A simplified model of predicting chemical SO 2 absorption by single freely falling raindrops with internal circulation in the atmosphere is developed in the present study. By multiplying a modification factor α into the model of interfacial velocity established from creeping flow, it is found that the relative error between the simplified model and the two-phase simulation method is less than 4%. Accordingly, the simplified model enables us to simulate the atmospheric SO 2 absorption process with less computational effort and without losing accuracy. The simulated results indicate that the dissociation of H 2SO 3 governs the mass transfer process and the concentration of HSO 3 - is by far larger than those of SO 3 2- and H 2SO 3. As a result, the chemical absorption takes a much longer period of time to achieve the uptake process. Specifically, for the raindrop radius in the range of 200-500 μm, the absorption time of chemical absorption is larger than that of physical absorption by the factors of 70-290. From the perspective of characteristic time, mass diffusion is the controlling mechanism for SO 2 absorption. When chemical absorption is carried out, the absorption period is 28-33 folds of the characteristic time of mass diffusion, implying that the former is always larger than the latter by over an order of magnitude.
All Science Journal Classification (ASJC) codes
- Environmental Chemistry