Heavy Metal Contamination of Ground Water from an Unlined Landfill in Bulawayo, Zimbabwe

摘要

Background. Developing countries such as Zimbabwe deal with challenges in solid waste management such as insufficient waste recycling, hazardous wastes that are not separated for safe disposal, and landfills that are not properly engineered to prevent groundwater pollution. For these reasons, landfills in developing countries pose serious environmental and public health hazards. Objectives. The objective of this study was to assess heavy metal release and groundwater pollution from an unlined landfill in Bulawayo, Zimbabwe. The purpose of the study was to explore environmental and public health risks posed by improperly managed landfills in developing countries. Methods. We assessed levels of metal release from Richmond landfill in the city of Bulawayo, Zimbabwe by measuring lead, cadmium, chromium and copper levels in landfill soil, leachate and plants. We also monitored metal levels in groundwater from boreholes located in a residential area in the vicinity and downgradient of the landfill within a range of 800–2135 m. Soil was characterized at the landfill to assess potential sources of heavy metals. Results. All metals that were assessed were present in landfill soil and in leachate. There was high metal accumulation in weeds that were growing at the landfill, indicating mobility and bioavailability of the metals. Groundwater from nearby boreholes had high levels of lead (Pb) and cadmium (Cd) which were negatively correlated to distance from the landfill (p<0.01), indicating contamination from the landfill. The Pb and Cd levels exceeded World Health Organization standards for drinking water quality, posing health hazards to the communities who rely on the water. Solid waste at the landfill consisted of soft plastics (33%), hard plastics (18.6%), metals (3%), paper (8%), electronic waste (0.8%), organics (15.3%) and various other types (21.3%). Discussion. A combination of factors may be attributed to groundwater contamination. These include the co-disposal of metallic and electronic wastes at the landfill, lack of membrane lining at the landfill, inadequate leachate management and the porous geo-physical characteristics of the sub-surface at the landfill site. Conclusions. Our study highlights adverse environmental and public health consequences of co-disposal of metals and electronic wastes at improperly engineered municipal landfills. This is a ‘wake-up’ call for policy makers in developing countries to improve solid waste management. Competing Interests. The authors declare they have no competing financial interests.