Chromium dust deposition on Moringa oleifera leaves harvested by local communities in Sekhukhuneland, South Africa

S. Adhikari, S.J. Siebert, A. Jordaan
Sekhukhuneland, in Limpopo, South Africa, is the cultural homeland of the Bapedi. A surfeit of native and exotic plants is used by the Bapedi for cultural, food and medicinal purposes. Although exotic to South Africa, Moringa oleifera is a popular and widely cultivated tree species in home gardens. Leaves of the species are renowned for their medicinal and nutritional value. Bapedi villages lie interspersed with chromium (Cr) and platinum mines in Sekhukhuneland, as this area holds some of the world's most valuable deposits thereof. Mining is, therefore, a major driving force behind the socio-economic development of Sekhukhuneland, but daily mining activities with associated ore transport generate and disperse large volumes of dust. These dust particles contain Cr, amongst other metals, which settle on vegetation. Potential human intake of Cr particles through contaminated useful plants is a serious health concern as Cr is a recognised human carcinogen. In general, leaves present larger aerial surfaces for dust deposition and adhesion. Leaves of cultivated M. oleifera were tested for Cr dust deposition with scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) that detected Cr (~0.16 weight %) along with other elements, e.g., calcium (~1.43 wt. %), magnesium (~1.01 wt. %), potassium (~0.85 wt. %), sulphur (~0.23 wt. %), sodium (~0.2 wt.) and iron (~0.22 wt. %). Foliar elemental analysis of samples taken from four other useful tree species from the same region also indicated Cr dust deposition, i.e., Carica papaya (~1.56 wt. %), Ozoroa paniculosa (~0.13 wt. %), Peltophorum africanum (~0.28 wt. %) and Psidium guajava (~0.15 wt. %). Findings confirm dust deposition and Cr contamination of the leaves of cultivated M. oleifera and other species in Sekhukhuneland. Further research is required to assess whether Cr pollution of useful plants threatens the well-being of local communities.
Adhikari, S., Siebert, S.J. and Jordaan, A. (2021). Chromium dust deposition on Moringa oleifera leaves harvested by local communities in Sekhukhuneland, South Africa. Acta Hortic. 1306, 99-106
DOI: 10.17660/ActaHortic.2021.1306.12
mine pollution, human well-being, dust adhesion, foliar surface, elemental analysis, scanning electron microscopy

Acta Horticulturae