Heavy metal pollution index of surface and groundwater from around an abandoned mine site, Klein Aub

Abstract

There is a lack of documented scientific studies on heavy metal pollution and overall quality of water with respect to heavy metal concentrations of water bodies around abandoned mine sites in Namibia. The aim of this study was to assess and interpret spatial and seasonal heavy metal pollution load and the overall quality of water with respect to heavy metal concentrations of different water bodies in a dormant mining settlement, Klein Aub. An assessment of heavy metal pollution was carried out on water samples collected from the dam, borehole, river, mine pit and piped treated domestic water (house) in Klein Aub Settlement using the Heavy Metal Pollution Index (HPI) method. The water samples were analyzed for As, Mn, Fe, Ni, Cu, Zn, Pb and Hg using the Inductively Coupled Plasma Atomic Emission Spectrometry (ICP-OES). Overall, the highest average concentrations (mg/l) recorded per element were 0.059 ± 0.070 (Mn), 1.054 ± 2.176 (Fe), 0.010 ± 0.002 (Ni), 0.014 ± 0.006 (Cu), 0.137 ± 0.014 (Zn), 0.026 ± 0.006 (As), 0.005 ± 0.002 (Pb) and 0.002 ± 0.001 (Hg). All water samples recorded heavy metal values (except Iron) below Group B levels of the Namibian Water Quality Standards, which is classified as “good water quality”. However, various elements recorded concentration levels above WHO limits, with high Arsenic concentrations observed in all samples except from the upstream sample. The overall HPI value of 115. 53 for borehole water indicated high risk water that is not suitable for human consumption. Treated water also recorded high Arsenic concentrations exceeding the WHO limit for drinking water, rendering it not suitable for human consumption. The findings of this study may aid the water supply authorities in Namibia in decision making regarding the pollution level and appropriate treatment methods of water in Klein Aub.