Understanding and improving model representation of aerosol optical properties for a Chinese haze event measured during KORUS-AQ

Abstract. KORUS-AQ was an international cooperative air quality field study in South Korea that measured local and remote sources of air pollution affecting the Korean peninsula during May–June 2016. Some of the largest aerosol mass concentrations were measured during a Chinese haze transport event (May 24th). Air quality forecasts using the WRF-Chem model with aerosol optical depth (AOD) data assimilation captured AOD during this pollution episode but over-predicted surface particulate matter concentrations, especially PM2.5 often by a factor of 2 or larger. Analysis revealed multiple sources of model deficiency related to the calculation of optical properties from aerosol mass that explain these discrepancies. Using in-situ observations of aerosol size and composition as inputs to the optical properties calculations showed that using a low resolution size bin representation under-estimates the efficiency at which aerosols scatter and absorb light (mass extinction efficiency). Besides using finer-resolution size bins, it was also necessary to increase the refractive indices and hygroscopicity of select aerosol species within the range of values reported in the literature to achieve consistency with measured values of mass/volume extinction efficiencies and light scattering enhancement factor (f(RH)) due to aerosol hygroscopic growth. Furthermore, evaluation of optical properties obtained using modeled aerosol properties revealed the inability of sectional and modal aerosol representations in WRF-Chem to properly reproduce the observed size distribution, with the models displaying a much wider accumulation mode. Other model deficiencies included an under-estimate of organic aerosol density and an over-prediction of the fractional contribution of inorganic aerosols other than sulfate, ammonium, nitrate, chloride and sodium (mostly dust). These results illustrate the complexity of achieving an accurate model representation of optical properties and provide potential solutions that are relevant to multiple disciplines and applications such as air quality forecasts, health-effect assessments, climate projections, solar-power forecasts, and aerosol data assimilation.

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Understanding and improving model representation of aerosol optical properties for a Chinese haze event measured during KORUS-AQ

Atmospheric Chemistry and Physics ◽

10.5194/acp-20-6455-2020 ◽

2020 ◽

Vol 20 (11) ◽

pp. 6455-6478 ◽

Cited By ~ 1

Author(s):

Pablo E. Saide ◽

Meng Gao ◽

Zifeng Lu ◽

Daniel L. Goldberg ◽

David G. Streets ◽

...

Keyword(s):

Optical Properties ◽

Air Quality ◽

Data Assimilation ◽

South Korea ◽

Mass Extinction ◽

Model Representation ◽

Climate Projections ◽

Extinction Efficiency ◽

Aerosol Mass ◽

Mass Extinction Efficiency

Abstract. KORUS-AQ was an international cooperative air quality field study in South Korea that measured local and remote sources of air pollution affecting the Korean Peninsula during May–June 2016. Some of the largest aerosol mass concentrations were measured during a Chinese haze transport event (24 May). Air quality forecasts using the WRF-Chem model with aerosol optical depth (AOD) data assimilation captured AOD during this pollution episode but overpredicted surface particulate matter concentrations in South Korea, especially PM2.5, often by a factor of 2 or larger. Analysis revealed multiple sources of model deficiency related to the calculation of optical properties from aerosol mass that explain these discrepancies. Using in situ observations of aerosol size and composition as inputs to the optical properties calculations showed that using a low-resolution size bin representation (four bins) underestimates the efficiency with which aerosols scatter and absorb light (mass extinction efficiency). Besides using finer-resolution size bins (8–16 bins), it was also necessary to increase the refractive indices and hygroscopicity of select aerosol species within the range of values reported in the literature to achieve better consistency with measured values of the mass extinction efficiency (6.7 m2 g−1 observed average) and light-scattering enhancement factor (f(RH)) due to aerosol hygroscopic growth (2.2 observed average). Furthermore, an evaluation of the optical properties obtained using modeled aerosol properties revealed the inability of sectional and modal aerosol representations in WRF-Chem to properly reproduce the observed size distribution, with the models displaying a much wider accumulation mode. Other model deficiencies included an underestimate of organic aerosol density (1.0 g cm−3 in the model vs. observed average of 1.5 g cm−3) and an overprediction of the fractional contribution of submicron inorganic aerosols other than sulfate, ammonium, nitrate, chloride, and sodium corresponding to mostly dust (17 %–28 % modeled vs. 12 % estimated from observations). These results illustrate the complexity of achieving an accurate model representation of optical properties and provide potential solutions that are relevant to multiple disciplines and applications such as air quality forecasts, health impact assessments, climate projections, solar power forecasts, and aerosol data assimilation.

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Ion-molecule interactions enable unexpected phase transitions in organic-inorganic aerosol

Science Advances ◽

10.1126/sciadv.abb5643 ◽

2020 ◽

Vol 6 (47) ◽

pp. eabb5643 ◽

Cited By ~ 1

Author(s):

David S. Richards ◽

Kristin L. Trobaugh ◽

Josefina Hajek-Herrera ◽

Chelsea L. Price ◽

Craig S. Sheldon ◽

...

Keyword(s):

Air Quality ◽

Inorganic Ions ◽

Climate Projections ◽

Atmospheric Models ◽

Inorganic Aerosols ◽

Low Mass ◽

Inorganic Aerosol ◽

Semi Solid ◽

Molecule Interactions ◽

Inorganic Fraction

Atmospheric aerosol particles are commonly complex, aqueous organic-inorganic mixtures, and accurately predicting the properties of these particles is essential for air quality and climate projections. The prevailing assumption is that aqueous organic-inorganic aerosols exist predominately with liquid properties and that the hygroscopic inorganic fraction lowers aerosol viscosity relative to the organic fraction alone. Here, in contrast to those assumptions, we demonstrate that increasing inorganic fraction can increase aerosol viscosity (relative to predictions) and enable a humidity-dependent gel phase transition through cooperative ion-molecule interactions that give rise to long-range networks of atmospherically relevant low-mass oxygenated organic molecules (180 to 310 Da) and divalent inorganic ions. This supramolecular, ion-molecule effect can drastically influence the phase and physical properties of organic-inorganic aerosol and suggests that aerosol may be (semi)solid under more conditions than currently predicted. These observations, thus, have implications for air quality and climate that are not fully represented in atmospheric models.

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Effects of two different biogenic emission models on modelled ozone and aerosol concentrations in Europe

10.5194/acp-2018-920 ◽

2018 ◽

Author(s):

Jianhui Jiang ◽

Sebnem Aksoyoglu ◽

Giancarlo Ciarelli ◽

Emmanouil Oikonomakis ◽

Imad El-Haddad ◽

...

Keyword(s):

Air Quality ◽

Model Performance ◽

Organic Aerosol ◽

Air Quality Model ◽

Quality Model ◽

Inorganic Aerosols ◽

Aerosol Mass ◽

Emission Models ◽

Summer Time ◽

Paul Scherrer

Abstract. Biogenic volatile organic compound (BVOC) emissions are one of the essential inputs for chemical transport models (CTMs), but their estimates are associated with large uncertainties leading to significant influences on air quality modelling. This study aims at investigating the effects of using different BVOC emission models on the performance of a CTM in simulating secondary pollutants, i.e. ozone, organic and inorganic aerosols. The European air quality was simulated for the year 2011 by the regional air quality model Comprehensive Air Quality Model with Extensions (CAMx) version 6.3, using BVOC emissions calculated by two emission models: the Paul Scherrer Institute (PSI) model and the Model of Emissions of Gases and Aerosol from Nature (MEGAN) v2.1. Comparison of isoprene and monoterpene emissions from both models showed large differences in their general amounts as well as their spatial distribution both in summer and winter. MEGAN produced more isoprene emissions by a factor of 3 while the PSI model generated three times of monoterpene emissions in summer, while there was negligible difference (~ 4 %) in sesquiterpene emissions associated with the two models. Despite the large differences in isoprene emissions (i.e. 3-fold), the resulting impact in predicted summer-time ozone proved to be minor ( 60 ppb). A much larger effect of the different BVOC emissions was found for the secondary organic aerosol (SOA) concentrations. The higher monoterpene emissions (a factor of ~ 3) by the PSI model led to higher SOA by ~ 110 % on average in summer, compared to MEGAN, improving substantially the model performance for organic aerosol (OA): the mean bias between modelled and measured OA at 8 Aerodyne aerosol chemical speciation monitor (ACSM)/Aerodyne aerosol mass spectrometer (AMS) measurement stations was reduced by 21 %–83 % in rural/remote stations. Effects on inorganic aerosols (particulate nitrate, sulphate, and ammonia) were relatively smaller (

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Tropical biomass burning smoke plume size, shape, reflectance, and age based on 2001–2009 MISR imagery of Borneo

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-11-30989-2011 ◽

2011 ◽

Vol 11 (11) ◽

pp. 30989-31030

Author(s):

C. S. Zender ◽

A. G. Krolewski ◽

M. G. Tosca ◽

J. T. Randerson

Keyword(s):

Optical Properties ◽

Air Quality ◽

Tropical Forests ◽

Optical Depth ◽

Biomass Burning ◽

Single Scattering ◽

Particle Dispersion ◽

Hygroscopic Growth ◽

Smoke Plume ◽

Plume Geometry

Abstract. Land clearing for crops and plantations and grazing results in anthropogenic burning of tropical forests and peatlands in Indonesia, where images of fire-generated aerosol plumes have been captured by the Multi-angle Imaging SpectroRadiometer (MISR) since 2001. Our modeling studies show this smoke increases atmospheric heating, and reduces regional SST and dry-season precipitation, causing a potential feedback that increases drought-stress and air quality problems during El Niño years. Here we analyze the size, shape, optical properties, and age of fire-generated plumes in Borneo from 2001–2009. Most smoke flows with the prevailing southeasterly surface winds at 3–4 m s−1, and forms ovoid plumes whose mean length, height, and cross-plume width are 41 ± 1.4 (mean ± std. error) km, 708 ± 13 m, and 27 ± 0.75% of the plume length, respectively. Borneo smoke plume heights are similar to previously reported plume heights, yet Borneo plumes are nearly three times longer than previously studied plumes, possibly due to more persistent fires and greater fuel loads in peatlands than in other tropical forests. Plume area (median 169 ± 15 km2) varies exponentially with length, though for most plumes a linear relation provides a good approximation. The MISR-estimated plume optical properties involve greater uncertainties than the geometric properties, and show patterns consistent with smoke aging. Optical depth increases by 15–25% in the down-plume direction, consistent with hygroscopic growth and nucleation overwhelming the effects of particle dispersion. Both particle single-scattering albedo and top-of-atmosphere albedo peak about halfway down-plume, at values about 3% and 10% greater than at the origin, respectively. The initially oblong plumes become brighter and more circular with time, increasingly resembling smoke clouds. Wind speed does not explain a significant fraction of the variation in plume geometry. We provide a parameterization of plume shape that can help atmospheric models estimate the effects of plumes on weather, climate, and air quality. Plume age, the age of smoke furthest down-plume, is lognormally distributed with a median of 2.8 ± 0.3 h, significantly different than median ages reported in other studies. Intercomparison of our results with previous studies shows that the shape, height, optical depth, and lifetime characteristics reported for tropical biomass burning plumes on three continents are dissimilar and distinct from the same characteristics of wildfire plumes from the extratropics.

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Effects of two different biogenic emission models on modelled ozone and aerosol concentrations in Europe

Atmospheric Chemistry and Physics ◽

10.5194/acp-19-3747-2019 ◽

2019 ◽

Vol 19 (6) ◽

pp. 3747-3768 ◽

Cited By ~ 10

Author(s):

Jianhui Jiang ◽

Sebnem Aksoyoglu ◽

Giancarlo Ciarelli ◽

Emmanouil Oikonomakis ◽

Imad El-Haddad ◽

...

Keyword(s):

Air Quality ◽

Model Performance ◽

Organic Aerosol ◽

Air Quality Model ◽

Quality Model ◽

Mass Spectrometers ◽

Inorganic Aerosols ◽

Aerosol Mass ◽

Emission Models ◽

Paul Scherrer

Abstract. Biogenic volatile organic compound (BVOC) emissions are one of the essential inputs for chemical transport models (CTMs), but their estimates are associated with large uncertainties, leading to significant influence on air quality modelling. This study aims to investigate the effects of using different BVOC emission models on the performance of a CTM in simulating secondary pollutants, i.e. ozone, organic, and inorganic aerosols. European air quality was simulated for the year 2011 by the regional air quality model Comprehensive Air Quality Model with Extensions (CAMx) version 6.3, using BVOC emissions calculated by two emission models: the Paul Scherrer Institute (PSI) model and the Model of Emissions of Gases and Aerosol from Nature (MEGAN) version 2.1. Comparison of isoprene and monoterpene emissions from both models showed large differences in their general amounts, as well as their spatial distribution in both summer and winter. MEGAN produced more isoprene emissions by a factor of 3 while the PSI model generated 3 times the monoterpene emissions in summer, while there was negligible difference (∼4 %) in sesquiterpene emissions associated with the two models. Despite the large differences in isoprene emissions (i.e. 3-fold), the resulting impact in predicted summertime ozone proved to be minor (<10 %; MEGAN O3 was higher than PSI O3 by ∼7 ppb). Comparisons with measurements from the European air quality database (AirBase) indicated that PSI emissions might improve the model performance at low ozone concentrations but worsen performance at high ozone levels (>60 ppb). A much larger effect of the different BVOC emissions was found for the secondary organic aerosol (SOA) concentrations. The higher monoterpene emissions (a factor of ∼3) by the PSI model led to higher SOA by ∼110 % on average in summer, compared to MEGAN, and lead to better agreement between modelled and measured organic aerosol (OA): the mean bias between modelled and measured OA at nine measurement stations using Aerodyne aerosol chemical speciation monitors (ACSMs) or Aerodyne aerosol mass spectrometers (AMSs) was reduced by 21 %–83 % at rural or remote stations. Effects on inorganic aerosols (particulate nitrate, sulfate, and ammonia) were relatively small (<15 %).

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The impacts of aerosol loading, composition, and water uptake on aerosol extinction variability in the Baltimore–Washington, D.C. region

Atmospheric Chemistry and Physics ◽

10.5194/acp-16-1003-2016 ◽

2016 ◽

Vol 16 (2) ◽

pp. 1003-1015 ◽

Cited By ~ 18

Author(s):

A. J. Beyersdorf ◽

L. D. Ziemba ◽

G. Chen ◽

C. A. Corr ◽

J. H. Crawford ◽

...

Keyword(s):

Optical Properties ◽

Air Quality ◽

Relative Humidity ◽

Spatial Variability ◽

Black Carbon ◽

Aerosol Extinction ◽

Diurnal Variability ◽

Aerosol Loading ◽

Aerosol Mass ◽

Aerosol Hygroscopicity

Abstract. In order to utilize satellite-based aerosol measurements for the determination of air quality, the relationship between aerosol optical properties (wavelength-dependent, column-integrated extinction measured by satellites) and mass measurements of aerosol loading (PM2.5 used for air quality monitoring) must be understood. This connection varies with many factors including those specific to the aerosol type – such as composition, size, and hygroscopicity – and to the surrounding atmosphere, such as temperature, relative humidity (RH), and altitude, all of which can vary spatially and temporally. During the DISCOVER-AQ (Deriving Information on Surface conditions from Column and Vertically Resolved Observations Relevant to Air Quality) project, extensive in situ atmospheric profiling in the Baltimore, MD–Washington, D.C. region was performed during 14 flights in July 2011. Identical flight plans and profile locations throughout the project provide meaningful statistics for determining the variability in and correlations between aerosol loading, composition, optical properties, and meteorological conditions. Measured water-soluble aerosol mass was composed primarily of ammonium sulfate (campaign average of 32 %) and organics (57 %). A distinct difference in composition was observed, with high-loading days having a proportionally larger percentage of sulfate due to transport from the Ohio River Valley. This composition shift caused a change in the aerosol water-uptake potential (hygroscopicity) such that higher relative contributions of inorganics increased the bulk aerosol hygroscopicity. These days also tended to have higher relative humidity, causing an increase in the water content of the aerosol. Conversely, low-aerosol-loading days had lower sulfate and higher black carbon contributions, causing lower single-scattering albedos (SSAs). The average black carbon concentrations were 240 ng m−3 in the lowest 1 km, decreasing to 35 ng m−3 in the free troposphere (above 3 km). Routine airborne sampling over six locations was used to evaluate the relative contributions of aerosol loading, composition, and relative humidity (the amount of water available for uptake onto aerosols) to variability in mixed-layer aerosol extinction. Aerosol loading (dry extinction) was found to be the predominant source, accounting for 88 % on average of the measured spatial variability in ambient extinction, with lesser contributions from variability in relative humidity (10 %) and aerosol composition (1.3 %). On average, changes in aerosol loading also caused 82 % of the diurnal variability in ambient aerosol extinction. However on days with relative humidity above 60 %, variability in RH was found to cause up to 62 % of the spatial variability and 95 % of the diurnal variability in ambient extinction. This work shows that extinction is driven to first order by aerosol mass loadings; however, humidity-driven hydration effects play an important secondary role. This motivates combined satellite–modeling assimilation products that are able to capture these components of the aerosol optical depth (AOD)–PM2.5 link. Conversely, aerosol hygroscopicity and SSA play a minor role in driving variations both spatially and throughout the day in aerosol extinction and therefore AOD. However, changes in aerosol hygroscopicity from day to day were large and could cause a bias of up to 27 % if not accounted for. Thus it appears that a single daily measurement of aerosol hygroscopicity can be used for AOD-to-PM2.5 conversions over the study region (on the order of 1400 km2). This is complimentary to the results of Chu et al. (2015), who determined that the aerosol vertical distribution from "a single lidar is feasible to cover the range of 100 km" in the same region.

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Urban Air Quality Modeling Using Low-Cost Sensor Network and Data Assimilation in the Aburrá Valley, Colombia

Atmosphere ◽

10.3390/atmos12010091 ◽

2021 ◽

Vol 12 (1) ◽

pp. 91

Author(s):

Santiago Lopez-Restrepo ◽

Andres Yarce ◽

Nicolás Pinel ◽

O.L. Quintero ◽

Arjo Segers ◽

...

Keyword(s):

Air Quality ◽

Data Assimilation ◽

Transport Model ◽

Cost Model ◽

Low Cost ◽

Model Performance ◽

Monitoring Network ◽

Correlation Factor ◽

Chemical Transport Model ◽

High Quality

The use of low air quality networks has been increasing in recent years to study urban pollution dynamics. Here we show the evaluation of the operational Aburrá Valley’s low-cost network against the official monitoring network. The results show that the PM2.5 low-cost measurements are very close to those observed by the official network. Additionally, the low-cost allows a higher spatial representation of the concentrations across the valley. We integrate low-cost observations with the chemical transport model Long Term Ozone Simulation-European Operational Smog (LOTOS-EUROS) using data assimilation. Two different configurations of the low-cost network were assimilated: using the whole low-cost network (255 sensors), and a high-quality selection using just the sensors with a correlation factor greater than 0.8 with respect to the official network (115 sensors). The official stations were also assimilated to compare the more dense low-cost network’s impact on the model performance. Both simulations assimilating the low-cost model outperform the model without assimilation and assimilating the official network. The capability to issue warnings for pollution events is also improved by assimilating the low-cost network with respect to the other simulations. Finally, the simulation using the high-quality configuration has lower error values than using the complete low-cost network, showing that it is essential to consider the quality and location and not just the total number of sensors. Our results suggest that with the current advance in low-cost sensors, it is possible to improve model performance with low-cost network data assimilation.

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Aerosol chemical and optical properties over the Paris area within ESQUIF project

Atmospheric Chemistry and Physics ◽

10.5194/acp-6-3257-2006 ◽

2006 ◽

Vol 6 (11) ◽

pp. 3257-3280 ◽

Cited By ~ 29

Author(s):

A. Hodzic ◽

R. Vautard ◽

P. Chazette ◽

L. Menut ◽

B. Bessagnet

Keyword(s):

Optical Properties ◽

Secondary Organic Aerosols ◽

Organic Aerosols ◽

Dust Particles ◽

Aerosol Size Distribution ◽

Aerosol Composition ◽

Aerosol Mass ◽

Coarse Mode ◽

Paris Area ◽

Flight Trajectories

Abstract. Aerosol chemical and optical properties are extensively investigated for the first time over the Paris Basin in July 2000 within the ESQUIF project. The measurement campaign offers an exceptional framework to evaluate the performances of the chemistry-transport model CHIMERE in simulating concentrations of gaseous and aerosol pollutants, as well as the aerosol-size distribution and composition in polluted urban environments against ground-based and airborne measurements. A detailed comparison of measured and simulated variables during the second half of July with particular focus on 19 and 31 pollution episodes reveals an overall good agreement for gas-species and aerosol components both at the ground level and along flight trajectories, and the absence of systematic biases in simulated meteorological variables such as wind speed, relative humidity and boundary layer height as computed by the MM5 model. A good consistency in ozone and NO concentrations demonstrates the ability of the model to reproduce the plume structure and location fairly well both on 19 and 31 July, despite an underestimation of the amplitude of ozone concentrations on 31 July. The spatial and vertical aerosol distributions are also examined by comparing simulated and observed lidar vertical profiles along flight trajectories on 31 July and confirm the model capacity to simulate the plume characteristics. The comparison of observed and modeled aerosol components in the southwest suburb of Paris during the second half of July indicates that the aerosol composition is rather correctly reproduced, although the total aerosol mass is underestimated by about 20%. The simulated Parisian aerosol is dominated by primary particulate matter that accounts for anthropogenic and biogenic primary particles (40%), and inorganic aerosol fraction (40%) including nitrate (8%), sulfate (22%) and ammonium (10%). The secondary organic aerosols (SOA) represent 12% of the total aerosol mass, while the mineral dust accounts for 8%. The comparison demonstrates the absence of systematic errors in the simulated sulfate, ammonium and nitrates total concentrations. However, for nitrates the observed partition between fine and coarse mode is not reproduced. In CHIMERE there is a clear lack of coarse-mode nitrates. This calls for additional parameterizations in order to account for the heterogeneous formation of nitrate onto dust particles. Larger discrepancies are obtained for the secondary organic aerosols due to both inconsistencies in the SOA formation processes in the model leading to an underestimation of their mass and large uncertainties in the determination of the measured aerosol organic fraction. The observed mass distribution of aerosols is not well reproduced, although no clear explanation can be given.

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Organic aerosol source apportionment by offline-AMS over a full year in Marseille

10.5194/acp-2017-54 ◽

2017 ◽

Cited By ~ 2

Author(s):

Carlo Bozzetti ◽

Imad El Haddad ◽

Dalia Salameh ◽

Kaspar Rudolf Daellenbach ◽

Paola Fermo ◽

...

Keyword(s):

Particulate Matter ◽

Air Quality ◽

Mediterranean Sea ◽

Source Apportionment ◽

Organic Aerosol ◽

Aerodynamic Diameter ◽

Aerosol Mass Spectrometer ◽

Aerosol Mass ◽

Aerosol Source

Abstract. We investigated the seasonal trends of OA sources affecting the air quality of Marseille (France) which is the largest harbor of the Mediterranean Sea. This was achieved by measurements of nebulized filter extracts using an aerosol mass spectrometer (offline-AMS). PM2.5 (particulate matter with an aerodynamic diameter

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Relationship between the Optical Properties and Chemical Composition of Urban Aerosol Particles in Lithuania

Advances in Meteorology ◽

10.1155/2018/8674173 ◽

2018 ◽

Vol 2018 ◽

pp. 1-10 ◽

Cited By ~ 1

Author(s):

Julija Pauraite ◽

Kristina Plauškaitė ◽

Vadimas Dudoitis ◽

Vidmantas Ulevicius

Keyword(s):

Optical Properties ◽

Chemical Composition ◽

Organic Aerosol ◽

Single Scattering ◽

Chemical Compositions ◽

Spectra Analysis ◽

Average Value ◽

Aerosol Mass ◽

In Situ Investigation

In situ investigation results of aerosol optical properties (absorption and scattering) and chemical composition at an urban background site in Lithuania (Vilnius) are presented. Investigation was performed in May-June 2017 using an aerosol chemical speciation monitor (ACSM), a 7-wavelength Aethalometer and a 3-wavelength integrating Nephelometer. A positive matrix factorisation (PMF) was used for the organic aerosol mass spectra analysis to characterise the sources of ambient organic aerosol (OA). Five OA factors were identified: hydrocarbon-like OA (HOA), biomass-burning OA (BBOA), more and less oxygenated OA (LVOOA and SVOOA, respectively), and local hydrocarbon-like OA (LOA). The average absorption (at 470 nm) and scattering (at 450 nm) coefficients during the entire measurement campaign were 16.59 Mm−1 (standard deviation (SD) = 17.23 Mm−1) and 29.83 Mm−1 (SD = 20.45 Mm−1), respectively. Furthermore, the absorption and scattering Angström exponents (AAE and SAE, respectively) and single-scattering albedo (SSA) were calculated. The average AAE value at 470/660 nm was 0.97 (SD = 0.16) indicating traffic-related black carbon (BCtr) dominance. The average value of SAE (at 450/700 nm) was 1.93 (SD = 0.32) and could be determined by the submicron particle (PM1) dominance versus the supermicron ones (PM > 1 µm). The average value of SSA was 0.62 (SD = 0.13). Several aerosol types showed specific segregation in the SAE versus SSA plot, which underlines different optical properties due to various chemical compositions.

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