Groundwater contamination from a municipal landfill: Effect of age, landfill closure, and season on groundwater chemistry

Abstract

Groundwater reservoirs continue to be threatened globally, mainly from anthropogenic activities. There is need to understand how remediation of groundwater can be influenced by site-specific factors. There are few studies, if any, that incorporate at least three site-specific factors in a single investigation of groundwater contamination from landfills. We report a study where waste age, landfill closure, and season were compared with changes in water quality, using a twenty-four-year groundwater chemistry dataset. Groundwater samples were extracted from monitoring wells and analysed for twenty-eight physicochemical parameters. Results showed discharge of both legacy pollutants and elevated inorganic pollutants into the groundwater. Among the site-specific factors, waste age was the most influential. At the landfill age of 21 years, concentrations of pollutants became close to the reference value. The result also indicated that closing the landfill caused significant decrease in concentrations of contaminants in the groundwater (P < 0.05). Season was the least influential, registering significant results only for dissolved oxygen, sulphate and chloride (P < 0.05). Lastly, the result showed strong attenuation of pollutants with distance, thereby demonstrating the feasibility of the aquifer acting as a natural treatment plant to the pollutants. This eliminates any serious environmental risk associated with the emanating leachate, but at a cost of prohibiting abstraction of the groundwater for human use, due to potential health risks.