Mitigating the Release of Acidity and Metals from an Acid Sulfate Soil : A study using Column Experiments

Abstract

Acid sulfate soils are soils containing rich sulfide minerals found mostly in low-lying coastal areas. Upon exposure to atmospheric oxygen, these sulfide minerals oxidize,producing more sulfuric acid than can be neutralized by the buffering capacity of the soil. This thesis aimed at developing and testing methods to mitigate the release of acidic and metals from acid sulfate soils, which will be used as a study case at Risöfladan experimental field in Vaasa, using column leaching test as experimental technique. The column test were carried out in NOVIA University of Applied Sciences laboratory using CaCO3 (Enrich C and FC 2.5) and peat suspensions as treatment chemicals. During the initial flushing of all the acid sulfate samples with autoclaved water, the pH of the permeate was at a value of circa four. During CaCO3 (Enrich C and FC 2.5) treatments, the pH of the permeate increased to a value of circa 7 and remained at this value even after switching to autoclaved water. In contrast to CaCO3 treatments,treatment with peat suspension had little or no effects on the pH. All treatments on the other hand, had significant effects on the temperature-corrected conductivity and redox potential of the permeate leached from the acid sulfate soil samples.