Photochemical evolution of submicron aerosol chemical composition in the Tokyo megacity region in summer

Abstract. During the Carbonaceous Aerosols and Radiative Effects Study (CARES), activation fraction of size-resolved aerosol particles and aerosol chemical composition were characterized at the T1 site (~60 km downwind of Sacramento, California) from 10 June to 28 June 2010. The hygroscopicity of CCN-active particles (κCCN) with diameter from 100 to 171 nm, derived from the size-resolved activated fraction, varied from 0.10 to 0.21, with an average of 0.15, which was substantially lower than that proposed for continental sites in earlier studies. The low κCCN value was due to the high organic volume fraction, averaged over 80% at the T1 site. The derived κCCN exhibited little diurnal variation, consistent with the relatively constant organic volume fraction observed. At any time, over 90% of the size selected particles with diameter between 100 and 171 nm were CCN active, suggesting most particles within this size range were aged background particles. Due to the large organic volume fraction, organic hygroscopicity (κorg) strongly impacted particle hygroscopicity and therefore calculated CCN concentration. For vast majority of the cases, an increase of κorg from 0.03 to 0.18, which are within the typical range, doubled the calculated CCN concentration. Organic hygroscopicity was derived from κCCN and aerosol chemical composition, and its variations with the fraction of total organic mass spectral signal at m/z 44 (f44) and O : C were compared to results from previous studies. Overall, the relationships between κorg and f44 are quite consistent for organic aerosol (OA) observed during field studies and those formed in smog chamber. Compared to the relationship between κorg and f44, the relationship between κorg and O : C exhibits more significant differences among different studies, suggesting κorg may be better parameterized using f44. A least squares fit yielded κorg = 2.04 (± 0.07) × f44 − 0.11 (± 0.01) with the Pearson R2 value of 0.71. One possible explanation for the stronger correlation between κorg and f44 is that the m/z 44 signal (mostly contributed by the CO2+ ion) is more closely related to organic acids, which may dominate the overall κorg due to their relatively high water solubility and hygroscopicity.

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Chemical composition, concentration and source apportionment of atmospheric submicron aerosol particles at urban and background sites

Lithuanian Journal of Physics ◽

10.3952/physics.v54i4.3013 ◽

2015 ◽

Vol 54 (4) ◽

Cited By ~ 1

Author(s):

Ernesta Meinorė ◽

Jonas Šakalys ◽

Kęstutis Kvietkus

Keyword(s):

Chemical Composition ◽

Source Apportionment ◽

Aerosol Particles ◽

Submicron Aerosol

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Characterization of aerosol chemical composition from urban pollution in Brazil and its possible impacts on the aerosol hygroscopicity and size distribution

Atmospheric Environment ◽

10.1016/j.atmosenv.2019.01.024 ◽

2019 ◽

Vol 202 ◽

pp. 149-159 ◽

Cited By ~ 2

Author(s):

Gerson P. Almeida ◽

Antônio T. Bittencourt ◽

Marçal S. Evangelista ◽

Marcelo S. Vieira-Filho ◽

Adalgiza Fornaro

Keyword(s):

Chemical Composition ◽

Size Distribution ◽

Urban Pollution ◽

Aerosol Hygroscopicity ◽

Aerosol Chemical Composition

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Towards an online-coupled chemistry-climate model: evaluation of trace gases and aerosols in COSMO-ART

Geoscientific Model Development ◽

10.5194/gmd-4-1077-2011 ◽

2011 ◽

Vol 4 (4) ◽

pp. 1077-1102 ◽

Cited By ~ 63

Author(s):

C. Knote ◽

D. Brunner ◽

H. Vogel ◽

J. Allan ◽

A. Asmi ◽

...

Keyword(s):

Chemical Composition ◽

Size Distribution ◽

Urban Areas ◽

Climate Model ◽

Transport Model ◽

Climate Impacts ◽

Chemistry Transport Model ◽

Pm2.5 And Pm10 ◽

Phase Chemistry ◽

Aerosol Chemical Composition

Abstract. The online-coupled, regional chemistry transport model COSMO-ART is evaluated for periods in all seasons against several measurement datasets to assess its ability to represent gaseous pollutants and ambient aerosol characteristics over the European domain. Measurements used in the comparison include long-term station observations, satellite and ground-based remote sensing products, and complex datasets of aerosol chemical composition and number size distribution from recent field campaigns. This is the first time these comprehensive measurements of aerosol characteristics in Europe are used to evaluate a regional chemistry transport model. We show a detailed analysis of the simulated size-resolved chemical composition under different meteorological conditions. Mean, variability and spatial distribution of the concentrations of O3 and NOx are well reproduced. SO2 is found to be overestimated, simulated PM2.5 and PM10 levels are on average underestimated, as is AOD. We find indications of an overestimation of shipping emissions. Time evolution of aerosol chemical composition is captured, although some biases are found in relative composition. Nitrate aerosol components are on average overestimated, and sulfates underestimated. The accuracy of simulated organics depends strongly on season and location. While strongly underestimated during summer, organic mass is comparable in spring and autumn. We see indications for an overestimated fractional contribution of primary organic matter in urban areas and an underestimation of SOA at many locations. Aerosol number concentrations compare well with measurements for larger size ranges, but overestimations of particle number concentration with factors of 2–5 are found for particles smaller than 50 nm. Size distribution characteristics are often close to measurements, but show discrepancies at polluted sites. Suggestions for further improvement of the modeling system consist of the inclusion of a revised secondary organic aerosols scheme, aqueous-phase chemistry and improved aerosol boundary conditions. Our work sets the basis for subsequent studies of aerosol characteristics and climate impacts with COSMO-ART, and highlights areas where improvements are necessary for current regional modeling systems in general.

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