Assessment of heavy metals pollution status of surface soil dusts at the Katima Mulilo urban motor park, Namibia

Abstract

The aim of the study was to examine the pollution status of environmentally concerned heavy metals: lead, cadmium, chromium, arsenic, cobalt, nickel, copper, zinc, vanadium, and manganese in surface soil dusts at the Katima Mulilo urban motor park (KMUMP), Namibia. Composite surface soil dusts samples were randomly collected from three points at 10 m apart within the motor park, and a control site on a weekly basis over 8 weeks. Pooled sampled were homogenized and 20 sub-samples (<75 μm soil fraction) were taken from the large sieved sample and digested according to EPA method 3050B. The digestates were analyzed for concentrations of the heavy metals using ICP-OES (Perkin Elmer Optima 7000 DV). The results showed a wide range of heavy metals concentrations from 0.33 mg/kg Cd to 13.7 mg/kg Zn, and differed statistically between study locations (p < 0.05). The results were generally lower than their WHO’s maximum permissible concentrations in soils for the protection of ecosystem’s health. The ecological risk indexes of the heavy metals suggest that the surface soil dusts at KMUMP were not contaminated by the heavy metals at this point. However, this does not preclude exposure risks to travelers, especially vulnerable children due to heavy metals’ toxicity and bioaccumulation.