Investigation of nanomaterial and hazardous emissions at coal-fired power stations in Mpumalanga, South Africa

Abstract

Coal-fired power stations remain the main source of electricity generation in South Africa. The combustion of coal creates fly ash and slag, and increases emissions of particulate matter, which is composed of nano-sized materials. In this study, we investigated nanoparticle emissions from coal-fired power stations. Soil samples were collected at 500 m and 1 km radii from Matla and Kriel power stations. The soil samples were examined using scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray fluorescence (XRF) spectrometry. SEM images confirmed polydisperse particles in the form of semi-spherical, semi-oval, irregular-shaped and amorphous particles in dust and soil samples. The particle size range was 4–150 nm. Carbon sheet–metal oxide composites of As, Zn, Cu, Cr, Ni and V were observed. We found that coal-fired power stations are a potential source of nano-pollution, pointing to elevated human and environmental exposure around such sites. Currently, there are no environmental limits for nanomaterials due to the lack of robust risk assessment; however, this study suggests that coal-fired power stations may be hotspots that could be used as priority cases to examine the environmental implications of nano-pollution.