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Particulate matter (PM) in 11 different sizes was collected at a semi-rural site in Ulsan, a multi-industrial city in South Korea, over one year from 2019 to 2020 to investigate the temporal patterns in size distribution and potential sources of polycyclic aromatic hydrocarbons (PAHs). The mean concentration of Σ 21 PAHs was higher in winter (0.29 and 0.45 ng/m3 for coarse and fine PM, respectively) than in summer (0.06 and 0.07 ng/m3). Although there was no statistically significant difference between day and night for the concentration of individual PAHs in both coarse and fine PM, the concentrations were generally higher during the day than at night. During the day, Σ 21 PAHs had two distinct peaks (0.056–0.10 μm and 3.20–5.60 μm) in winter, but they tended to partition to larger particles (1.00–1.80 μm and >18.0 μm) in summer. This result suggests that the volatilization of PAHs in smaller particles was enhanced by high-temperature conditions in summer, followed by their condensation onto larger particles. At night, Σ 21 PAH peaks were mainly around the size of 0.7 μm (droplet mode), suggesting the importance of heterogeneous-aqueous reactions. The results of the conditional bivariate probability function and concentration-weighted trajectory indicate that the high concentrations of PAHs in summer and winter were more affected by local pollution and long-range atmospheric transport, respectively. The results of the health risk assessment demonstrate that PAHs in fine PM contributed significantly to cancer risk compared to those in coarse PM. In conclusion, investigating the size distribution of PAHs in particles is necessary to understand their environmental behaviors and evaluate potential health risks. [Display omitted] • Polycyclic aromatic hydrocarbons (PAHs) were higher during the day than at night. • Day–night variation in the particle-size distribution of PAHs was apparent. • Long-range atmospheric transport became more significant in winter. • The concentration of PAHs in summer was more affected by local pollution. • Fine particles had a higher cancer risk of PAHs than coarse particles. [ABSTRACT FROM AUTHOR]

The vertical structure of meteorological elements, black carbon (BC), and aerosols were in situ characterized by the King Air 350 aircraft measurements over the northeast of China during an East Asian dust storm event from April 10 to 13, 2023. The main causes of this dust storm event were the strong winds generated by the Mongolian cyclone, the cold front on the ground provided dynamic conditions, and the unstable atmospheric state provided thermal conditions and less precipitation in the dust source areas led to exposed the ground surface. The number concentrations of BC and aerosol had significant vertical distribution. The number concentration of aerosol in the dust storm (DS) layer increased rapidly with height, while the number and mass concentrations of BC were higher and varied slightly with height. The BC core mass median diameters (MMD) first increased with height, reaching a maximum value of 0.24 μm at 3000 m; and it rapidly decreased to 0.18 μm at 3200 m and then varied slightly with height above 3200 m. BC's bulk relative coating thickness (coated diameter divided by uncoated core diameter Dp/Dc) first decreased with height, reaching a minimum value of 1.16 at 3000 m, then increased with height, reaching a maximum of 1.38 (4250 m). A wind shear layer (7.9 m s−1 at 1850 m) with a sudden drop in temperature (the cooling rate can reach 7.4 °C·(100 m)−1) at 1900 m hinders the transportation of dust particles to the ground, allowing the dust particles to be transported at long-term distances. There were two stratifications in the dust storm layer: DS1 (1700–3000 m, the vertical wind speed was downward, the horizontal wind speed was small) and DS2 (3000–4500 m, the vertical wind speed was upward, the horizontal wind speed was large). The distinct atmospheric flow field conditions between DS1 and DS2 led to different BC and aerosol pollution characteristics. In DS2, the number concentrations of BC and aerosol were higher, the aging ratio of BC particles was higher, and the size of the core particle of BC was smaller. The concentrations of BC, aerosol, Dp/Dc, and MMD in DS2 were 1.1, 59.0, 1.02, and 0.84 times higher than those in DS1, respectively. Dust particles transported over long distances were primarily small. The number concentrations of aerosols at 0.1–0.12 μm and 0.1–0.24 μm were higher in DS1 and DS2, respectively. Still, the number concentration of aerosol at 0.12–0.28 μm in DS1 was lower than in the planetary boundary layer (PBL) and residual layer (RL). [Display omitted] • Aircraft in situ observations of aerosol and BC during the East Asian dust storm. • Two dust layers: Dust Storm (DS)1/DS2 (vertical wind speed (WS) downward/upward, horizontal WS small/large). • Wind shear layer with T sudden drop at 1900m hinders dust transport to ground. • Dust particles were mainly small particles (0.1–0.24 μm) during the long-term distance transport. [ABSTRACT FROM AUTHOR]

This study addresses the ongoing debate concerning the origin of ambient sulfate in northern China, and provides more evidence for primary sulfate from the perspective of source emission. An extensive field experiment was conducted, involving the collection of size-segregated particulate matter emitted under various coal types and combustion conditions for subsequent analysis. Our findings reveal that residential coal combustion (RCC) emits significant amounts of primary sulfate, constituting approximately 26.48 ± 15.43% of the particulate mass. Moreover, these emissions exhibit a strong association with NH 4 +, leading to the formation of stable ammonium sulfate compounds. The emission of sulfate is intricately linked to both coal quality and combustion conditions. Notably, the oversight of δ34S isotope enrichment in RCC particulate matter, which distinctly differs from the raw coal, introduces uncertainties in the quantitative assessment of sulfate sources and formation pathways. Therefore, more in-depth explorations are necessary to elucidate the precise processes involved in RCC sulfate transformation and to accurately determine its environmental impact. • Increase knowledge of RCC sulfate emission characteristics and influences. • Demonstrate RCC emits stable primary sulfate from multiple evidences. [ABSTRACT FROM AUTHOR]

The size-resolved chemical composition and mixing state of single particles were observed by using single particle aerosol mass spectrometry (SPAMS) from May 12 to June 8, 2017. A total of 979,899 particles were successfully ionized to identify 6 main particle groups including carbon-rich particles (47.66%), K-rich particles (28.78%), heavy-metal particles (10.12%), sodium particles (8.86%), dust particles (3.89%), and ammonium particles (0.67%). The wind direction and speed had large impacts on the proportion of carbonaceous aerosol particles and had little influence on heavy-metal particles. The relative humidity (RH) had great impacts on the chemical components of aerosol particles. The proportion of secondary particles increased, while the primary particles diminished as RH increased. The proportion of carbon-rich particles decreased with increasing particle size. However, the size distributions varied significantly for different types of carbonaceous particles. Sodium particles and heavy-metal particles were mainly concentrated at sizes larger than 1 μm. K-rich particles had a maximum proportion at 0.5–1.0 μm. The number fraction of ammonium particles predominated chiefly at 0.6–2.0 μm. It has been found that aerosol particles, mainly from burning processes, were mixed with 36 [C 3 ]+ to different degrees at Mt. Tai. A high proportion of ammonium particles were mixed with organics and elemental carbon (OCEC), elemental carbon-sulfate (EC-sulfate), and elemental carbon-secondary (EC-secondary) particles, while few of these particles were mixed with EC-nitrate particles, which indicated that the ammonia in the air was inclined to combine with organic species and sulfate. A higher proportion of atmospheric particles mixed with nitrate were observed compared to those mixed with sulfate. Image 1 • SPAMS was used for the first time to observe at Mt. Tai. • The proportion of primary/secondary particles diminished/increased as RH increased. • Higher proportions of particles mixed with nitrate than with sulfate. [ABSTRACT FROM AUTHOR]

The "Campaign on Atmospheric Aerosol Research" network of China (CARE-China) is a long-term project for the study of the spatio-temporal distributions of physical aerosol characteristics as well as the chemical components and optical properties of aerosols over China. This study presents the size-segregated sugars from the CARE-China network. Sugars associated with size-segregated particulate matter at 8 regions (North China (NC), East China (EC), Northeast China (NE), and Central China (CC), South China (SC), Northwest China (NE), Southwest China (SW) and the Tibetan Plateau (TP)) including 14 sites over China from January 2013 to December 2014 were analyzed via gas chromatography mass spectrometry. Mass concentrations of measured sugars varied considerably with location and season, ranging from 0.20 to 5588 ng m−3, with the majority from levoglucosan (170 ± 207 ngm−3, accounting for 48% of total sugars), followed by sucrose (44.6 ± 39.6 ngm−3, accounting for 11.3% of sugar), and sorbitol (35.5 ± 42.2 ng m−3, accounting for 10.0% of sugars). The highest levels of sugars were observed in urban sites in Central and Southwest China, whereas the lowest concentrations occurred in background and Tibetan Plateau sites. A distinct seasonal variability of sugars was observed, with higher in the winter or autumn and lower during the summer at urban sites. Inconsistent seasonal trends were observed at the background sites located in the higher latitudes, which were characteristic with the highest concentration occurred in spring. Levoglucosan, galactosan and mannosan were found to be dominant in fine size range <1.1 μm, accounting approximately 59% of all size-segregated sugars. Sucrose was enriched in the size range of 3.3–9.0 μm for almost all sampling sites. Concentrations of trehalose and sorbitol in the three size particles were similar. The OC from biomass burning was estimated to be in the range of 0.93–58.7 μg C m−3, with the highest level OC BB % were observed in urban sites in summer and winter. The contributions of biomass burning to OC in the rest of sites were higher in autumn and winter than in spring and summer. Higher OC BB % was observed in spring at the background sites located in Northwest and Northeast China. Image 1 • Spatio-temporal distributions of size-segregated sugars in China were investigated. • Sugars were more abundant in Central, Southwest, North China and northeastern areas than that in East and Northeast China. • Levoglucosan, galactosan and mannosan were found to be dominant in fine particles. • Higher contribution levels of biomass burning to OC were observed in the urban sites in autumn. [ABSTRACT FROM AUTHOR]

Abstract New particle formation (NPF) events are important phenomena that generate nanoparticles and even fine particles via gas-to-particle conversion. These events have clear effects on aerosol loading, atmospheric chemistry and global climate. Long-term field measurements were used to characterize aerosol size distributions and to examine the role of atmospheric volatile organic compounds (VOCs) in NPF events in the urban environment of Shanghai. Aitken and accumulation particles are dominant and account for 85–95% of the total particles, whereas coarse particles are negligible. Particles in the four size-models show the same seasonality: highest in winter and lowest in autumn. The mean particle size distributions display different patterns of diurnal fluctuation, including bimodal in spring and winter, tri-modal in autumn, and "banana" shaped in summer due to highly frequent NPF events. The geometric mean diameter (GMD) is often 20–30 nm or 40–60 nm. Overall, NPF events occur on 89 days out of 335 measurement days (26.5%), and the newly formed particles have a mean growth rate of 6.28 nm h−1. Two typical anthropogenic aromatics, benzene and toluene, from traffic emissions closely match the occurrence of NPF events and have a weakly positive correlation with the nucleation particle number concentrations. The enhanced VOCs as precursors of organic vapors may contribute to the growth process of NPF events to some extent (e.g., growth rate) so that newly formed particles can grow into a detectable size. Highlights • Aitken and accumulation particles account for 85–95% of total particles. • Aerosol size distributions display different diurnal patterns. • The NPFs occur on 89 days out of 335 days with the highest frequency in summer. • Two anthropogenic aromatics have correlations with nucleation particle. • Enhanced VOCs may contribute to the growth of newly formed particles. [ABSTRACT FROM AUTHOR]

Soil is heated or burned during field biomass burning, including forest fires, grassland fires, and open straw burning. The characteristics of the aerosols released from the high-temperature heated soil have not been reported, according to our knowledge. In this work, three types of soil were heated at different temperatures in a tubular furnace to mimic the heating process during field burning. The particulate emission factors (EF PM), particle size distributions, organic carbon (OC) contents, and organic compositions of the emitted aerosols were investigated in detail. It was found that the particulate matter (PM) produced by soil at high temperature (≥300 °C) cannot be neglected. The PM emission flux of the shallow surface of soil (with depth less than 5 cm) could be dozens of times higher than those from biomass burning when the surface temperature rises to 500 °C. The soil heated at higher temperatures emitted more particles with smaller sizes. These aerosols also contain toxic and harmful substances such as aromatics, heterocycles and nitriles. Therefore, the results strongly suggest that aerosol emissions from the heated soil during the field biomass burning cannot be ignored and could have significant environmental impacts. [Display omitted] • Amounts of aerosol particles were emitted from the high-temperature heated soil. • PM emission factors and OC contents were higher for the soil heated at ≥ 300 °C. • PM emission flux for the heated soil was near or higher than the biomass burning. • The soil-emitted PM were smaller with the increasing heating temperature and time. • Soil thermal-volatility and pyrolysis contribute to the field burning aerosol emission. [ABSTRACT FROM AUTHOR]

Abstract Despite of extensive efforts on investigation into characteristics of severe haze pollution in megacities of China, the accurate relationships among the aerosol composition, mass-size distribution and optical properties during pollution episodes remain poorly understood. Here, we conducted in situ measurements of the mass size distribution of submicron aerosol (PM 1) species by using a High-Resolution Time-of-Flight Aerosol Mass Spectrometer (HR-ToF-AMS), particle light scattering by a Cavity Attenuated Phase Shift ALBedo monitor (CAPS-ALB) and a Photoacoustic Extinctionmeter (PAX) during the winter of 2017 in Shanghai, China. The average PM 1 concentration was 85.9 ± 14.7 μg/m3 during the haze episodes, of which was ∼7 times higher than that of clean period (12.1 ± 3.1 μg/m3). Organic aerosol (OA) and inorganic species (SO 4 2− + NO 3 − + NH 4 +) contributed 39.9% and 51.2% of the total mass of PM 1 during the haze episodes, respectively. OA exhibited a single or bimodal distribution during the haze episodes with the peak concentration of 51.8 μg/m3. There were no obvious differences between ammonium nitrate (NH 4 NO 3) and ammonium sulfate ((NH 4) 2 SO 4) during the haze episodes, which exhibited single peak distributions at the sizes of 650–700 nm and ∼700 nm, respectively. The peak positions of OA, NH 4 NO 3 and (NH 4) 2 SO 4 in clean period were in the range of 450–500 nm, 550–600 nm and 450–500 nm with the peak concentrations of 5.5 μg/m3, 3.1 μg/m3 and 3.8 μg/m3, respectively. The increased scattering coefficients in the haze episodes were positively correlated with higher secondary inorganic aerosols and organic aerosol (OA). The high scattering coefficient contribution fraction peak diameter of NH 4 NO 3 and (NH 4) 2 SO 4 were in the range of 600–800 nm and 600–750 nm with the peak scattering coefficient of 352.6 Mm−1 and 165.7 Mm−1, respectively. The size distribution of scattering for OA showed bimodal modes during all episodes. OA and NH 4 NO 3 were the largest contributors to scattering coefficients of PM 1 during the haze episodes, accounting for 45.5% and 37.8%, respectively. The contribution of (NH 4) 2 SO 4 to the scattering (24%) exceeded that of NH 4 NO 3 during clean period. Our results elucidated that substantial changes in the aerosols optical properties due to the changes in chemical compositions and size distribution during the haze events. Highlights • Hourly size distribution of PM 1 species and optical properties were measured. • Particle size increased from 450 to 600 to 600–800 nm and triggered the haze events. • OM and NH 4 NO 3 contributed 46% and 38% of scattering coefficient during haze events. [ABSTRACT FROM AUTHOR]

Abstract Household air pollution is one important environmental risk to human health in China, however, rural air pollution is often underappreciated and field measurements are limited compared to studies in urban area. The present study investigated indoor and outdoor polycyclic aromatic hydrocarbons (PAHs), and population inhalation exposure from two rural counties in Shanxi and Guizhou provinces, respectively. The indoor levels were higher than the corresponding outdoor concentration in both sites, which was mainly affected by the indoor fuel combustion emissions. A majority of particulate PAHs was found in submicron PM 1.0. Fuel types had significant impacts on the total PAHs mass concentration but also composition profiles. In homes using electricity, the PAHs concentration was lower than those burning solid fuels, and there were relatively more fractions of low molecular weight PAHs with 2–3 rings, while for those burning solid fuels, higher fractions of high molecular weight PAHs with 5–6 rings may pose larger adverse health impacts. Although the daily inhalation exposure level for the population using electricity was much lower than those using solid fuels, the estimated Incremental Lifetime Cancer Risk still exceeded the deemed safe risk of 10−6. Inhalation exposure amounts measured by using portable carried samplers were compared to the estimation based on area concentration. The substantial discrepancy between them confirmed a preferable use of portable carried samplers in exposure evaluation and health risk assessment. Graphical abstract Image 1 Highlights • Higher fractions of particulate PAHs in fine PM 2.5 and submicron PM 1.0. • For cooking fuel, burning of coal briquette had lower PAHs pollution that from wood combustion. • For heating fuel, raw coal chunk may produce lower pollution in comparison with low-quality peats. [ABSTRACT FROM AUTHOR]

Abstract Total and size-resolved concentrations and emission factors are used to compare fleet-averaged vehicle emissions in Pittsburgh, PA in 2002 and 2014. Winter-time traffic tunnel measurements acquired using dual scanning mobility particle sizers (SMPS) over the size range 3–500 nm form the key input for the analysis. Size-resolved mass emission factors were calculated assuming a nanoparticle aggregate model. The ultrafine particle (<30 nm) emissions of diesel vehicles significantly dropped from 2002 to 2014. In the 2014 study, a thermodenuder (TD) was deployed together with the SMPS to measure emissions of non-volatile particles. After evaporation at 250 °C inside the TD, the median diameter of the number-size distribution shifted from 16 nm to ∼7 nm. The total particle number decreased significantly (69%) after evaporating inside the TD, indicating that vehicle emitted particles may be largely externally mixed and that a large fraction of these particles may be purely composed of volatile components. Based on the SMPS-TD measurements, we report a size-resolved volatile-to-non-volatile-component-ratio for vehicle emitted particles. It shows that smaller particles (10–60 nm) emitted by vehicles are dominantly (over 75%) composed of volatile components. We also apportioned the size-resolved particles and non-volatile particle mass and number emission factors for both gasoline and diesel vehicles. Diesel vehicles emitted significantly more ultrafine particles and non-volatile particles than gasoline vehicles. Graphical abstract Image 1 Highlights • Size-resolved particle emission factors for on-road vehicles show that particles are largely externally mixed. • Particles smaller than 50 nm are dominated by volatile components. • Emissions from gasoline and diesel vehicles have been reduced since 2002, with larger reductions in diesel emissions. [ABSTRACT FROM AUTHOR]

A regional air quality model system (RAQMS) was developed by coupling the treatment of heterogeneous reactions between sea salt aerosols (SSAs) and trace gases and applied to the investigation of aerosol properties and evolutionary features in the western Pacific Ocean in the spring of 2014. Model results for meteorological variables, PM concentrations, and size-resolved water soluble inorganic aerosol (WSIA) concentrations were compared and analyzed with a variety of observations from in situ measurements and the research cruise Dongfanghong II . Model validation demonstrated that the model can simulate the spatial-temporal distribution and size distribution of aerosol inorganic components in the marine atmosphere over East Asia, and the inclusion of heterogeneous reactions on SSAs apparently improved the model simulation for WSIA concentration, especially for aerosol size distribution. In the western Pacific Ocean, the non-sea salt SO 4 2− and NO 3 − formed on SSAs accounted for up to 30% and 90% of surface SO 4 2− and NO 3 − concentrations on average, respectively. The atmospheric depositions of total inorganic sulfur and nitrogen were estimated to be 13184 × 10 3 kgS/d and 10728 × 10 3 kgN/d, respectively. Wet deposition was the dominant removal pathway, which accounted for 75% and 68% of sulfur and nitrogen depositions, respectively. The deposition of fine-mode SO 4 2− exceeded that of coarse-mode SO 4 2− , whereas the deposition of coarse-mode NO 3 − was comparable to that of fine-mode NO 3 − . The non-sea salt SO 4 2− and NO 3 − formed on SSAs contributed 16% and 9% of total sulfur and nitrogen depositions on average, respectively. The above results revealed the important role of SSAs in both atmospheric chemistry and deposition in the western Pacific Ocean. [ABSTRACT FROM AUTHOR]

Polar polycyclic aromatic hydrocarbons (PAHs) derivatives like nitrated and oxygenated PAHs have higher toxic potentials than the parent one, and are receiving growing interests. In this study, we investigated household air pollution and personal exposure to nitro- and oxy-PAHs during a winter period in rural Shanxi, northern China. The overall arithmetic means of 24-h average indoor nitro-PAHs and oxy-PAHs were 10.2 ± 3.6 and 76.8 ± 51.8 ng/m 3 , respectively, that were much higher than the 7.98 ± 4.30 and 54.7 ± 45.4 ng/m 3 in the outdoor air. Nearly 90% of particulate PAHs derivatives were enriched in fine PM 2.5 and even finer PM 1.0 fraction. Daily inhalation exposure to nitro- and oxy-PAHs for the rural population were 8.41 ± 3.08 and 68.5 ± 79.7 ng/m 3 , respectively. Residents burning briquette for cooking were found to have lower household air pollution and exposure levels compared with those burning wood. The calculated time-weighted average concentration overestimated, though correlated positively, the daily inhalation exposure compared to the that from personal carried samplers. [ABSTRACT FROM AUTHOR]

A lack of information on the radiative effects of refractory black carbon (rBC) emitted from biomass burning is a significant gap in our understanding of climate change. A custom-made combustion chamber was used to simulate the open burning of crop residues and investigate the impacts of rBC size and mixing state on the particles' optical properties. Average rBC mass median diameters ranged from 141 to 162 nm for the rBC produced from different types of crop residues. The number fraction of thickly-coated rBC varied from 53 to 64%, suggesting that a majority of the freshly emitted rBC were internally mixed. By comparing the result of observed mass absorption cross-section to that calculated with Mie theory, large light absorption enhancement factors (1.7–1.9) were found for coated particles relative to uncoated cores. These effects were strongly positively correlated with the percentage of coated particles but independent of rBC core size. We suggest that rBC from open biomass burning may have strong impact on air pollution and radiative forcing immediately after their production. [ABSTRACT FROM AUTHOR]

Size-segregated PM 10 samples were collected in Guangzhou, China during autumn of 2014. Nine amines, including seven aliphatic amines and two heterocyclic amines, were detected using a gas chromatography-mass spectrometer after derivatization by benzenesulfonyl chloride. The total concentration of the nine amines (Ʃamines) was 79.6–140.9 ng m −3 in PM 10 . The most abundant species was methylamine (MA), which had a concentration of 29.2–70.1 ng m −3 . MA, dimethylamine (DMA), diethylamine (DEA) and dibutylamine (DBA) were the predominant amines in the samples and accounted for approximately 80% of Ʃamines in each size segment. Two heterocyclic amines, pyrrolidine (PYR) and morpholine (MOR), were detected in all samples and had average concentrations of 1.14 ± 0.37 and 1.89 ± 0.64 ng m −3 , respectively, in particles with aerodynamic diameters < 3 μm. More than 80% of Ʃamines were found in particles with diameters <1.5 μm, indicating that amines are mainly enriched in fine particles. All amines exhibited a bimodal distribution with a fine mode at 0.49–1.5 μm and a coarse mode at 7.2–10 μm. The maximum contributions of amines to particles (0.21%) and amines-N to water-soluble organic nitrogen (WSON) (3.1%) were found at the sizes < 0.49 μm. The maximum contribution of amines-C to water-soluble organic carbon (WSOC) was 1.6% over the size range of 0.95–1.5 μm. The molar ratio of Ʃamines to ammonium ranged from 0.0068 to 0.0107 in particles with diameters <1.5 μm, and the maximum ratio occurred in the smallest particles (diameter< 0.49 μm). The average dry deposition flux and velocity of Ʃamines in PM 10 were 7.9 ± 1.6 μg m −2 d −1 and 0.084 ± 0.0021 cm s −1 , respectively. The results of this study provide essential information on the contribution of amines to secondary organic aerosols and dry removal mechanisms in urban areas. [ABSTRACT FROM AUTHOR]

The size of the atmospheric soot is a critical parameter in many perspectives starting from climate impact through health relevance ended with air quality regulations. In this study, we propose a novel methodology for soot selective size measurement of atmospheric aerosol. The proposed method is based on the synergy of selectivity of the aerosol photoacoustic (PA) spectroscopy for highly absorbing atmospheric components and size dependency of the measured phase of the PA signal. The proposed experimental set-up is based on the instrument combination of 4λ-PAS and scanning mobility particle sizer (SMPS) in a closed loop arrangement. We experimentally demonstrated here, first that the PA phase of the photoacoustic signal depends on the characteristic size of the soot aerosol. In order to better understand the effect of morphology, nigrosine particles with spherical shape are also studied. The comparison of the measured data and the theoretical calculation is also investigated. Comparison of the theoretical simulation and the measured data shows increasing differences towards the higher size of the measured aerosol in all samples. We also demonstrated that the inherent system phase is independent of the phase shift related to particles. • Novel method for selective size measurement of light absorbing carbonaceous particulate matter in the atmosphere. • Experimental verification of the particle size dependency of the photoacoustic signal. • Comparison of the theoretical calculation and measured data. [ABSTRACT FROM AUTHOR]

Size-segregated aerosol particles were collected with a 10-stage Micro-Orifice Uniform Deposit Impactor (MOUDI) at an urban site in Shanghai, China for four non-consecutive months representing four seasons from 2015 to 2016. Chemical composition, including water-soluble ions as well as organic carbon (OC), elemental carbon (EC) and secondary organic carbon (SOC) of size-resolved (0.056–18 μm) atmospheric aerosols in four seasons and in different polluted cases were studied. The size distributions of sulfate, nitrate and ammonium (SNA) and carbonaceous aerosol (OC, EC and SOC) were discussed and the potential sources of PM 1.8 -associated secondary species (SO 4 2− , NO 3 − , SNA and SOC) in different seasons were identified by potential source contribution function (PSCF) model. Results showed that atmospheric ultrafine and fine particle pollution in Shanghai were very serious during the study period. Most of the water-soluble ions tended to be enriched in fine particles, especially being abundant in the droplet mode in polluted cases. Compared with sulfate, size distributions of nitrate and ammonium presented more significant seasonal variations and showed distinctive characteristics in polluted days. Abundant nitrate was concentrated in fine particles in cold seasons (spring and winter), whereas it was enriched in coarse mode during summer and autumn. The droplet mode sulfate with high concentration did not result in the aggravation of air pollution, while the nucleation mode sulfate may have made a great contribution to the air pollution in urban Shanghai. It was also found that the formation of air pollution in urban Shanghai had a significant link with nitrate and ammonium, especially with nitrate and ammonium in condensation mode and droplet mode, and the contribution of sulfate to the pollution formation in Shanghai would somehow be surpassed by the increasing nitrate and ammonium. OC and EC concentrations from spring to winter were found to be 11.10, 7.10, 12.30, 20.16, and 3.73, 2.84, 4.63, 7.10 μg m −3 , respectively, distinctly presenting the summer minima and winter maxima in this study. The maximum OC/EC was in the droplet mode and the minimum was in the nucleation mode for both clean and polluted days. The great contribution of SOC to OC in droplet mode and the occurrence of PM pollution necessarily had an important bearing on the SOC formation in droplet mode particles. Particle acidity may play a key role in secondary organic aerosol formation and the particles with the size of 0.056–0.1 μm was the most sensitive particles to acid catalysis in SOA formation. The similar PSCF results of PM 1.8 -associated SOC to those of SO 4 2− , NO 3 − and SNA indicated possible connections between the formation of SOC and secondary inorganic species in PM. [ABSTRACT FROM AUTHOR]

Water-soluble organic carbon (WSOC) is a significant part of ambient aerosol and plays an active role in contributing to aerosol's effect on visibility degradation and radiation budget through its interactions with atmospheric water. Size-segregated aerosol samples in the range of 0.056–18 μm were collected using a ten-stage impactor sampler at an urban site in Hong Kong over one-year period. The WSOC samples were separated into hydrophilic (termed WSOC_h) and hydrophobic fractions (i.e., the humic-like substances (HULIS) fraction) through solid-phase extraction procedure. Carbon in HULIS accounted for 40 ± 14% of WSOC. The size distribution of HULIS was consistently characterized in all seasons with a dominant droplet mode (46–71%) and minor condensation (9.0–18%) and coarse modes (20–35%). The droplet mode had a mass median aerodynamic diameter in the range of 0.7–0.8 μm. This size mode showed the largest seasonal variation in abundance, lowest in the summer (0.41 μg/m 3 ) and highest in the winter (3.3 μg/m 3 ). WSOC_h also had a dominant droplet mode, but was more evenly distributed among different size modes. Inter-species correlations within the same size mode suggest that the condensation-mode HULIS was partly associated with combustion sources and the droplet-mode was strongly associated with secondary sulfate formation and biomass burning particle aging processes. There is evidence to suggest that the coarse-mode HULIS largely originated from coagulation of condensation-mode HULIS with coarse soil/sea salt particles. The formation process and possible sources of WSOC_h was more complicated and multiple than HULIS and need further investigation. Our measurements indicate that WSOC components contributed a dominant fraction of water-soluble aerosol mass in particles smaller than 0.32 μm while roughly 20–30% in the larger particles. [ABSTRACT FROM AUTHOR]

A two-week measurement campaign by a mobile laboratory van was performed in urban environments in the Helsinki metropolitan area, Finland, in winter 2012, to obtain a comprehensive view on aerosol properties and sources. The abundances and physico-chemical properties of particles varied strongly in time and space, depending on the main sources of aerosols. Four major types of winter aerosol were recognized: 1) clean background aerosol with low particle number (Ntot) and lung deposited surface area (LDSA) concentrations due to marine air flows from the Atlantic Ocean; 2) long-range transported (LRT) pollution aerosol due to air flows from eastern Europe where the particles were characterized by the high contribution of oxygenated organic aerosol (OOA) and inorganic species, particularly sulphate, but low BC contribution, and their size distribution possessed an additional accumulation mode; 3) fresh smoke plumes from residential wood combustion in suburban small houses, these particles were characterized by high biomass burning organic aerosol (BBOA) and black carbon (BC) concentrations; and 4) fresh emissions from traffic while driving on busy streets in the city centre and on the highways during morning rush hours. This aerosol was characterized by high concentration of Ntot, LDSA, small particles in the nucleation mode, as well as high hydrocarbon-like organic aerosol (HOA) and BC concentrations. In general, secondary components (OOA, NO 3 , NH 4 , and SO 4 ) dominated the PM 1 chemical composition during the LRT episode accounting for 70–80% of the PM 1 mass, whereas fresh primary emissions (BC, HOA and BBOA) dominated the local traffic and wood burning emissions. The major individual particle types observed with electron microscopy analysis (TEM/EDX) were mainly related to residential wood combustion (K/S/C-rich, soot, other C-rich particles), traffic (soot, Si/Al-rich, Fe-rich), heavy fuel oil combustion in heat plants or ships (S with V-Ni-Fe), LRT pollutants (S/C-rich secondary particles) and sea salt (Na/Cl-rich). Tar balls from wood combustion were also observed, especially (∼5%) during the LRT pollution episode. [ABSTRACT FROM AUTHOR]

An extensive air quality campaign was performed at differently designed station platforms in the Barcelona metro system, aiming to investigate the factors governing airborne particle number (N) concentrations and their size distributions. The study of the daily trends of N concentrations by different size ranges shows that concentrations of N 0.3–10 are closely related with the schedule of the metro service. Conversely, the hourly variation of N 0.007–10 (mainly composed of ultrafine particles) could be partly governed by the entrance of particles from outdoor emissions through mechanical ventilation. Measurements under different ventilation settings at three metro platforms reveal that the effect on air quality linked to changes in the tunnel ventilation depends on the station design. Night-time maintenance works in tunnels are frequent activities in the metro system; and after intense prolonged works, these can result in higher N concentrations at platforms during the following metro operating hours (by up to 30%), this being especially evident for N 1–10 . Due to the complex mixture of factors controlling N, together with the differences in trends recorded for particles within different size ranges, developing an air quality strategy at metro systems is a great challenge. When compared to street-level urban particles concentrations, the priority in metro air quality should be dealing with particles coarser than 0.3 μm. In fact, the results suggest that at narrow platforms served by single-track tunnels the current forced tunnel ventilation during operating hours is less efficient in reducing coarse particles compared to fine. [ABSTRACT FROM AUTHOR]

Particle number concentration and size distribution are important for better understanding the characteristics of aerosols. However, their measurements are scarce in western China. Based on the first measurement of particle number size distribution (10–487 nm) in the suburb of Xi'an, northwest China from November 2013 to December 2014, the seasonal, monthly and diurnal average particle number concentrations were investigated, and the characteristics of new particle formation (NPF) events and their dependencies on meteorological parameters also discussed. The results showed that the annual average particle number concentrations in the nucleation (N NUC ), Aitken (N AIT ), and Accumulation (N ACC ) size ranges were 960 cm −3 , 4457 cm −3 , 3548 cm −3 , respectively. The mean total particle number concentration (N TOT ) was 8965 cm −3 and largely dominated by particles in Aitken mode. The number concentration was dominated by particles around 67.3 nm in spring, summer and fall, while about 89.8 nm in winter. The percentage of the ultrafine size range (UFP, particles of diameter below 100 nm) to total particle number concentration was 63.2%, 69.6%, 62.2% and 58.1% in four seasons. The diurnal variation of the nucleation mode particles was mainly influenced by NPF events in summer, while by both traffic densities and NPF events in spring, fall and winter. The diurnal variation of the number concentration of Aitken mode particles correlated with the traffic emission in spring, fall and winter, while in summer it more correlated with contribution of the growth of the nucleation mode particles. The burst of nucleation mode particles typically started in the daytime (08:15–16:05, LST). The growth rates of nucleated particles ranged from 2.8 to 10.7 nm h -1 with an average of 5.0 ± 1.9 nm h -1 . Among observed 66 NPF events from 347 effective measurement days, 85 percent of their air masses came from north or northwest China, resulting in a low concentration of pre-existing particles, and only 15 percent came southerly from Qingling Mountains. Based on their growth rate, 64 and 36 percent of their subsequent particles, corresponding to types 1 and 2 NPF events, grew and seldom grew after the burst of nucleation mode particles. For type 1 NPF event, the nucleated particles could grow up to 40 nm or larger when surface winds shifted from westerly to easterly or southeasterly (from village areas). For type 2 NPF events, the particles kept almost unchanged when the winds stayed westerly. This implied that the surface wind direction with different emissions might play an important role in new particle growth in suburb of Xi'an. [ABSTRACT FROM AUTHOR]

Current science and policy requirements have focused attention on the need to expand and improve particulate matter (PM) sampling methods. To explore how sampling filter type affects artifacts in PM composition measurements, size-resolved particulate SO 4 2− , NO 3 − and NH 4 + (SNA) were measured on quartz fiber filters (QFF), glass fiber filters (GFF) and cellulose membranes (CM) concurrently in an urban area of Beijing on both clean and hazy days. The results showed that SNA concentrations in most of the size fractions exhibited the following patterns on different filters: CM > QFF > GFF for NH 4 + ; GFF > QFF > CM for SO 4 2− ; and GFF > CM > QFF for NO 3 − . The different patterns in coarse particles were mainly affected by filter acidity, and that in fine particles were mainly affected by hygroscopicity of the filters (especially in size fraction of 0.65–2.1 μm). Filter acidity and hygroscopicity also shifted the peaks of the annual mean size distributions of SNA on QFF from 0.43–0.65 μm on clean days to 0.65–1.1 μm on hazy days. However, this size shift was not as distinct for samples measured with CM and GFF. In addition, relative humidity (RH) and pollution levels are important factors that can enhance particulate size mode shifts of SNA on clean and hazy days. Consequently, the annual mean size distributions of SNA had maxima at 0.65–1.1 μm for QFF samples and 0.43–0.65 μm for GFF and CM samples. Compared with NH 4 + and SO 4 2− , NO 3 − is more sensitive to RH and pollution levels, accordingly, the annual mean size distribution of NO 3 − exhibited peak at 0.65–1.1 μm for CM samples instead of 0.43–0.65 μm. These methodological uncertainties should be considered when quantifying the concentrations and size distributions of SNA under different RH and haze conditions. [ABSTRACT FROM AUTHOR]

An in-situ measurement of the particle number size distribution and optical properties (scattering and absorption coefficients) of PM 2.5 was conducted at Mt. Tai, a mountain top station in central east China in the spring of 2011. It was found that the particle size distribution, mass concentration, as well as the optical properties have been modified during the dust periods. The mean mass concentration of PM 2.5 during the dust periods was nearly twice of that during the non-dust period. The number and volume size distribution showed a higher concentration in the size range of 0.5–2.5 μm during the dust period, which were identified as dust particles. The absorption coefficient increased by ∼40%, while the scattering coefficient did not show much difference. The single scattering albedo of 0.85 during dust period was also comparable with the value of 0.89 during non-dust period. The Mie model was applied to simulate the aerosol optical properties and validated through a closure study for an intensive dust event. This study quantitatively demonstrated that dust particles contributed to nearly 63% of the scattering coefficient, while the remainder was mainly due to anthropogenic particles on dust days. The dust particles took a lower portion to the absorption, about 40%, indicating the anthropogenic particles still played a more dominant role in absorbing. This study also indicated that although there were only a few tens of dust particles during dust period, they could influence in particle optical properties significantly. [ABSTRACT FROM AUTHOR]

This paper presents the long – term observational studies on aerosol optical properties measured at Sri Krishnadevaraya University (SKU) campus (14° 62′ N, 77° 65′ E, 331m asl), Anantapur, in southern India during 2007–2013 using a ground based Multi – Wavelength solar Radiometer (MWR). Seasonal mean values of Aerosol Optical Depth (AOD) for the whole study period were observed to be 0.34 ± 0.03, 0.45 ± 0.04, 0.24 ± 0.04, and 0.31 ± 0.03 during the winter, summer, monsoon and post – monsoon, respectively. Annual mean values of Ångström exponent (α) (turbidity coefficient (β)) varied from 0.68 ± 0.25 (0.18 ± 0.03) to 1.1 ± 0.12 (0.32 ± 0.12) during 2007–2013. However, high values of α in the range of 0.8–1.1 were observed during the winter, while low values in the range 0.3–0.7 were noticed during the monsoon. The frequency distribution of AODs during winter in the range of 0.2–0.4 is about 78%, while summer these were shifted from 0.3 to 0.6 around ∼70%, which indicated the dust strongly affects this region. The accumulated frequencies of Ångström exponent (α) less than 1.0 and greater than 1.0 were about 69% and 31%, respectively, occurred in the summer months indicates the dominance of coarse particles. Columnar size distributions, retrieved from the spectral optical depths, in general, show a bimodal log normal distribution in the optically active size range. The seasonal mean effective radius (R eff ) was found to be high in monsoon (∼0.61 μm) and low in winter (∼0.38 μm). The highest mean mass loading values are lies between 475 ± 36 to 769 ± 49 mg m −2 during the summer, whereas the lowest value in the range 204 ± 19 to 278 ± 23 mg m −2 during the monsoon. The difference between α and curvature effect have been studied as a function of AOD on seasonal basis. Finally, to understand the contribution of long range transported aerosols, we have investigated this analysis making use of back trajectories obtained from the HYSPLIT model for different seasons. [ABSTRACT FROM AUTHOR]

Lung deposited surface area (LDSA) concentration is considered as a relevant metric for the negative health effects of aerosol particles. We report for the first time the size distributions of the LDSA measured in urban air. The measurements were carried out in the metropolitan area of Helsinki, including mobile laboratory and stationary measurements in different outdoor environments, such as traffic sites, a park area, the city center and residential areas. The main instrument in this study was an electrical low pressure impactor (ELPI), which was calibrated in the field to measure the LDSA concentration. The calibration factor was determined to be 60 μ m 2 /(cm 3 pA). In the experiments, the LDSA size distributions were found to form two modes at the traffic sites and in the city center. Both of these traffic related particle modes, the nucleation mode and the soot mode, had a clear contribution to the total LDSA concentration. The average total concentrations varied from 12 to 94 μ m 2 /cm 3 , measured in the park area and at the traffic site next to a major road, respectively. The LDSA concentration was found to correlate with the mass of fine particles (PM2.5), but the relation of these two metrics varied between different environments, emphasizing the influence of traffic on the LDSA. The results of this study provide valuable information on the total concentrations and size distributions of the LDSA for epidemiological studies. The size distributions are especially important in estimating the contribution of outdoor concentrations on the concentrations inside buildings and vehicles through size-dependent penetration factors. [ABSTRACT FROM AUTHOR]

In this paper, the number concentration and the size distribution of diluted diesel exhaust particulate matter were measured at three different engine operating points in the speed-load range of the engine as follows: 1600 rpm; 50% load, 1900 rpm; 25% load, 1900 rpm; 75% load, adopted from the UN ECE Vehicle Regulation no. 49 (Revision 2) test protocol using pure diesel and biodiesel fuels, as well as their controlled blends. The emitted particulate assembly had lognormal size distribution in the accumulation mode regardless of the engine operational condition and the type of fuel. The total number and volume concentration emitted by the diesel engine decreased with increasing revolution per minute and rated torque in case of all the fuel types. The mixing ratio of the fuels did not linearly affect the total emission but had a minimum at 75% biodiesel content. We also studied the thermal evolution of the emitted particulates using a specially designed thermodenuder (TD) heated at specific temperatures (50 °C, 120 °C, and 250 °C). The first transition, when the temperature was increased from 50 °C to 120 °C resulted in lower number concentrations with small relative shifts of the peak position. However, in case of the second transition, when the temperature reached 250 °C the individual volatile particulates adsorbed onto the surface of soot particles were completely or partly vaporised resulting in lower total number concentrations with a substantial shift in peak position. [ABSTRACT FROM AUTHOR]

In order to investigate the regional variations of water-soluble ions (WSIs), size-resolved measurement of aerosol particles and WSIs was conducted by using Anderson Sampler and Ion Chromatography at five sites (Nanjing, Suzhou, Lin'an, Hangzhou and Ningbo) in the Yangtze River Delta (YRD) region, China in the Autumn of 2012 and Winter, Spring and Summer of 2013. WSIs exhibited obvious seasonal variations due to the monsoon conversion, with the highest level in winter and lowest level in summer. The aerosol mass concentrations and WSIs in different size segments varied with four seasons. The dominant ions concentrations in PM 2.1 ranked in the order of SO 4 2 − > NO 3 − > NH 4 + > Cl − > K + > Ca 2+ , and the dominant ions concentrations in PM 2.1–10 ranked in the order of Ca 2+ > NO 3 − > SO 4 2 − > Cl − > NH 4 + > Na + . The size spectra of mass and WSIs concentration peaked mostly at 0.43–0.65 μm in four seasons. The concentration discrepancies of WSIs in different cities were caused by the geographic locations and emission source. It's belonged to ammonium-rich distribution in PM 2.1 and ammonium-poor distribution in PM 2.1–10 in the YRD region. The impact of temperature on mass concentrations of NO 3 − and NH 4 + in PM 2.1 were stronger than those in PM 2.1−10 . PCA analysis shows that the sources of WSIs dominant by anthropogenic sources, soil particles or falling dust, sea salt and burning process. [ABSTRACT FROM AUTHOR]

In recent years, haze pollution has become one of the most critical environmental issues in Xi'an, China, with particular matter (PM) being one of the top pollutants. As an important fraction of PM, bioaerosols may have adverse effects on air quality and human health. In this study, to better understand the characteristics of such biological aerosols, airborne microbial samples were collected by using an Andersen six-stage sampler in Xi'an from October 8th to 22nd, 2014. The concentration, size distribution and genera of airborne viable bacteria and fungi were comparably investigated during the haze days and non-haze days. Correlations of bioaerosol levels with meteorological parameters and PM concentrations were also examined. The results showed that the daily average concentrations of airborne viable bacteria and fungi during the haze days, 1102.4–1736.5 and 1466.2–1703.9 CFU/m 3 , respectively, were not only much higher than those during the non-haze days, but also exceeded the recommended permissible limit values. Comparing to size distributions during the non-haze days, slightly different patterns for bacterial aerosols and similar single-peak distribution pattern for fungal aerosols were observed during the haze days. Moreover, more allergic and infectious genera (e.g. Neisseria, Aspergillus , and Paecilomyces ) in bioaerosols were identified during the haze days than during non-haze days. The present results reveal that bioaerosols may have more significant effects on public health and urban air quality during the haze days than during non-haze days. [ABSTRACT FROM AUTHOR]

A novel in-situ, real time method for the determination of inherent absorption properties of light absorbing carbonaceous particulate matter and its possible application for source apportionment are introduced here. The method is deduced from a two-week campaign under wintry urban conditions during which strong correlation was found between aerosol number size distribution and wavelength dependent optical absorption coefficient ( AOC(λ) ), measured by a Single Mobility Particle Sizer (SMPS) and a multi-wavelength photoacoustic absorption spectrometer, respectively, while wood burning and traffic (i.e. fossil fuel burning) activity were identified to be the dominant sources of carbonaceous particulate. Indeed, during the whole campaign, regardless of the actual emission strength of the aerosol sources, the measured number size distributions were always dominated by two unimodal modes with Count Mean Diameter (CMD) of 20 and 100 nm, which could be correlated to traffic and wood burning activities, respectively. AAE ff , AAE wb (i.e. the Aerosol Angström Exponent of traffic and wood burning aerosol, respectively), σ ff (266 nm) , σ ff (1064 nm) , σ wb (266 nm) and σ ff (1064 nm) (i.e. the segregated mass specific optical absorption coefficients at two of the measurement wavelengths) were found to be 1.17 ± 0.18, 2.6 ± 0.14, 7.3 ± 0.3 m 2 g −1 , 1.7 ± 0.1 m 2 g −1 3.4 ± 0.3 m 2 g −1 and 0.31 ± 0.08 m 2 g −1 , respectively. Furthermore the introduced methodology can also disentangle and quantify the temporal variation of both the segregated optical absorptions and the segregated mass concentrations of traffic and wood burning aerosol. Accordingly, the contribution of wood burning to optical absorption of PM was found to be negligible at 1064 nm but increased gradually towards the shorter wavelengths and became commensurable with the optical absorption of traffic at 266 nm during the whole measurement period. Furthermore, the contribution of wood burning mass to CM (mass of carbonaceous particulate matter) was dominant regardless of the strength of the emission activity of traffic and wood burning during the whole measurement period. [ABSTRACT FROM AUTHOR]

Cooking is an important source of indoor emissions, and exposure to cooking emissions can instigate adverse health effects. Oxidative potential (OP) is a good indicator for assessing health risk, but studies detecting the OP of cooking emissions are rare. In this paper, size-segregated samples were collected at four sites in the canteen to study the chemical characteristics and OP of particulate matter (PM) emitted from cooking. The four sites were set to study the effects of different cooking styles and kitchen types. The results showed that the concentrations of most metals, water-soluble ions, PAHs, and OP at four sites followed the trend: deep-frying > stir-frying > second floor hall > first floor hall. And the concentration at the fine fraction (PM 0.056-3.2) was much higher than that at coarse fraction (PM 3.2-18). The PM OP at four sites were 1.1642 nmol m−3·min−1, 1.2088 nmol m−3·min−1, 0.8589 nmol m−3·min−1 and 0.9507 nmol m−3·min−1, respectively. The correlation between OP and other components showed that Zn (|r| = 0.444) and DBA (|r| = 0.507) were moderately related to OP, which suggested that heavy metals and PAHs might be contributed to PM OP. The carcinogenic risk assessments of heavy metals and PAHs showed that, there might be an increasing of potential carcinogenic risk if exposure to cooking environment for lifetime. Our results were firstly helpful for PM characteristics researches on cooking emissions, and also significant to public health protection, especially for people who usually cook. • The concentration of metals and PAHs was ranked as deep-frying area > stir-frying area > hall. • The values of OP followed the trend: deep-frying area > stir-frying area > second floor hall > first floor hall. • Zn, Mn, Pb and water-soluble Mo were related to OP of PM. • The values of the carcinogenic risk assessment of heavy metals and c-PAHs were above the tolerant level. [ABSTRACT FROM AUTHOR]

The variability of aerosol chemical composition and the impact of the origin of respective air masses were studied in high time resolution for selected periods of high and low levels of aerosol burden at a suburban station in Prague-Suchdol, Czech Republic in summer and winter. Ambient aerosol measurements were performed using the compact-Time of Flight-Aerosol Mass Spectrometer (c-ToF-AMS) and variations in concentration of the main species are discussed. The average mass concentrations for the main species were (summer; winter): organic matter (4.2 μg/m 3 ; 8.4 μg/m 3 ), SO 4 2 − (2.0 μg/m 3 ; 4.4 μg/m 3 ), NH 4 + (1.2 μg/m 3 ; 2.8 μg/m 3 ), NO 3 − (0.8 μg/m 3 ; 5.4 μg/m 3 ) and Cl − (0.1 μg/m 3 ; 0.23 μg/m 3 ). We found an inverse relationship between non-refractory submicron particulate matter (NR-PM 1 ) levels and the boundary layer height, mainly in winter. Furthermore, levels of pollution were influenced by the air mass origin, where cleaner maritime air masses resulted in lower aerosol levels compared to those of continental origin. Analysis of the diurnal variation of NR-PM 1 showed minimum concentrations in the afternoon caused by dilution as a result of an increase in the boundary layer height. Most maximum concentrations of the main species occurred in the morning or night except sulphate which had a midday maximum, probably due to downdraft from upper boundary layer air and photochemical formation in the afternoon. [ABSTRACT FROM AUTHOR]

In recent years, haze events in Beijing have significantly increased in frequency. On haze days, airborne microorganisms are considered to be a potential risk factor for various health concerns. However, limited information on bioaerosols has prevented our proper understanding of the possible threat to human health due to these bioaerosols. In this study, we used a six-stage impactor for sampling culturable bioaerosols and the LUDEP 2.07 computer-based model for calculating their deposition on human lungs to investigate seasonal concentration, size distribution, and corresponding deposition efficiency and flux in the human respiratory tract during different haze-level events. The current results of the analysis of 398 samples over four seasons indicate that the concentration of culturable airborne bacteria decreased with increasing haze severity. The bioaerosol concentration ratio was skewed towards larger particle sizes on heavy haze days leading to larger bioaerosol aerodynamic diameters than on non-haze days. During nasal breathing by an adult male engaged in light exercise in an outdoor environment, the total deposition efficiency of culturable bioaerosols is 80–90% including approximately 70% in the upper respiratory tract, 5–7% in the alveoli, and about 3% in the bronchial couple with bronchiolar regions. Although the difference in culturable bioaerosol aerodynamic diameters at different haze levels was not large enough to cause obvious differences in lung deposition efficiency, the deposition fluxes clearly varied with the degree of haze owing to the varied concentration of culturable airborne bacteria and fungi. The results here could improve our understanding of the seasonal health threat due to culturable bioaerosols during non-haze and haze days. [ABSTRACT FROM AUTHOR]

Chemical evolution of East Asian dust during transpacific transport has been given much attention for inorganic species such as sulfate, nitrate and ammonium. However, the role of organic species during the transport has almost entirely been ignored. To understand the formation mechanism of secondary organic aerosols (SOA) on dust surfaces, this study investigated the concentrations and compositions of dicarboxylic acids, keto-carboxylic acids, α-dicarbonyls and inorganic ions in size-segregated aerosols (9-stages) collected in Xi'an, central China during the two dust storm episodes in the springs of 2009 and 2011 and compared with those in nondust storm periods. During the events the ambient particulate dicarboxylic acids were 932–2240 ng m −3 , which are comparable and even higher than those in nondust periods. Molecular compositions of the above SOA are similar to those in nondust periods with oxalic acid being the leading species. In the presence of the dust storms, all the above mentioned SOA species in Xi'an were predominantly enriched on the coarse particles (>2.1 μm), and oxalic acid well correlated with NO 3 − (R 2 = 0.72, p < 0.001) rather than SO 4 2 − . This phenomenon differs greatly from the SOA in any other nondust period that is usually characterized by an enrichment of oxalic acid in fine mode and a strong correlation of oxalic acid with SO 4 2 − . We propose a formation pathway to explain these observations, in which nitric acid and/or nitrogen oxides react with dust to produce Ca(NO 3 ) 2 and form a liquid phase on the surface of dust aerosols via water vapor-absorption of Ca(NO 3 ) 2 , followed by a partitioning of the gas-phase water-soluble organic precursors (e.g.,glyoxal and methylglyoxal) into the aqueous-phase and a subsequent oxidation into oxalic acid. To the best of our knowledge, we found for the first time the enrichment of glyoxal and methylglyoxal on dust surface. Our data suggest an important role of nitrate in the heterogeneous formation process of SOA on the surface of dust. [ABSTRACT FROM AUTHOR]

A long-lasting haze episode has been first observed with a mean atmospheric visibility of 8.6 km since last decades over Xiamen. An Aerodyne Aerosol Mass Spectrometer (AMS) was deployed to obtain the size-resolved chemical composition of non-refractory submicron particles (NR-PM 1 ) at 10 min resolution. Characteristics of aerosol particles in haze days have been analyzed and compared to in clear days and rainy days. The mean concentration of PM 2.5 was about 213.3 μg m −3 (±16.9 μg m −3 ) during haze days, which was about 4 times higher than during clear days. Organics, sulfate and ammonium were the major components in these supper fine particles, accounting for 37.2% (±0.11), 28.7% (±0.11) and 12.0% (±0.11), respectively, during haze days. The size distributions of aerosol species were characterized by a major accumulation mode peaking at a vacuum aerodynamic diameter of 390 nm during clear days, 427 nm during rainy days and 579 nm during haze days. High concentrations of SO 4 2 − , NO 3 − and NH 4 + were observed and the average values of sulfur oxidation ratios (SOR) and nitrogen oxidation ratios(NOR) were up to 0.56 (±0.17) and 0.25 (±0.11) during haze days. Positive Matrix Factorization (PMF) was used to identity a hydrocarbon-like organic aerosol (HOA) and an oxygenated organic aerosol (OOA) component. It showed that OOA components were probably representative of SOA in Xiamen. The average value of NO 3 − / SO 4 2 − was 0.28 during clear days, 0.20 during rainy days and 0.59 during haze days, indicating that pollutants from local vehicle exhaust sources were accumulated in haze days. During haze days, the main air mass (accounted for 81%) transported from the northeast of China, implying that the haze pollution was partly influenced by the pollutants transported from heavy haze areas in China. Pollution accumulated by local processes, secondary aerosol formation and the stagnation meteorological atmosphere dominated the formation of the haze event. [ABSTRACT FROM AUTHOR]

Seventy-five paired PM2.5 (aerodynamic diameter less than 2.5 μm) and TSP (total suspended particle) samples collected from a pristine island in the East China Sea (ECS) between October 2011 and August 2012 were analyzed for organic carbon (OC), elemental carbon (EC), and n -alkanes. The island lies in the pathway of continental outflow from Mainland China to the northwest Pacific Ocean driven by the East Asian Monsoon. The concentrations of OC, EC (in μg/m 3 ), and n -alkanes (in ng/m 3 ) were highest in winter (means: 4.7, 1.3, 140.1, respectively) and lowest in summer (means: 1.1, 0.3, 17.0, respectively). PM2.5 contained approximately 88% of the OC, 80% of the EC, and 61% of the n -alkanes in TSP. Petroleum residue was the dominant contributor to the n -alkanes. C 12 –C 22 n -alkanes with strong even-to-odd predominance observed in winter were attributed to the microbial contribution from sea spray aerosol (SSA) driven by the higher wind speed. There was a higher secondary organic carbon (SOC)/OC ratio in warm seasons (summer and fall) than that in cold seasons (spring and winter). The dominance of primary organic carbon (POC) and EC in cold seasons was possibly mainly due to the influence of the East Asian continental outflow. Three episodes of high concentrations of carbonaceous aerosols were observed, and we focused on the impact of these pollutants from East Asia on the air quality over the ECS. Carbonaceous pollutants were more concentrated in PM2.5 during the fall episode triggered by biomass burning in East China. The winter haze associated with intensive indoor heating in North China brought substantial carbonaceous pollutants, with a minor influence on their size distribution. The dust episode in spring was related to coarse particles (i.e., TSP–PM2.5), yielding a distinctly different size distribution. [ABSTRACT FROM AUTHOR]

Biomass burning activities in China are ubiquitous and the resulting smoke emissions may pose considerable threats to human health and the environment. In the present study, size-segregated biomass burning tracers, including anhydrosugars (levoglucosan (LG) and mannosan (MN)) and non-sea-salt potassium (nss-K + ), were determined at an urban and a suburban site in the Pearl River Delta (PRD) region. The size distributions of biomass burning tracers were generally characterized by a unimodal pattern peaking in the particle size range of 0.44–1.0 μm, except for MN during the wet season, for which a bimodal pattern (one in fine and one in coarse mode) was observed. These observed biomass burning tracers in the PRD region shifted towards larger particle sizes compared to the typical size distributions of fresh biomass smoke particles. Elevated biomass burning tracers were observed during the dry season when biomass burning activities were intensive and meteorological conditions favored the transport of biomass smoke particles from the rural areas in the PRD and neighboring areas to the sampling sites. The fine mode biomass burning tracers significantly correlated with each other, confirming their common sources. Rather high ΔLG/ΔMN ratios were observed at both sites, indicating limited influence from softwood combustion. High Δnss-K + /ΔLG ratios further suggested that biomass burning aerosols in the PRD were predominately associated with burning of crop residues. Using a simplified receptor-oriented approach with an emission factor of 0.075 (LG/TC) obtained from several chamber studies, average contributions of biomass burning emissions to total carbon in fine particles were estimated to be 23% and 16% at the urban and suburban site, respectively, during the dry season. In contrast, the relative contributions to total carbon were lower than 8% at both sites during the wet season. [ABSTRACT FROM AUTHOR]

This study presents the seasonal size distribution of particulate polycyclic aromatic hydrocarbons (PAHs), polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) and dioxin-like polychlorinated biphenyls (dl-PCBs) in the atmosphere. Particles were sampled from October 2009 to October 2010 on a seasonal basis using a cascade impactor collecting six size fractions at a rural and urban site in the Brno area, Czech Republic. Higher concentrations of PAHs, PCDD/Fs and dl-PCBs were observed in cold seasons at both sites, attributed to the seasonality of the gas-particle partitioning, the increase of emissions and the lower boundary mixing layer in winter. All of the compounds showed a strong accumulation in the fine fraction, with, on average, 71% of ΣPAHs, 73% of ΣPCDD/Fs and 60% of Σdl-PCBs associated with particles <0.95 μm. The human risk assessment via inhalation was addressed and followed the same pattern as for concentrations, with 41 and 7 times higher risk in winter compared to summer at the rural and urban sites, respectively. More than 70% of cancer risks of PAHs, PCDD/Fs and dl-PCBs was associated with particles <0.95 μm. Moreover, an overestimation of the cancer risk via inhalation of up to 50% occurred when the size distribution of related compounds was not considered. [ABSTRACT FROM AUTHOR]

Two separate Asian dust events occurred before and after the passage of a cold front over Japan on 21 March 2010. According to back trajectories and a model simulation, the two dusty air-masses originated from the same region in Mongoria or northern China and were transported over different routes to Japan. Samples of aerosol particles from both airmasses were collected at Tsukuba and Mt. Haruna and examined by single-particle analysis using a transmission electron microscope and an energy dispersive X-ray analyzer. The mixing properties of mineral aerosol were quite different in the two airmasses and size ranges. In the prefrontal airmass, which were associated with pollution, most of fine (<1 μm) mineral aerosol was internally mixed with sulfate. On the contrary, mineral aerosols in the postfront airmass, which were relatively natural, were mostly externally mixed. In the latter case, the internal mixing was associated with Ca, however in the former case, mixing processes not concerning mineralogy was suggested. [ABSTRACT FROM AUTHOR]

This work presents first data on the particle size distribution of 16 pesticides currently used in Mediterranean agriculture in the atmosphere. Particulate matter air samples were collected using a cascade impactor distributed into four size fractions in a rural site of Valencia Region, during July to September in 2012 and from May to July in 2013. A total of 16 pesticides were detected, including six fungicides, seven insecticides and three herbicides. The total concentrations in the particulate phase (TSP: Total Suspended Particulate) ranged from 3.5 to 383.1 pg m-3. Most of the pesticides (such as carbendazim, tebuconazole, chlorpyrifos-ethyl and chlorpyrifos-methyl) were accumulated in the ultrafine-fine (<1 µm) and coarse (2.5-10 µm) particle size fractions. Others like omethoate, dimethoate and malathion were presented only in the ultrafine-fine size fraction (<1 µm). Finally, diuron, diphenylamine and terbuthylazine-desethyl-2-OH also show a bimodal distribution but mainly in the coarse size fractions. [ABSTRACT FROM AUTHOR]

Abstract: Airborne particles are an important type of air pollutants in aircraft cabin. Finding sources of particles is conducive to taking appropriate measures to remove them. In this study, measurements of concentration and size distribution of particles larger than 0.3 μm (PM>0.3) were made on nine short haul flights from September 2012 to March 2013. Particle counts in supply air and breathing zone air were both obtained. Results indicate that the number concentrations of particles ranged from 3.6 × 102 counts L−1 to 1.2 × 105 counts L−1 in supply air and breathing zone air, and they first decreased and then increased in general during the flight duration. Peaks of particle concentration were found at climbing, descending, and cruising phases in several flights. Percentages of particle concentration in breathing zone contributed by the bleed air (originated from outside) and cabin interior sources were calculated. The bleed air ratios, outside airflow rates and total airflow rates were calculated by using carbon dioxide as a ventilation tracer in five of the nine flights. The calculated results indicate that PM>0.3 in breathing zone mainly came from unfiltered bleed air, especially for particle sizes from 0.3 to 2.0 μm. And for particles larger than 2.0 μm, contributions from the bleed air and cabin interior were both important. The results would be useful for developing better cabin air quality control strategies. [Copyright &y& Elsevier]

Abstract: Large spatial variations of black carbon (BC) concentrations in the on-road and near-road environments necessitate measurements with high spatial resolution to assess exposure accurately. A series of measurements was made comparing the performance of several different BC instruments (Single Particle Soot Photometer, Photo-Acoustic Soot Spectrometer, and Aethalometer) for high time resolution mobile measurements, capable of mapping spatial gradients. All instruments were highly correlated at high time resolution (r 2 = 0.80–0.89 at a 2-s resolution), however the slope ranged from 0.52 to 1.03, with the Single Particle Soot Photometer (SP2) consistently reporting the lowest BC concentrations. BC and ultrafine particle (UFP) concentrations were two-fold higher on the highway compared to surrounding roads with lower traffic counts. The BC size distribution had a mass median diameter of approximately 120 nm, which was smaller and less coated than aged urban BC. Mean UFP and BC concentrations were 2 and 1.4 times greater, respectively, during free flowing traffic on the highway compared with times when there was stop-and-go congestion, providing evidence that transit time is not a good predictor of BC or UFP exposure. [Copyright &y& Elsevier]

Abstract: Residual aerosols, the particles left behind after droplet evaporation, are important tracers for aerosols processed by cloud and/or fog. Based on ground-based CIMEL sun–sky radiometer measurements during an extreme winter pollution event in Beijing, we present observations of the decrease of residual aerosol with dissipation of cloud and an unusual case of residual aerosol increase after partial dissipation of fog. This unusual increase might be an important mechanism for the haze growth in polluted regions. The aerosol single scattering albedo is found to increase with the increase of residual aerosol. We also find that residual aerosol dominated cases with significant water content gain can occur in a short time (e.g. one hour) with the increase of aerosol volume size and decrease of particle number. A lognormal residual aerosol size distribution model is proposed based on sun–sky radiometer measurements with center peak radius at 0.44 micron and geometric standard deviation of about 1.49. [Copyright &y& Elsevier]

Abstract: Simultaneous and collocated estimates of near-surface mass concentration of black carbon (BC), number size distribution (NSD) and total number concentration (NT) of composite aerosols, columnar spectral aerosol optical depth (AOD) and local meteorological parameters were made from Aug 2009 to July 2012 at the high altitude (4520 m amsl), remote location Hanle in western trans-Himalayas. Even though all the aerosol parameters remain quite low, large annual variations are seen in the monthly mean values of BC (25 ng m−3–181 ng m−3), total number concentrations of composite aerosols (628 cm−3–1500 cm−3) and AOD (0.05–0.16). Size segregated correlation analysis reveals that the BC mass contributes significantly to the size range of 200–400 nm of the submicron aerosol size spectra. The diurnal variation of BC mostly has been dampened; yet seems to be prominent during spring, showing the presence of weak boundary layer dynamics. In contrast, the diurnal fluctuations in total number concentration have been mostly controlled by the new particle formation events, leading to bursts of large concentrations of ultrafine particles, which subsequently undergo coagulation. Spectral dependence of AOD also shows large monthly variations, with the Angstrom exponent varying from ∼0.52 to 1.3, with a mean value of ∼0.95 ± 0.21. The vertical distribution of extinction coefficients, obtained from CALIPSO data, indicates the presence of elevated aerosol layers, attributed mainly to the influence of long range transport of aerosols from the west Asian and Indian desert region. [Copyright &y& Elsevier]

Abstract: To obtain a representative sampling of aerosol vertical profiles, we performed an extensive airborne characterization of aerosols under different environmental conditions over Shijiazhuang, China. Surface aerosol concentration and aerosol vertical distribution were analyzed using a set of 104 vertical profiles of aerosol number concentration and size distribution ranging from 0.1 to 3 &#x03bc;m observed by PCASP-100X. A four modal lognormal size distribution with 10-based logarithm was applied to fit measured aerosol size distributions at different altitudes of three seasons (spring, summer and autumn). It was found that the surface aerosol number concentration had a negative correlation with wind speed. In addition to wet removal of aerosols owing to precipitation in summer, vertical transport of aerosols from the surface to high levels is strongly influenced by convective instability, which contributes to the seasonality of aerosol vertical profiles. The aerosol vertical profiles under a wide range of synoptic conditions can be categorized as &#x201c;ED&#x201d; (exhibiting an exponential declining tendency with altitude), &#x201c;SAL&#x201d; (aerosol layers existing near surface), and &#x201c;BAL&#x201d; (aerosol layers at the boundary layer height). The multi-lognormal fitting captures the total aerosol number size distribution at 0.1&#x2013;3 &#x03bc;m reasonably well. The average scale height of aerosols during spring, summer and autumn is 1.0 km, 1.6 km and 1.0 km, respectively. [ABSTRACT FROM AUTHOR]

Abstract: This work presents first data on the particle size distributions of current-used pesticides in the atmosphere. Ambient air samples were collected using a cascade impactor distributed into four size fractions in a rural site of Centre Region (France). Most pesticides were accumulated in the fine (0.1&#x2013;1 &#x03bc;m) particle size fraction such as cyprodinil, pendimethalin, fenpropidin, fenpropimorph and spiroxamine. Other pesticides such as acetochlor and metolachlor presented a bimodal distribution with maximum concentrations in the ultrafine (0.03&#x2013;0.1 &#x03bc;m)&#x2013;coarse (1&#x2013;10 &#x03bc;m) and in the ultrafine&#x2013;fine size ranges, respectively. No pesticides were detected in the size fraction &gt;10 &#x03bc;m. [ABSTRACT FROM AUTHOR]

Abstract: Particle number concentration was measured between June 2009 and June 2010 at Akrotiri research station in a rural/suburban region of western Crete (Greece). Overall, the available data covered 157 days during the aforementioned period of measurements. The objectives were to study the number size distribution characteristics of ambient aerosols and furthermore to identify new particle formation events and to evaluate particle formation rates and growth rates of the newborn particles. Aerosol particles with mobility diameters between 10 and 1100 nm were measured using a Scanning Mobility Particle Sizer (SMPS) system. Measurements were performed at ambient relative humidities. The median total particle number concentration was 525 #/cm3 whereas the number concentration ranged between 130 #/cm3 and 9597 #/cm3. The average percentage of particles with diameters between 10 nm and 100 nm (N10–100) to total particles was 53% during summer and spring, but reached 80% during winter. Maximum average contribution of nano-particles (10 nm < D p < 50 nm) to total particles was recorded also in winter and was attributed partly to the effect of local heating. Furthermore, back trajectories (HYSPLIT model) showed that different air mass origins are linked to different levels of particle number concentrations, with higher values associated with air masses passing from polluted areas before reaching the Akrotiri station. Modal analysis of the measured size distribution data revealed a strong nucleation mode during winter (15–25 nm), which can be correlated with emissions from local sources (domestic heating). The nucleation mode was observed also during the spring campaigns and was partly linked to new particle formation events. On the contrary, an accumulation mode (80–120 nm) prevailed in the measurements during summer campaigns, when the station area was influenced by polluted air masses arriving mainly from Eastern Europe. In total, 13 new particle formation events were recorded during the 157 days of measurements. Nucleation events were associated with low values of N100 particle number concentration and reduced coagulation sinks. Mean growth and formation rates were calculated and showed values equal to 6 nm hr−1 and 13 cm−3 s−1, respectively. [Copyright &y& Elsevier]

On-road emission measurements of gasoline- and diesel-fueled vehicles were conducted by a portable emission measurement system (PEMS) in Shanghai, China. Horiba OBS 2200 and TSI EEPS 3090 were employed to detect gaseous and ultrafine particle emissions during the tests. The driving-based emission factors of gaseous pollutants and particle mass and number were obtained on various road types. The average NO x emission factors of the diesel bus, diesel car, and gasoline car were 8.86, 0.68, and 0.17 g km−1, all of which were in excess of their emission limits. The particle number emission factors were 7.06 × 1014, 6.08 × 1014, and 1.57 × 1014 km−1, generally higher than the results for similar vehicle types reported in the previous studies. The size distributions of the particles emitted from the diesel vehicles were mainly concentrated in the accumulation mode, while those emitted from the gasoline car were mainly distributed in the nucleation mode. Both gaseous and particle emission rates exhibit significant correlations with the change in vehicle speed and power demand. The lowest emission rates for each vehicle type were produced during idling. The highest emission rates for each vehicle type were generally found in high-VSP bins. The particle number emission rates of the gasoline car show the strongest growth trend with increasing VSP and speed. The particle number emission for the gasoline car increased by 3 orders of magnitude from idling to the highest VSP and driving speed conditions. High engine power caused by aggressive driving or heavy loads is the main contributor to high emissions for these vehicles in real-world situations. [ABSTRACT FROM AUTHOR]

Abstract: Size-resolved measurements of particulate matter (PM) emissions from 10 biomass materials (rice straw, soybean stem, green perilla stem, red pepper stem, pine needles, cherry leaves, cherry stem, maple leaves, gingko leaves and gingko stem) were conducted in a laboratory hood chamber environment using a 10-stage MOUDI. Samples were analyzed to determine the mass, water soluble organic carbon (WSOC), and water soluble inorganic species. This study examines how particle emissions and size distributions of chemical components vary with biomass materials. Mass fractions of water soluble organic mass (WSOM) (=1.6 × WSOC) and ionic species to the PM1.8 emissions varied significantly depending on the biomass type burned. The percent mass of WSOM in PM1.8 emissions ranged from 19.8% (green perilla stem) to 41.9% (red pepper stem) for agricultural crop residues, while the tree category accounted for 9.6% (gingko leaves) to 44.0% (gingko stem) of the PM1.8 emissions. Total ionic species contents in the PM1.8 mass ranged from 7.4% (rice straw) to 26.9% (green perilla stem) for the agricultural waste category, and 5.8% (maple leaves) to 23.5% (gingko stem) for the tree category. The ionic species fraction of the PM1.8 emission was dominated by K+, Cl−, and , while Ca2+ was important in the coarse mode particles (>3.1 μm). PM1.8 emissions of K+, Cl−, and were as high as 16.9%, 9.0%, and 5.8%, respectively, and were from the green perilla stem, red pepper stem, and gingko stem emissions. Normalized size distributions of mass, WSOC, K+, Cl−, , and oxalate in the biomass burning emissions showed a unimodal size distribution, peaking in the size ranges of 0.32–0.55 μm and 0.55–1.0 μm. Size-resolved PM mass fractions of WSOM, K+, Cl−, and showed fairly consistent distributions for each biomass type, with higher fractions in the ultrafine mode (<0.10 μm) and lower fractions in the accumulation mode of 0.32–1.0 μm. The size distributions of WSOC were strongly correlated (mostly R 2 > 0.90) with those of K+ in the particle size range of <0.1 μm and 0.1–1.8 μm and the biomass types. Strong correlations between the concentrations of K+–Cl− and were observed for the following size ranges; <0.1 μm, 0.1–1.0 μm, 1.0–1.8 μm, and 1.8–3.1 μm for most biomass burning emissions. Regression line slopes for K+/WSOC (i.e., mass of K+/mass of WSOC from biomass burning emissions) were not significantly changed for particle size and biomass type, but slopes for Cl−/K+ and /K+ varied significantly with the particle size (ultrafine, condensation, droplet, and coarse modes) and biomass type. [Copyright &y& Elsevier]

Abstract: This study presents a description of the emission, transport, dispersion, and deposition of heavy metals contained in atmospheric aerosols emitted from a large industrial complex in southern Spain using the HYSPLIT model coupled with high- (MM5) and low-resolution (GDAS) meteorological simulations. The dispersion model was configured to simulate eight size fractions (<0.33, 0.66, 1.3, 2.5, 5, 14, 17, and >17 μm) of metals based on direct measurements taken at the industrial emission stacks. Twelve stacks in four plants were studied and the stacks showed considerable differences for both emission fluxes and size ranges of metals. We model the dispersion of six major metals; Cr, Co, Ni, La, Zn, and Mo, which represent 77% of the total mass of the 43 measured elements. The prediction shows that the modeled industrial emissions produce an enrichment of heavy metals by a factor of 2–5 for local receptor sites when compared to urban and rural background areas in Spain. The HYSPLIT predictions based on the meteorological fields from MM5 show reasonable consistence with the temporal evolution of concentrations of Cr, Co, and Ni observed at three sites downwind of the industrial area. The magnitude of concentrations of metals at two receptors was underestimated for both MM5 (by a factor of 2–3) and GDAS (by a factor of 4–5) meteorological runs. The model prediction shows that heavy metal pollution from industrial emissions in this area is dominated by the ultra-fine (<0.66 μm) and fine (<2.5 μm) size fractions. [Copyright &y& Elsevier]

Abstract: An extensive measurement campaign was conducted in the Milan subway system in order to investigate PM10 concentrations, to determine its physical and elemental composition, its origins, and to attempt to quantify source contributions. The Milan subway system includes three lines and stations typically consist of two underground levels: an intermediate floor (mezzanine) where the turnstiles for accessing the platform are located, and a platform level, one floor down. Measurements were performed in two stations for each line, and both microenvironments (platform and mezzanine) were investigated in all cases. PM10 samples were collected at all twelve sites over three daily periods for nine consecutive days at each site. Particle number concentrations were also measured with Optical Particle Counters (OPC) and size-number distributions were determined. X-ray fluorescence analysis was also performed on the samples to determine element concentrations. The results indicate PM sources related with train operations as the dominant impact on particulate concentrations. Average weekday PM10 concentrations between 105 and 283 μg m− 3 were observed at the platform level, while average ambient concentrations of 36 μg m− 3 were observed. Fe, Ba, Sb, Mn and Cu were found to be significantly enriched. Metal particles, occurring mostly in the range of diameters between 1 and 5 μm, and therefore likely originating from mechanical processes, account for most of the PM10 mass at the platform level. Wheel, brake and track wear are found to contribute 40–73% of total PM10 mass and electric cable wear (Cu and Zn oxides) 2%–3%. Concentrations measured on the mezzanine levels are intermediate between those found in ambient air and on the platform level, with average daytime PM10 values ranging from 50 to 80 μg m−3. The situation observed on the mezzanine can well be described through an appropriate mixing of ambient and platform level air. A decreasing, albeit still significant, impact from internal sources is observed, with particulate from wheel, brake and track wear contributing an average of 2–25%, and electric cable wear 0.5–1.2%, to total PM10 mass. [Copyright &y& Elsevier]