Assessment of the concentration of heavy metals associated with landfill leachate in Gamodubu soils in the Kweneng District, Botswana

Abstract

Composting is a common method of household waste in developing countries such as Botswana. However, compost can introduce heavy metals which are harmful to the environment. High concentrations of heavy metals are toxic to plants and humans and can affect soil by killing soil microorganisms. The aim of this study was to investigate the amount of four heavy metals (Cr, Co, Cu and Pb) in Gamodubu soils that are associated with leachate from a landfill in that area. Soil samples were collected from five randomly selected points around the Gamodubu landfill. A control site was established 1000m away from the landfill i.e. free from landfill leachate. Water samples were collected in a control natural pond away from the landfill and a leachate pond within the landfill. Total recovery concentrations for Cr, Co, Cu and Pb were determined using microwave digestion with nitric acid. Our findings showed no evidence of heavy metal concentration in Gamodubu soils as these metals were detected at negligible amounts. The presence of these metals in the soil was greater than their presence in water. Concentrations of all metals (except Pb) in the control water sample were within the chemical requirements of drinking water as set by the Botswana Bureau of Standards. Findings of this study will contribute to the inadequate knowledge on the soils and drinking waters of Botswana. Furthermore, this study will guide similar future studies in Botswana.