Physico-chemistry, mineralogy, geochemistry and nutrient bioaccessibility of geophagic soils from Eastern Cape, South Africa

Abstract

The consumption of soils is widely practiced in several rural communities in the world including the Eastern Cape Province of South Africa which is considered to be poor with a large rural population where culture and indigenous practices remain endemic and well entrenched. This pioneering study of geophagic soils from the province had its primary objective of understanding their physico-chemistry, mineralogy, and geochemistry, and inferring on nutrient bioaccessibilty. Geophagic soil samples obtained from selected sites were subjected to the following laboratory analyses: colour, particle size distribution (PSD), pH, cation exchange capacity (CEC), X-ray diffractometry, and X-ray fluorescence spectrometry. Results depicted values close to those obtained for other geophagic soils from different parts of the world. Elemental concentrations were used to calculate the nutrient bioavailability of the soils consumed by the individuals. The pH of the soils ranged from 4.9 – 8.3, whereas their CEC values ranged from 4.69 – 18.95 cmol (+)/kg. The samples were mainly siliceous with quartz being the dominant mineral in most of the samples. The low nutrient content of the soils raises questions about their suitability as nutrient supplements to geophagic individuals. Key words: Geophagic individuals, kaolinite, principal component analysis, quartz.