The spatial distribution of soil lead pollution in the Middle Mukuvisi Catchment, Harare, Zimbabwe

This research determined the spatial variation in soil lead pollution in the Middle Mukuvisi Catchment in Harare. Lead is one of the commonest urban pollutants and it induces negative effects on biophysical resources and humans. Part of the study area has been target of landfill programmes dating back to the 1950s. It is also subjected to industrial discharges from the Graniteside and Masasa Industrial Areas. The study catchment was stratified into two strata namely: Strata A (8 x 105 m2) and Strata B (10 x 105 m2) upstream and downstream with respect of the centre of the landfilled area respectively. These strata were digitized in Arc View Geographic Information System (GIS). Stratification enabled the testing of differences in soil lead pollution levels in the two study strata. Thirty soil samples were then collected from random points in the study area for laboratory chemical analysis. Fifteen points were randomly selected for each stratum. The results showed that soil lead concentration varies spatially in the study catchment. In comparison the strata upstream has lower average soil lead concentration than strata downstream with respect to the centre of the landfilled area. However, the difference in soil lead concentration between the two strata is not significant (p > 0.05). This can be explained by introduction of lead into the study catchment by other sources of pollution upstream such as Masasa Industrial Area. The other sources of lead into the study strata besides landfill leachate can be leakages from fuel stations and leaded fuel spillages from vehicles. It is anticipated further research in this area will contribute to the sustainable utilization of urban river catchments, especially where they are used for dumping wastes.