Possible effects and reactions between leachate and different clay material types

Abstract

Interactions between landfill leachate and some clayey soils were investigated to elucidate their possible effects and reactions and the extent to which the chemical composition of landfill leachate influences the chemical and mineralogical properties of the soils upon leachate contact. Physicochemical properties of landfill leachate was obtained while the clay mineralogy, major and minor oxides composition, pH, cation exchange capacity (CEC), carbonate content and total organic carbon of Shale (Sedimentary), Migmatite gneiss and Quartzite (Basement Complex)-derived clayey soils after three-weeks saturation with leachate were determined. Dark brown colour and malodorous smell of landfill leachate is linked to high concentration of dissolved organic substances in the leachate composition while high leachate pH indicates an old and stabilized leachate with its temperature impacting the bacterial growth and chemical reaction. Significant changes were observed in both chemistry and mineralogy of the clays after leachate contact with observed appearance of Illite in the migmatite gneiss-derived clayey soil, an indication of mineralogical changes caused by ionic solutions. Enrichment of Ca, SiO2 and Cl; in addition to increased CEC for all the soils is generally noticed. Furthermore, leachate contact resulted in modification of Basement Complex-derived soils from acidic to alkaline soils while the sedimentary terrain-derived soils retained its alkaline pH nature. Hence, alteration in mineralogical and chemical properties observed in the different derived clayey soils is a function of the leachate composition, sorptive capacity of the soils, parent material and especially the inherent reactions upon leachate contact.