African Journal of Environmental Economics and Management ISSN 2375-0707 Vol. 8 (4), pp. 001-011, April, 2020. © International Scholars Journals

Full Length Research Paper

Assessment of heavy metal pollution in soils along major roadside areas in Botswana

K. B. Mmolawa1*, A. S. Likuku2 and G. K. Gaboutloeloe1

1Department of Agricultural Engineering and Land Planning, Botswana College of Agriculture, Private Bag 0027, Gaborone, Botswana.

2Department of Basic Sciences, Botswana College of Agriculture, Private Bag 0027, Gaborone, Botswana.

Accepted 21 January, 2020


Assessment of heavy metal pollutants: Al, Co, Cu, Fe, Pb, Mn, Ni and Zn was conducted along major roadside soils of Botswana, lying between latitudes 18°S to 27°S and longitudes 20°E to 29°E using enrichment factor ratios (EF), contamination factor (CF), pollution load index (PLI) and geoaccumulation index (Igeo) methods. The studied sites were demarcated into five zones referred to as FN (Francistown-Nata), NM (Nata-Maun), MG (Maun-Ghanzi), GK (Ghanzi-Kang) and TS (Tshabong-Sekoma). All the four pollution assessment methods revealed that zones FN, NM and MG are pollution impacted as compared to GK and TS zones. Results of multivariate analysis suggest mixed origins of pollution sources including human activities, vehicular emissions and lithogenic occurrences. Al, Cu, Fe, Mn, Zn and Co is of mixed origins of pollutants, with Fe and Mn being predominantly lithogenic, and vehicular emissions characterised by Pb and Ni. The findings in this study will serve to create awareness of vehicular heavy metal pollution to Botswana policy makers in the mitigation of vehicular pollution, as it is barely monitored.

Key words: Heavy metal contamination, roadside soils, enrichment factors, contamination factor, pollution load index, geoaccumulation index, cluster analysis, factor analysis.