ASSESSMENT OF WET AND DRY DEPOSITION OF SO2 ATTRIBUTABLE TO A SULFURIC-ACID PLANT AT ANNABA, ALGERIA

Acid deposition was evaluated around a sulfuric acid plant situated ne ar Annaba in the east of Algeria. According to the local meteorologica l station of Annaba, the precipitating and the nonprecipitating clouds over the area surrounding the plant at a radius of 10 km are too high to be reached by SO2-containing plumes. Removal by wet deposition is thus minimised by switching off rain scavenging of aerosol sulfate and the transfer of pollutants from cloud droplets to precipitation. Negl ecting below-cloud aerosol sulfate scavenging by rain, the only proces s allowed is the aqueous-phase chemistry of SO2 scavenged between clou d base and the earth. The available meteorological data from the meteo rological station of Annaba was used to compute the pH in rainfall as well as the annual impacts of the wet and dry components. The computat ion of both deposition rates was based on the 1995 meteorological data . Precipitation coinciding with the plume was found to be acidic with a pH ranging from 4.2 to 4.7. However, wet acid deposition, while diff ering from one season to another, is negligible if compared to the wet critical sulfate loading of 20 kg ha(-1) y(-1). The maximum wet depos ition of SO2 predicted was 0.41 kg ha(-1) y(-1) within sector 25, whil e the maximum amount of dry deposition was 14.7 10(3) kg ha(-1) y(-1). Dry deposition accounted for more than 99.99% of the total deposition in the 20 sectors considered east of the coast. (C) 1998 Elsevier Sci ence Ltd.