Modelling of radiation quantities and photolysis frequencies in the aqueous phase in the troposphere

Abstract

In order to provide information about photolysis frequencies in the aqueous phase for chemical transport models including wet chemistry a parameterization which can be added to gaseous-phase photolysis models was developed. The actinic fluxes inside cloud droplets are calculated on the basis of rigorous Mie theory taking into account the effect of dissolved particulate aerosol material and 10 representative cloud droplet size distributions. The results show that the actinic flux inside cloud droplets are on the average more than twice as large as compared to the interstitial air. The newly developed parameterization has been applied together with the model STAR (System for Transfer of Atmospheric Radiation). Apart from the parameters influencing gas-phase photolysis frequencies the radiation quantities inside the cloud droplets and therefore the photolysis frequencies in the aqueous phase depend on the droplet size distribution, the mixing ratio of dry aerosol particulate material to c loud droplet water, and the amount of light absorbing material in the droplets. In-droplet radical source strengths have been calculated for the most important photolytic sources of OH and SO(4- )

The role of transition metal ions on HO<sub>x</sub> radicals in clouds: a numerical evaluation of its impact on multiphase chemistry

“…Sheng (1993) made this hypothesis that the reaction between Mn 2+ and ozone produced Mn(III) and free OH radical based upon a theoretical study. Jacobsen et al (1998a) (Ruggaber et al, 1997) and we use available laboratory data (cross sections and quantum yields). Photodissociation coefficients at noon are shown in Table 6.…”

Modeling Cl2 formation from aqueous NaCl particles: Evidence for interfacial reactions and importance of Cl2 decomposition in alkaline solution

“…Calculations of the light intensity in droplets based on Mie theory provide evidence that the actinic flux in aqueous particles may be enhanced, with respect to intensity, on average by a factor of two compared to the surrounding gas [ Madronich , 1987; Ruggaber et al , 1997]. Such an enhancement would affect the photolysis rates inside the droplets.…”

Sea‐salt aerosol chemistry in coastal areas: A model study

“…Absorption cross sections for the gaseous species were assumed to be valid also in the aqueous phase for C12, HOC1, C1NO2, Br2, HOBr, and BrC1. The actinic flux in aerosol particles was enhanced by a factor of 2 following a suggestion in the literature [Ruggaber et al, 1997]. Average daytime values of the photolytic rate constants are listed in Table 12. The aqueous phase diffusion limitation for OH was treated by the method described by Schwartz [ 1986] and applied by LelieveM and Crutzen [ 1991 ].…”