pH and redox buffering systems of landfill leachate contaminated aquifer materials

Abstract

Introduction of landfill leachate into an aerobic aquifer leads to a variety of redox and pH buffering reactions between dissolved chemical species and aquifer sediments, which play profound effects on the behaviours of contaminants beneath and down gradient from the landfill. The specific objective of this study was to determine the spatial and temporal variations of pH and redox buffering capacity of aquifer sediments. Experimental results indicated that the Total pH Buffering Capacity (TpHBC) of uncontaminated aquifer material was 212.5 mmol/kg·pH–1. Fe(III) was the predominant constituent of Oxidation Capacity (OXC). TOC accounted for 98.7% of reduction capacity (RDC) in uncontaminated aquifer material. With the progressive development of the aquifer pollution, RDC was increasing while OXC was decreasing. Fe(III) oxides were reduced to Fe(II) which lead to the increase of RDC in anaerobic aquifer. Fe(II) distribution was controlled by the pH and redox environment of the subsurface.