Identifying Common Trees and Herbaceous Plants to Mitigate Particulate Matter Pollution in a Semi-Arid Mining Region of South Africa

Abstract

Plants provide long-term and sustainable solutions to mitigate particulate matter (PM) pollution in urban environments. We evaluated total, fine, coarse and large particle trapping abilities of an equal number of common trees (Carica papaya, Citrus limon, Moringa oleifera, Ozoroa paniculosa, Peltophorum africanum, Psidium guajava) and herbaceous species (Argemone ochroleuca, Catharanthus roseus, Gomphocarpus fruticosus, Ipomoea batatas, Senna italica, Tribulus terrestris) to identify dust accumulators for Sekhukhuneland, a mining–smelting region of South Africa where desertification is becoming problematic. Scanning electron microscopy techniques were used to count and measure particles and relate leaf surface micromorphology to dust accumulation. Three tree and three herbaceous species showed superior dust collection capacity (G. fruticosus > P. guajava > I. batatas > O. paniculosa > C. roseus > M. oleifera). Variations in accumulation of PM sizes were noted among these six species and between adaxial and abaxial leaf surfaces. Compared with large PM, all plants accumulated more fine and coarse fractions which are respirable and thus hazardous to human health. Leaf surface roughness, epicuticular wax and epidermal glands improved dust accumulation. The six preferred plants may serve as forerunner species to abate PM pollution in Sekhukhuneland and other arid regions facing similar climate change and pollution challenges.