Heavy metals in wastes in Mathare Valley and formulation of a waste Management database

Abstract

The concentration levels of Cadmium and Lead in garbage waste, water and top soil in Mathare Valley has been investigated using atomic absorption and polarographic techniques. Further to this, a waste management database consisting of literature on waste management technologies was established. In determining the concentrations of the metal ions in the garbage, a digestion procedure was developed for the analysis of the matrix. In the digestion of garbage samples for the extraction of Cadmium, Nitric, Sulphuric and Perchloric acids in the ration of 2: 1: 1 maintained at room temperature (23±2°C) for 1 hour was found as the most suitable method for digestion. Higher temperatures were found to be unfavourable. The concentrations in garbage and top soil ranged between 0.01-2.86 mg/kg of dry waste and 1.40-2.13 mg/kg respectively. In water, detectable Cb concentration did not exceed 0.007 ppm. comparatively lower than the WHO limit for drinking water of 0.01 ppm. In the digestion of garbage samples for the extraction of Lead, Nitric and Perchloric acids in the ratio of 4: 1 at room temperature (23 ± 2°C) for 1 hour followed by 40°C for 1 hour was found to be the most appropriate procedure. Concentrations in garbage and top soil ranged between 34.48-54.36 mg/kg of dry weight and 30.84-54.36 mg/kg respectively. In water, detectable Cb concentration did not exceed 0.008 ppm which is lower than the who limit for drinking water of 0.05 ppm. A drop in the concentration levels in garbage, top soil and water was observed during the rainy season suggesting leaching and dilution effects. iii The above results suggest that there is no immediate danger of direct Cadmium and Lead pollution as a result of the garbage dumps, yet the health hazards possed by the presence of these dumps in the vicinity houses should not be overlooked. The information contained in the database showed that methods for the handling of urban waste are available and have been tested in real life situations. The task is to appropriately apply these techniques in Nairobi.