood and/or C₄ plants were the major burning materials in E1, while burning of softwood and/or C₃ plants played important role in E2. Furthermore, more complex sources and enhanced secondary contribution were found to play a part in organic aerosols in E2. This study highlights the significant influence of springtime biomass burning in the northern SEA to the organic molecular compositions of marine aerosols over the Gulf of Tonkin.

Assessment of Polycyclic Aromatic Hydrocarbons in School Playground Soils in Urban Gwangju, South Korea

Soil samples from school playground of Gwangju City were analyzed for 16 polycyclic aromatic hydrocarbons (PAHs), and the soil contamination status and the potential cancer risk for students and adults were investigated. Soil samples were collected from 57 sites from 5 districts of Gwangju City in the summer of 2013. Regardless of the sampling site, the ∑PAHs concentrations ranged from 13.2 to 145.5 ng/g (mean 51.2 ng/g). Four and five-ring PAHs were predominant in the soil samples while the fraction of two-ring PAHs was the lowest. Seven carcinogenic PAHs contributed ~ 55% of ∑PAHs in school playground soils. The benzo[a]pyrene (46.4%) and dibenz[a,h]anthracene (41.2%) were the major contributors to toxic equivalent quantity. The strong correlation between carcinogenic PAHs suggested that they originated from the same source either vehicular emission or coal combustion, because they are markers of these pollution sources. The mean cancer risk for students (3.61 × 10^-7) and adults (8.41 × 10^-6) was in the U.S. EPA safety range (< 10^-6).

Chemical composition and redox activity of PM0.25 near Los Angeles International Airport and comparisons to an urban traffic site

To investigate the relative impacts of emissions from Los Angeles International Airport (LAX), as well as the impacts of traffic emissions from freeways, on the oxidative potential of particulate matter (PM), PM_0.25 were collected at two urban background locations in Los Angeles. Redox activity of the PM samples was measured by means of an in vitro alveolar macrophage assay that quantifies the formation of reactive oxygen species (ROS) in cells, and detailed chemical analyses were performed to determine the speciated chemical composition of collected PM. A molecular marker-based chemical mass balance (MM-CMB) model was applied to estimate the relative contributions from the following primary sources to the organic carbon (OC) component of PM: mobile sources (combined gasoline and diesel vehicles), wood smoke, vegetative detritus, road dust and ship emissions. A source profile of aircraft emissions was not included in the model; however its contribution was estimated from un-apportioned primary OC in the MM-CMB model ("other OC") after accounting for the contribution of secondary organic carbon (SOC) to OC. The contribution of mobile sources to OC was 82% and 28% at the central Los Angeles site (freeway emissions) and the LAX site, respectively. The estimated contribution of aircraft emissions to PM_0.25 OC was 36% at the LAX site. ROS activity levels showed little spatial variability, with no statistically significant difference between the averages observed at LAX (24.75±4.01μgZymosan/m³) and central Los Angeles (27.77±2 0.32μgZymosan/m³), suggesting similar levels of inhalation exposure to redox active species of PM_0.25. A multiple linear regression analysis indicated that the variability in ROS activity is best explained by the chemical markers of major identified sources: EC emitted by traffic, and sulfur, considered in our study as a potential tracer of aircraft emissions, with statistically significantly higher concentrations of sulfur at the LAX site (p<0.001).

Chemical characteristics of dicarboxylic acids and related organic compounds in PM2.5 during biomass-burning and non-biomass-burning seasons at a rural site of Northeast China

Fine particulate matter (PM2.5) samples were collected using a high-volume air sampler and pre-combusted quartz filters during May 2013 to January 2014 at a background rural site (47^∘35 N, 133^∘31 E) in Sanjiang Plain, Northeast China. A homologous series of dicarboxylic acids (C₂-C₁₁) and related compounds (oxoacids, α-dicarbonyls and fatty acids) were analyzed by using a gas chromatography (GC) and GC-MS method employing a dibutyl ester derivatization technique. Intensively open biomass-burning (BB) episodes during the harvest season in fall were characterized by high mass concentrations of PM2.5, dicarboxylic acids and levoglucosan. During the BB period, mass concentrations of dicarboxylic acids and related compounds were increased by up to >20 times with different factors for different organic compounds (i.e., succinic (C₄) acid > oxalic (C₂) acid > malonic (C₃) acid). High concentrations were also found for their possible precursors such as glyoxylic acid (ωC₂), 4-oxobutanoic acid, pyruvic acid, glyoxal, and methylglyoxal as well as fatty acids. Levoglucosan showed strong correlations with carbonaceous aerosols (OC, EC, WSOC) and dicarboxylic acids although such good correlations were not observed during non-biomass-burning seasons. Our results clearly demonstrate biomass burning emissions are very important contributors to dicarboxylic acids and related compounds. The selected ratios (e.g., C₃/C₄, maleic acid/fumaric acid, C₂/ωC₂, and C₂/levoglucosan) were used as tracers for secondary formation of organic aerosols and their aging process. Our results indicate that organic aerosols from biomass burning in this study are fresh without substantial aging or secondary production. The present chemical characteristics of organic compounds in biomass-burning emissions are very important for better understanding the impacts of biomass burning on the atmosphere aerosols.

Seasonal variation, spatial distribution and source apportionment for polycyclic aromatic hydrocarbons (PAHs) at nineteen communities in Xi'an, China: The effects of suburban scattered emissions in winter

Seasonal variation and spatial distribution of PM_2.5 bound polycyclic aromatic hydrocarbons (PAHs) were investigated at urban residential, commercial area, university, suburban region, and industry in Xi'an, during summer and winter time at 2013. Much higher levels of total PAHs were obtained in winter. Spatial distributions by kriging interpolations principle showed that relative high PAHs were detected in western Xi'an in both summer and winter, with decreasing trends in winter from the old city wall to the 2^nd-3rd ring road except for the suburban region and industry. Coefficients of diversity and statistics by SPSS method demonstrated that PAHs in suburban have significant differences (t < 0.05) with those in urban residential in both seasons. The positive Matrix Factorization (PMF) modeling indicated that biomass burning (31.1%) and vehicle emissions (35.9%) were main sources for PAHs in winter and summer in urban, which different with the suburban. The coal combustion was the main source for PAHs in suburban region, which accounted for 46.6% in winter and sharp decreased to 19.2% in summer. Scattered emissions from uncontrolled coal combustion represent an important source of PAHs in suburban in winter and there were about 135 persons in Xi'an will suffer from lung cancer for lifetime exposure at winter levels. Further studies are needed to specify the effluence of the scattered emission in suburban to the city and to develop a strategy for controlling those emissions and lighten possible health effects.

Application of a self-organizing map and positive matrix factorization to investigate the spatial distributions and sources of polycyclic aromatic hydrocarbons in soils from Xiangfen County, northern China

The concentrations of 16 priority polycyclic aromatic hydrocarbons (PAHs) were measured in 128 surface soil samples from Xiangfen County, northern China. The total mass concentration of these PAHs ranged from 52 to 10,524ng/g, with a mean of 723ng/g. Four-ring PAHs contributed almost 50% of the total PAH burden. A self-organizing map and positive matrix factorization were applied to investigate the spatial distribution and source apportionment of PAHs. Three emission sources of PAHs were identified, namely, coking ovens (21.9%), coal/biomass combustion (60.1%), and anthracene oil (18.0%). High concentrations of low-molecular-weight PAHs were particularly apparent in the coking plant zone in the region around Gucheng Town. High-molecular-weight PAHs mainly originated from coal/biomass combustion around Gucheng Town, Xincheng Town, and Taosi Town. PAHs in the soil of Xiangfen County are unlikely to pose a significant cancer risk for the population.

Ultrafine and Fine Particulate Matter Inside and Outside of Mechanically Ventilated Buildings

The objectives of this study were to measure levels of particulate matter (PM) in mechanically ventilated buildings and to improve understanding of filtration requirements to reduce exposure. With the use of an Ultra High Sensitivity Aerosol Spectrometer and an Aerodyne Mass Spectrometer, ultrafine (0.055–0.1 μm) and fine (0.1–0.7 μm) indoor and outdoor PM was measured as a function of time in an office, a university building, and two elementary schools. Indoor particle levels were highly correlated with outdoor levels. Indoor and outdoor number concentrations in Denver were higher than those in Boulder, with the highest number concentrations occurring during summer and fall. The ratio of indoor-to-outdoor (I/O) PM was weakly but positively correlated with the amount of ventilation provided to the indoor environment, did not vary much with particle size (ranged between 0.48 and 0.63 for the entire size range), and was similar for each period of the week (weekend vs. weekday, night vs. day). Regression analyses showed that ultrafine indoor PM baseline concentrations were higher at night from nighttime infiltration. A lag time was observed between outdoor and indoor measurements. Weekday days had the shortest lag time of 11 min, and weekend nighttime lags when the HVAC was not in use were 50 to 148 min. Indoor-outdoor PM concentration plots showed ultrafine PM was more correlated compared to fine, and especially when the HVAC system was on. Finally, AMS data showed that most of the PM was organic, with occasional nitrate events occurring outdoors. During nitrate events, there were less indoor particles detected, indicating a loss of particulate phase nitrate. The results from this study show that improved filtration is warranted in mechanically ventilated buildings, particularly for ultrafine particles, and that nighttime infiltration is significant depending on the building design.

Seasonal variations and source profile of n-alkanes in particulate matter (PM10) at a heavy traffic site, Delhi

Delhi is one of the most polluted cities in the world. The generation of aerosols in the lower atmosphere of the city is mainly due to a large amount of natural dust advection and sizable anthropogenic activities. The compositions of organic compounds in aerosols are highly variable in this region and need to be investigated thoroughly. Twenty-four-hour sampling to assess concentrations of n-alkanes (ng/m³) in PM₁₀ was carried out during January 2015 to June 2015 at Indira Gandhi Delhi Technical University for Women (IGDTUW) Campus, Delhi, India. The total average concentration of n-alkanes, 243.7 ± 5.5 ng/m³, along with the diagnostic tools has been calculated. The values of CPI₁, CPI₂, and CPI₃ for the whole range of n-alkanes series, petrogenic n-alkanes, and biogenic n-alkanes were 1.00, 1.02, and 1.04, respectively, and C _max were at C₂₅ and C₂₇. Diagnostic indices and curves indicated that the dominant inputs of n-alkanes are from petrogenic emissions, with lower contribution from biogenic emissions. Significant seasonal variations were observed in average concentrations of n-alkanes, which is comparatively higher in winter (187.4 ± 4.3 ng/m³) than during the summer season (56.3 ± 1.1 ng/m³).

Evaluation of a Conceptual Model for Gas-Particle Partitioning of Polycyclic Aromatic Hydrocarbons Using Polyparameter Linear Free Energy Relationships

A model for gas-particle partitioning of polycyclic aromatic hydrocarbons (PAHs) was evaluated using polyparameter linear free energy relationships (ppLFERs) following a multiphase aerosol scenario. The model differentiates between various organic (i.e., liquid water-soluble (WS)/organic soluble (OS) organic matter (OM), and solid/semisolid organic polymers) and inorganic phases of the particulate matter (PM). Dimethyl sulfoxide and polyurethane were assigned as surrogates to simulate absorption into the above-mentioned organic phases, respectively, whereas soot, ammonium sulfate, and ammonium chloride simulated adsorption processes onto PM. The model was tested for gas and PM samples collected from urban and nonurban sites in Europe and the Mediterranean, and the output was compared with those calculated using single-parameter linear free energy relationship (spLFER) models, namely Junge-Pankow, Finizio, and Dachs-Eisenreich. The ppLFER model on average predicted 96 ± 3% of the observed partitioning constants for semivolatile PAHs, fluoranthene, and pyrene, within 1 order of magnitude accuracy with root-mean-square errors (RMSE) of 0.35-0.59 across the sites. This was a substantial improvement compared to Finizio and Dachs-Eisenreich models (37 ± 17 and 46 ± 18% and RMSE of 1.03-1.40 and 0.94-1.36, respectively). The Junge-Pankow model performed better among spLFERs but at the same time showed an overall tendency for overestimating the partitioning constants. The ppLFER model demonstrated the best overall performance without indicating a substantial intersite variability. The ppLFER analysis with the parametrization applied in this study suggests that the absorption into WSOSOM could dominate the overall partitioning process, while adsorption onto salts could be neglected.

Associations of oxidative stress and inflammatory biomarkers with chemically-characterized air pollutant exposures in an elderly cohort

BACKGROUND

Exposure to air pollution has been associated with cardiorespiratory morbidity and mortality. However, the chemical constituents and pollution sources underlying these associations remain unclear.

METHOD

We conducted a cohort panel study involving 97 elderly subjects living in the Los Angeles metropolitan area. Airway and circulating biomarkers of oxidative stress and inflammation were measured weekly over 12 weeks and included, exhaled breath condensate malondialdehyde (EBC MDA), fractional exhaled nitric oxide (FeNO), plasma oxidized low-density lipoprotein (oxLDL), and plasma interleukin-6 (IL-6). Exposures included 7-day personal nitrogen oxides (NOx), daily criteria-pollutant data, five-day average particulate matter (PM) measured in three size-fractions and characterized by chemical components including transition metals, and in vitro PM oxidative potential (dithiothreitol and macrophage reactive oxygen species). Associations between biomarkers and pollutants were assessed using linear mixed effects regression models.

RESULTS

We found significant positive associations of airway oxidative stress and inflammation with traffic-related air pollutants, ultrafine particles and transition metals. Positive but nonsignificant associations were observed with PM oxidative potential. The strongest associations were observed among PM variables in the ultrafine range (PM <0.18µm). It was estimated that an interquartile increase in 5-day average ultrafine polycyclic aromatic hydrocarbons was associated with a 6.3% (95% CI: 1.1%, 11.6%) increase in EBC MDA and 6.7% (95% CI: 3.4%, 10.2%) increase in FeNO. In addition, positive but nonsignificant associations were observed between oxLDL and traffic-related pollutants, ultrafine particles and transition metals while plasma IL-6 was positively associated with 1-day average traffic-related pollutants.

CONCLUSION

Our results suggest that exposure to pollutants with high oxidative potential (traffic-related pollutants, ultrafine particles, and transition metals) may lead to increased airway oxidative stress and inflammation in elderly adults. This observation was less clear with circulating biomarkers.

One-year study of polycyclic aromatic compounds at an urban site in Grenoble (France): Seasonal variations, gas/particle partitioning and cancer risk estimation

21 PAHs, 27 oxy-PAHs and 32 nitro-PAHs were measured every third day over a year in both gaseous (G) and particulate PM10 (P) phases in ambient air of Grenoble (France). Mean total concentrations (G+P) of PAHs and oxy-PAHs were in the same range and about 10ngm(-3). Nitro-PAHs were 50 to 100 times less concentrated averaging 100pgm(-3). Polycyclic aromatic compound (PAC) concentrations were 5 to 7 times higher in "cold" period (October to March) than in "warm" period (April to September). Seasonal variations may be explained by higher primary emissions from residential heating, especially biomass burning in "cold" season. Meteorological conditions and influence of the geomorphology around Grenoble, with the formation of thermal inversion layers leading to the stagnation of pollutants, were additional key parameters. Maximum individual PAC concentrations were observed during two PM10 pollution events in December and February-March. Chemical processes and secondary formation of oxy- and nitro-PAH were probably enhanced by the accumulation of the pollutants during these events. PAC gas/particle partitioning depended on compound molecular weight and vapour pressure. Gas/particle partitioning of oxy- and nitro-PAHs were evaluated using a multi-phase poly-parameter linear free energy relationship model. The PAC cancer risk was assessed using toxic equivalency factors available in the literature (19 PAHs, 10 nitro-PAHs and 1 oxy-PAH). Overall, particle-bound PACs contributed about 76% of the cancer risk. While PAHs accounted for most of the total PAC cancer risk, oxy- and nitro-PAHs could account for up to 24%. The risk quantification across substance classes is limited by toxicological data availability.

Direct Analysis of Low-Volatile Molecular Marker Extract from Airborne Particulate Matter Using Sensitivity Correction Method

Molecular marker analysis of environmental samples often requires time consuming preseparation steps. Here, analysis of low-volatile nonpolar molecular markers (5-6 ring polycyclic aromatic hydrocarbons or PAHs, hopanoids, and n-alkanes) without the preseparation procedure is presented. Analysis of artificial sample extracts was directly conducted by gas chromatography-mass spectrometry (GC-MS). After every sample injection, a standard mixture was also analyzed to make a correction on the variation of instrumental sensitivity caused by the unfavorable matrix contained in the extract. The method was further validated for the PAHs using the NIST standard reference materials (SRMs) and then applied to airborne particulate matter samples. Tests with the SRMs showed that overall our methodology was validated with the uncertainty of ~30%. The measurement results of airborne particulate matter (PM) filter samples showed a strong correlation between the PAHs, implying the contributions from the same emission source. Analysis of size-segregated PM filter samples showed that their size distributions were found to be in the PM smaller than 0.4 μm aerodynamic diameter. The observations were consistent with our expectation of their possible sources. Thus, the method was found to be useful for molecular marker studies.

Speciation and source identification of organic compounds in PM₁₀ over Seoul, South Korea

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.

Load-Dependent Emission Factors and Chemical Characteristics of IVOCs from a Medium-Duty Diesel Engine

A detailed understanding of the climate and air quality impacts of mobile-source emissions requires the characterization of intermediate-volatility organic compounds (IVOCs), relatively-low-vapor-pressure gas-phase species that may generate secondary organic aerosol with high yields. Due to challenges associated with IVOC detection and quantification, IVOC emissions remain poorly understood at present. Here, we describe measurements of the magnitude and composition of IVOC emissions from a medium-duty diesel engine. Measurements are made on an engine dynamometer and utilize a new mass-spectrometric instrument to characterize the load dependence of the emissions in near-real-time. Results from steady-state engine operation indicate that IVOC emissions are highly dependent on engine power, with highest emissions at engine idle and low-load operation (≤25% maximum rated power) with a chemical composition dominated by saturated hydrocarbon species. Results suggest that unburned fuel components are the dominant IVOCs emitted at low loads. As engine load increases, IVOC emissions decline rapidly and become increasingly characterized by unsaturated hydrocarbons and oxygenated organics, newly formed from incomplete combustion processes at elevated engine temperatures and pressures. Engine transients, including a cold-start ignition and engine acceleration, show IVOC emission profiles that are different in amount or composition compared to steady-state combustion, underscoring the utility of characterizing IVOC emissions with high time resolution across realistic engine operating conditions. We find possible evidence for IVOC losses on unheated dilution and sampling surfaces, which need to be carefully accounted for in IVOC emission studies.

Characteristics and major sources of carbonaceous aerosols in PM2.5 from Sanya, China

PM2.5 samples were collected in Sanya, China in summer and winter in 2012/2013. Organic carbon (OC), elemental carbon (EC), and non-polar organic compounds including n-alkanes (n-C14-n-C40) and polycyclic aromatic hydrocarbons (PAHs) were quantified. The concentrations of these carbonaceous matters were generally higher in winter than summer. The estimated secondary organic carbon (OCsec) accounted for 38% and 54% of the total organic carbon (TOC) in winter and summer, respectively. The higher value of OCsec in addition to the presences of photochemically-produced PAHs in summer supports that photochemical conversions of organics are much active at the higher air temperatures and with stronger intense solar radiation. Carbon preference index (CPI) and percent contribution of wax n-alkanes suggest that anthropogenic sources were more dominant than derivation from terrestrial plants in Sanya. Diagnostic ratios of atmospheric PAHs further indicate that there was a wide mix of pollution sources in winter while fossil fuel combustion was the most dominant in summer. Positive Matrix Factorization (PMF) analysis with 18 PAHs in the winter samples found that motor vehicle emissions and biomass burning were the two main pollution sources, contributing 37.5% and 24.6% of the total quantified PAHs, respectively.