World Bank assisted National Agricultural Research Project (NARP) - University of Port Harcourt
Abstract
Studies were carried out on subsurface sediments obtained around the
Gaborone landfill area Botswana, in order to characterize their
mineralogy and physico-chemistry, appraise any contaminant inputs from
the landfill and assess their ability to attenuate contaminants from
the landfill. Physico-chemical properties investigated included
particle size distribution (PSD), moisture content, bulk density (Db),
porosity, surface area, pH, electrical conductivity (EC), and cation
exchange capacity (CEC). The mineral phases occurring in the subsurface
sediments were identified by use of X-ray powder diffraction (XRPD)
technique. Grain size analyses of the subsurface sediments revealed
sandy loam, silty loam, and silt as the main textural classes. The
values obtained for Db and porosity is reflective of the textural
classes of the different samples. Moisture content values of the
studied samples are characteristic of sediments in semi-arid
environments. Apart from two samples, which were acidic, others were
alkaline. The EC values were indicative of significant amounts of total
dissolved salts (TDS) especially along the eastern corner of the
landfill. Cation exchange capacity values were relatively low. Minerals
identified by XRPD included quartz, microcline, muscovite and kaolinite
in bulk subsurface sediments, whereas kaolinite, smectite and /or
illite occurred in the clay fractions. Sediment pH, EC and TDS suggests
inputs from the landfill. The sediments seem to have a low attenuation
capacity as a result of their physico-chemical and mineralogical
properties. Further geophysical and hydrogeochemical research is needed
to verify if the Gaborone landfill area is environmentally safe. @JASE