Dry deposition of sulphur on the Mpumalanga highveld: a pilot study using the inferential method

Abstract

A pilot study which uses the inferential method to estimate dry deposition of sulphur on the central Mpumalanga highveld is discussed in this paper. Ambient concentrations of sulphur dioxide, particulates and micro-meteorological measurements from 2 two-week field experiments, one in winter and the other in summer are used as input to the NOAA/ATDD inferential model. The majority of dry deposited sulphur; 80% and 82% in winter and summer respectively, come from SO2 during the daytime. Smaller contributions come from SO2 at night and from particulates during the day in both seasons. The contribution to the total dry deposition sulphur load by particulates at night appears to be negligible. Assuming that sulphur precipitation for the two monitoring periods represents a full year then a dry deposition rate of 8.22 kg S ha(-1) yr(-1), which exceeds the wet deposition rate of 5.7 kg S ha(-1) yr(-1), is recorded for the central Mpumalanga highveld.