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The understanding of new particle formation and growth processes is critical for evaluating the role of aerosols in climate change. One of the knowledge gaps is the ion-particle interaction during the early growth process, especially in the sub-3 nm range, where direct observations are sparse. While molecular interactions would imply faster growth rates of ions compared to neutral particles, this phenomenon is not widely observed in the atmosphere. Here, we show field measurements in the boreal forest indicating a smaller apparent growth rate of the ion population compared to the total particles. We use aerosol dynamics simulations to demonstrate that this effect can be caused by a changing importance of ion-induced nucleation mechanisms during the day. We further compare these results with chamber experiments under similar conditions, where we demonstrate that this effect critically depends on the abundance of condensable vapors and the related strength of ion-induced nucleation. Our results imply that atmospheric ion growth rate measurements below 3 nm need to be evaluated very carefully as they do not represent condensational growth alone but are influenced by ion-particle population interactions.

Nucleation of neutral iodine particles has recently been found to involve both iodic acid (HIO3) and iodous acid (HIO2). However, the precise role of HIO2in iodine oxoacid nucleation remains unclear. Herein, we probe such a role by investigating the cluster formation mechanisms and kinetics of (HIO3)m(HIO2)n(m = 0-4, n = 0-4) clusters with quantum chemical calculations and atmospheric cluster dynamics modeling. When compared with HIO3, we find that HIO2binds more strongly with HIO3and also more strongly with HIO2. After accounting for ambient vapor concentrations, the fastest nucleation rate is predicted for mixed HIO3-HIO2clusters rather than for pure HIO3or HIO2ones. Our calculations reveal that the strong binding results from HIO2exhibiting a base behavior (accepting a proton from HIO3) and forming stronger halogen bonds. Moreover, the binding energies of (HIO3)m(HIO2)nclusters show a far more tolerant choice of growth paths when compared with the strict stoichiometry required for sulfuric acid-base nucleation. Our predicted cluster formation rates and dimer concentrations are acceptably consistent with those measured by the Cosmic Leaving Outdoor Droplets (CLOUD) experiment. This study suggests that HIO2could facilitate the nucleation of other acids beyond HIO3in regions where base vapors such as ammonia or amines are scarce. publishedVersion

Intense new particle formation events are regularly observed under highly polluted conditions, despite the high loss rates of nucleated clusters. Higher than expected cluster survival probability implies either ineffective scavenging by pre-existing particles or missing growth mechanisms. Here we present experiments performed in the CLOUD chamber at CERN showing particle formation from a mixture of anthropogenic vapours, under condensation sinks typical of haze conditions, up to 0.1 s$^{-1}$ . We find that new particle formation rates substantially decrease at higher concentrations of pre-existing particles, demonstrating experimentally for the first time that molecular clusters are efficiently scavenged by larger sized particles. Additionally, we demonstrate that in the presence of supersaturated gas-phase nitric acid (HNO$_3$) and ammonia (NH$_3$), freshly nucleated particles can grow extremely rapidly, maintaining a high particle number concentration, even in the presence of a high condensation sink. Such high growth rates may explain the high survival probability of freshly formed particles under haze conditions. We identify under what typical urban conditions HNO$_3$ and NH$_3$ can be expected to contribute to particle survival during haze.

Liu et al. found that the formation rate of particulate ammonium is slower in the atmosphere than that observed in the laboratory, while it is sped up due to an increase in aerosol acidity driven by an emission reduction of dust in North China Plain.Ammonium salt is an important component of particulate matter with aerodynamic diameter less than 2.5 mu m (PM2.5) and has significant impacts on air quality, climate, and natural ecosystems. However, a fundamental understanding of the conversion kinetics from ammonia to ammonium in unique environments of high aerosol loading is lacking. Here, we report the uptake coefficient of ammonia (gamma(NH3)) on ambient PM2.5 varying from 2.2 x 10(-4) to 6.0 x 10(-4) in the North China Plain. It is significantly lower than those on the model particles under simple conditions reported in the literature. The probability-weighted gamma(NH3) increases obviously, which is well explained by the annual decrease in aerosol pH due to the significant decline in alkali and alkali earth metal contents from the emission source of dust. Our results elaborate on the complex interactions between primary emissions and the secondary formation of aerosols and the important role of dust in atmospheric chemistry.

During the monsoon season of the year 2017 the airborne StratoClim mission took place in Kathmandu, Nepal, with eight mission flights of the M-55 Geophysica in the upper troposphere–lower stratosphere (UTLS) of the Asian monsoon anticyclone (AMA) over northern India, Nepal, and Bangladesh. More than 100 events of new particle formation (NPF) were observed. In total, more than 2 h of flight time was spent under NPF conditions as indicated by the abundant presence of nucleation-mode aerosols, i.e. with particle diameters dp smaller than 15 nm, which were detected in situ by means of condensation nuclei counting techniques. Mixing ratios of nucleation-mode particles (nnm) of up to ∼ 50 000 mg−1 were measured at heights of 15–16 km (θ ≈ 370 K). NPF was most frequently observed at ∼ 12–16 km altitude (θ ≈ 355–380 K) and mainly below the tropopause. Resulting nnm remained elevated (∼ 300–2000 mg−1) up to altitudes of ∼ 17.5 km (θ ≈ 400 K), while under NPF conditions the fraction (f) of sub-micrometre-sized non-volatile residues (dp > 10 nm) remained below 50 %. At ∼ 12–14 km (θ ≈ 355–365 K) the minimum of f (< 15 %) was found, and underneath, the median f generally remains below 25 %. The persistence of particles at nucleation-mode sizes is limited to a few hours, mainly due to coagulation, as demonstrated by a numerical simulation. The frequency of NPF events observed during StratoClim 2017 underlines the importance of the AMA as a source region for UTLS aerosols and for the formation and maintenance of the Asian tropopause aerosol layer (ATAL). The observed abundance of NPF-produced nucleation-mode particles within the AMA is not unambiguously attributable to (a) specific source regions in the boundary layer (according to backward trajectory analyses), or (b) the direct supply with precursor material by convective updraught (from correlations of NPF with carbon monoxide), or (c) the recent release of NPF-capable material from the convective outflow (according to air mass transport times in the tropical tropopause layer, TTL). Temperature anomalies with ΔT of 2 K (peak-to-peak amplitude), as observed at a horizontal wavelength of ∼ 70–100 km during a level flight of several hours, match with NPF detections and represent an additional mechanism for local increases in supersaturation of the NPF precursors. Effective precursor supply and widely distributed temperature anomalies within the AMA can explain the higher frequency of intense NPF observed during StratoClim 2017 than all previous NPF detections with COPAS (COndensation PArticle counting System) at TTL levels over Brazil, northern Australia, or West Africa.

Graphical abstract An analytical method was validated with two reference materials of polycyclic aromatic hydrocarbons in atmospheric particles. Standard reference materials (SRMs) were incorporated into the matrix of unexposed cut quartz filters. The methodology was previously designed and extraction of polycyclic aromatic hydrocarbons (PAHs) from fortified filters was based on a rapid low-cost method, for a low consumption of volume and time. The optimisation combined a low-volume Soxhlet apparatus used in hot Soxhlet mode with a quick clean-up by solid-phase extraction with special cartridges. The quantification of target compounds was performed by gas chromatography/mass spectroscopy in SIM mode. Temperatures of injector and oven program of the GC-MS were also optimised. Experimental variables of both systems were successfully optimised and validated, achieving a robust analytical methodology. Supplementary Information The online version contains supplementary material available at 10.1007/s00216-021-03188-9.

With the increase of particulate pollution in the atmosphere, it becomes extremely significant to understand the overall distribution characteristics of particulates and their adsorption of toxic gases for the source analysis and precise controlling of atmospheric particulate matters. The fractal theory was adopted to analyze particle sizes distribution characteristics in Xi?an city, China. Results showed the fractal dimension of particulate matters distribution ranged from 4.32-4.83, with an average fractal dimension of 4.54. A higher fractal dimension predicts a higher concentration of fine particles. Additionally the effects of outdoor temperature, humidity, and wind speed on the fractal dimension were also studied experimentally

506 σ., Αντικείμενο της διατριβής αποτέλεσε η μελέτη του προβλήματος της σωματιδιακής ρύπανσης στην Αθήνα, όπως διαμορφώθηκε κατά την περίοδο που ακολούθησε την εξαγγελία της οδηγίας 99/30/EC. Βασικό μέσο προσέγγισης ήταν η πραγματοποίηση μετρήσεων πεδίου για τον χαρακτηρισμό των αιωρουμένων σωματιδίων. Οι μετρήσεις επικεντρώθηκαν στα κλάσματα PM10, PM2.5 και PM1, στις κατ’αριθμό ολικές σωματιδιακές συγκεντρώσεις (TNC) και τις κατανομές τους και στη χημική σύσταση των σωματιδίων σε στοιχειακό και οργανικό άνθρακα. Η κύρια κατεύθυνση της διαδικασίας χαρακτηρισμού στοχεύει στον εντοπισμό των παραγόντων που ελέγχουν τις χρονικές/χωρικές διακυμάνσεις των επιπέδων. Η αξιοποίηση των μετρήσεων πραγματοποιήθηκε σε ένα πλαίσιο στοχαστικής ανάλυσης δεδομένων, που περιέλαβε τεχνικές διερευνητικής και επαγωγικής στατιστικής, πολυμεταβλητής ανάλυσης, ανάλυσης χρονοσειρών - φασματικής ανάλυσης και γεωστατιστικής. Τα ευρήματα απ’ τη διαδικασία χαρακτηρισμού αξιοποιήθηκαν στην ανάπτυξη μοντέλων πρόβλεψης συγκεντρώσεων. Για την χωρική εκτίμηση, αναπτύχθηκαν μοντέλα τύπου regression mapping, με χρήση δεδομένων GIS. Παράλληλα αξιολογήθηκαν μοντέλα χωρικής παρεμβολής. Κύρια μεθοδολογία χρονικής πρόρρησης ήταν τα τεχνητά νευρωνικά δίκτυα, τα οποία αξιολογήθηκαν συγκριτικά με εναλλακτικές μεθόδους (MLR, ARIMA, PLSR, CART). Εξετάσθηκαν τεχνικές επιλογής μεταβλητών εισόδου (όπως γενετικοί αλγόριθμοι) και η αποτελεσματικότητα της εκμάθησης με αλγορίθμους τοπικής και ολικής (προσομοιωμένη ανόπτηση) βελτιστοποίησης. Από τα αποτελέσματα προέκυψαν υπερβάσεις των οριακών τιμών για τις συγκεντρώσεις PM10 και PM2.5, ενώ υψηλά ήταν τα επίπεδα PM1. Οι συσχετίσεις μεταξύ των κατά μάζα και κατ’αριθμό συγκεντρώσεων ΤΝC ήταν ασθενέστατες. Ενώ τα επίπεδα στοιχειακού άνθρακα χαρακτηρίζονται ως μέτρια, για τον οργανικό άνθρακα ήταν υψηλά, αναδεικνύοντας τα οργανικά σωματίδια ως τη χημική ομάδα με την υψηλότερη συμμετοχή στις συγκεντρώσεις PM. Διαπιστώθηκε, μέσω της μεθοδολογίας EC tracer, ότι σημαντικό ποσοστό των οργανικών σωματιδίων είναι δευτερογενούς προέλευσης. Ως κύριοι παράγοντες που σχετίζονται με τις παρατηρούμενες χρονικές διακυμάνσεις, προσδιορίσθηκαν η κυκλοφορία οχημάτων, οι δευτερογενείς διαδικασίες σχηματισμού και η ενδο-αστική μεταφορά. Σε χωρικό επίπεδο, ενώ η κατανομή των επιπέδων είναι σχετικά ανομοιογενής, παρατηρούνται σημαντικές συσχετίσεις μεταξύ θέσεων μέτρησης. Τα μοντέλα χωρικής πρόβλεψης PM10 που αναπτύχθηκαν εμφάνισαν πολύ υψηλή απόδοση, παρέχοντας ικανοποιητική χαρτογραφική απεικόνιση των επιπέδων PM10 στην περιοχή. Σχετικά με τη βραχυχρόνια σημειακή πρόβλεψη αναπτύχθηκαν δυο κατηγορίες μοντέλων, για μέσες ημερήσιες και ωριαίες συγκεντρώσεις PM10 της επόμενης ημέρας, σε διάφορες θέσεις στην περιοχή. Η προγνωστική ικανότητα των μοντέλων νευρωνικών δικτύων ήταν υψηλή, ειδικά σε σύγκριση με τα εναλλακτικά στοχαστικά μοντέλα., The aim of the dissertation was to study the particle pollution problem in Athens, as it was established during the period that followed the promulgation of EU directive 99/30/EC. Field measurements were conducted for the characterization of ambient particles. Measurements were centered on PM10, PM2.5 and PM1 fractions, on total number concentrations (TNC) and their size distributions and on the chemical composition of particles regarding elemental and organic carbon. The characterization process was directed towards the identification of factors controlling temporal/spatial variations of concentration levels. Data utilization was carried out in a stochastic data mining framework, involving exploratory and inferential statistics, multivariate analysis, time-series and spectral analysis and geostatistics. The findings from the characterization procedure were employed in the development of predictive models for particle concentrations. Regression mapping models, using GIS data, were built for spatial estimation. Spatial interpolation models were evaluated in parallel. Artificial neural networks comprised the principal methodology used for short-term forecasting and they were assessed comparatively to alternative methods (MLR, ARIMA, PLSR, CART). Input variable selection techniques were examined (e.g. genetic algorithms) and the efficiency of network training with local and global (simulated annealing) optimization algorithms was tested. The results revealed exceedances of limit values for PM10 and PM2.5 concentrations, while PM1 levels were elevated as well. Statistical associations between particle mass and number (TNC) concentrations were very weak. While elemental carbon levels were characterized as moderate, organic carbon levels were high, thus making organic aerosols the chemical group with the highest participation in particle mass. By means of the EC tracer methodology it was concluded that a significant fraction of organic particles is of secondary origin. Vehicular traffic, secondary processes and intra-urban transport were determined as the principal factors associated to the observed temporal variability. At the spatial level, while distribution of concentration levels was moderately heterogenous, significant correlations were observed among measurement locations. The developed models for spatial estimation produced a very strong performance, also providing satisfactory mapping of PM10 annual levels in the area. Regarding short-term forecasting, two model categories where examined; for daily mean and hourly PM10 concentrations, 24-h in advance in various locations within the study area. The predictive ability of neural network models was high, especially in comparison to alternative stochastic models., Γεώργιος Ι. Γρίβας

Intense and frequent new particle formation (NPF) events have been observed in polluted urban environments, yet the dominant mechanisms are still under debate. To understand the key species and governing processes of NPF in polluted urban environments, we conducted comprehensive measurements in downtown Beijing during January–March, 2018. We performed detailed analyses on sulfuric acid cluster composition and budget, as well as the chemical and physical properties of oxidized organic molecules (OOMs). Our results demonstrate that the fast clustering of sulfuric acid (H2SO4) and base molecules triggered the NPF events, and OOMs further helped grow the newly formed particles toward climate- and health-relevant sizes. This synergistic role of H2SO4, base species, and OOMs in NPF is likely representative of polluted urban environments where abundant H2SO4 and base species usually co-exist, and OOMs are with moderately low volatility when produced under high NOx concentrations. publishedVersion

The COVID-19 pandemic has triggered an industrial and financial slowdown due to unprecedented regulations imposed with the purpose to contain the spread of the virus. Consequently, the positive effect on the environment has been witnessed. One of the most prominent evidences has been the drastic air quality improvement, as a direct consequence of lower emissions from reduced industrial activity. While several studies have demonstrated the validity of this hypothesis in mega-cities worldwide, it is still an unsubstantiated fact whether the same holds true for cities with a smaller urban extent and population. In the present study we investigate the temporal development of atmospheric constituent concentrations as retrieved concurrently from the Sentinel-5P satellite and a ground meteorological station. We focus on the period before and during the COVID-19 pandemic over the city of Hat Yai, Thailand and present the effect of the lockdown on the atmospheric quality over this average populated city (156,000 inhabitants). NO2, PM2.5 and PM10 concentrations decreased by 33.7%, 21.8% and 22.9% respectively in the first 3 weeks of the lockdown compared to the respective pre-lockdown period; O3 also decreased by 12.5% and contrary to similar studies. Monthly averages of NO2, CO and PM2.5 for the month April exhibit in 2020 the lowest values in the last decade. Sentinel-5P retrieved NO2 tropospheric concentrations, both locally over the ground station and the spatial average over the urban extent of the city, are in agreement with the reduction observed from the ground station. Numerous studies have already presented evidence of the bettering of the air quality over large metropolitan areas during the COVID-19 pandemic. In the current study we demonstrate that this holds true for Hat Yai, Thailand; we propound that the environmental benefits documented in major urban agglomerations during the lockdown may extend to medium-sized urban areas as well., Graphical abstract Unlabelled Image, Highlights • The effect of lock-down on the air quality of a medium-sized urban area was assessed. • NO2 concentration decreased by 33.7% during the first 3 weeks of lock-down. • Likewise, PM2.5, PM10 and O3 decreased by 21.8%, 22.9% and 12.5% respectively. • Average NO2, CO and PM2.5 for April 2020 exhibit the lowest values in the last decade. • Sentinel-5P observations mirror the observations of the ground station.

Long-term measurements of PM2.5 mass concentrations and aerosol particle size distributions from 2008 to 2015, as well as hygroscopicity measurements conducted over one year (2008–2009) at Cabauw, The Netherlands, are compiled here in order to provide a comprehensive dataset for understanding the trends and annual variabilities of the atmospheric aerosol in the region. PM2.5 concentrations have a mean value of 14.4 μg m-3 with standard deviation 2.1 μg m-3, and exhibit an overall decreasing trend of −0.74 μg m-3 year-1. The highest values are observed in winter and spring and are associated with a shallower boundary layer and lower precipitation, respectively, compared to the rest of the seasons. Number concentrations of particles smaller than 500 nm have a mean of 9.2 × 103particles cm-3 and standard deviation 4.9 × 103particles cm-3, exhibiting an increasing trend between 2008 and 2011 and a decreasing trend from 2013 to 2015. The particle number concentrations exhibit highest values in spring and summer (despite the increased precipitation) due to the high occurrence of nucleation-mode particles, which most likely are formed elsewhere and are transported to the observation station. Particle hygroscopicity measurements show that, independently of the air mass origin, the particles are mostly externally mixed with the more hydrophobic mode having a mean hygroscopic parameter κ of 0.1 while for the more hydrophilic mode κ is 0.35. The hygroscopicity of the smaller particles investigated in this work (i.e., particles having diameters of 35 nm) appears to increase during the course of the nucleation events, reflecting a change in the chemical composition of the particles.

The main objective of this study was to estimate the contribution of emissions from wood burning (WB) combustion to particulate matter (PM10) oxidative potential (OP) in relation to its chemical composition. A sampling campaign was carried out at an Alpine rural site during winter 2016–2017, when wood is largely used as fuel for domestic heating and therefore WB is a prevalent PM emission source. PM10 samples were analyzed for their chemical constituents, including metals and trace elements, water soluble total carbon (WSTC), sugars, and Polycyclic Aromatic Hydrocarbons (PAHs), with specific concern to anhydrosugars, K+ and Rb, as markers of WB. The OP was measured by the dithiothreitol (DTT) and ascorbic acid (AA) acellular assays and the volume normalized responses were investigated, OPDTTV and OPAAV, respectively. On average, the two assays measured similar values, even though the mean OPDTTV response was significantly higher than OPAAV, i.e., 0.33 ± 0.07 nmol min−1 m−3 and 0.28 ± 0.08 nmol min−1 m−3, respectively. To identify the species mostly contributing to the PM10 OP, a series of statistical analyses was performed, namely Pearson correlation analysis, multiple linear regression, hierarchical cluster and partial least squares regression analyses. Results from this study indicated that the PM10 redox activity was strongly correlated with the characteristic components of WB emissions, namely WSTCnet, the net water-soluble carbonaceous component, total concentrations of anhydrosugars (Σanhydr) and of Polycyclic Aromatic Hydrocarbons (ΣPAHs).

New particle formation driven by acid–base chemistry was initiated in the CLOUD chamber at CERN by introducing atmospherically relevant levels of gas-phase sulfuric acid and dimethylamine (DMA). Ammonia was also present in the chamber as a gas-phase contaminant from earlier experiments. The composition of particles with volume median diameters (VMDs) as small as 10 nm was measured by the Thermal Desorption Chemical Ionization Mass Spectrometer (TDCIMS). Particulate ammonium-to-dimethylaminium ratios were higher than the gas-phase ammonia-to-DMA ratios, suggesting preferential uptake of ammonia over DMA for the collected 10–30 nm VMD particles. This behavior is not consistent with present nanoparticle physicochemical models, which predict a higher dimethylaminium fraction when NH3 and DMA are present at similar gas-phase concentrations. Despite the presence in the gas phase of at least 100 times higher base concentrations than sulfuric acid, the recently formed particles always had measured base : acid ratios lower than 1 : 1. The lowest base fractions were found in particles below 15 nm VMD, with a strong size-dependent composition gradient. The reasons for the very acidic composition remain uncertain, but a plausible explanation is that the particles did not reach thermodynamic equilibrium with respect to the bases due to rapid heterogeneous conversion of SO2 to sulfate. These results indicate that sulfuric acid does not require stabilization by ammonium or dimethylaminium as acid–base pairs in particles as small as 10 nm.

We present a novel automated system for real-time measurements of water-soluble reactive phosphate (SRP) ions in atmospheric particles. Detection of SRP is based on molybdenum blue chemistry with Sn(II) chloride dihydrate reduction. The instrumentation consists of one particle-into-liquid sampler (PILS) coupled with a 250 cm path length liquid waveguide capillary cell (LWCC) and miniature fiber optic spectrometer, with detection wavelength set at 690 nm. The detection limit was 0.4 nM P, equivalent to 0.03 nmol P m-3 in atmospheric particles. Comparison of SRP in collocate PM2.5 aerosol filter sampling with the PILS-LWCC on line system were in good agreement (n = 49, slope = 0.84, R2 = 0.78). This novel technique offers at least an order of magnitude enhancement in sensitivity over existing approaches allowing for SRP measurements of unprecedented frequency (8 min), which will lead to greater understanding of the sources and impacts of SRP in atmospheric chemistry. © 2016 American Chemical Society.

A escala global, los incendios forestales son una fuente de emisiones significativas de gases y partículas a la atmosfera, emisiones que llegan a afectar grandes extensiones y pueden transportarse a distancias de escala continental. En este trabajo se han estimado las emisiones de los gases de efecto invernadero (GEI) procedentes de grandes incendios forestales ocurridos en los últimos 10 años en Cataluña, España, una región mediterránea muy afectada por la incidencia de fuegos de origen antrópico. Estas estimaciones se basan en la caracterización y cuantificación de la biomasa total de los combustibles forestales preexistentes en las áreas que se queman, la cuantificación de las pérdidas debidas a la combustión según la severidad del incendio y la aplicación de factores de emisión a la biomasa consumida. Los resultados obtenidos indican que los grandes incendios de la última década consumieron porcentajes variables entre 44,4% y 70,3% de la biomasa total disponible en las zonas incendiadas, con emisiones totales de carbono equivalente de entre 15 013 t y 387 335 t por incendio. Para determinar las trayectorias de los penachos de humo y concentraciones alcanzadas se utilizó el modelo Hybrid Single Particle Lagrangian Integrated Trajectory. Los penachos de humo de los incendios estudiados se desplazaron a grandes distancias, generalmente bajo situación anticiclónica, afectando al Mediterráneo y Norte de África. At the global scale, forest fires are a source of significant emissions of gases and particles to the atmosphere that disperse over a large area and can be transported over great distances at the continental scale. Among these emissions, there are greenhouse gases, which are released in large quantities into the atmosphere after a forest fire. In this work, an attempt has been made to estimate greenhouse gas (GHG) emissions from large forest fires in recent years in Catalonia, Spain. These estimates are based on the characterization and quantification of the biomass that makes up the pre-existing forest fuels in the burned areas, the assessment of fire severity and consumption rates, and the application of published emission factors. The results obtained indicate that percentages between 44,4% and 70,3% of pre-fire biomass were consumed, corresponding respectively to total equivalent carbon emissions between 15 013 t and 387 335 t. A Lagrangian model (Hybrid Single Particle Lagrangian Integrated Trajectory) was used in order to determine the dispersion ranges and trajectories of the smoke plumes. The smoke plumes from the fires reached large distances, mainly affecting the Mediterranean region and North of Africa.

Atmospheric particulate is one of the main responsible for the environmental pollution of highly populated cities. The particulate matter can be considered an aerosol of many particles, with different shapes, morphologies and sizes down to few micrometers. These small particles are responsible for climate changes and, when inhaled, can reach the lungs causing respiratory and cardiovascular diseases. Usually commercial sensors are based on passive filters and are designed to measure only particles whose size is below a certain value. Therefore, a measuring system capable of assessing the quality of air and evaluating not only the amount of particles, but also the size distribution of the particulate matter in urban atmospheres could be extremely helpful. This paper describes a simple and cheap optical solution, which is able to detect the total amount of solid pollution particles and classify them according to their average size, giving a fast response to the users.

Ambient particle number size distributions were measured in Paris, France, during summer (1–31 July 2009) and winter (15 January to 15 February 2010) at three fixed ground sites and using two mobile laboratories and one airplane. The campaigns were part of the Megacities: Emissions, urban, regional and Global Atmospheric POLlution and climate effects, and Integrated tools for assessment and mitigation (MEGAPOLI) project. New particle formation (NPF) was observed only during summer on approximately 50 % of the campaign days, assisted by the low condensation sink (about 10.7 ± 5.9 × 10−3 s−1). NPF events inside the Paris plume were also observed at 600 m altitude onboard an aircraft simultaneously with regional events identified on the ground. Increased particle number concentrations were measured aloft also outside of the Paris plume at the same altitude, and were attributed to NPF. The Paris plume was identified, based on increased particle number and black carbon concentration, up to 200 km away from the Paris center during summer. The number concentration of particles with diameters exceeding 2.5 nm measured on the surface at the Paris center was on average 6.9 ± 8.7 × 104 and 12.1 ± 8.6 × 104 cm−3 during summer and winter, respectively, and was found to decrease exponentially with distance from Paris. However, further than 30 km from the city center, the particle number concentration at the surface was similar during both campaigns. During summer, one suburban site in the NE was not significantly affected by Paris emissions due to higher background number concentrations, while the particle number concentration at the second suburban site in the SW increased by a factor of 3 when it was downwind of Paris.

The present work aimed the study of atmospheric deposition of toxic elements near to a tannery industry by collecting black material deposited on leaf surfaces of cinnamon trees (Cinnamomum zeylanicum). Elements such as As, Ba, Cr, Cu, Fe, Ni, Pb, Sb, V, and Zn were analyzed by inductively coupled plasma mass spectrometry (ICP-MS). For comparison purpose, black particles deposited on the leaf surface of lemon trees (Citrus lemon) collected away from the tannery industry were also analyzed. Results showed that the amount of toxic elements found in the black particles collected near tannery area was significantly higher than the amount of those measured in the comparison site. Enrichment factors (EF) of As and Cr were markedly impacted by anthropogenic emissions, whereas the other elements were moderately/slightly enriched. Cluster analysis (CA) identified the leather industry as the anthropogenic source, while As possibly comes from the wide use of pesticides and herbicides in agricultural practices. The results indicated that emissions from the leather industry and agricultural activities are the main source of pollution in this area.

SPEX (Spectropolarimeter for Planetary EXploration) is an innovative, compact remotesensing instrument for measuring and characterizing aerosols in the atmosphere. The shoebox size instrument is capable of accurate full linear spectropolarimetry without moving parts or liquid crystals. High precision polarimetry is performed through encoding the degree and angle of linear polarization of the incoming light in a sinusoidal modulation of the spectrum. Measuring this intensity spectrum thus provides the spectral dependence of the degree and angle of linear polarization. Polarimetry has proven to be an excellent tool to study microphysical properties of atmospheric particles. Such information is essential to better understand the weather and climate of a planet. Although SPEX can be used to study any planetary atmosphere, including the Earth's, the current design of SPEX is tailored to study Martian dust and clouds from an orbiting platform. SPEX’ 9 entrance pupils can simultaneously measure intensity spectra from 0.4 to 0.8 microns, in different directions along the flight direction (including two limb viewing directions). This way, the scattering phase functions of dust and cloud particles within a ground pixel are sampled while flying over it. SPEX can provide synergy with instruments on rovers and landers, as it provides an overview of spatial and temporal variations of the Martian atmosphere.

In order to accurately assess the influence of fatty acids on the hygroscopic and other physicochemical properties of sea salt aerosols, hexanoic, octanoic or lauric acid together with sodium halide salts (NaCl, NaBr and NaI) have been chosen to be investigated in this study. The hygroscopic properties of sodium halide sub-micrometre particles covered with organic acids have been examined by Fourier-transform infrared spectroscopy in an aerosol flow cell. Covered particles were generated by flowing atomized sodium halide particles (either dry or aqueous) through a heated oven containing the gaseous acid. The obtained results indicate that gaseous organic acids easily nucleate onto dry and aqueous sodium halide particles. On the other hand, scanning electron microscopy (SEM) images indicate that lauric acid coating on NaCl particles makes them to aggregate in small clusters. The hygroscopic behaviour of covered sodium halide particles in deliquescence mode shows different features with the exchange of the halide ion, whereas the organic surfactant has little effect in NaBr particles, NaCl and NaI covered particles experience appreciable shifts in their deliquescence relative humidities, with different trends observed for each of the acids studied. In efflorescence mode, the overall effect of the organic covering is to retard the loss of water in the particles. It has been observed that the presence of gaseous water in heterogeneously nucleated particles tends to displace the cover of hexanoic acid to energetically stabilize the system. The authors are grateful to Ministerio de Ciencia e Innovacion (Madrid) for grant-in-aids (CGL2011-22441 and Consolider CSD-2007-00013), to Gobierno Vasco/Eusko Jaurlaritza (Vitoria-Gasteiz) for a Consolidated Research Group grant (IT520-10), and UPV/EHU for UFI11/23, SEM facilities (SGI/IZO-SGIker) and general support. L. Minambres thanks UPV/EHU for a postdoctoral research grant. We are grateful to Cristina Gutierrez from UPV/EHU for the use of the butanol CPC.

A one-year-long aerosol characterization study was conducted from July 2002 through July 2003, in Beijing, China. Twenty-four hour PM2.5 and PM10 filter samples were collected, and about 50 aerosol samples of each type were obtained. Organic, elemental, and total carbon, levoglucosan and other organic compounds, and inorganic ionic species were measured. The overall mean PM mass concentrations were 99 and 175 mu g/m(3) for PM2.5 and PM10, respectively. Total carbon was the main component in both PM2.5 and PM10, with overall mean concentrations of 21 and 30 mu g/m(3), respectively. Of the organic compounds measured, levoglucosan exhibited the highest levels (overall mean of 0.31 mu g/m(3) in PM2.5 and of 0.40 ng/m(3) in PM10). Sulfate was the most prominent inorganic ionic species, with overall mean levels of 15.6 and 17.0 mu g/m(3) in PM2.5 and PM10, respectively. Most components measured were predominantly present in the PM2.5 size fraction; the overall mean PM2.5/PM10 ratio was typically in the range of 0.7-0.8, but this ratio was only 0.55 for the PM mass and for Ca2+ it was as low as 0.19. In PM2.5, total carbon exhibited relatively larger concentration levels (30 mu g/m(3)) in winter than in the other seasons. K+ also exhibited a relatively high concentration level in the winter season, with 2.3 mu g/m(3) in PM2.5. The contribution from biomass burning to K+ in PM2.5 was estimated on the basis of the levoglucosan data and the minimum K+/levoglucosan ratios obtained throughout the year; it was found that the contribution was largest in autumn, with 44%.

Aerosol loading in the marine environment is investigated using aerosol composition measurements from several research ship campaigns (ICEALOT, MAP, RHaMBLe, VOCALS and OOMPH), observations of total AOD column from satellite (MODIS) and ship-based instruments (Maritime Aerosol Network, MAN), and a global chemical transport model (GEOS-Chem). This work represents the most comprehensive evaluation of oceanic OM emission inventories to date, by employing aerosol composition measurements obtained from campaigns with wide spatial and temporal coverage. The model underestimates AOD over the remote ocean on average by 0.02 (21 %), compared to satellite observations, but provides an unbiased simulation of ground-based Maritime Aerosol Network (MAN) observations. Comparison with cruise data demonstrates that the GEOS-Chem simulation of marine sulfate, with the mean observed values ranging between 0.22 μg m−3 and 1.34 μg m−3, is generally unbiased, however surface organic matter (OM) concentrations, with the mean observed concentrations between 0.07 μg m−3 and 0.77 μg m−3, are underestimated by a factor of 2–5 for the standard model run. Addition of a sub-micron marine OM source of approximately 9 TgC yr−1 brings the model into agreement with the ship-based measurements, however this additional OM source does not explain the model underestimate of marine AOD. The model underestimate of marine AOD is therefore likely the result of a combination of satellite retrieval bias and a missing marine aerosol source (which exhibits a different spatial pattern than existing aerosol in the model).

The Centro de Investigação Geológica, Ordenamento e Valorização de Recursos is supported by the Pluriannual program of the Fundação para a Cência e a Tecnologia, funded by the national budget of the Portuguese Republic., Deposition of gaseous and particulate atmospheric pollutants causes decay of historic mortars to give gypsum-rich coatings by sulphation of lime mortars and blackening of gypsum mortar, resulting in gypsum coatings. Particulate pollution emitted by industrial sources and vehicular traffic is responsible for the deterioration. XRF and SEM analyses of these coatings and their comparison with both the composition of dust coatings formed by the deposition of gaseous and particulate matter in an urban and a rural locality allows assessing which pollution sources are the most damaging for these materials, knowing the elemental composition of these emissions., Fundação para a Ciência e a Tecnologia (FCT)

Fourier Transform Infrared (FTIR) and X-ray Fluorescence (XRF) were used to measure organic functional groups and elements of submicron particles collected during MILAGRO in March 2006 on three platforms: the Mexico City urban area (SIMAT), the high altitude site at 4010 m (Altzomoni), and the NCAR C130 aircraft. Scanning transmission X-ray Microscopy (STXM) and Near-Edge X-ray Absorption Fine Structure (NEXAFS) were applied to single particle organic functional group abundance analysis of particles simultaneously collected at SIMAT and C130. Correlations of elemental concentrations showed different groups of source related elements at SIMAT, Altzomoni, and C130, suggesting different processes affecting the air masses sampled at the three platforms. Cluster analysis resulted in seven distinct Clusters of FTIR spectra, with the last three clusters consisting of spectra collected almost exclusively on the C130 platform, reflecting the variety of sources contributing to C130 samples. Positive Matrix Factorization (PMF) of NEXAFS-STXM spectra identified three main factors representing soot, secondary, and biomass burning type spectra. PMF of FTIR spectra resulted in three fossil fuel combustion type factors, one biomass burning factor, and one mixed or processed factor. The fossil fuel combustion type factors were found to have the largest contributions to OM, while the processed factor has the largest O/C among all factors. Alkane, carboxylic acid, and amine functional groups were mainly associated with combustion related sources, while alcohol groups were likely from atmospheric processing of mixed sources. While the processed factor has the highest O/C, half of the OM and O/C measured could be attributed directly to fossil fuel combustion sources. Both PMF of NEXAFS-STXM spectra and PMF of FTIR spectra indicate that the combustion type factors are more affected by fluctuations in local sources, while the processed factors are more consistent during the sampling period.

The present paper has as objective to apply a sequential Cluster Analysis to the atmospheric particles: Hierarchical Cluster Analysis followed by Nonhierarchical Cluster Analysis. The hierarchical cluster analysis results were used as start point for the nonhierarchical cluster analysis as an agglomerative technique. These particles were taken from two areas of the metropolitan region of Porto Alegre, Charqueadas and Sapucaia do Sul., from may /97 to may/98, using a High Volume Sampler (Hi-Vol). Around 10,000 particles were analysed by Scanning Electron Microscope with Energy-Dispersive X-Ray microanalysis (SEM-EDS). The Hierarchical Cluster Analysis allowed the identification of five groups of particles, whose amounts were differentiated according to the summer and the winter campaigns. The abundance of each type of particles inside each group according to the different sections was verified by the Nonhierarchical Cluster Analysis, resulting in information about the emissions sources. The groups of particles of Si/Al and Si and of Fe/Zn and Fe for Charqueadas were more significant in section 2 and 3 (NW and W wind directions) and in section 1 (SE wind direction), evidencing the influence of the coal power plant and steel industry, respectively located in these quadrants. In Sapucaia do Sul the data were more heterogeneous, causing a certain difficulty to identify the source as anthropogenic. Nevertheless the group of particles containing Fe was found in sectors of NW/W wind directions which shows the influence of the steel plant.

The chemical composition of 15–85 nm diameter particles was measured at Mace Head, Ireland, during May 2011 using the TDCIMS (thermal desorption chemical ionization mass spectrometer). Measurable levels of chloride, sodium, and sulfate were present in essentially all collected samples of these particles at this coastal Atlantic site. Acetaldehyde and benzoic acid were also frequently detected. Concomitant particle hygroscopicity observations usually showed a sea-salt mode and a lower hygroscopicity mode with growth factors near to that of ammonium sulfate. There were many periods lasting from hours to about 2 days during which the 10–60 nm particle number increased dramatically in polar oceanic air. These periods were correlated with the presence of benzoic acid in the particles and an increase in the number of lower hygroscopicity mode particles. Very small (< 10 nm) particles were also present, suggesting that new particle formation contributed to these nanoparticle enhancement events.

Beddows, D. C. S. ... et. al.-- 22 pages, 11 figures, 1 table, supplementary material related to this article is available online at http://www.atmos-chem-phys.net/14/4327/2014/acp-14-4327-2014-supplement.pdf, Clusteranalysis of particle number size distributions frombackground sites across Europeis presented. This generated a total of nine clusters of particle size distributions which could be further combined into two main groups, namely: a south-to-north category (four clusters) and a west-to-east category (five clusters). The first group was identified as most frequently being detected inside and around northern Germany and neighbouring countries, showing clear evidence of local afternoon nucleation and growth events that could be linked to movement of air masses from south to north arriving ultimately at the Arctic contributing to Arctic haze.The second group of particle size spectra proved to have narrower size distributions and collectively showed a dependence of modal diameter upon the longitude of the site (west to east) at which they were most frequently detected.These clusters indicated regional nucleation (at the coastal sites) growing to larger modes further inland. The apparent growth rate of the modal diameter was around 0.6-0.9 nm h-1. Four specific air mass back-trajectories were successively taken as case studies to examine in real time the evolution of aerosol size distributions across Europe. While aerosol growth processes can be observed as aerosol traverses Europe, the processes are often obscured by the addition of aerosol by emissions en route. This study revealed that some of the 24 stations exhibit more complex behaviour than others, especially when impacted by local sources or a variety of different air masses. Overall, the aerosol size distribution clustering analysis greatly simplifies the complex data set and allows a description of aerosol aging processes, which reflects the longer-term average development of particle number size distributions as air masses advect across Europe. © 2014 Author(s), The National Centre for Atmospheric Science is funded by the UK Natural Environment Research Council. This work was also supported by the European Union EUCAARI (Contract Ref. 036833) and EUSAAR (Contract Ref. 026140) research projects

A time-serial analysis of atmospheric particles collected since 1990 at a coastal site bordering the northeastern Mediterranean Sea shows that the collected samples, display seasonal patterns in both concentration and color. The 1990–91 and 1992 collections yield an annualised average of around 0.5 g/day dust loading reducing to around 0.3 g/day when the sea-salt contribution is excluded. The highest concentrations of atmospheric particles of continental origin for both natural (e.g. Fe, Mn) and anthropogenic (e.g. Cd, Pb) materials are observed between April and October and this variability is inversely related to the frequency and the amount of rainfall. Sea-salt aerosol (Na) contents do not follow this pattern but are related to local wind speeds. Trace elements in the dusts also display seasonal variations in enrichment factors (EF), with respect to average elemental abundances in crustal rocks. The non-enriched (crustal) elements appear to be indicators of long-distance supply while the strongly enriched (anthropogenic) and moderately enriched suites of elements represents inputs from local or “anomalous” sources. The similar morphology of quartz and calcite grains and the uniformity of the clay mineral assemblages in samples collected over a two-year period strongly indicate a common source for the bulk of the atmospheric particles. The dominant clay types (palygorskite and smectite) document a desertic source areas.

We report measurements of the subsaturated hygroscopic growth of aerosol particles composed of single organic components of varying oxygen-to-carbon ratio up to relative humidities approaching saturation using the techniques of aerosol optical tweezers and an electrodynamic balance. The variation in the hygroscopicity parameter kappa between compounds of even the same O/C ratio is found to be significant with, for example, a range in kappa values from 0.12 to 0.38 for compounds with an O/C of 1. The measurements are compared with a review of all of the available literature data for which both the kappa value and O/C ratio are reported, and a new parametrization is determined. Critical supersaturations predicted using this parametrization yield values that have associated uncertainties that are comparable to typical uncertainties in experimental measurements of critical supersaturations. However, the systematic variability between kappa parametrizations determined remains large, consistent with the O/C ratio providing only an approximate guide to aerosol hygroscopicity and reflecting significant variations for aerosols of different chemical functionality, composition, and oxidation history. from different studies

Dual carbon isotope analysis of marine aerosol samples has been performed for the first time demonstrating a potential in organic matter apportionment between three principal sources: marine, terrestrial (non-fossil) and fossil fuel due to unique isotopic signatures. The results presented here, utilising combinations of dual carbon isotope analysis, provides conclusive evidence of a dominant biogenic organic fraction to organic aerosol over biologically active oceans. In particular, the NE Atlantic, which is also subjected to notable anthropogenic influences via pollution transport processes, was found to contain 80 % organic aerosol matter of biogenic origin directly linked to plankton emissions. The remaining carbonaceous aerosol was of terrestrial origin. By contrast, for polluted air advected out from Europe into the NE Atlantic, the source apportionment is 30 % marine biogenic, 40 % fossil fuel, and 30 % continental non-fossil fuel. The dominant marine organic aerosol source in the atmosphere has significant implications for climate change feedback processes.

Seasonal variations in cloud droplet number concentration (NCD) in low-level stratiform clouds over the boreal forest are estimated from MODIS observations of cloud optical and microphysical properties, using a sub-adiabatic cloud model to interpret vertical profiles of cloud properties. An uncertainty analysis of the cloud model is included to reveal the main sensitivities of the cloud model. We compared the seasonal cycle in NCD, obtained using 9 yr of satellite data, to surface concentrations of potential cloud activating aerosols, measured at the SMEAR II station at Hyytiälä in Finland. The results show that NCD and cloud condensation nuclei (CCN) concentrations have no clear correlation at seasonal time scale. The fraction of aerosols that actually activate as cloud droplet decreases sharply with increasing aerosol concentrations. Furthermore, information on the stability of the atmosphere shows that low NCD is linked to stable atmospheric conditions. Combining these findings leads to the conclusion that cloud droplet activation for the studied clouds over the boreal forest is limited by convection. Our results suggest that it is important to take the strength of convection into account when studying the influence of aerosols from the boreal forest on cloud formation, although they do not rule out the possibility that aerosols from the boreal forest affect other types of clouds with a closer coupling to the surface.

21 transp.-- Presentación incluida entre las actividades de divulgación del IV Clare Hall Spain meeting (San Sebastián, Oct 3, 2009)., [ES] Se presenta una introducción a dos de las líneas de investigación de nuestro Departamento, consistentes en el estudio de fases condensadas (hielos) de gases de interés atmosférico o astrofísico. Los sistemas descritos en esta presentación son hidratos de ácido nítrico y clorhídrico (atmósfera) y mezclas de CO2 y CH4 con hielo de agua (astrofísica)., [EN] An introduction is presented to two of the main research lines in our Department, namely the study of condensed phases (ices) of atmospheric or astrophysical interest. The systems described in this presentation are nitric and chlorhydric acid hydrates (atmosphere) and mixtures of CO2 and CH4 with water ice (astrophysics).

Pb-LIII edge XANES spectra of atmospheric particles are directly obtained by fluorescent XAFS spectroscopy using a 19-element solid state detector (SSD). Particulate sample was collected on a quartz fiber filter using a high-volume air sampler, and the filter was cut into small pieces (25 × 25 mm). Then, surface layer of the filter piece was scaled and accumulated in order to enhance the particle density per filter unit. Use of 10 pieces of the surface layer enables the measurement of Pb-LIII edge XANES spectra on beamline BL01B1 at SPring-8, Hyogo, Japan. The shape of the Pb-LIII edge XANES spectra of the particulate sample is similar to the shapes of the spectra for PbS, PbCO 3 , PbSO 4 and/or PbCl 2 . Additionally, the filter sample is also divided into water-soluble, 0.1 M HCl-extractable, and residual fractions of Pb compounds by a simple acid extraction procedure. We discuss the possibility of Pb speciation in the particulate samples with combination of highly sensitive XANES spectroscopy and simple acid extraction.

[1] The formation and evolution of new particles during coastal nucleation events are examined using the aerosol dynamic and gas-phase chemistry model AEROFOR2. Coastal regions are known to be a strong source of natural aerosol particles and are also strong sources of biogenic vapors which can condense onto aerosol particles, thus resulting in particle growth. A number of model simulations were performed to determine the instantaneous nucleation rate along with the source rate of a generic biogenic vapor leading to the observed particle size distributions which indicate the rapid appearance of similar to10(5)-10(6) cm(-3) nucleation mode particles in this environment. Model calculations suggest values of 3 x 10(5) cm(-3) s(-1) to 3 x 10(6) cm(-3) s(-1) for the instantaneous nucleation rate and a value of 5 x 10(7) cm(-3) s(-1) for the condensable vapor source rate in order to reproduce the observed concentrations. A significant fraction of these new particles survive to grow into cloud condensation nuclei (CCN) sizes for supersaturations typically encountered in boundary layer clouds during subsequent evolution over 3 days under clear-sky conditions, thus contributing to the indirect radiative effect of aerosols. The amount of CCN is mainly affected by coagulation between particles and condensation of the biogenic vapor and, to a lesser extent, by condensation of sulphuric acid formed by DMS oxidation. In all simulated cases, an increase of more than 100% in CCN concentration, for supersaturations >0.35% was observed.

An analysis of new particle formation probability in the marine boundary layer (MBL) is conducted using a detailed aerosol dynamics and gas-phase chemistry model, thermodynamically correct classical binary (H2O-H2SO4) nucleation theory, and recently developed tel nary (H2O-H2SO4-NH3) nucleation theory. Additionally, the effect of boundary-layer meteorology (i.e., adiabatic cooling, small scale fluctuations, and entrainment) in enhancing nucleation is also examined. The results indicate that for typical marine conditions, binary nucleation does not occur for any realistic conditions regardless of adiabatic cooling, turbulent fluctuations, or entrainment. For polar marine conditions, binary nucleation does occur due to lower temperatures, and is enhanced due to turbulent fluctuations. An increase in detectable particle sizes (N-3>3 nm), is only seen after multiple boundary layer circulations for conditions of high dimethyl sulphide (DMS) concentrations (400 ppt). Under extreme conditions of entrainment of fi ee-troposphere layers containing very low aerosol condensation sinks and extraordinary high sulphuric acid concentrations (>10(8) molecules cm(-3)), increases in detectable particles up to 10,000 cm are predicted only in polar marine air, but are viewed as unlikely to occur in reality. Comparison of model simulations with observed values of DMS and sulphuric acid in polar marine air masses suggest that binary nucleation may lead to an enhancement of approximate to 1000 cm(-3) in N-3 particle concentration, but not to enhancements of approximate to 10,000 cm(-3) Ternary nucleation is predicted to occur under realistic sulphuric acid (1.2 x 10(7) molecules cm(-3)) and ammonia (>5 ppt) concentrations; however, significant growth to detectable sizes (N-3) only occurs for DMS concentrations of the order of 400 ppt and very low aerosol condensation sinks, but these conditions are thought to be very infrequent in the MBL and are unlikely to make a significant contribution to the general MBL aerosol concentration. It is plausible that the background MBL aerosol concentration could be maintained by a slow, almost undetectable production rate, and not by noticeable nucleation events where large enhancements in N-3 concentrations are observed. The former requires sustained DMS concentrations of the order of 100 ppt which seems unlikely. In summary, the occurrence of new particles in the unperturbed MBL would be difficult to explain by DMS emissions alone. DMS emissions can explain the occurrence of thermodynamically stable sulphate clusters, but under most conditions, to grow these clusters to detectable sizes before they are scavenged by coagulation, an additional condensable species other than DMS-derived sulphuric acid would be required. In the event, however, of significant removal of the preexisting aerosol due to precipitation, the MBL aerosol can be replenished through growth of new particle formed through ternary nucleation under moderately high DMS concentrations.

Ammonium is one of the dominant inorganic water-soluble ions in fine particulate matter (PM2.5). In this study, source apportionment and thermodynamic equilibrium models were used to analyze the relationship between pH and the partitioning of ammonium (epsilon(NH4+)) using hourly ambient samples collected from Tianjin, China. We found a "Reversed-S curve" between pH and epsilon(NH4+) from the ambient hourly aerosol dataset when the theoretical epsilon(NO3-)* (an index identified in this work) was within specific ranges. A Boltzmann function was then used to fit the Reversed-S curve. For the summer data set, when epsilon(NO3-)* was between 0.7 and 0.8, the fitted R-2 was 0.88. Through thermodynamic analysis, we found that the values of k[H+](2) (k = 3.08 X 10(4) L-2 mol(-2)) and epsilon(NO3-)* can influence the pH- epsilon(NH4+) curve. Under certain situations, the values of k[H+](2) and epsilon(NO3-)* are similar to each other, and epsilon(NH4+) is sensitive to pH, suggesting that epsilon(NO3-)* plays an important role in affecting the epsilon(NH4+). During summer, winter, and spring seasons, when the relative humidity was greater than 0.36 and epsilon(NO3-)* was between 0.8 and 0.95, there was an obvious Reversed-S curve, with R-2 = 0.60. The theoretical k[H+](2) and epsilon(NO3-)* developed in this work can be used to analyze the gas-particle partitioning of ammonia-ammonium and nitrate-nitric acid in the ambient atmosphere. Also, it is the first time that we created the joint source-NH3 /HNO3 maps to integrate sources, aerosol pH and liquid water content, and ions (altogether in one map), which can provide useful information for designing effective strategies to control particulate matter pollution.

Single particles were collected from an aircraft platform as part of the Intercontinental Chemical Transport Experiment – Phase B (INTEX-B) conducted over the eastern Pacific and western North America. Single particle spectra were obtained using scanning transmission X-ray microscopy-near edge X-ray absorption fine structure spectroscopy (STXM-NEXAFS). Bulk submicron particles were also collected and organic functional group and elemental concentrations were quantified with Fourier transform infrared (FTIR) spectroscopy and X-ray fluorescence (XRF). Single particle spectra were classified into metaclasses associated with different sources and atmospheric processing. Particles with spectra indicative of secondary organic aerosol production and combustion sources were found at several locations and a range of altitudes. At lower altitudes, particles with spectra resembling soil dust and biomass burning fingerprints were commonly observed. The types of particle spectra most commonly observed aloft were similar to those observed during a previous study over the northwestern Pacific, indicating that long-range transport may have been an important particle source. Single particle spectra provided evidence that condensation and surface-limited oxidation contributed to particle growth. Organic mass (OM) concentrations ranged from 1 to 7 μg m−3 and averaged 2.4–4.1 μg m−3. Alkane functional groups were the largest fraction of OM, averaging 1.9–2.1 μg m−3 or 50–76% of OM, followed by alcohol functional groups (0.35–0.39 μg m−3, 9–14%). Organic and elemental concentrations are compared within and among geographical air mass regions: "Pacific" free troposphere, "Continental" free troposphere, "Seattle" metropolitan region, and the California "Central Valley". OM concentrations were highest and most variable in the Central Valley (3.5±2 μg m−3). Oxygen-to-carbon ratios were relatively constant in the Central Valley but variable for the Continental air masses. Overall, the OM concentrations showed greater variability within air mass categories as compared to averages among them, suggesting sampled air mass regions included a variety of sources and processing of organic aerosol.

As the water uptake by particles and clouds influences the radiative balance of the Earth, it is desirable to understand the mechanisms and parameters, which regulate water uptake in these colloidal particles. In this work, molecular dynamics simulations were used to simulate scattering or accommodation of water vapor molecules impinging on a slab of water and slabs of water coated by monomolecular amphiphile films: octanoic acid (C-8) at surface densities of 29 and 18 angstrom(2) per molecule and myristic acid (C-14) at 29 angstrom(2) per molecule. The mass accommodation coefficient of near unity on a pure water slab is in agreement with values estimated using similar scattering simulations using other potentials for water. The addition of surface-active organic molecules in quantities corresponding to less than 1% of mass in a typical cloud droplet are predicted to reduce this mass accommodation coefficient by 70-100% in similar types of scattering simulations. The mass accommodation coefficient decreased monotonically with projected surface coverage of the hydrocarbon backbones, although the accommodation mechanisms differed by packing density and type of organic molecule. The mechanisms of interaction of the impinging water vapor molecules with the simulated organic films are discussed in the context of their chemical characteristics and physical structures (e.g., fatty acid chain orientation).

Purpose In this study, the spatial and temporal relationship of wind speed, atmospheric particles concentration, and the industrial-induced noise levels during different times of the day were examined, using sawmill industrial location around Ile-Ife in Osun of Nigeria as a case study. Methods Mobile devices were used to measure noise level and basic meteorological parameters were examined and their influences on the noise levels distribution were assessed. The maximum and minimum sound levels; Lmax and Lmin, the PM10 and PM1 particle concentrations, wind speeds and directions were measured in the morning (7–9 a.m.), afternoon (12–2) and evening (4–6 p.m.) over 14 consecutive days. Results The results revealed that the noise level varies spatiotemporally, much more consistent spatial distribution along the vicinity of sawmill industries. A higher level of noise occurred during the weekday (WD), Leq > 70 dB(A), compared to weekends (WE). Extreme average noise levels are associated with the immediate neighbourhood of sawmill industrial areas during WD compared to streets and road annexes of the study area. The results also show a very weak relationship between noise and PM10 and PMcoarse for both WD and WE with r 0.51. Conclusion The slight relationship between noise and PM1 is perhaps a result of wind movement that carries particles from the source region since booth noise and particles mostly originate from the sawmill. The study concludes that wind speeds and directions have a significant influence on both noise level and particle concentration within the study sites.

It has long been hypothesized that acids formed from anthropogenic pollutants and natural emissions dissolve iron (Fe) in airborne particles, enhancing the supply of bioavailable Fe to the oceans. However, field observations have yet to provide indisputable evidence to confirm this hypothesis. Single-particle chemical analysis for hundreds of individual atmospheric particles collected over the East China Sea shows that Fe-rich particles from coal combustion and steel industries were coated with thick layers of sulfate after 1 to 2 days of atmospheric residence. The Fe in aged particles was present as a “hotspot” of (insoluble) iron oxides and throughout the acidic sulfate coating in the form of (soluble) Fe sulfate, which increases with degree of aging (thickness of coating). This provides the “smoking gun” for acid iron dissolution, because iron sulfate was not detected in the freshly emitted particles and there is no other source or mechanism of iron sulfate formation in the atmosphere. © 2017 The Authors, some rights reserved.

The ability of airborne particles to take up water may be enhanced by surface-active components, but the importance of this effect is controversial because direct measurement of the surface tension of microscopic droplets has not been possible. Here we infer droplet surface tension from water uptake measurements of mixed organic-inorganic particles at relative humidities just below saturation (99.3-99.9%). The surface tension of droplets formed on particles composed of NaCl and-pinene ozonolysis products was reduced by 50-75%, but only when enough organic material was present to form a film on the droplet surface at least 0.8nm thick. This study suggests that if atmospheric particles are predominantly (≳80%) composed of surface-active material, their influence on cloud properties and thus climate could be enhanced, and their atmospheric lifetimes could be reduced. © 2012. American Geophysical Union. All Rights Reserved.

[ 1] The formation of aerosols, and subsequent cloud condensation nuclei, remains one of the least understood atmospheric processes upon which global climate change critically depends. Under atmospheric conditions, the process of homogeneous nucleation (formation of stable clusters -1 nm in size), and their subsequent growth into new particles (>3 nm), determines the aerosol and cloud nuclei population, yet, hitherto, no theory has elucidated the new particle formation phenomenon in detail. In this study, we present a new theory which provides a mechanistic explanation for new particle formation via activation of stable inorganic clusters by organic vapors. The new nano-particle activation theory is analogous to Kohler theory which describes cloud formation in a supersaturated water vapor field but differs in that it describes the activation of inorganic stable nano-clusters into aerosol particles in a supersaturated organic vapor which initiates spontaneous and rapid growth of clusters. Inclusion of the new theory into aerosol formation models predicts that increases in organic vapor densities lead to even greater increases in particle production, which, in turn, will influence the global radiative cooling effect of atmospheric aerosols.

A escala global, los incendios forestales son una fuente de emisiones significativas de gases y partículas a la atmosfera, emisiones que llegan a afectar grandes extensiones y pueden transportarse a distancias de escala continental. En este trabajo se han estimado las emisiones de los gases de efecto invernadero (GEI) procedentes de grandes incendios forestales ocurridos en los últimos 10 años en Cataluña, España, una región mediterránea muy afectada por la incidencia de fuegos de origen antrópico. Estas estimaciones se basan en la caracterización y cuantificación de la biomasa total de los combustibles forestales preexistentes en las áreas que se queman, la cuantificación de las pérdidas debidas a la combustión según la severidad del incendio y la aplicación de factores de emisión a la biomasa consumida. Los resultados obtenidos indican que los grandes incendios de la última década consumieron porcentajes variables entre 44,4% y 70,3% de la biomasa total disponible en las zonas incendiadas, con emisiones totales de carbono equivalente de entre 15 013 t y 387 335 t por incendio. Para determinar las trayectorias de los penachos de humo y concentraciones alcanzadas se utilizó el modelo Hybrid Single Particle Lagrangian Integrated Trajectory. Los penachos de humo de los incendios estudiados se desplazaron a grandes distancias, generalmente bajo situación anticiclónica, afectando al Mediterráneo y Norte de África. At the global scale, forest fires are a source of significant emissions of gases and particles to the atmosphere that disperse over a large area and can be transported over great distances at the continental scale. Among these emissions, there are greenhouse gases, which are released in large quantities into the atmosphere after a forest fire. In this work, an attempt has been made to estimate greenhouse gas (GHG) emissions from large forest fires in recent years in Catalonia, Spain. These estimates are based on the characterization and quantification of the biomass that makes up the pre-existing forest fuels in the burned areas, the assessment of fire severity and consumption rates, and the application of published emission factors. The results obtained indicate that percentages between 44,4% and 70,3% of pre-fire biomass were consumed, corresponding respectively to total equivalent carbon emissions between 15 013 t and 387 335 t. A Lagrangian model (Hybrid Single Particle Lagrangian Integrated Trajectory) was used in order to determine the dispersion ranges and trajectories of the smoke plumes. The smoke plumes from the fires reached large distances, mainly affecting the Mediterranean region and North of Africa.