Granulometric characterisation of the subsurface sediments around the Gaborone landfill area, Botswana

Abstract

Investigations on granulometric characteristics of the subsurface sediments around the Gaborone Landfill, Botswana were carried out in order to elucidate their implicatory roles on environmental contamination. The particle size (PS) and particle size distribution (PSD), specific surface area (SSA), median diameter (MED) and modal diameter (MD) of 50 subsurface samples collected from the surroundings of the landfill were determined. Results obtained showed a range of 9.82 wt % to 82.8 wt % for sand, 16.44 wt % to 89.64 wt % for silt and 0.00 wt % to 6.73 wt % for clay. Values for SSAs were very low ranging from 0.12 m2g-1 to 0.56 m2g-1. The MD and MED lay within the coarse and medium silt range of sediments. These results suggest a subsurface terrain with increased permeability and pore space volume. The sediments are likely to have a low ability to adsorbed contaminants from any plume due to the low clay content and SSA. Based on the granulometric characteristics of the landfill sediments, seepage from the landfill to its surrounding subsurface environment may result in subsurface contamination. (Botswana Journal of Technology: 2002 11(2): 46-53)