SO/sub 2/ flux to a falling raindrop in a polluted atmosphere

An analysis of the transfer of sulfur dioxide to droplets is presented. A physicochemical model for the accumulation of sulfur species in raindrops is developed in which account is taken of the mass transfer of sulfur dioxide and ozone into ideal raindrops (of radii 0.1 and 0.001 cm) and of the oxidation of SO/sub 2/ in the presence of O/sub 3/ and catalysts. Ignoring charge separation, we use equations which describe the time development of chemical species within droplets. The model predicts the formation of sulfate due to ozone, catalytic oxidation, and ammonia. The expressions provide an analysis of rain composition as a function of fall distance for various atmospheric conditions of pH, SO/sub 2/, O/sub 3/, and catalyst concentration and fall velocities. After a fall distance 2,000 meters, the concentration of sulfate in the droplets is a function of droplet radius and background pollutant concentrations. The calculations indicate that the pH of the precipitation varies from 3.9 to 6.4 in polluted regions and is independent of the initial pH of the droplet. However, for the large droplet and initial pH of 10, the droplet remained basic.