Effect of landfill leachates on urban soil: A review

The increasing generation of Municipal Solid Waste (MSW) is a significant global concern, with landfills receiving around 1.4 billion tonnes of MSW yearly. Inadequate landfill management contributes to environmental degradation, with landfill leachate being a substantial outcome of MSW decomposition. Leachate contains inorganic nutrients, volatile and dissolved organic molecules and heavy metals and its properties vary depending on waste composition, moisture content and seasonal elements. Heavy metals found in leachate include Pb, Cu, Cr, Ni, Mn, Hg, Fe, Zn and Cd and Emerging Organic Contaminants (EOCs) such as Persistent Organic Pollutants (POPs), Endocrine Disrupting Chemicals (EDC), pharmaceuticals and Personal Care Products (PCPs) are also prevalent. Microplastics (MPs) have been found in raw leachate samples at concentrations ranging from 49.0 +/- 24.3 to 507.6 +/- 37.3 items/L. Landfill leachate production ranks among the most aggressive pollutants to the environment, particularly to soil and poses a danger of contaminating both surface and groundwater. This review examines the potential impacts of landfill leachate on soil quality and the broader implications of this phenomenon, summarizing recent scientific studies and presenting the direct and indirect effects of leachate on soil based on the literature. Bibliometric analysis of publications in the Scopus database reveals a growing scholarly interest in this topic, with the number of publications in the Science Citation Index (SCI) database increasing dramatically to over 464 articles between 2009 and 2024.