Study of Interfacial Mass-transport Process of Active Species by Laser-spectroscopic Measurements

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Heterogeneous reactions of trace species, particularly active species, on aerosol surfaces play very important roles in many aspects of the atmospheric chemistry, particularly in the case of acid-rain formation in the troposphere, and in ozone depletion in the stratosphere. Gas absorption by liquids is also an essential step in the field of chemical engineering.In the present research, the transport of trace gaseous species from the bulk atmosphere across aqueous surfaces was studied in order to determin the relevant uptake coefficients. A direct observation of the distribution of the trace species in the gas phase above the surface between the gas and aqueous phase was conducted, for the first time, in an impinging flow field using a laser-spectroscopic detection technique. By analysing the experimental results and comparing them to simulation results, the applicability of the present method to obtaining the uptake coefficients was demonstrated in the case of SO_2. The uptake coefficient was strongly dependent on pH but was hardly affected by temperature. The relevant aqueous reactions were discussed.