Long-Range Transport and Transformation of SO2 and Sulfate

摘要

Technical descriptions and computer programs are presented for two models that calculate long-range transport, diffusion, transformation of SO2 to sulfate, and dry and precipitation deposition of initially emitted SO2. One model treats the mixing layer height as constant; the other (at the expense of computer time) varies the mixing layer height diurnally and tracks pollutants in three layers--the daytime mixing layer, the nocturnal ground-based stable layer, and the daytime mixed layer that remains above the nocturnal stable layer. Application of the multi-layer model over a region encompassing the Ohio River Basin produced patterns of SO2 and sulfate concentrations that are statistically correlated with observed concentrations. An empirical formula for the transformation rate of SO2 to sulfate is derived. Using a cumulus cloud model, results showed that sulfate aerosol capture by cloud water through microphysical processes is sufficient to produce observed levels of sulfate in rain water.