Abstract
Abstract. In this work, impact of aerosol solar extinction on the photochemistry over eastern Europe during the 2010 wildfires episode is discussed for the period from 5 to 12 August 2010, which coincides to the peak of fire activity. The methodology is based on an online coupling between the chemistry-transport model CHIMERE (extended by an aerosol optical module) and the radiative transfer code TUV. Results of simulations indicate an important influence of the aerosol solar extinction, in terms of intensity and spatial extent, with a reduction of the photolysis rates of NO2 and O3 up to 50 % (in daytime average) along the aerosol plume transport. At a regional scale, these changes in photolysis rates lead to a 3–15 % increase in the NO2 daytime concentration and to an ozone reduction near the surface of 1–12 %. The ozone reduction is shown to occur over the entire boundary layer, where aerosols are located. Also, the total aerosol mass concentration (PM10) is shown to be decreased by 1–2 %, on average during the studied period, caused by a reduced formation of secondary aerosols such as sulfates and secondary organics (4–10 %) when aerosol impact on photolysis rates is included. In terms of model performance, comparisons of simulations with air quality measurements at Moscow indicate that an explicit representation of aerosols interaction with photolysis rates tend to improve the estimation of the near-surface concentration of ozone and nitrogen dioxide as well as the formation of inorganic aerosol species such as ammonium, nitrates and sulfates.
Highlights
For several years, it has been well recognized that air pollution of gaseous and particulate origin can have adverse health effects (Miller et al, 2012; Beelen et al, 2014)
The model underestimation is of 60–75 % due to some model deficiencies in simulating the transport of the intense aerosol plume over Moscow
It is interesting to note that the impact of the aerosol solar extinction is more pronounced for J [O3] than for J [NO2], for each day of the studied period
Summary
It has been well recognized that air pollution of gaseous and particulate origin can have adverse health effects (Miller et al, 2012; Beelen et al, 2014). The exceedance of these thresholds is evaluated from an air quality numerical forecast such as in France where the regional chemistry-transport model CHIMERE (Menut et al, 2013) is used in the French national air quality forecasting and monitoring system known as PREV’AIR (Honoré et al, 2008). ), which are formed from photo-dissociation of precursors such as nitrogen dioxide (NO2) and volatile organic compounds (VOCs) (Jenkin and Clemitshaw, 2000), are of particular interest for air quality monitoring (Honoré et al, 2008) due to their negative impacts on both environment and human health (Amin, 2014; Hunova et al, 2014). The key parameter that governs the photo-dissociation of photochemical precursors in the atmosphere is the photolysis rate, which mainly depends on the available actinic flux (Seinfeld and Pandis, 2006). Wai and Tanner (2010) showed, by using a combination of Published by Copernicus Publications on behalf of the European Geosciences Union
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