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A tethered balloon sampling system was used to measure vertical profiles of ozone, particles, and solar radiation in the atmospheric boundary layer on the northern edge of Mexico City, in March 2006 as part of the Megacity Impact on Regional and Global Environment-Mexico experiment. Several commercial sensors, designed for surface applications, were deployed on a tethered balloon platform. Profiles indicate that for these 3 scalars the boundary layer (surface up to 700 m) was well mixed in the period 10:00-16:00 LST. Good agreement was observed for median surface and balloon ozone and particle number concentrations. For most profiles, the surface deposition of ozone was not significant compared to median profile concentrations. Particle number concentration (0.3, 0.5, 1.0 and 5.0 μm) also showed little variation with attitude. Radiatprofiles showed a monotonic increase in diffuse radiation from the maximum altitude of profiles to the surface. Consequently, it was inferred that surface measurements of these likely were representative of lower boundary layer values during this time period. © 2009 Elsevier Ltd. All rights reserved.

We apply a simulation model to explore the effect of a house's multicompartment character on a nonsmoker's inhalation exposure to secondhand tobacco smoke (SHS). The model tracks the minute-by-minute movement of people and pollutants among multiple zones of a residence and generates SHS pollutant profiles for each room in response to room-specific smoking patterns. In applying the model, we consider SHS emissions of airborne particles, nicotine, and carbon monoxide in two hypothetical houses, one with a typical 4-room layout and one dominated by a single large space. We use scripted patterns of room-to-room occupant movement and a cohort of 5,000 activity patterns sampled from a US nationwide survey. The results for scripted and cohort simulation trials indicate that the multicompartment nature of homes, manifested as inter-room differences in pollutant levels and the movement of people among zones, can cause substantial variation in nonsmoker SHS exposure.

This work presents a comprehensive study of the size-resolved particle hygroscopicity measurements in a suburban ambient in Southern Europe (Madrid). Measurements were obtained by an H-TDMA instrument during a 16-month period for the size particles of 50, 80, 110, 190 and 265 nm. The annual, seasonal and daily patterns were investigated with the aim of characterizing the hygroscopic growth of ambient aerosol particles and their mixing state in the atmosphere. Simultaneously, the particle number size distributions, gaseous species (SO 2 , NO, NO 2 , and O 3) and meteorological factors were measured and analyzed, complementing this study. The growth factor probability density functions (GF-PDFs) at the measurement site normally exhibit a multimodal pattern with two hygroscopic groups of particles clearly differentiated, indicating that the aerosol particles were externally mixed. Generally, particle hygroscopicity increased as particles were larger, indicating an increase less-to-more hygroscopic species. In cold seasons, aerosol particles were more externally mixed than in warm seasons. Thus, the growth factor of the more hygroscopic particle group (GF MH) was higher than in warm seasons varying from 1.41 (50 nm)-1.70 (265 nm). However, the number fraction of more hygroscopic particle group (NF MH) was lower. The persistence of anticyclonic stagnation conditions and the enhanced particulate nitrate formation from traffic emissions seemed to be the two main factors responsible for this result. A dominant hygroscopic particle group was often observed in warm seasons, due to frequent NPF bursts. In these seasons, and probably associated to the high atmospheric oxidative capacity, the highest average growth factors (GF mean) of the study period were obtained. This finding was also reflected in the diurnal cycle. Thus, GF mean and NF MH during rush-hour periods usually reached the minimum values of the day, especially in cold seasons. When comparing weekdays and weekends, the strong influence of traffic emissions on particle hygroscopicity was evidenced (WKs/WEs ratios for NF MH were <1.00). The more dispersive atmospheric conditions in the warm seasons hampered the impact of traffic emissions on particle hygroscopicity. Results from H-TDMA measurements obtained here are similar to those found in other suburban European sites and lower than in suburban Asian ones. With respect to urban sites, our values were lower than those found in urban European and Asian sites. Overall, the findings of this study highlight the strong dependence of the hygroscopic behavior of aerosol particles on the atmospheric conditions and particle sources, and thus, aerosol composition. • H-TDMA measurements obtained in a suburban site were analyzed for 16 months. • Annual cycle of aerosol hygroscopicity is controlled by its sources and meteorology. • Particle hygroscopicity was strongly dependent on traffic, especially in cold seasons. • Particles were less externally mixed in warm seasons associated with NPF bursts. • Particle hygroscopicity increased with particle size in all seasons. [ABSTRACT FROM AUTHOR]

We designed and evaluated the performance of a tandem technique, consisting of a previously developed versatile aerosol concentration enrichment system (VACES) combined with a compact screen-type diffusion battery that removes ambient ultrafine particles (UFP) from the airflow to enable us to conduct exposures directly on concentrated ambient accumulation mode (0.18–2.5 μm) particles. The performance of the diffusion battery was evaluated first under controlled conditions using NaCl laboratory-generated aerosols. Based on the laboratory tests, the optimum operational conditions of the diffusion battery were selected in terms of the flow rate (i.e., 5 lpm) and number of stages (i.e., 6). The diffusion battery was then deployed to our sampling site in central Los Angeles and connected to the VACES in order to evaluate the performance of the VACES/diffusion battery tandem using concentrated ambient particulate matter (PM 2.5). Results of the field tests confirmed the ability of this tandem technique to concentrate effectively the accumulation mode PM with the majority of the ultrafine particles removed from the concentrated aerosol. The 50% cutpoint of the diffusion battery was at around 100 nm, while the removal efficiency exceeded 70–90% for particles smaller than 50 nm. Comparison of the mass concentrations and chemical composition of the accumulation mode PM collected using the tandem technique with those collected using a MOUDI sampler operating in parallel showed excellent overall agreement (within 5–15% variation), corroborating the effectiveness of the VACES/diffusion battery tandem technique for application in exposure studies to concentrated ambient accumulation mode PM. [ABSTRACT FROM AUTHOR]

Vape shops are widespread due to the popularity of electronic cigarettes (e-cigs) as an alternative to tobacco cigarettes. In this study, sixty-seven Southern California vape shops were randomly surveyed for building characteristics, ventilation, and business patterns. Based on the survey results, six representative shops were recruited for real-time measurements of indoor and outdoor fine and ultrafine particles concentrations on a busy and less busy day. Occupancy, vaping frequency, and opening and closing of doors were recorded, and shop air exchange rate was determined. Indoor CO 2 , relative humidity, and temperature were also recorded. In addition, simultaneous measurements were taken at increasing distances away from a vaping area to assess the mixing and spatial profiles of particle levels inside the shops. During active vaping, real-time indoor particle number concentration and gravimetric-corrected PM 2.5 mass concentration across the six vape shops varied from 1.3 × 104 to 4.8 × 105 particles/cm3 and from 15.5 to 37,500 μg/m3, respectively. The spatial profiles of particle number and mass were more uniformly mixed than expected in an indoor environment. Total vaping frequency was the main predictor of particle concentrations inside the vape shops when indoor-outdoor particle mass transfer is minimal (doors closed). Image 1 • Sixty-seven vape shops were surveyed and pollutants were measured in six of them. • During vaping, PM 2.5 and PNC can be 10,000 times above background in vape shops. • Exhaled e-cig particles persist in the air, traveling and mixing in vape shops. • PM 2.5 decayed faster than PNC over distances >1.5 m from a vaping source. [ABSTRACT FROM AUTHOR]

In this study, we investigated the cell-free ascorbic acid assay (OPAA response) to quantify the oxidative potential (OP) of particle matter (PM), as a promising metric for studying the association between the chemical properties and toxicological effects of PM. With the purpose of designing an experimental set-up mostly representative of the intracellular oxidation, the assay was performed in different media, representing an artificial respiratory tract lining fluid (RTLF), i.e., simple ascorbate (Asc) or mixtures of reduced glutathione (GSH), urate (UA) and citrate (Cit). The study was performed on real PM 2.5 samples collected at an urban and rural site in the Po Valley (northern Italy). For comparison, standard solutions of redox-active species were investigated, i.e., Cu2+, Fe2+, 1,2-naphthoquinone, 1,4-naphthoquinone and 9,10-phenantrenequinone, that are known to give positive response to the AA assay. The composition of the synthetic RTLF strongly effected the OPAA responses, as they decreased with increasing the mixture complexity, following the order: Asc > Asc + Cit > Asc + UA > Asc + GSH > Asc + Cit + GSH ∼ Asc + Cit + GSH + UA. Based on comparison of the dependence of OPAA on RTLF composition, we could infer that Cu2+ and quinones were the redox active species most responsible of the OPAA response of the analysed PM 2.5 samples. Image 1 • Oxidative potential of PM real samples was measured by cell-free ascorbate assay. • Composite mixtures of endogenous antioxidants simulate lung fluid. • Addition of citrate, urate and glutathione to ascorbate decreases PM response. • Copper and quinones are mainly responsible for changes of assay response. [ABSTRACT FROM AUTHOR]

In this study, PM 2.5 airborne particulate matter was collected over a full year at a costal site of the Central Mediterranean Sea and analysed for its chemical composition and oxidative potential (OP), determined by the dithiothreitol (DTT) and the ascorbic acid (AA) assays. In autumn-winter, the volume normalized oxidative OP (OP V) were 0.29 ± 0.03 nmol min−1 m−3 and 0.21 ± 0.03 nmol min−1 m−3 for the DTT (OPDTT V) and AA (OPAA V) assay, respectively. In spring-summer the OPDTT V values were higher than OPAA V responses, i.e., 0.19 ± 0.02 nmol min−1 m−3 vs. 0.09 ± 0.01 nmol min−1 m−3. Overall, marked seasonality was observed with higher values in Autumn-Winter (AW) than in Spring-Summer (SS), i.e., 1.5 and 2.3 times increase for OPDTT V and OPAA V , respectively. In the cold season, the OP V activity was broadly correlated with metals and carbon species, such as K+, NO 3 −, Ba, Cd, Cu, Fe, Mn, P, V, OC, EC, Acetate, Oxalate and Glycolate (p < 0.05). This suggested the main contribution of a "mixed anthropogenic" source, consisting of the biomass burning (K+, OC and EC) and traffic (Ba, Cu, Fe, Mn, V, EC) emissions. In SS, OP V was significantly correlated with only few species i.e., OC, EC, Cu, and NO 3 −, suggesting main association with the "mixed anthropogenic" and the "reacted dust" sources. For each sampling day, PM 2.5 and PM 10 samples were simultaneously collected and analysed to investigate the variation of the OP activity in relation with the particle size and chemical composition. OPDTT V values exhibited a poor particle-size dependence, with similar values close to 0.20 ± 0.04 nmol min−1 m−3 in both fractions. This could be explained by the association of OPDTT V with species mainly accumulated in the fine fraction, i.e., OC, POC and EC and K+. Otherwise, the OPAA V responses exhibited a clear particle-size dependence, with significantly higher values for PM 10 than for PM 2.5 , i.e., 0.35 ± 0.06 vs. 0.21 ± 0.03 nmol min−1 m−3 in AW and 0.23 ± 0.04 vs. 0.09 ± 0.01 in SS. This may be supported by the strong correlation of OPAA V with Cu and Fe, which were most abundant metals in the PM 10 fraction. The data of specific monitoring days were investigated in detail to better highlight the impact of some individual redox active species on the OPDTT V and OPAA V responses. Image 1 • Oxidative potential was assessed for PM 2.5 at a Central Mediterranean Site. • Oxidative potential and chemical composition of PM 2.5 and PM 10 were compared. • The dependence of the OPDTT and OPAA responses on seasons were investigated. • OPDTT were similar in PM 2.5 and PM 10 and highly associated with OC, EC and K+. • OPAA were higher in PM 10 than in PM 2.5 and highly associated with Cu and Fe. The oxidative potential of PM 2.5 and PM 10 samples was assessed with Dithiothreitol and Ascorbic Acid assays: the variation of OP responses was related with the PM size and chemical composition. [ABSTRACT FROM AUTHOR]

Abstract Laboratory experiments were conducted to investigate femtosecond filamentation induced particle formation and growth in particle-free air as well as in the presence of pre-existing ammonium sulfate aerosols. The ability of laser induced particles to act as cloud condensation nuclei (CCN) was explored. The influence of water vapor and the pulse energy on the production efficiency and activation properties of particles were also examined. In particle-free air, laser filaments could lead to a significant production of new particles, the number concentration of which was comparable to or larger than that in polluted ambient air, depending upon the pulse energy and humidity. Total particle number and mass concentrations within 20–708 nm were predominantly contributed by particles with a diameter smaller than 100 nm. Remarkably high NOx up to an order of ∼101 ppm was generated in the chamber, allowing sufficient production of HNO 3 and probably subsequent HNO 3 -H 2 O binary nucleation. In the presence of pre-existing particles, the yield of particle number was largely enhanced in laser filaments, especially in humid air. Particle number size distribution shifted towards smaller particle size, leading to a slight increase in particle mass. It was found that a considerable portion of laser induced particles, no matter generated with or without pre-existing particles, could act as CCN. The amount of CCN at 0.80% supersaturation was in the magnitude of 104∼105 cm−3 in all experiments, nearly one order larger than the average ambient level even in severely polluted regions. Overall, increasing the pulse energy and water vapor would favor particle formation and growth as well as the production of CCN. Raising the pulse energy also resulted in a decline of the hygroscopic parameter κ , implying the modification of aerosol chemical composition. Though more investigative studies are still needed to explore mechanisms underlying some of these experimental results, laser filaments are undoubtedly capable of inducing substantial particle formation and modifying microphysical/chemical properties of pre-existing particles. By influencing these crucial properties and thereby aerosol direct/indirect climatic and environmental effects, laser filamentation would provide a promising potential for related atmospheric applications. Highlights • Femtosecond filamentation induced a significant production of gases and particles. • Microphysical/hygroscopic properties of pre-existing particles were modified. • Laser induced particles provided abundant cloud condensation nuclei. • Increasing the pulse energy and water vapor would favor gas/particle production. [ABSTRACT FROM AUTHOR]

Abstract Urban green spaces function as biological filters in reducing atmospheric particles. Yet there is a profound requisite to identify the most effective plant species by their leaf traits that can enhance particle capture and improve ambient air quality. In this study, we investigated leaves of 96 perennial urban plant species consisting of 43 deciduous broadleaf trees, 32 deciduous broadleaf shrubs, 14 deciduous and evergreen needle/scale-like, 5 evergreen broadleaves, and 2 climber species for their differences in net particle accumulation. Leaf saturation isothermal remanent magnetization (SIRM), a proxy for traffic and industry induced particle accumulation, along with morphological and anatomical leaf traits were analyzed in a common garden experiment in June and September 2016. Leaf SIRM varied significantly between plant species. The most effective net particle accumulating plant species with a median value of 23.0 μA were Buddleja davidii , Viburnum opulus, Carpinus betulus , Quercus ilex, Viburnum lantana, Rosa rugosa, Sorbus aria, Aesculus hippocastanum , Pseudotsuga menziesii , Acer campestre. The least effective net particle accumulating plant species with a median value of 10.4 μA were Populus alba, Alnus glutinosa, Larix kaempferi, Larix decidua, Plantanus x acerilifolia, Acer pseudoplatanus, Robinia pseudoacacia, Quercus palustris, Rosa canina, Liquidambar styraciflua. The "variable importance" in net particle accumulation for the investigated plant species was achieved using ®randomForest. The presence of leaf trichomes and specific leaf area were identified as important leaf traits for categorization of the selected plant species in low, medium, and high net particle accumulators. The extensive analysis of plant species at leaf-level with distinct micro-morphology contributes to a better understanding of plant species behavior in net particle capture and their contribution in reducing atmospheric particulate matter. Furthermore, this study has practical implications for policymakers in making informed choices when planning urban green infrastructures. Lastly, our study can become a basis to validate atmospheric deposition model using species-specific information. Highlights • Leaves of 96 perennial urban plant species were investigated for differences in net particle accumulation. • Leaves of Buddleja davidii and Populus alba were most and least effective respectively in net particle accumulation. • Leaves with trichomes were more effective in net particle accumulation. • Low net particle accumulation was observed for leaves with low leaf wettability. • The ® randomForest indicated SLA and presence of trichomes as variable of importance in net particle accumulation. [ABSTRACT FROM AUTHOR]

Abstract The climatic effect of atmospheric particles is greatly dependent on their hygroscopicity and chemical composition. Although the hygroscopic behavior of individual components of aerosol has been widely studied, the effect of coexisting species on the hygroscopic behavior of mixed constituents is still not clear. In this study, we used Raman spectroscopy to investigate how particles with different hygroscopic behaviors affect each other when they are combined together in mixtures. The effect of coexisting hygroscopic components, e.g. NaCl, NH 4 NO 3 , and (NH 4) 2 SO 4 , on the hygroscopic behavior of externally mixed H 2 C 2 O 4 /CaCO 3 was studied. We found that coexisting NH 4 NO 3 can promote the conversion of H 2 C 2 O 4 /CaCO 3 to CaC 2 O 4 ·H 2 O in the humidifying process by providing a deliquesced solution to dissolve H+ in the oxalic acid matrix. Moreover, competition and blocking effects existed in the case of coexisting (NH 4) 2 SO 4. Reactions between (NH 4) 2 SO 4 and CaCO 3 led to the formation of CaSO 4 ·2H 2 O and (NH 4) 2 C 2 O 4 instead of CaC 2 O 4. NaCl reacted with H 2 C 2 O 4 in solution to form Na 2 C 2 O 4. These results suggested that synergistic effects between coexisting components in mixed particles during the humidifying-dehumidifying process may change their chemical composition, mixing state, and hygroscopicity. In addition, chemical reactions should be considered in future studies on the hygroscopic behavior of mixed particles. Graphical abstract Image 1 Highlights • Hygroscopic behaviors of oxalic acid containing mixed particles were studied. • Reactions occurred during the humidifying process of mixed particles. • Coexisting hygroscopic components promote the reaction between H 2 C 2 O 4 and CaCO 3. • The final composition depends on the hygroscopicity of the products. [ABSTRACT FROM AUTHOR]

Abstract Chemical characteristics and the sources of submicron particles (<1 μm in diameter) were investigated in Valle Alegre, the coastal area of Central Chile. The chemical composition of particles was studied by using a Soot particle Aerosol Mass Spectrometer and Multi-Angle Absorption Photometer. Submicron particles were dominated by organics (42% of mass) and sulfate (39% of mass) while the mass fractions of ammonium, nitrate and black carbon were much smaller (13, 2 and 4% of mass, respectively). Additionally, several metals (V, Zn, Fe, Cd, Cu, K, Na and Mg) were detected in submicron particles and also some of their inorganic salts (e.g. NaCl+, MgCl 2 +, CaCl 2 +, KCl+ and KNO 3 +). The sources of particles were examined by using Positive Matrix Factorization (PMF). Organic aerosol (OA) was divided into five factors by using PMF; hydrocarbon-like OA (HOA), biomass burning OA (BBOA), low-volatility oxygenated OA (LV-OOA), semi-volatile OA (SV-OOA) and marine oxygenated OOA (MOOA). Oxygenated factors (LV-OOA; SV-OOA and MOOA) comprised 75% of total OA with LV-OOA being the dominant factor (38% of OA). Sulfate had two major sources in Valle Alegre; ∼70% of sulfate was related to anthropogenic sources through the oxidation of gas phase SO 2 whereas ∼24% of sulfate was associated with biogenic origin related to the oxidation of dimethyl sulfide in the marine environment. Regarding total submicron particle mass (campaign-average 9.5 μg m−3), the contribution of anthropogenic sources was at least as large as that of biogenic origin. Highlights • Several areas of Chile have been suffering from poor air quality. • Chemistry and sources of particles were examined by aerosol mass spectrometer. • Submicron particle mass was dominated by organic compounds and sulfate. • Statistical analysis was utilized to identify the origin of organic and sulfate. • At least half of the total particle mass was related to anthropogenic sources. [ABSTRACT FROM AUTHOR]

Abstract In this paper, the real driving particle number (PN) emissions from two China-6 compliant hybrid electrical vehicles (HEVs) were measured using a certification-level portable emission measurement system (PEMS) and strict adherence to the regulatory procedures for real driving emission (RDE) testing. The results show that the trip-averaged PN emission factors for the port fuel injection (PFI) HEV and the gasoline direct injection (GDI) HEV were 1.15E+12 and 1.71E+12#/km respectively, much higher than the engine-only counterparts and failing the existing RDE limits. Enriched air-fuel mixtures and probably lowered catalyst conversion efficiencies as a result of more frequent engine stop-and-goes of the HEVs are found to be the underlying reasons for the extra PN emissions. The test results also suggest the necessity to amend the power management strategy currently widely used in HEVs to deal with the PN issue. Highlights • Real-word PN emissions of two China-6 HEVs were tested following RDE procedures. • The RDE PN for the PFI and GDI-HEVs were 1.15E+12 and 1.71E+12#/km respectively. • Fuel-rich and low TWC efficiency since frequent engine-starts caused HEVs' more PN. • The power management strategy of HEVs may need amending to cope with high PN. [ABSTRACT FROM AUTHOR]

Abstract To reveal PM 1 vertical profiles and key affecting factors in a typical urban valley, daytime and nighttime PM 1 (the particles with diameters less than 1 μm) samples were collected with medium volume air samplers during 26 December 2017 to 11 January 2018 at five different altitudes by means of high topographic relief at urban areas of Lanzhou. The synchronous boundary layer temperature and humidity profiles were observed by a microwave radiometer. Daytime PM 1 concentrations reduced by about 3.86 μg m−3 when the height above the surface increased by 100 m, which was much lower than that for nighttime (5.68 μg m−3 100 m−1) as particles were easily accumulated near the surface when the air was stable during the nighttime. The three typical PM 1 vertical profiles were identified by K-means clustering technique. The most frequent cluster with elevated PM 1 concentrations near the surface was closely related to temperature inversion around the ground, while the cluster with relatively uniform PM 1 within the boundary layer was mainly induced by unstable atmospheric stratification and thus relatively good vertical dispersion. About 50%–60% of PM 1 variations could be attributed to atmospheric stratification near the surface in the valley city, which was much higher than that at the hilltop. The PM 1 difference increased by 47.14 (36.91) μg m−3 when inversion layer thickness (intensity) increased by 100 m (1 °C 100 m−1). The newly calculated inversion index considering both inversion layer thickness and intensity explained about 87% of PM 1 differences between near the surface and at the hilltop. The vertical dispersion had a more significant effect on PM 1 than horizontal dispersion near the surface, while PM 1 was more largely affected by horizontal dispersion at the hilltop, which was closely related to the valley terrain. Highlights • PM 1 vertical profiles were revealed in urban areas of Lanzhou for the first time. • Three typical PM 1 profile types were identified using K-means clustering technique. • PM 1 concentrations reduced by about 3–5 μg m−3 when the height increased by 100 m. • 50%–60% of PM 1 variations were attributed to atmospheric stratification near the surface. • PM 1 was more largely affected by vertical dispersion near the surface. [ABSTRACT FROM AUTHOR]

Abstract The Daesan industrial complex is one of the largest petrochemical and oil refinery industrial complexes in South Korea, which is believed to be a major source of polycyclic aromatic hydrocarbons (PAHs). Total suspended particle (TSP) samples (n = 84) were seasonally collected at two industrial sites and one residential site, and 19 PAHs were analyzed. Concentrations of individual PAHs ranged from 0.01 to 2.52 ng/m3, and annual mean concentrations of Σ 19 PAHs at Sites 1, 2, and 3 were 5.88, 4.52, and 5.08 ng/m3, respectively. The concentrations of Σ 19 PAHs in warm seasons (spring and summer) were lower than those in cold seasons (autumn and winter). Annual fractions of low molecular weight (LMW)-PAHs (2–3 rings, 12.1%) and high molecular weight (HMW)-PAHs (4–7 rings, 87.9%) indicated a strong contribution of thermal processes. Significant correlations between Σ 19 PAHs and TSP (p < 0.01) at all the sampling sites were observed, implying that increased TSP levels were responsible for elevated levels of PAHs. There were strong seasonal variations in the profiles of PAHs, and they were clearly reflected in the results of the principal component analysis. Diagnostic ratios and backward air trajectories suggested seasonal variations in the contribution of local emissions and long-range transport. The diagnostic ratios suggested that mixed sources were dominant in cold seasons, while coal/biomass burning and non-traffic sources were prevailing in warm seasons. BeP/BaP ratios indicated that local emissions were major sources compared with long-range transport except for summer. Backward air trajectories in winter suggested the influence of long-range transport, but local emissions were more important in this study area. Graphical abstract Image 1 Highlights • Levels of particulate PAHs were monitored near a petrochemical industrial complex. • The concentrations of PAHs in warm seasons were lower than those in cold seasons. • Strong seasonal variations in the levels and profiles of PAHs were found. • The influence of local emissions and long-range transport was evaluated. • The industrial complex and domestic burning were identified as major sources of PAHs. [ABSTRACT FROM AUTHOR]

Abstract Concern about the health impact of exposure to ultrafine particles has prompted a large number of research studies in the last twenty years. Attention focussed on conventional sources of pollution: vehicle emissions, generation of heat and power, as these are likely to be the most relevant sources of emission to which the general public are exposed. As a result, emissions from road vehicles are well characterised and regulated within Europe. In contrast, until relatively recently, little research into ultrafine particles had been specifically targeted at measurement of direct emissions from aircraft or their potential impact on the communities around airports. As a result, there are a number of gaps in our understanding of these emissions, behaviour in the atmosphere and the potential impact. Aircraft engines, especially the jet turbines used in commercial airliners, are known to emit large quantities of ultrafine particles under a wide range of operating modes, yet detailed information about the physical and chemical properties of these particles is poorly documented. This review aims to outline the background for the development of research studies, summarise the research and assessment of aircraft ultrafine particle emissions, and explore possible areas for future research in this area. Highlights • Brings together key research on UFP from aircraft exhaust measurements. • Brings together key research on UFP measurements close to airports. • High numbers of particles <20 nm linked to aircraft. Different to normal environments. • Provides recommendations for further research. • QA/QC procedures need to be better documented to enhance comparability of research. [ABSTRACT FROM AUTHOR]

Long-lasting elevated indoor air concentrations of semi-volatile organic compounds (SVOCs) can cause contamination of indoor surface materials because these compounds have physical-chemical properties causing them to be sorbed (and desorbed) from various surfaces in the indoor environment. Due to this material-gas partitioning and the extensive area of surface materials, the surfaces have the potential to counteract changes in gaseous air concentrations by re-emitting or absorbing SVOCs. In the air itself a partitioning between the gaseous and particulate bound SVOCs exists, relying on among other things the amount and characteristics of the particles. The aim of this study was to investigate the impact of increased particle matter in a contaminated environment, i.e. whether an increase in particles would increase the total air concentration of SVOC through a displacement from the gaseous to the particle phase and at the same time a re-establishment of the gaseous concentration caused by desorption from the surface materials. The study was conducted by measuring the gas and particle bound concentration of SVOCs among a range of congeners of polychlorinated biphenyls (PCBs) in indoor air and quantify the influence of an increased concentration of particulate matter. The experiments were conducted in a room within a dwelling that had elevated levels of PCBs for the last five decades. The increased amount of particulate matter was generated by burning candles and cigarettes, which was measured as particle number concentration and size fractions. Increased cigarette particle concentration increased the indoor air concentration of the sum of all congeners measured by almost 70% compared to background level. Particles from candle burning did not have a similarly significant effect, even though their number concentration was higher. This was likely due to the chemical composition of the particles; cigarette smoke consists primarily of organic particles, while the steady burning of candles produces smaller, mainly inorganic particles. The concentrations of 15 PCB congeners were determined and it was observed that their sorption to cigarette smoke increased with increasing chlorination. A partitioning model indicates absorptive behaviour of PCB to cigarette particles. The results show that smoking inside a residence with long-lasting, elevated PCB concentrations can further increase the concentration of PCB in the air due to its interaction with particulate matter. [Display omitted] • Cigarette smoke increased air concentrations of PCB in a PCB contaminated environment. • The partitioning of PCBs seems influenced by the chemical composition of particles. • The PCB congeners showed absorptive partitioning with cigarette smoke. [ABSTRACT FROM AUTHOR]

Exhaust particle emissions are mostly made of black carbon and/or organic compounds, with some of these organic compounds existing in both the gas and particle phases. Although emissions of volatile organic compounds (VOC) are usually measured at the exhaust, emissions in the gas phase of lower volatility compounds (POA vapor ) are not. However, these gas-phase emissions may be oxidised after emission and enhance the formation of secondary organic aerosols (SOA). They are shown here to contribute to most of the SOA formation in Central Paris. POA vapor emissions are usually estimated from primary organic aerosol emissions in the particle phase (POA). However, they could also be estimated from VOC emissions for both gasoline and diesel vehicles using previously published measurements from chamber measurements. Estimating POA vapor from VOC emissions and ageing exhaust emissions with a simple model included in the Polyphemus air-quality platform compare well to measurements of SOA formation performed in chamber experiments. Over Greater Paris, POA vapor emissions estimated using POA and VOC emissions are compared using the HEAVEN bottom-up traffic emissions model. The impact on the simulated atmospheric concentrations is then assessed using the Polyphemus/Polair3D chemistry-transport model. Estimating POA vapor emissions from VOC emissions rather than POA emissions lead to lower emissions along motorway axes (between −50% and −70%) and larger emissions in urban areas (up to between +120% and +140% in Central Paris). The impact on total organic aerosol concentrations (gas plus particle) is lower than the impact on emissions: between −8% and 25% along motorway axes and in urban areas respectively. Particle-phase organic concentrations are lower when POA vapor emissions are estimated from VOC than POA emissions, even in Central Paris where the total organic aerosol concentration is higher, because of different assumptions on the emission volatility distribution, stressing the importance of characterizing not only the emission strength, but also the emission volatility distribution. [ABSTRACT FROM AUTHOR]

The dry deposition process is recognized as an important pathway among the various removal processes of pollutants in the atmosphere. In this field, there are several models reported in the literature useful to predict the dry deposition velocity of particles of different diameters but many of them are not capable of representing dry deposition phenomena for several categories of pollutants and deposition surfaces. Moreover, their applications is valid for specific conditions and if the data in that application meet all of the assumptions required of the data used to define the model. In this paper a new dry deposition velocity model based on an electrical analogy schema is proposed to overcome the above issues. The dry deposition velocity is evaluated by assuming that the resistances that affect the particle flux in the Quasi-Laminar Sub-layers can be combined to take into account local features of the mutual influence of inertial impact processes and the turbulent one. Comparisons with the experimental data from literature indicate that the proposed model allows to capture with good agreement the main dry deposition phenomena for the examined environmental conditions and deposition surfaces to be determined. The proposed approach could be easily implemented within atmospheric dispersion modeling codes and efficiently addressing different deposition surfaces for several particle pollution. [ABSTRACT FROM AUTHOR]

Combustion processes related to industry, traffic, agriculture, and waste treatment and disposal increase the amount of outdoor ultrafine particles (UFPs), which have adverse effects on human health. Given that people spend the majority of their time indoors, it is critical to understand the penetration of outdoor UFPs through building cracks in order to estimate human exposure to outdoor-originated UFPs. Lagrangian tracking is an efficient approach for modeling particle penetration. However, the Brownian motion for Lagrangian tracking in ANSYS Fluent ® , a widely used software for particle dispersion modeling, is not able to model UFP dispersion accurately. In this study, we modified the Brownian force by rewriting the Brownian diffusion coefficient and particle integration time step with a user-defined function in ANSYS Fluent ® to model particle penetration through building cracks. The results obtained using the modified model agree much better with the experimental results, with the averaged relative error less than 14% for the smooth crack cases and 21% for the rough crack case. We expect the modified Brownian force model proposed herein to be applied for UFP dispersion modeling in more indoor air quality studies. [ABSTRACT FROM AUTHOR]

This study provides observational results of aerosol optical and radiative characteristics over four locations in IGP. Spectral variation of Aerosol Optical Depth (AOD), Single Scattering Albedo (SSA) and Asymmetry Parameter (AP) were analysed using AErosol RObotic NETwork (AERONET) data. The analysis revealed that coarse particles were dominant in summer and pre-monsoon, while fine particles were more pronounced in winter and post-monsoon. Furthermore, the spatio-temporal variations of Shortwave Direct Aerosol Radiative Forcing (SDARF) and Shortwave Direct Aerosol Radiative Forcing Efficiency (SDARFE) at the Top Of Atmosphere (TOA), SURface (SUR) and within ATMosphere (ATM) were calculated using SBDART model. The atmospheric Heating Rate (HR) associated with SDARF ATM were also computed. It was observed that the monthly averaged SDARF TOA and SDARF SUR were found to be negative leading to positive SDARF ATM during all the months over all sites. The increments in net atmospheric forcing lead to maximum HR in November–December and May. The seasonal analysis of SDARF revealed that SDARF TOA and SDARF SUR were negative during all seasons. The SW atmospheric absorption translates to highest atmospheric HR during summer over Karachi and during pre-monsoon over Lahore, Jaipur and Kanpur. Like SDARF, the monthly and seasonal variations of SDARFE TOA and SDARFE SUR were found to be negative, resulting in positive atmospheric forcing. Additionally, to compare the model estimated forcing against AERONET derived forcing, the regression analysis of AERONET-SBDART forcing were carried out. It was observed that SDARF at SUR and TOA showed relatively higher correlation over Lahore, moderate over Jaipur and Kanpur and lower over Karachi. Finally, the analysis of National Oceanic and Atmospheric Administration Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) model revealed that air masses were arriving from multiple source locations. [ABSTRACT FROM AUTHOR]

In the winter and summer of 2013–2014, we used a sampling system, which consists of annular denuder, back-up filter and thermal desorption set-up, to measure the speciation of major inorganic salts in aerosols and the associated trace gases in Beijing. This sampling system can separate volatile ammonium salts (NH 4 NO 3 and NH 4 Cl) from non-volatile ammonium salts ((NH 4 ) 2 SO 4 ), as well as the non-volatile nitrate and chloride. The measurement data was used as input of a thermodynamic equilibrium model (ISORROPIA II) to investigate the gas–aerosol equilibrium characteristics. Results show that (NH 4 ) 2 SO 4 , NH 4 NO 3 and NH 4 Cl were the major inorganic salts in aerosols and mainly existed in the fine particles. The sulfate, nitrate and chloride associated with crustal ions were also important in Beijing where mineral dust concentrations were high. About 19% of sulfate in winter and 11% of sulfate in summer were associated with crustal ions and originated from heterogeneous reactions or direct emissions. The non-volatile nitrate contributed about 33% and 15% of nitrate in winter and summer, respectively. Theoretical thermodynamic equilibrium calculations for NH 4 NO 3 and NH 4 Cl suggest that the gaseous precursors were sufficient to form stable volatile ammonium salts in winter, whereas the internal mixing with sulfate and crustal species were important for the formation of volatile ammonium salts in summer. The results of the thermodynamic equilibrium model reasonably agreed with the measurements of aerosols and gases, but large discrepancy existed in predicting the speciation of inorganic ammonium salts. This indicates that the assumption on crustal species in the model was important for obtaining better understanding on gas–aerosol partitioning and improving the model prediction. [ABSTRACT FROM AUTHOR]

We have derived a time scale τ eq that describes the characteristic time for a single compound i with a saturation vapour concentration C eff,i to reach thermodynamic equilibrium between the gas and particle phases. The equilibration process was assumed to take place via gas-phase diffusion and absorption into a liquid-like phase present in the particles. It was further shown that τ eq combines two previously derived and often applied time scales τ a and τ s that account for the changes in the gas and particle phase concentrations of i resulting from the equilibration, respectively. The validity of τ eq was tested by comparing its predictions against results from a numerical model that explicitly simulates the transfer of i between the gas and particle phases. By conducting a large number of simulations where the values of the key input parameters were varied randomly, it was found out that τ eq yields highly accurate results when i is a semi-volatile compound in the sense that the ratio of total (gas and particle phases) concentration of i to the saturation vapour concentration of i , μ, is below unity. On the other hand, the comparison of analytical and numerical time scales revealed that using τ a or τ s alone to calculate the equilibration time scale may lead to considerable errors. It was further shown that τ eq tends to overpredict the equilibration time when i behaves as a non-volatile compound in a sense that μ > 1. Despite its simplicity, the time scale derived here has useful applications. First, it can be used to assess if semi-volatile compounds reach thermodynamic equilibrium during dynamic experiments that involve changes in the compound volatility. Second, the time scale can be used in modeling of secondary organic aerosol (SOA) to check whether SOA forming compounds equilibrate over a certain time interval. [ABSTRACT FROM AUTHOR]

A national survey on indoor environmental quality covering 567 residences in mainland France was performed during 2003–2005. The measured parameters were temperature, relative humidity, CO 2 , and the indoor air pollutants: fourteen individual volatile organic compounds (VOC), four aldehydes and particulate matter PM 10 and PM 2.5. The measured indoor concentrations were analyzed for correlations with the building characteristics: type of dwelling, period of construction, dwelling location, type of ventilation system, building material, attached garage and retrofitting. The median night time air exchange rate (AER) for all dwellings was 0.44 h −1 . The night time AER was higher in apartments (median = 0.49 h −1 ) than in single-family houses (median = 0.41 h −1 ). Concentration of formaldehyde was approximately 30% higher in dwellings built after 1990 compared with older ones; it was higher in dwellings with mechanical ventilation and in concrete buildings. The VOC concentrations depended on the building characteristics to various extents. The sampling season influenced the majority of the indoor climate parameters and the concentrations of the air pollutants to a higher degree than the building characteristics. Multivariate linear regression models revealed that the indoor–outdoor difference in specific humidity, a proxy for number of occupants and their indoor activities, remained a significant predictor for most gaseous and particulate air pollutants. The other strong predictors were outdoor concentration, smoking, attached garage and AER (in descending order). [ABSTRACT FROM AUTHOR]

The hygroscopic properties of two water-soluble organic compounds (WSOCs) relevant to urban haze pollution (phthalic acid and levoglucosan) and their internally mixtures with inorganic salts (ammonium sulfate and ammonium nitrate) are investigated using a hygroscopicity tandem differential mobility analyzer (H-TDMA) system. The multi-component particles uptake water gradually in the range 5–90% relative humidity (RH). The experimental results are compared with the thermodynamic model predictions. For most mixtures, Extended Aerosol Inorganic Model (E-AIM) predictions agree well with the measured growth factors. The hygroscopic growth of mixed particles can be well described by the Zdanovskii–Stokes–Robinson (ZSR) relation as long as the mixed particles are completely liquid. ZSR calculations underestimate the water uptake of mixed particles at moderate RH due to the partial dissolution of ammonium sulfate in the organic and ammonium nitrate solution in this RH region. The phase of ammonium nitrate in the initial dry particles changes dramatically with the composition of mixtures. The presence of organics in the mixed particles can inhibit the crystallization of ammonium nitrate during the drying process and results in water uptake at low RH (RH < 60%). These results demonstrate that certain representative WSOCs can substantially influence the hygroscopicity of inorganic salts and overall water uptake of particles. [ABSTRACT FROM AUTHOR]

Road dust emission is an emerging issue in air quality due to the lack of remediation measures in contrast to vehicle exhaust emissions. The evidence of receptor modeling studies allows for quantifying impact on a few receptors, but the high cost of PM chemical speciation data and the questionable representativeness of single monitoring sites, limit considerably the development of population exposure estimates and epidemiologic studies based on georeferenced data. This study attempts to initiate and promote urban-scale dispersion modeling for road dust emissions, which will allow for a more robust estimate of population exposure and health outcomes. The TNO URBIS (URBan Information System) model was applied in the city of Barcelona, implementing a Gaussian line source and a street canyon dispersion model, together with new experimental estimates of road dust emission factors and algorithm to describe the time variability. Annual, daily and hourly road dust contributions were simulated and validated against observation of PM10, mineral dust and hourly PM2.5-10 concentrations. Results show that road dust contributed 9–15% to PM10 levels at background sites, and 23–44% at traffic sites. Highest contributions were modeled in the commercial/residential district where most of population live and work (Eixample) structured by 120 m wide square blocks, separated by roads with >10,000 vehicles per day. Street level contributions rise up to 20 μ g/m 3 (96% of roads) and an additional 3% of roads within 20–40 μ g/m 3 . Hourly simulations of road dust contributions revealed to benefit from the implementation of the new emission module ( Amato et al., 2012 ), able to describe the exponential recovery of road dust emission potential after rain events, when compared to common approach such as the use of constant emission factor or an ON/OFF approach. Correlation coefficients with observed data varied from 0.61, 0.58 and 0.43 for annual, daily and hourly means, respectively, revealing a clear improvement in terms of both spatial and temporal variability. However, more efforts need to be done in validating the model in different climatic scenarios and evaluating the seasonal variation of road dust emissions, due to droughts or Saharan dust events. [ABSTRACT FROM AUTHOR]

In this study we analyzed dust events records of surface meteorological stations on Tibetan Plateau (TP) during 1961–2010 and provided the spatial and temporal distribution of dust events. The occurrence of dust events has significantly decreased since the 1970s. We defined the Tibetan Plateau Dust Index (TPDI) for the most dust active periods, spring and winter, to characterize the large scale variability of dust events over TP. Mann–Kendall test suggested the decreasing trend was possibly an abrupt change in the 1990s. The decline of surface wind speeds could partly explain the decrease of dust events over TP. TPDI is positively correlated to the surface winds, with correlation coefficients of 0.42 for spring and 0.46 for winter, respectively. The averaged number days with strong winds (wind speed greater than 6.5 ms -1 ) for the 4 selected stations, which were chosen to define TPDI, are significantly correlated with TPDI for both spring (correlation coefficient = 0.69) and winter (correlation coefficient = 0.76) and also showed a deceasing trend. The upward trend of vegetation cover was indicated by the normalized difference vegetation index (NDVI), which can be attributed as another factor driving the decrease of dust events over TP. TPDI is negatively correlated to the NDVI, with correlation coefficients of −0.48 for spring and −0.29 for winter. Additionally, analysis of geopotential height fields and wind fields indicate an enhanced ridge in the north of TP and weakened westerly jet in the low-frequency years of dust events, which also drive the decline of dust events over TP. [ABSTRACT FROM AUTHOR]

Highlights • The importance of atmospheric ice nucleating particles (INPs) is introduced. • Research advancements in atmospheric INPs are presented. • Challenges and opportunities in atmospheric INPs research are discussed. [ABSTRACT FROM AUTHOR]

The ozonolysis of reactive organic gases (ROG), e.g. terpenes, generates secondary organic aerosol (SOA) indoors. The SOA formation strength of such reactions is parameterized by the aerosol mass fraction (AMF), a.k.a. SOA yield, which is the mass ratio of generated SOA to oxidized ROG. AMFs vary in magnitude both among and for individual ROGs. Here, we quantified dynamic SOA formation from the ozonolysis of α-pinene with ‘transient AMFs,’ which describe SOA formation due to pulse emission of a ROG in an indoor space with air exchange, as is common when consumer products are intermittently used in ventilated buildings. We performed 19 experiments at low, moderate, and high (0.30, 0.52, and 0.94 h −1 , respectively) air exchange rates (AER) at varying concentrations of initial reactants. Transient AMFs as a function of peak SOA concentrations ranged from 0.071 to 0.25, and they tended to increase as the AER and product of the initial reactant concentrations increased. Compared to our similar research on limonene ozonolysis (Youssefi and Waring, 2014), for which formation strength was driven by secondary ozone reactions, the AER impact for α-pinene was opposite in direction and weaker, while the initial reactant product impact was in the same direction but stronger for α-pinene than for limonene. Linear fits of AMFs for α-pinene ozonolysis as a function of the AER and initial reactant concentrations are provided so that future indoor models can predict SOA formation strength. [ABSTRACT FROM AUTHOR]

For the assessment of personal exposure, information about the concentration of pollutants when people are in given indoor environments (occupancy time) are of prime importance. However this kind of data frequently is not reported. The aim of this study was to assess differences in particle characteristics between occupancy time and the total monitoring period, with the latter being the most frequently used averaging time in the published data. Seven indoor environments were selected in Sweden and Finland: an apartment, two houses, two schools, a supermarket, and a restaurant. They were assessed for particle number and mass concentrations and number size distributions. The measurements using a Scanning Mobility Particle Sizer and two photometers were conducted for seven consecutive days during winter in each location. Particle concentrations in residences and schools were, as expected, the highest during occupancy time. In the apartment average and median PM 2.5 mass concentrations during the occupancy time were 29% and 17% higher, respectively compared to total monitoring period. In both schools, the average and medium values of the PM 2.5 mass concentrations were on average higher during teaching hours compared to the total monitoring period by 16% and 32%, respectively. When it comes to particle number concentrations (PNC), in the apartment during occupancy, the average and median values were 33% and 58% higher, respectively than during the total monitoring period. In both houses and schools the average and median PNC were similar for the occupancy and total monitoring periods. General conclusions on the basis of measurements in the limited number of indoor environments cannot be drawn. However the results confirm a strong dependence on type and frequency of indoor activities that generate particles and site specificity. The results also indicate that the exclusion of data series during non-occupancy periods can improve the estimates of particle concentrations and characteristics suitable for exposure assessment, which is crucial for estimating health effects in epidemiological and toxicological studies. [ABSTRACT FROM AUTHOR]

The Yangtze River Delta (YRD) is one of the regions with the most dynamic economy and severe atmospheric pollution in China. In order to characterize the particle features, especially the carbonaceous component in the YRD, particulate matter smaller than 2.5 μm (PM 2.5 ) and 10 μm (PM 10 ) samples in each season were collected in urban Nanjing, a typical city that locates in the west part of the YRD. The organic carbon (OC) and elemental carbon (EC) was differentiated using the thermal optical reflectance method. The average concentrations of PM 2.5 , OC and EC during the study periods were observed to be 117.6, 13.8, and 5.3 μg/m 3 respectively, with all the highest levels in winter. The mass fraction of the Total carbonaceous aerosol (TCA) in PM 2.5 was estimated at 23% on average, lower than those reported for other cities in the YRD. The OC and EC correlated well in all the seasons, especially in spring and winter, implying that OC and EC were attributed to common emission sources. Good correlation was observed between OC and estimated K + from biomass burning in the harvest season in autumn and summer, indicating biomass burning a significant source of carbonaceous aerosols. This could also be confirmed by the lower fraction of OC3 + OC4 in OC during autumn and summer. The secondary organic carbon (SOC) estimated by EC-tracer method was the highest in winter (7.3 μg/m 3 ) followed by autumn (6.7 μg/m 3 ), summer (3.7 μg/m 3 ) and spring (2.0 μg/m 3 ). However, the SOC/OC in winter was not as high as that in summer and autumn, implying the high concentration of OC in winter was probably due to the stable weather but not mainly caused by SOC formation. The high SOC/OC ratio in summer was attributed to stronger oxidation, which could be suggested by higher sulfur oxidation ratio (SOR). [ABSTRACT FROM AUTHOR]

Ozone-terpene reactions are important sources of indoor ultrafine particles (UFPs), a potential health hazard for human beings. Humans themselves act as possible sites for ozone-initiated particle generation through reactions with squalene (a terpene) that is present in their skin, hair, and clothing. This investigation developed a numerical model to probe particle generation from ozone reactions with clothing worn by humans. The model was based on particle generation measured in an environmental chamber as well as physical formulations of particle nucleation, condensational growth, and deposition. In five out of the six test cases, the model was able to predict particle size distributions reasonably well. The failure in the remaining case demonstrated the fundamental limitations of nucleation models. The model that was developed was used to predict particle generation under various building and airliner cabin conditions. These predictions indicate that ozone reactions with human-worn clothing could be an important source of UFPs in densely occupied classrooms and airliner cabins. Those reactions could account for about 40% of the total UFPs measured on a Boeing 737-700 flight. The model predictions at this stage are indicative and should be improved further. [ABSTRACT FROM AUTHOR]

To fill the blank information for aerosol precipitation-scavenging research in north-west of China, the aerosol particle and raindrop size distributions were measured simultaneously during 1 September 2012 to 31 August 2013 in urban Lanzhou. The scavenging coefficients of thunderstorm and non-thunderstorm rain and snow events were studied and presented on the basis of nine selected precipitation cases including 3 snow and 6 rain events. The variation of scavenging coefficients of snowfall across the size distribution clearly exhibited a trough of lower values for particles of 1000 nm–2000 nm in diameter, while the particles smaller than 500 nm were scavenged efficiently by non-thunderstorm rain, and thunderstorm rain more effectively scavenged the particles in 500–1000 nm. The snow scavenging coefficients varied between 3.11 × 10 −7 s −1 and 1.18 × 10 −3 s −1 in the 10–10,000 nm size range. The scavenging coefficients of thunderstorm (non-thunderstorm) rain were between 8.25 × 10 −7 s −1 (7.48 × 10 −6 s −1 ) and 1.23 × 10 −3 s −1 (7.46 × 10 −4 s −1 ). Additionally, the number of particles in 10–50 nm was more sensitive to duration of snow, while snowfall intensity was more responsible for particle number concentrations in 50–100 nm and 100–1000 nm. The longer period of precipitation with lower raindrop velocity can more effectively scavenge the particles in the size range of 10–50 nm. [ABSTRACT FROM AUTHOR]

People spend the majority of their time indoors and the composition and toxicity of indoor particles is very complex and present significant differences comparing with outdoor aerosols. Consequently, ambient particles cannot represent a real exposure. The aim of this work was to determine the daily exposure and the daily inhaled dose to particle components of elders living in Elderly Care Centers. A questionnaire was applied to 193 institutionalized elders in order to achieve their daily time pattern and to define the micro-environments where PM 10 and its components (carbonaceous components and trace elements) were assessed. Daily exposure was calculated by integrating the elder's time spend in each micro-environment and the concentration of the pollutants for the period of interest. This parameter, together with the inhalation rate and the standard body weight, were used to calculate the daily inhaled dose. PM 10 daily exposure and daily inhaled dose ranged between 11 – 16 μg m −3 and 20 × 10 −3 – 28 × 10 −3 μg kg −1 , respectively. This work not only allowed a fully quantification of the magnitude of the elders exposure, but also showed that the assessment of the integrated exposure to PM components is determinant to accomplish the dose inhaled by elders living in ECCs. [ABSTRACT FROM AUTHOR]

The impact of biogenic emissions on ozone and PM 2.5 levels over Europe is assessed using CMAQ. Biogenic emissions are predicted to increase Max8hrO 3 mixing ratios by 5.7% and to decrease PM 2.5 concentrations by 1.9%, increasing PM 2.5 _ OC by 13.6% and decreasing PM 2 . 5 _SO 4 , PM 2 . 5 _NO 3 and PM 2 . 5 _NH 4 by 5.6%, 3.7% and 5.6%, respectively, on average over Europe due to their interactions with anthropogenic emissions. A suite of perturbations in temperature is imposed individually on the base case conditions in order to determine the sensitivities to air temperature changes. Temperature increases of 1, 2 or 3° K suggest an average increase in Max8hrO 3 mixing ratios of 0.9%, 1.8% or 2.9%, respectively, and an average decrease in daily average PM 2.5 concentrations of 2.5%, 4.2% and 5.8%, respectively, increasing PM 2.5 _ OC and decreasing PM 2 . 5 _SO 4 , PM 2 . 5 _NO 3 and PM 2 . 5 _NH 4 component concentrations on average over Europe. In order to examine if abatement measures for anthropogenic emissions could offset ozone increases in higher temperatures and their effect on PM 2.5 concentrations, a simulation with a domain wide reduction in anthropogenic NO x emissions of 10% is performed. This is estimated to reduce Max8hrO 3 mixing ratios by 1.3% on average over Europe. However, NO x reduction is estimated to increase Max8hrO 3 in VOCs limited areas. The reduction in anthropogenic NO x emissions is predicted to reduce PM 2.5 concentrations by 1.0% enhancing the reduction simulated, here, with temperature increase but further modifying PM 2.5 component concentrations. [ABSTRACT FROM AUTHOR]

Abstract: The reaction of sulfur dioxide and hydrogen peroxide in the presence of deliquesced (>75% RH) sodium chloride (brine) particles was studied by utilizing a cross flow mini-reactor. The reaction kinetics were followed by observing chloride depletion in particles by computer-controlled scanning electron microscope with energy dispersive X-ray analysis, namely CCSEM/EDX. The reactions take place in concentrated mixed salt brine aerosols, for which no complete kinetic equilibrium data previously existed. We measured the Henry's law solubility of H2O2 in brine solutions to close that gap. We also calculated the reaction rate as the particle transforms continuously from concentrated NaCl brine to, eventually, a mixed NaHSO4 plus H2SO4 brine solution. The reaction rate of the SO2 oxidation by H2O2 was found to be influenced by the change in ionic strength as the particle undergoes compositional transformation, following closely the dependence of the third order rate constant on ionic strength as predicted using established rate equations. This is the first study that has measured the ionic strength dependence of sulfate formation (in non-aqueous media) from oxidation of mixed salt brine aerosols in the presence of H2O2. It also gives the first report of the dependence of the Henry's law constant of H2O2 on ionic strength. [Copyright &y& Elsevier]

Abstract: The main purpose of this study was to monitor ambient air particulates and metallic pollutants (Cu, Cd, Cr, Pb and Zn) concentrations, dry deposition during day and nighttime sampling periods at a traffic sampling site during 2012 March to 2013 February, In addition, four ambient air dry deposition models (Wood's, Petroff & Zhang, Baklanov and Noll & Fang) were also used to evaluate the ambient air dry deposition pollutants differences between monitored and modeling results. The result indicated that: 1) Petroff & Zhang's model exhibited better performances for the ambient air particles dry deposition predictions at the particles sizes of 10 μm, 20 μm, 23 μm than those of the other dry deposition models for both day and nighttime sampling periods: 2) Noll & Fang, Woods, and Petroff & Zhang's models exhibited best dry deposition prediction results for both day and nighttime sampling periods for metallic element Zn at the particles sizes of 10 μm, 20 μm at this traffic sampling site. However, metallic elements Cu and Cr have the least dry deposition predictions results for all the models mentioned in this study at the particles size of 23 μm for both day and nighttime sampling periods. [Copyright &y& Elsevier]

France, in particular the Rhône-Alpes region, is one of the three main centres of ragweed (Ambrosia) in Europe. The aim of this study is to develop a gridded ragweed pollen source inventory for all of France that can be used in assessments, eradication plans and by atmospheric models for describing concentrations of airborne ragweed pollen. The inventory combines information about spatial variations in annual Ambrosia pollen counts, knowledge of ragweed ecology, detailed land cover information and a Digital Elevation Model. The ragweed inventory consists of a local infection level on a scale of 0–100% (where 100% is the highest plant abundance per area in the studied region) and a European infection level between 0% and 100% (where 100% relates to the highest identified plant abundance in Europe using the same methodology) that has been distributed onto the EMEP grid with 5 km × 5 km resolution. The results of this analysis showed that some of the highest mean annual ragweed pollen concentrations were recorded at Roussillon in the Rhône-Valley. This is reflected by the inventory, where the European infection level has been estimated to reach 67.70% of the most infected areas in Europe i.e. Kecskemét in central Hungary. The inventory shows that the Rhône Valley is the most heavily infected part of France. Central France is also infected, but northern and western parts of France are much less infected. The inventory can be entered into atmospheric transport models, in combination with other components such as a phenological model and a model for daily pollen release, in order to simulate the dispersion of ragweed pollen within France as well as potential long-distance transport from France to other European countries. [ABSTRACT FROM AUTHOR]

Abstract: Scanning mobility particle sizers (SMPS) are common instruments in laboratory and field aerosol studies. They are, however, complex instruments whose accuracy depends in part on reproducible size calibration. The commonly recommended calibration procedure uses polystyrene latex spheres in a solution with surfactant added to minimize coagulation of the particles. The surfactant can contribute significantly to the overall particle number size distribution and in some cases overlap the peak due to the latex spheres. We describe here the application of surfactant-free latex spheres which to the best of our knowledge have not been used in atmospheric applications before but which have significant advantages, including ease of use and cost. [Copyright &y& Elsevier]

Abstract: In addition to direct photolysis, degradation of organic compounds by solar light can also occur by indirect photolysis or photo-sensitised processes. These reactions are important because they are involved in, among others, direct and indirect climate changes, adverse health effects from inhaled particles, effects on cloud chemistry and ozone production. In this work, the importance of atmospheric photo-sensitisation is evaluated in bulk aqueous solution and on the surface of aerosol deliquescent particles. Irradiation experiments in aqueous solution indicate that 4-carboxybenzophenone (CBP) is able to photosensitise the degradation of 4-phenoxyphenol (4 PP). The process takes place via the CBP triplet state (3CBP*), which has an oxidising nature. 4 PP is fluorescent, unlike the photosensitiser CBP, with two emission bands at &#x223c;320 and &#x223c;380 nm. However, addition of CBP to a 4 PP solution considerably decreases the intensity of 4 PP fluorescence bands and causes a very intense new band to appear at &#x223c;420 nm. This behaviour suggests a possible interaction between CBP and 4 PP in solution, which could favour further light-induced processes. Moreover, the new band overlaps with the fluorescence spectrum of atmospheric HULIS (HUmic-LIke Substances), suggesting that supramolecular photosensitiser&#x2013;substrate interactions may have a role in HULIS fluorescence properties. The interaction between CBP and 4 PP coated on silica particles (gas&#x2013;solid system) was also investigated under simulated sunlight, and in the presence of variable relative humidity. The water molecules inhibit the degradation of 4 PP, induced by 3CBP* on the surface of aerosol particles, indicating that the process could be even faster on particles than in solution. We demonstrate that phenol substances adsorbed on aerosol surfaces and in bulk solution are substantially altered upon photosensitised processes. [ABSTRACT FROM AUTHOR]

Abstract: PM10 aerosols from Xi'an, a mega city of China in winter and summer, 2009 were measured for secondary organic aerosols (SOA) (i.e., dicarboxylic acids (DCA), keto-carboxylic acids, and &#x03b1;-dicarbonyls), water-soluble organic (WSOC) and inorganic carbon (WSIC), elemental carbon (EC) and organic carbon (OC). Molecular compositions of SOA on haze and clean days in both seasons were compared to investigate their sources and formation mechanisms. DCA in the samples were 1843 ± 810 ng m&#x2212;3 in winter and 1259 ± 781 ng m&#x2212;3 in summer, respectively, which is similar and even higher than those measured in 2003. Oxalic acid (C2, 1162 ± 570 ng m&#x2212;3 in winter and 1907 ± 707 ng m&#x2212;3 in summer) is the predominant species of DCA, followed by t-phthalic (tPh) in winter and phthalic (Ph) in summer. Such a molecular composition is different from those in other Asian cities where succinic acid (C4) or malonic acid (C3) is the second highest species, which is mostly due to significant emissions from household combustion of coal and open burning of waste material in Xi'an. Mass ratios of C2/diacids, diacids/WSOC, WSOC/OC and individual diacid-C/WSOC are higher on the haze days than on the clean days in both seasons, suggesting an enhanced SOA production under the haze condition. We also found that the haze samples are acidic while the clean samples are almost neutral. Such a difference in particle acidity is consistent with the enhanced SOA production, because acid-catalysis is an important aqueous-phase formation pathway of SOA. Gly/mGly mass ratio showed higher values on haze days than on clean day in both seasons. We comprehensively investigated the ratio in literature and found a consistent pattern. Based on our observation results and those documented data we proposed for the first time that concentration ratio of Gly/mGly can be taken as an indicator of aerosol ageing. [ABSTRACT FROM AUTHOR]

Abstract: Within the European Aerosol Cloud Climate and Air Quality Interactions (EUCAARI) project, the Meteo France research aircraft ATR-42 was operated from Rotterdam (Netherlands) airport during May 2008, to perform scientific flights dedicated to the investigation of aerosol&#x2013;cloud interactions. The objective of this study is to illustrate the impact of cloud processing on the aerosol particle physical and chemical properties. The presented results are retrieved from measurements during flight operation with two consecutive flights, first from Rotterdam to Newcastle (United Kingdom) and subsequently reverse along the same waypoints back to Rotterdam using data measured with compact Time of Flight Aerosol Mass Spectrometer (cToF-AMS) and Scanning Mobility Particle Sizer (SMPS). Cloud-related measurements during these flights were performed over the North Sea within as well as in close vicinity of a marine stratocumulus cloud layer. Particle physical and chemical properties observed in the close vicinity, below and above the stratocumulus cloud, show strong differences: (1) the averaged aerosol size distributions, observed above and below the cloud layer, are of bimodal character with pronounced minima between Aitken and accumulation mode, very likely due to cloud processing. (2) the chemical composition of aerosol particles is strongly dependent on the position relative to the cloud layer (vicinity or below/above cloud). In general, the nitrate and organic relative mass fractions decrease with decreasing distance to the cloud, in the transit from cloud&#x2013;free conditions towards the cloud boundaries. This relative mass fraction decrease ranges from a factor of three to ten, thus leading to an increase of the sulfate and ammonium relative mass concentrations while approaching the cloud layer. (3), the chemical composition of cloud droplet residuals, analyzed downstream of a Counterflow virtual Impactor (CVI) inlet indicates increased fractions of mainly soluble chemical compounds such as nitrate and organics, compared to non cloud processed particles. Finally, a net overbalance of nitrate aerosol has been revealed by comparing cloud droplet residual and non cloud processed aerosol chemical compositions. Conclusively, this study highlights gaps concerning the sampling strategy that need to be addressed for the future missions. [ABSTRACT FROM AUTHOR]

Abstract: Evidence concerning the health risk of fine and coarse particles is limited in developing Asian countries. The modifying effect between particles and temperature and season also remains unclear. Our study is one of the first to investigate the acute effect of particles size fractions, modifying effects and interannual variations of relative risk in a developing megacity where particulate levels are extraordinarily high compared to other Asian cities. After controlling for potential confounding, the results of a time-series analysis during the period 2005&#x2013;2009 show that a 10 &#x03bc;g m&#x2212;3 increase in PM2.5 levels is associated with a 0.65% (95% CI: 0.29&#x2013;0.80%), 0.63% (95% CI: 0.25&#x2013;0.83%), and 1.38% (95% CI: 0.51&#x2013;1.71%) increase in non-accidental mortality, respiratory mortality, and circulatory mortality, respectively, while a 10 &#x03bc;g m&#x2212;3 increase in PM10 is similarly associated with increases of 0.15% (95% CI: 0.04&#x2013;0.22%), 0.08% (95% CI: 0.01&#x2013;0.18%), and 0.44% (95% CI: 0.12&#x2013;0.63%). We did not find a significant effect of PM2.5 &#x2013; 10 on daily mortality outcomes. Our analyses conclude that temperature and particulates, exposures to both of which are expected to increase with climate change, might act together to worsen human health in Beijing, especially in the cool seasons. The level of the estimated percentage increase assume an escalating tendency during the study period, in addition to having a low value in 2008, and after the Olympic Games, the values increased significantly as the temporary atmospheric pollution control measures were terminated mostly. [ABSTRACT FROM AUTHOR]

Abstract: Using daily PM2.5 concentration data from Beijing, surface observations and upper-air sounding data from regional weather stations in Beijing and North China from 2007 to 2008, 5-min AWS (automatic weather station) observations and hourly AMS (aerosol mass spectrum) data from July 2008, we analysed sensitive meteorological parameters and conditions that affect the concentration of PM2.5. We also diagnosed and identified the impact of meteorological conditions on air quality (AQ). The results show that the condensation function fc is a sensitive and significant parameter for PM2.5 concentration, favourable for generation of secondary aerosol particles. Statistical analysis of a large sample of PM2.5 and meteorological observation data indicates that adaptive weight parameter &#x03b2; is of great value in diagnosing changes in PM2.5 concentrations. When Beijing and North China experience dry, cold winters with a low fc, the parameter &#x03b2; will be large, creating conditions that are conducive to suspended fine particles. In moist, hot summers, the high temperature and humidity increase the fc, but &#x03b2; plays a much weaker role than in winter. &#x03b2; and fc influence and restrict each other, and their impacts on the changes in PM2.5 concentrations are consistent with the observed seasonal changes in meteorological elements and PM2.5 concentrations. In addition, a good correlation exists between the 24-h forecast of the I index and the PM2.5 observations in Beijing, which will prove useful in diagnosing, identifying and predicting the influence of meteorological conditions on AQ based on PM2.5 concentrations. [ABSTRACT FROM AUTHOR]

Urban air pollution is quite complex and exhibits significant spatial variability within communities. Traditional centralized monitoring captures temporal variability as well as the long-term trends of air pollution very well, but mapping spatial variability of air pollution in communities at high resolution would require large number of air quality monitors distributed across the community. Mobile monitoring complements stationary monitoring approaches by measuring pollution levels on accessible road networks in urban communities. This paper presents the application of an integrated mobile measurement and data analysis approach to study community-level air pollution patterns, separate the regional background and local contributions, and identify high pollution zones for black carbon (BC), ultrafine particles (UFP), and fine particulate matter (PM 2.5). This study was conducted during different periods from 2017 to 2019 in three California cities (Richmond, Stockton, and Commerce) with diverse community and source characteristics. The study found that traffic was the dominant primary source of air pollution in both urban and suburban settings. Urban areas adjacent to large area sources, such as ports and railyards had increased pollutant enhancements due to either direct or indirect emissions, while suburban areas containing unpaved roads were observed to have large PM 2.5 enhancement due to the resuspended dust. The analysis disaggregated the contribution of regional and local sources to local air pollution and found that regional background sources contributed up to 75% of the PM 2.5 concentrations, while local sources contributed more than half of BC and UFP. The study suggests that 15–30 repeated measurements may be sufficient to map the general air pollution patterns within the community, while some extreme high pollution zones can be identified with fewer repeats (5–10). These techniques can be used for initial screening of air pollution variability within the community, and help identify priority areas for conducting follow-up long-term air quality measurements. The techniques also informs the relative importance of regional and local actions to reduce community pollutant levels. • Mobile monitoring is effective to study spatial pattern of community air quality. • 5–15 repeats can help identify the most important HPZs. • High pollution zones identified near major traffic and industrial sources. • Regional background mainly affects PM2.5, while local sources affect BC and UFP. [ABSTRACT FROM AUTHOR]

This work focuses on transport and properties of ash from the Icelandic volcano Grímsvötn that erupted in spring 2011. Atmospheric transport of volcanic ash from the eruption was simulated using the Danish Emergency Response Model of the Atmosphere (DERMA). The arrivals of volcanic particles were detected on-line at Mace Head at the West coast of Ireland during volcanic plume advection identified by high resolution time of flight aerosol mass spectrometry (HR-ToF AMS). Based on DERMA information aerosol particles were collected in Copenhagen, Denmark, before predicted arrival of the ash plume and during a period where ash was present in the air. Analysis of the meteorological conditions shows that the particles collected before arrival of the volcanic ash may serve as a good reference sample allowing identification of significant changes in ambient aerosol properties during the volcanic ash event over Copenhagen. Using single particle analysis in scanning electron microscopy (SEM), data on structure, chemical composition, size and morphology of individual volcanic ash particles from the Grímsvötn eruption after atmospheric transport to Scandinavia are provided. Particles were sliced with Focused Ion Beam (FIB). Element mappings from cross-sections through collected volcanic ash particles reveal inhomogeneous distributions of the elements K, Mg, Fe and Ti. [ABSTRACT FROM AUTHOR]

Abstract: Ions play an important role in affecting climate and particle formation in the atmosphere. Small ions rapidly attach to particles in the air and, therefore, studies have shown that they are suppressed in polluted environments. Urban environments, in particular, are dominated by motor vehicle emissions and, since motor vehicles are a source of both particles and small ions, the relationship between these two parameters is not well known. In order to gain a better understanding of this relationship, an intensive campaign was undertaken where particles and small ions of both signs were monitored over two week periods at each of three sites A, B and C that were affected to varying degrees by vehicle emissions. Site A was close to a major road and reported the highest particle number and lowest small ion concentrations. Precursors from motor vehicle emissions gave rise to clear particle formation events on five days and, on each day this was accompanied by a suppression of small ions. Observations at Site B, which was located within the urban airshed, though not adjacent to motor traffic, showed particle enhancement but no formation events. Site C was a clean site, away from urban sources. This site reported the lowest particle number and highest small ion concentration. The positive small ion concentration was 10%–40% higher than the corresponding negative value at all sites. These results confirm previous findings that there is a clear inverse relationship between small ions and particles in urban environments dominated by motor vehicle emissions. [Copyright &y& Elsevier]

Abstract: Ozone-initiated chemistry in indoor air can produce sub-micron particles, which are potentially harmful for human health. Occupants in indoor spaces constitute potential sites for particle generation through ozone reactions with human skin and clothing. This investigation conducted chamber experiments to examine particle generation from ozone reactions with clothing (a T-shirt) under different indoor conditions. We studied the effect of various factors such as ozone concentration, relative humidity, soiling levels of T-shirt with human skin oils, and air change rate on particle generation. The results showed that ozone reactions with the T-shirt generated sub-micron particles, which were enhanced by the soiling of the T-shirt with human skin oils. In these reactions, a burst of ultrafine particles was observed about one hour after ozone injection, and then the particles grew to larger sizes. The particle generation from the ozone reactions with the soiled T-shirt was significantly affected by the different factors studied and these reactions were identified as another potential source for indoor ultrafine particles. [Copyright &y& Elsevier]

Abstract: An Aerosol Time-of-Flight Mass Spectrometer (ATOFMS) was deployed in summer 2010 in central Milwaukee as part of a study to understand the sources of primary and secondary aerosol in the non-attainment area of Southeast Wisconsin. Measurements were made continually from mid-July to mid-August, collecting time, size, and chemical composition data on aerosol particles. Trace metals including Se, Cd, Mo, and Sb were detected in the particles. These metals were found to be related and provided information on source types in Milwaukee, generally located southwest of the sampling site, from plumes that appear to originate from point sources. Additionally, Br was detected in individual particle mass spectra during this study, the first such observation at an inland site. Particles that contained Br were found in two different size modes, each of which had a different representative chemical composition. In combination with an analysis of wind direction, the data suggest that the two different size modes of Br-containing particles originate from chemically distinct sources. [Copyright &y& Elsevier]

Abstract: In addition to industrial facilities, fuel combustion, forest fires and dust erosion, exhaust and non-exhaust vehicle emissions are an important source of ambient air respirable particulate matter (PM10). Non-exhaust vehicle emissions are formed from wear particles of vehicle components such as brakes, clutches, chassis and tires. Although the non-exhaust particles are relatively minor contributors to the overall ambient air particulate load, reliable exposure estimates are few. In this study, a global sampling program was conducted to quantify tire and road wear particles (TRWP) in the ambient air in order to understand potential human exposures and the overall contribution of these particles to the PM10. The sampling was conducted in Europe, the United States and Japan and the sampling locations were selected to represent a variety of settings including both rural and urban core; and within each residential, commercial and recreational receptors. The air samples were analyzed using validated chemical markers for rubber polymer based on a pyrolysis technique. Results indicated that TRWP concentrations in the PM10 fraction were low with averages ranging from 0.05 to 0.70 μg m−3, representing an average PM10 contribution of 0.84%. The TRWP concentration in air was associated with traffic load and population density, but the trend was not statistically significant. Further, significant differences across days were not observed. This study provides a robust dataset to understand potential human exposures to airborne TRWP. [Copyright &y& Elsevier]