Particle size and temporal characteristics of aerosol composition near coal-fired electric power plants of the eastern transvaal

Abstract

Mine-mouth power plants near the rich coal deposits of the eastern Transvaal supply most of the electricity used in the Republic of South Africa. Their emissions of particulate matter are a significant fraction of the total from all sources in the region and may be partly the cause of visibility degradation, especially in the dry winter months. A study in the vicinity of seven plants was conducted during November and December 1980 in order to demonstrate the usefulness of cascade impactors, time sequence streaker filter samplers, and elemental analysis by particle-induced x-ray emission (PIXE) for characterizing coal combustion aerosol at a nonurban site where relatively few nearby industrial or natural aerosol sources were present. Particle size analysis indicated a distribution of elements on the particles from principally coarse to principally fine (submicrometer diameter) in the sequence Ti, Al, Ca, Fe, Mn, Cr, Zn, K, Si, and S, apparently reflecting a progression of element volatility during combustion. S and Si each contributed nearly half the total fine aerosol mass (< 2 μm aerodynamic diameter) of the elements determined. The identification of a distinct fine-mode Si aerosol is a reflection of the high initial ash content of the fuel and the lower efficiency of the particulate control devices in the submicrometer range. Time sequence analysis of aerosol composition with 2-hr resolution indicated associations of concentrations with wind direction and of elements with each other that permitted distinction of individual plumes in the complex source area. © 1983 Elsevier Science Publishing Co., Inc.