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.

SIGNIFICANT STATEMENT AND CONTRIBUTION TO LITERATURE

The capabilities of heavy metals to cause both acute and chronic toxicities have been widely reported in several pollution studies, making their presence at any levels in human environments such as the urban motor park with high human activities an important safety concern. This study provided baseline data of the pollution status of environmentally concerned heavy metals in the surface soil dusts at the Katima Mulilo urban motor park. The Katima Mulilo Urban motor park is a designated point of loading and dropping passengers by commercial vehicle transport operators in Katima Mulilo town and hence, constitute a significant source of heavy metals exposure risk for travelers and tourists, especially vulnerable children who frequently used the park. Despite the high human activities in and around the Katima Mulilo urban motor park due to its location bordering the Katima Mulilo Sport Centre and shopping areas, there is no documented study to establish any environmental pollutants such as heavy metals which have several routes of unintended population exposure in the environment. Thus, the present study provided important environmental pollution data of lead, cadmium, chromium, arsenic, cobalt, nickel, copper, zinc, vanadium, and manganese which can be used to monitor future phenomena associated with the presence of these heavy metals in the study area. Moreover, there is currently a dearth of heavy metal pollution data in motor parks in Namibia. Thus, apart from contributing the Namibia’s perspective to the global literature of heavy metals pollution of urban motor park soils, these data are critical to the Namibia government’s effort towards providing a clean and healthy environment across the country.

Keywords:

• Heavy metals
• pollution
• surface soil
• motor park
• Namibia

Acknowledgements

The authors greatly acknowledged the financial support provided by the University of Namibia, Katima Mulilo Campus to undertake this study under the campus Research Agenda project 5. The authors are also thankful to the Katima Mulilo Town Council for the approval granted to carry out the study on the Katima Mulilo urban motor park surface soil dusts. Finally, the authors thank the Analytical Services Laboratory Windhoek Namibia, for the laboratory preparations and analyses of the samples.

Disclosure statement

The authors hereby declared that there is no conflict of interest regarding the conduct and publication of this study. All the authors have read and approved the publication of the article.

Data availability statement

Upon reasonable request, the authors affirm to make the data that support the results or analyses presented in this paper freely available to the person concerned.