Trends in composition of rain quality data from the South African interior

Trends in rainfall signatures as well in rainfall acidity are monitored as part of Eskom's commitment to the protection of the environment. This repor t discusses the analysis of data from seven sites for which seven or more y ears of rain acidity data have been recorded. Changes in signatures are aff ected by biomass burning and agricultural influences related to rainfall, a nd by prevailing winds associated with drought and normal rainfall conditio ns. Of concern is the detection of changes that can be ascribed to emission s from power-station stacks and other industrial sources, as in time these may require the implementation of expensive control technologies. The rain event data at each site were decomposed into four signatures, using factor analysis, which summarized over 70 % of the variability in the data for alm ost all sites. Similar signatures were found for all sites, these being rel ated to industrial, maritime, biomass, and soil components. Trends in these indices were evident, mainly when the biomass component was concerned. Thi s may be a result of drought when there was little veld to be burned. There was little evidence of change in the industrial components.