Chemical analyses and geographical origins of residential attic dust in central South Africa

Abstract

Particulate matter (PM) is a widely used air pollution proxy indicator. Substantial supporting evidence links exposure to PM with adverse health effects. This study compares long-term accumulated particulate matter's chemical and morphological properties and possible sources from various locations in Bloemfontein, Kimberley, and the Vanderbijlpark residential areas. As the first study of this kind in South Africa, dust samples were collected from the attics of houses built over fifty years ago. Potential area PM sources located far away were identified by analyzing every tenth year from 1972 to 2022, representing five decades of backward Long-Range Transport (LRT) clusters, for air masses that passed the sampling sites. Several PM sources were determined by combining LRT geographic origin studies and chemical analyses of collected samples. Elemental compositions of samples were determined by the use of scanning electron microscopy, and electron dispersive spectroscopy. Mineral content was determined by X-ray fluorescence, X-ray diffraction, and electron probe microscopy techniques, revealing airborne sources that moved significantly due to climate change, over the 5-decade period. Potential area PM sources located far away included various South African provinces, neighboring states to the north, and the Atlantic and Indian Oceans west and east of South Africa. Elemental composition included: Al, Ag, C, Ca, Cl, Cu, Fe, K, Mg, Mn, Na, O, S, Si, Ti, and Zn. Mineral composition included SiO2, TiO2, Al2O3, Fe2O3, MnO, MgO, CaO, Na2O, K2O, P2O5, SO3, Cr2O3 and NiO. The most prominent minerals found were quarts and plagioclase. While considering relevant mining activities, combining methods allowed a successful study of change in source distribution associated with climate change.