Dry deposition of sulphur over eastern South Africa

Dry deposition of sulphur is estimated in three climatic regions of Mpumalanga, South Africa, using the inferential method. Data from June 1996 to May 1997 are used at Elandsfontein and Palmer on the industrialised highveld, as well as data from two-week monitoring campaigns in the late-winter and in summer at Blyde on the eastern escarpment and at Skukuza in the lowveld. Total dry deposition rates for sulphur range across the Mpumalanga highveld from 13.1 kg ha-1 a-1 at Elandsfontein to 3.1 kg ha-1 a-1 at Palmer, are associated with the strong SO2 gradient between the two stations and are attributed mostly to dry deposition of sulphur from SO2. The deposition flux varies less from Palmer eastward over the escarpment and the lowveld and ranges from 3.9 kg S ha-1 a-1 at Blyde to 3.3 kg S ha-1 a-1 at Skukuza. A weak seasonal variation in sulphur dry deposition flux occurs on the central highveld with the maximum in summer and the minimum in winter. Conversely, the maximum sulphur dry deposition on the periphery of the highveld, the escarpment and in the lowveld occurs in winter with the minimum in summer. More than 80% of the dry deposition of sulphur in Mpumalanga occurs during daytime in all seasons