Abstract:
River basins are vulnerable to pollution from anthropogenic activities such as the disposal of waste from domestic, commercial, industrial, and agricultural activities. The anthropogenic activities can be a source of contamination, consequently affecting the quality and quantity of groundwater. The study aimed at assessing the impact of the Omaruru municipal dumpsite on groundwater quality. Ideal individual sampling sites were selected based on their positions relative to the municipal dumpsite. Water and soil samples were analysed onsite for physical and chemical parameters including Total Dissolved Solids (3036 mg/L), Turbidity (1.69 NTU) and Electrical Conductivity (20 mS/cm) by using HANNA, H19811-5 multi-meter instrument. Heavy metals (lead, manganese, iron, copper, cadmium) that can impact groundwater quality were analysed in the laboratory using Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES) and geochemical analysis of soil samples were was conducted in a laboratory using X-ray Fluorescence (XRF). High concentrations of heavy metals were measured in water from boreholes located downgradient of the river sub-catchment. A strong correlation relationship was found between the concentration of chemical parameters found in the soil from the municipal dumpsite and groundwater from nearby water boreholes. Chemical parameters that exceeded the Namibian water quality standards were Calcium (Ca) 100-300 mg/l > (90 mg/l), Chloride (Cl) 250> (64 mg/l), Iron (Fe) 0.3 mg/l > (0.1mg/l) and Copper (Cu) 1.3mg/l > (0.5mg/l). Chemical parameters that were found within Namibian water quality standards and Environmental Protection Agency (EPA) standards were Potassium (K) 0.2 mg/l < (1 mg/l), Magnesium (Mg) 0.07 mg/l < (25 mg/l), Barium (Ba) 0.03 mg/l < (0.5 mg/l), Lead (Pb) 0.015mg/l < (0.05) mg/l, Cadmium (Cd) 0.03 mg/l < 0.01 mg/l) and Nickel(Ni) 0.07mg/l< (0.25 mg/l). Contamination Factor (CF) of the study area ranged between 0.8–2.7 indicating the degree of overall groundwater contamination of the sampled sites. The Geo-accumulation Index (Igeo) values from the study were measured between
0.003-0.7, while the value of Pollution Load Index (PLI) of the study area was at 2. The PLI value of
>1 is polluted whereas a value of <1 indicates no pollution. A strong positive correlation existed between heavy metals found in water and soil from the municipal dumpsite. Concentrations of physical and chemical parameters were benchmarked with Environmental Protection Agency (EPA) and Namibian water standards for drinking water quality.
