Modelling PM10 aerosol data from the Qalabotjha low-smoke fuels macro-scale experiment in South Africa

Abstract

D-grade (i.e. poor quality) coal is widely used for household cooking and heating purposes by lower-income urban communities in South Africa. The smoke from the combustion of coal has had a severe impact on the health of society in the townships and cities. To alleviate this escalating problem, the Department of Minerals and Energy of South Africa evaluated low-smoke fuels as an alternative source of energy. The technical and social implications of such fuels were investigated in the course of the Qalabotjha Low-Smoke Fuels Macro-Scale Experiment. Three low-smoke fuels (Chartech, African Fine Carbon [AFC], and Flame Africa) were tested in Qalabotjha during the winter of 1997. This paper examines diurnal variations of PM10 (particles with aerodynamic diameters less than 10 mu m) concentrations at the clinic site in Qalabotjha. Both the fuel type and the wind were found to have an effect on the air particulate concentrations. This paper demonstrates how continuous PM10 data together with wind measurements can be modelled. Pronounced dual-peak diurnal variations of PM10 concentrations were found in winter's stable atmosphere with 30-min PM10 levels often exceeding 1000 mu g/m(3) around 07:00-08:00 h in the morning and around 18:00 h in the evening. PM10 diurnal variations coincided with surface radiation inversions and residential cooking activity, suggesting that human exposure is confined to a very localized environment. On windy days, very low PM10 concentrations with very little to no diurnal variations were found. Much of the locally generated cooking emissions may have been diluted by dispersion and transport. An exponential model that allowed for all measured particulate concentrations to be re-calculated to 'zero wind' values was created to estimate the impact of D-grade coal combustion. From analysis of variance (ANOVA) calculations on the 'zero wind' concentrations, it is concluded that the combustion of low-smoke fuels would make a significant improvement to the air quality in Qalabotjha.