Chemical Speciation and Leaching of Trace Metals in Groundwater from the Depleted Landfills, India

Abstract

The poor groundwater quality through the leaching of contaminants from depleted landfill is a concern to the scientific community. Therefore, the role of landfills on groundwater quality cannot be neglected in an urban area. The factors influencing the leaching of trace metals in groundwater are soil profile, geochemical and environmental condition of disposed of refuse materials, groundwater-table depth, and climatic factors. This research work delineates landfill role in contaminating groundwater through the chemical speciation of trace metals. Analyzed groundwater quality data indicate most of the samples were classified under Ca2+-Na+ type cation and Cl- type of anion hydrogeochemical facies. The investigations of the mineral equilibrium indicate equilibrium with silicate minerals, which favors kaolinite formation. Saturation index indicates that hematite, goethite, chrysotile, dolomite, ferric-hydroxide, hydro-xyapatite, jarosite-K, cerussite, vivianite, and willemite are reactive minerals in the aquifer water and control their hydrogeochemistry. The study of chemical speciation of trace metals indicates the high possibility of oxidation-reduction, ion-exchange, and chemical-weathering reaction mechanism, which causes the release of trace metal ions and further contaminated aquifer water through leaching. It also justifies through study of contaminant movement in vertical profile of the soil. The chemical speciation of trace metals indicates a reducing atmosphere in the aquifer due to the dominance of Fe2+, Mn2+, Zn2+, Pb2+, and Cu2+ ions in aquifer water. Mn2+ and Zn2+ concentration decreases with depth, while Fe2+ and Pb2+ ion concentration low in the middle layer of the aquifer indicate the contribution through anthropogenic input since it is not available in geology of study area.