Landfill Leachate Generation, Migration and Impacts on Soil and Groundwater Systems: A Review of Global, African and Nigerian Perspective

Abstract

Municipal solid waste generation is rising rapidly worldwide, and in many low- and middle income countries disposal remains dominated by open dumping without engineered containment, creating persistent conditions for the generation and uncontrolled migration of landfill leachate. This review synthesises global, African and Nigerian evidence on the composition, environmental behaviour and public health implications of landfill leachate, with particular attention to humid tropical and Niger Delta settings. Leachate composition is shown to evolve with waste age, climate and landfill design, shifting from organically dominated, high-BOD acidogenic-phase leachate towards ammonia- and chloride-dominated methanogenic-phase leachate over time. Once generated, contaminant transport is governed by the interaction of climate-driven infiltration, subsurface lithology and groundwater flow, conceptualised through the Source-Pathway-Receptor framework and explained mechanistically by Darcy's Law, Toth's groundwater flow system theory and the water balance concept. Empirical studies from Europe, North America, Asia, Africa and Nigeria consistently associate unlined dumpsites with elevated heavy metals, nutrients, organic loading and microbial contamination in soil and groundwater, with health consequences ranging from methemoglobinemia and gastrointestinal disease to chronic heavy-metal toxicity, alongside socio-economic impacts including declining property values and disproportionate exposure of low-income communities. Within the Niger Delta and Port Harcourt specifically, high rainfall, unconsolidated sandy aquifers and shallow groundwater tables create conditions of especially high intrinsic vulnerability. The review identifies persistent gaps in the integration of hydrogeophysical, geotechnical, hydrochemical and public health evidence within a single analytical framework, and in the treatment of seasonal variability, and argues that closing these gaps is essential for developing context-specific groundwater protection strategies in rapidly urbanising tropical cities.