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Atmospheric Environment (v.40, #32)
Indoor and outdoor levels of respirable particulates (PM10) and Carbon Monoxide (CO) in high-rise apartment buildings by W.-K. Wan-Kuen Jo; J.-Y. Joon-Yeob Lee (pp. 6067-6076).
The present study evaluated exposure to two mobile source-related pollutants (CO and PM10) in high-rise apartment buildings, according to floor height. The outdoor air concentrations of CO and PM10 were higher for the lower-floor apartments than for the higher-floor apartments, and they were significantly higher in the winter and summer. However, the difference of indoor concentrations between the lower-floor and higher-floor apartments depended upon the season. Most indoor and outdoor concentrations of PM10 were significantly higher in apartments, which were in close proximity to a major roadway, as compared to those further away, whereas the indoor and outdoor concentrations of CO did not vary much according to distances from major roadways. Atmospheric stability was important regarding the level of exposure to both CO and PM10 for residents of high-rise apartment buildings. These parameters (apartment floor, proximity to roadways, season, and atmospheric stability) should be considered when evaluating the level of exposure to CO and PM10 for residents living in high-rise apartment buildings. The median PM10 outdoor concentrations were close to or lower than the Korean annual standard for PM10 (70μgm−3) or the American annual standard (50μgm−3). Neither the median nor the maximum outdoor CO concentrations were higher than the Korean 8-h CO standard (9ppm). However, the maximum PM10 concentrations substantially exceeded the Korean standard, thus suggesting the need for a management strategy regarding episodic ambient PM10 pollution.
Keywords: Apartment floor; Atmospheric stability; Proximity; Roadway; Exposure level
Organic positive ions in aircraft gas-turbine engine exhaust by Andrey Sorokin; Frank Arnold (pp. 6077-6087).
Volatile organic compounds (VOCs) represent a significant fraction of atmospheric aerosol. However the role of organic species emitted by aircraft (as a consequence of the incomplete combustion of fuel in the engine) in nucleation of new volatile particles still remains rather speculative and requires a much more detailed analysis of the underlying mechanisms. Measurements in aircraft exhaust plumes have shown the presence of both different non-methane VOCs (e.g. PartEmis project) and numerous organic cluster ions (MPIK-Heidelberg). However the link between detected organic gas-phase species and measured mass spectrum of cluster ions is uncertain. Unfortunately, up to now there are no models describing the thermodynamics of the formation of primary organic cluster ions in the exhaust of aircraft engines. The aim of this work is to present first results of such a model development. The model includes the block of thermodynamic data based on proton affinities and gas basicities of organic molecules and the block of non-equilibrium kinetics of the cluster ions evolution in the exhaust. The model predicts important features of the measured spectrum of positive ions in the exhaust behind aircraft. It is shown that positive ions emitted by aircraft engines into the atmosphere mostly consist of protonated and hydrated organic cluster ions. The developed model may be explored also in aerosol investigations of the background atmosphere as well as in the analysis of the emission of fine aerosol particles by automobiles.
Keywords: Charged clusters; Organics emission; Pre-nucleation cluster; Atmospheric aerosol
Measurement of chemical elements in rain from Rancho Viejo, a rural wooded area in the State of Mexico, Mexico by Garcia R. GarcÃa; C. del Torres Ma; H. Padilla; R. Belmont; E. Azpra; F. Arcega-Cabrera; Baez A. Báez (pp. 6088-6100).
A rural forested site was selected to measure Al, Cd, Cr, Mn, Ni, Pb and V (soluble and insoluble fractions), and the major inorganic ions Na+, K+, Ca+, Mg2+, NH4+, H+, Cl−, NO3− and SO42−. A total of 44 samples were collected during the rain seasons of 2001–02. Trace metals were analyzed by atomic absorption spectroscopy with a graphite furnace accessory. As for ion analysis a Perkin Elmer liquid chromatograph was used. The volume-weighted mean concentration (VWMC) results indicated that highest concentration was that of aluminum followed in decreasing order by Mn, V, Pb, Cr and Cd. Solubilities were calculated in rain samples at pH<5 and pH>5, solubilities at pH<5 were higher than the solubilities at pH>5, as it has been reported by other authors. The rains from Rancho Viejo had a pH of 4.5 indicating an acid nature. Comparing the VWMC of Ca2+ (7.79μeql−1) with NH4+ (46.36μeql−1), indicated that the NH4+ was the main neutralizing compound. The scatter plots showed that the acidity of rain was due mainly to H2SO4 plus HNO3 (55% and 22.7%, respectively). Backward trajectories using the NOAA HYSPLIT Model were calculated at 3000m above mean sea level (AMSL) and indicated significant differences in the mean concentrations that depended on the wind direction. Good and positive correlations were found among all trace metals that indicate a common origin. Factor Statistical Analysis 6.4 was applied to all data to have a better knowledge of the origin of the trace metals in rainwater. To evaluate the contribution of non-crustal sources an enrichment factor was also applied.
Keywords: Rainwater; Trace elements; Backward trajectories; Rural zone
Synthetic musk fragrances in urban and rural air of Iowa and the Great Lakes by Aaron M. Peck; Keri C. Hornbuckle (pp. 6101-6111).
Synthetic musk fragrances are semivolatile organic compounds used to scent a variety of household and personal care products. In this study, six polycyclic musk fragrances (HHCB, AHTN, ATII, AHMI, ADBI, and DPMI) and two nitro musk fragrances (musk xylene and musk ketone) were evaluated in 181 air samples collected at urban, suburban, and rural sites in Iowa and the Great Lakes. This is the largest reported study of the compounds in ambient air and reveals the ubiquitous nature of these environmental contaminants. HHCB and AHTN were detected most frequently and at the highest concentrations at all sites. Synthetic musk fragrance concentrations were highest in urban locations, including Milwaukee, WI (previously reported) and an urban location in Cedar Rapids, IA. Urban concentrations of HHCB and AHTN are on the order of 1–5ngm−3 and background terrestrial concentrations are about an order of magnitude less. In rural Iowa, the concentrations and frequency of detection of the synthetic musk fragrances are comparable to (and often greater than) gas-phase pesticide concentrations. The concentrations measured at the suburban location in Iowa City, IA and over the Lakes Erie, Ontario, and Michigan were generally intermediate of those measured at the rural and urban locations. Concentrations of HHCB and AHTN were correlated with temperature at the sampling sites in Iowa.
Keywords: Atmosphere; Emerging contaminants; Personal care products; PPCPs; Galaxolide; Tonalide; Fragrance chemicals; Synthetic musks
Decoupled direct 3D sensitivity analysis for particulate matter (DDM-3D/PM) by Sergey L. Napelenok; Daniel S. Cohan; Yongtao Hu; Armistead G. Russell (pp. 6112-6121).
The decoupled direct method (DDM) and DDM-3D have been implemented in air quality models in order to efficiently compute sensitivities. Initial implementation of DDM/DDM-3D in models was confined only to gas-phase species as the treatment of sensitivities in the dynamics of secondary aerosol formation is more complex. Here, it is extended to calculate particulate matter sensitivities. DDM-3D/particulate matter (PM) results compare well spatially and temporally with the traditional brute-force approach, particularly for species responses to emissions of their “parent� precursor (e.g., sulfate to SO2 emissions.) Correlations of more indirect relationships between aerosols and gaseous emissions (e.g., nitrate to SO2 emissions) are worse, but these sensitivities are usually small. DDM-3D/PM appears to work better than the brute-force approach in some cases due to numerical noise and other factors, as identified from the application on a southeastern US domain for a summer episode. DDM-3D/PM is also computationally efficient. While CPU usage was found to scale linearly with the number of sensitivity parameters of interest (for a given domain size), it was significantly less than using the brute-force approach.
Keywords: Atmospheric modeling; Sensitivity analysis; Decoupled direct method
Factors affecting ozone removal rates in a simulated aircraft cabin environment by G. Tamas Gyöngyi Tamás; Charles J. Weschler; Bako-Biro Zsolt Bakó-Biró; David P. Wyon; Strom-Tejsen Peter Strøm-Tejsen (pp. 6122-6133).
Ozone concentrations were measured concurrently inside a simulated aircraft cabin and in the airstream providing ventilation air to the cabin. Ozone decay rates were also measured after cessation of ozone injection into the supply airstream. By systematically varying the presence or absence of people, soiled T-shirts, aircraft seats and a used HEPA filter, we have been able in the course of 24 experiments to isolate the contributions of these and other factors to the removal of ozone from the cabin air. In the case of this simulated aircraft, people were responsible for almost 60% of the ozone removal occurring within the cabin and recirculation system; respiration can only have been responsible for about 4% of this removal. The aircraft seats removed about 25% of the ozone; the loaded HEPA filter, 7%; and the other surfaces, 10%. A T-shirt that had been slept in overnight removed roughly 70% as much ozone as a person, indicating the importance of skin oils in ozone removal. The presence of the used HEPA filter in the recirculated airstream reduced the perceived air quality. Over a 5-h period, the overall ozone removal rate by cabin surfaces decreased at ∼3%h−1. With people present, the measured ratio of ozone's concentration in the cabin versus that outside the cabin was 0.15–0.21, smaller than levels reported in the literature. The results reinforce the conclusion that the optimal way to reduce people's exposure to both ozone and ozone oxidation products is to efficiently remove ozone from the air supply system of an aircraft.
Keywords: Aircraft cabin air quality; Indoor air chemistry; Heterogeneous chemistry; Human bioeffluents; Skin oil; Deposition velocities
Evidence for increasing concentrations of primary PM10 in London by Gary W. Fuller; David Green (pp. 6134-6145).
Although annual mean concentrations of PM10 in and around London reduced during the 1990s, concentrations have been relatively stable since, with small increases during 2001–2003. A modelling method was used to apportion the measured annual mean concentration of PM10 between primary, and secondary and natural sources at monitoring sites in and around London between 1997 and 2004. The annual mean concentration of PM10 from primary sources reached a minimum during 1998. Between 1998 and 2003 the greatest change in the annual mean concentration of primary PM10 occurred at sites adjacent to busy roads: Marylebone Road (7.0±2.6μgm−3), Wandsworth 4 (6.0±1.1μgm−3) and Ealing 2 (4.5±1.4μgm−3). The smallest change in the concentration of PM10 from primary sources occurred at background locations in towns outside London. It is therefore likely that the additional primary PM10 arose from road traffic. These increases in PM10 from primary sources contradict emissions inventory estimates that indicate reductions in primary PM10. The annual mean concentration of PM10 from secondary and natural sources declined by 2.0±3.0μgm−3 or 11±16% between 1997 and 2003. The annual mean concentration of PM10 from these sources reduced until the year ended 1st July 2001 and then increased during the remainder of 2001, 2002 and 2003.
Keywords: London; PM; 10; source apportionment; Emissions inventory; Guide to the expression of uncertainty in measurement.
Uncertainty in mass balance critical loads and exceedance: Application to a UK national data set by Liz Heywood; Jane Hall; Rognvald Smith (pp. 6146-6153).
It is generally accepted that uncertainty should be taken into account in environmental assessments and the subsequent decision-making. This paper undertakes an uncertainty assessment for acidity and nutrient nitrogen critical loads and their exceedances, which is important in determining national and international policy on the emissions of acidifying air pollutants. This is the first time such an analysis has been done for the UK at the national scale. In this paper we illustrate the process and issues with reference to “managed coniferous woodland�, one of a number of habitat types for which critical loads are calculated. Again using coniferous woodland as an example Monte Carlo analysis showed that the uncertainties in the national critical loads varied between 14 and 29%. Policy makers are however primarily concerned with whether the critical load is exceeded and therefore the uncertainty in exceedance is also estimated. Again using coniferous woodland as an example, Monte Carlo analysis showed that for acidity, it was uncertain whether the critical load was exceeded or not for the majority of the coniferous woodland habitat. For nutrient nitrogen, most of the habitat had a very high probability of exceedance.
Keywords: Acidification; Eutrophication; Policy; Monte Carlo
Studies of some measures to reduce road dust emissions from paved roads in Scandinavia by Michael Norman; Christer Johansson (pp. 6154-6164).
In this paper we present quantitative assessments of different measures to reduce the PM10 levels along streets in Scandinavian cities based on tests in Stockholm. The effect of the use of studded tyres on concentrations in a street canyon has been quantitatively assessed using monitoring data. A 10% decrease in the fraction of studded tyres was estimated to reduce the weekly average street canyon PM10 levels (due to local road abrasion) by about 10μgm−3 if only daytime and dry street conditions were considered. These results are obtained by correlating the increase in PM10 levels during autumn with the increased use of studded tyres. Since the share of studded tyres is around 75% in Stockholm during wintertime, the peak springtime PM10 levels that occur during dry road conditions would be substantially lower if the use of studded tyres were regulated. Intense sweeping or washing of the pavements resulted in marginal reductions (<10%) and will have no important influence on the PM10 levels with the methodologies and working machineries tested here. Application of calcium magnesium acetate (CMA, Ice Away, as 25% water solution) on the road surface of a highway during dry conditions resulted in an average reduction of around 35% in the daily PM10 averages. The most efficient way to reduce PM10 levels in the long-term and for a large area is to reduce the use of studded tyres, while application of CMA may be efficient to reduce peak levels, which frequently occur during dry road conditions in spring.
Keywords: PM10; Studded tyres; Sweeping of roads; Dust binding; Road wear
Hydroperoxides in dew water in downtown Santiago, Chile. A comparison with gas-phase values by M.A. M. Angélica Rubio; M. José Guerrero; Guillermo Villena; Eduardo Lissi (pp. 6165-6172).
Gas phase and dew incorporated concentrations of hydrogen peroxide were measured during late autumn at downtown Santiago, Chile. Dews were collected in non-stabilized and stabilized (HgCl2 rinsed) Teflon collectors. The values measured in both type of collectors were considerably lower than those predicted from gas-phase concentrations and Henry's law, suggesting a lack of equilibration between dew droplets and the surrounding air mass.Concentrations of hydrogen peroxide measured in dews collected in stabilized samplers are considerably higher than those measured in non-stabilized samplers. This difference is related to the decomposition of the peroxides in the collected dews. It is proposed that this decomposition is, at least partially, associated to the oxidation of S(IV) by hydrogen peroxide. This is supported by a slower rate of decomposition of externally added hydrogen peroxide after removal of S(IV) compounds from dew matrices.
Keywords: Dew chemistry; Hydrogen peroxide; Peroxide decomposition; Sulfite
Neural networks for analysing the relevance of input variables in the prediction of tropospheric ozone concentration by Juan Gómez-Sanchis; J.D. José D. MartÃn-Guerrero; Emilio Soria-Olivas; Joan Vila-Francés; José L. Carrasco; Secundino del Valle-Tascón (pp. 6173-6180).
This paper deals with tropospheric ozone modelling by using Artificial Neural Networks (ANNs). In this study, ambient ozone concentrations are estimated using surface meteorological variables and vehicle emission variables as predictors. The work is especially focused on analysing the importance of the input variables used by these models. This analysis is carried out in different time windows: all the time of study (April of 1997, 1999 and 2000), one month (April 1999), and finally, an hourly analysis. All the information extracted from these analyses can determine the most important factors in tropospheric ozone formation, thus achieving a qualitative model from the quantitative model obtained by neural networks. The relative importance of both meteorological and vehicle emission variables on the surface ozone prediction is of great interest to establish the legislative measures that permit to reduce the tropospheric ozone levels. The methodology developed in this study is applied to a small town near Valencia (Spain), but it can be generalisable to other locations.
Keywords: Artificial neural networks; Forecasting models; Sensitivity analysis; Ozone
Biogenic vanadium in total suspended particulate matter from Cabo Frio upwelling region, Southeast, Brazil by Silvia M. Sella; Alessandra F. Neves; Josino Costa Moreira; Emmanoel V. Silva-Filho (pp. 6181-6191).
In this work total suspended particulate (TSP) was collected during a year, in two municipalities located in a coastal region of Rio de Janeiro State, Southeast, Brazil, from February 2004 to January 2005. Two sites were chosen: site 1 located in front of the sea and representative of sea salt spray influence; site 2 in a tall booth of a highway representing vehicle exhaust influence. Samples were collected in glass fibre filters using Hi-Vol samplers and stored. 1/8 of those loaded filters were cut and digested in a microwave oven. The extract obtained was used to determine metal Ca, Cu, Mo, Mn, Ti, V, Zn and K concentration in the atmosphere. The results showed that TSP levels in site 1 (23.1–659μgm−3) was higher than in site 2 (24.5–55.6μgm−3) due to marine aerosol which is responsible for particle emissions with higher diameter. Vanadium was the only element studied whose concentration were higher in site 1 (0.840–20.9ngm−3) compared to site 2 (0.655–7.07ngm−3). The highest vanadium concentrations in site 1 were obtained during upwelling events, with NE winds predominance at high speed, which indicates the influence of this phenomena in V presence in the atmosphere. Principal components analysis was able to identify atmospheric particulate sources distributed in four factors. In site 1, those factors explain 86.5% of total data variance and indicate two sources: continental and marine. In site 2, those factors explain 89.2% of total data variance and indicate that vehicle exhaust is the main metals source in the atmosphere.
Keywords: Trace metals; Atmospheric particulate; Biogenic vanadium; Coastal upwelling; Sea salt spray; PCA analysis
Size-resolved particle deposition velocities of sub-100nm diameter particles over a forest by S.C. Pryor (pp. 6192-6200).
Despite their importance to accurate prediction of the particle ensemble and associated impacts, few empirical studies have attempted to quantify the dependence of deposition velocities ( vd) on friction velocity ( u*) and particle diameter for sub-100nm particles. Data from a pilot study conducted over a Beech forest in Denmark are used here in to test an indirect method of assessing these dependencies where particle fluxes derived using eddy covariance are conditionally sampled based on parameters of the particle size distribution. The data indicate strongly bi-directional fluxes, with almost13 of all12-h periods exhibiting upwards fluxes particularly during particle formation events. Vertical velocities for particle ensembles with number geometric mean diameter (GMD) of 20–30, 30–40, 40–50, 50–60 and 60–70nm have an approximately equal magnitude during deposition and emission periods which may imply that surface uptake does not strongly limit deposition rates of these particles. The results also indicate a marked size dependence of vd. During deposition periods the median vd for particle ensembles with a number GMD of 20–30nm is 4.5mms−1 and decreases to 1.5mms−1 for particle ensembles with a GMD of 60–70nm. The median vd for periods when the GMD was approximately 55nm is 2.7mms−1 and the mean is 4.2mms−1, which agrees well with the mean vd of 4.3mms−1 for 50nm particles over a Scots Pine forest at Hyytiälä in central Finland. Also, as in the data from Hyytiälä, the vd for GMD of 50–60nm increases markedly with u* from 1 to 1.8mms−1 at u*<0.4ms−1, to 7.5mms−1 at u*>1ms−1.
Keywords: Deposition velocity; Friction velocity; Geometric mean diameter; Aerosol particles; Forest
UV-induced NO y emissions from Scots pine: Could they originate from photolysis of deposited HNO3? by Maarit Raivonen; Boris Bonn; M. Jose Sanz MarÃa José Sanz; Timo Vesala; Markku Kulmala; Pertti Hari (pp. 6201-6213).
Production of NO y on Scots pine branch surfaces by ultraviolet radiation is observed in Hyytiälä, southern Finland. Similar irradiance-dependent NO y emissions from snow and different chamber surfaces have been observed to originate from HNO3 or nitrate photolysis. In this study, we investigate whether also the NO y emitted from pine shoots could originate from photolysis of HNO3 attached to the needle surface. We used field data of several years from Hyytiälä to test this hypothesis. The HNO3 deposition, estimated for the Hyytiälä site, had been high enough to account for the NO y emission rates observed from the chambers. We could not find the particular characteristics of the daily pattern of CO2 exchange or stomatal control reflected in the NO y flux. When a pine branch was rinsed, which reduced the amount of water-soluble nitrogen compounds (e.g., HNO3, nitrates and HONO) from the needle surface, NO y emissions from that branch decreased compared to another non-rinsed branch. Therefore, we conclude that the results support the hypothesis and that HNO3 photolysis on plant surfaces needs to be taken into account both from air chemistry and plant sciences point of view.
Keywords: Scots pine; Nitrogen oxides; Chamber; Gas exchange; Ultraviolet
Dynamics of fine particles and photo-oxidants in the Eastern Mediterranean (SUB-AERO) by M. Lazaridis; K. Eleftheriadis; J. Smolik; I. Colbeck; G. Kallos; Y. Drossinos; V. Zdimal; Z. Vecera; N. Mihalopoulos; P. Mikuska; C. Bryant; C. Housiadas; A. Spyridaki; Marina Astitha; V. Havranek (pp. 6214-6228).
As part of the European project SUB-AERO, comprehensive aerosol and gaseous pollutant measurement campaigns were performed at the Finokalia station (July 2000 and January 2001) on the island of Crete (Greece) in combination with boat measurements in the eastern part of the Mediterranean area. The measurements were performed with the participation of nine European research institutions. The objective of the measurement campaigns was to evaluate and assess the spatial and temporal variability of photochemical pollutants and fine particles. The current overview paper presents the framework and main results of the measurements and modelling studies performed during the project. Extensive measurements of gaseous and atmospheric-aerosol physical, chemical and optical characteristics were performed during the measurement campaigns in conjunction with detailed chemical analyses of the aerosol species. Along with the experimental work mesoscale modelling, using a combination of the UAM-AERO air quality model together with the RAMS prognostic meteorological model, was used to reveal the dynamics of particulate matter and photo-oxidants. Furthermore, regional chemistry transport models were applied to determine the background and initial conditions for the mesoscale modelling.
Keywords: Particulate matter composition; Eastern Mediterranean; Mesoscale modelling
Optical properties of aerosols over the eastern Mediterranean by C. Bryant; K. Eleftheriadis; J. Smolik; V. Zdimal; N. Mihalopoulos; I. Colbeck (pp. 6229-6244).
Measurements of aerosol optical properties, size distribution and chemical composition were conducted at Finokalia, a remote coastal site on the Greek island of Crete (35°19′N, 25°40′E) during July 2000 and January 2001. During the summer campaign the total scattering coefficient,σSP, (at a wavelength of 550nm) ranged from 13 to 120Mm−1 (mean=44.2Mm−1, standard deviation=17.5) whilst during the winter it ranged from 7.22 to 37.8Mm−1 (mean=18.42Mm−1, standard deviation=6.61). A distinct diurnal variation in scattering coefficients was observed, with minima occurring during the early morning and maxima in the late afternoon during the summer and late evening during the winter. The mean value of the Ångström exponent was 1.47 during the summer and 1.28 during the winter, suggesting a larger fraction of smaller particles at the site during the summer. This was confirmed by continuous measurements of the aerosol size distribution. An analysis of the single scattering albedo suggests that there is a more absorbing fraction in the particle composition in the summer than during the winter. An investigation of air mass origins on aerosol optical properties indicated that those from Turkey and Central/Eastern Europe were highly polluted with a corresponding impact on aerosol optical properties. A linear relationship was obtained between the total scattering coefficient and both the non-sea-salt sulphate concentrations and the fine aerosol fraction.
Keywords: Aerosol optical properties; Particulate matter; Radiative forcing
Size distribution, composition and origin of the submicron aerosol in the marine boundary layer during the eastern Mediterranean “SUB-AEROâ€? experiment by K. Eleftheriadis; I. Colbeck; C. Housiadas; M. Lazaridis; N. Mihalopoulos; C. Mitsakou; Smolik J. SmolÃk; Zdimal V. ŽdÃmal (pp. 6245-6260).
A period of intensive physical and chemical aerosol characterisation measurements was held over 5 days during July 2000 as part of the European SUB-AERO experiment.. Concurrent measurements were performed at the Finokalia remote coastal site on the island of Crete (Greece) and onboard the R/V “ Aegaeon� which cruised in south part of the Aegean Sea northwards of Crete. The objective of the study was to investigate the spatial and temporal variability of microphysical parameters of the submicron aerosol and their dependence on airmass origin and chemical composition. The results reflect the submicron aerosol properties during airmass transport from the north including Europe and the Balkans and are in line with other studies on the aerosol properties of polluted continental air entering the marine boundary layer (MBL). Concentrations of submicron particulate matter (PM) mass were relatively higher at sea (20μgm−3) compared to the coastal site (16μgm−3). Concentrations of both organic carbon and sulphate, being the major water soluble component, were also higher at sea than at land. The high concentrations of ammonium and those of the water soluble organics, such as oxalate, can be attributed to emissions from mainland forest fires. The submicron aerosol number size distribution was unimodal with mobility mean diameters ( dg) ranging from 98 to 144μm and standard deviations ( σg) from 1.56 to 1.9. Aerosol number concentrations at Finokalia were at least 50% lower especially when R/V Aegaeon sampled polluted air, but the modal parameters of the size distribution were very similar ( dg: 111–120, σg: 1.55–1.91). The surface MBL, under these conditions, was an aerosol rich environment where aerosol particles were transported both by the surface wind, advected from higher layers, chemically processed by interactions with gaseous precursors and physically altered by water vapour. The number to volume ratio for the submicrometer aerosol fraction reflected the effect of these mechanisms on the size distribution.
Keywords: Particulate matter composition; Eastern Mediterranean; Fine aerosol; Black carbon; Size distribution
Modelling and evaluation of size-resolved aerosol characteristics in the Eastern Mediterranean during the SUB-AERO project by A. Spyridaki; M. Lazaridis; K. Eleftheriadis; J. Smolik; N. Mihalopoulos; V. Aleksandropoulou (pp. 6261-6275).
The mesoscale air-quality modelling system UAM-AERO has been applied to study the dynamics of aerosols in the Eastern Mediterranean area. The objective of the current work is to validate the model against extensive field aerosol data for the realistic determination of the aerosol size distribution/chemical composition. The model has been studied against comprehensive aerosol size distribution data during the periods July 2000 and January 2001 at the Eastern Mediterranean area. Comparison of the model results with the field data shows that the model predicts a bimodal size distribution for the aerosol mass, which is in agreement with the experimental data, but underpredicts the total mass during the summer period, whereas the agreement for the total aerosol mass is better during the winter period. The model is capable of reproducing the size distribution characteristics of sulphate, ammonium and nitrate, but discrepancies have occurred in relation to their mass concentration during the period 26–30 July 2000. Discrepancies have also been observed in the determination of the size distribution characteristics of crustal aerosol mass and sea salt. The disagreement between the modelled results and the field data is attributed to uncertainties in the primary aerosol emissions such as sea salt and resuspended dust, and unresolved emissions from sources such as forest fires and Saharan dust episodes. It is evident that the use of the mesoscale model UAM-AERO in the Mediterranean area requires the parallel use of a regional model, which needs to incorporate emissions of Saharan dust and forest fires.
Keywords: Particulate matter size distribution; Eastern Mediterranean; Mesoscale modelling