Variations of heavy metals from geothermal spring to surrounding soil and Mangifera indica-Siloam village, Limpopo Province

Abstract

Assessment of seasonal variation in concentration of heavy metals-As, Cd, Co, Cr, Cu, Ni, Pb, and Zn from the Siloam Geothermal Spring and their impacts on surface soils and Mangifera indica were undertaken during winter and summer seasons in South Africa. This was done to determine the environmental pollution status of surface soils and Mangifera indica around the geothermal spring. The geothermal spring water, surface soil (0-15 cm) and Mangifera indica (bark and leaves) samples were collected during 2014 winter and summer seasons. Soil and Mangifera indica samples were treated and digested using microwave and block digestion methods, respectively. The heavy metal concentrations were determined with inductively coupled plasma-mass spectrometer (ICP-MS) (Agilent 7700). The result from this study showed that levels of heavy metals were higher in summer compared to winter season for geothermal spring water, surface soil, and Mangifera indica (barks and leaves). In two-tailed tests (Mann-Whitney U-test), geothermal spring water alone showed significant differences (Z = -2.1035, p < 0.05), whereas the surface soil and barks and leaves of Mangifera indica showed no significant differences (Z = 0.053; 0; -0.524, p > 0.05) in both seasons. Some heavy metals concentrations were above the standard guidelines for drinking water and typical soil, making the soil contaminated. This is a cause for concern as it can affect the environment and the health of the inhabitants of Siloam village, who depend on the geothermal spring as their source of domestic water, irrigation, and other uses. This study also showed that Mangifera indica has a phytoremediative property, which lessens the heavy metal concentrations absorbed from the contaminated soil.