Unsaturated Characteristics of Acid Sulfate Soils before and after Neutralization Treatment

Abstract

Acid sulfate soils (ASSs) are naturally formed soils or sediments that are produced under waterlogged and poorly drained conditions. The sulfides can move to the surface water and into subsurface water and cause loss of nutrients in the soil and destroy the soil structure. To perform effective management of the ASSs located above and under the groundwater table, the unsaturated characteristics of ASSs before and after neutralization treatments should be investigated. An ASS was sampled from the natural soil layer around Ilkwang mine in Busan, South Korea, and CaCO3, which is a neutralizer, and polyacrylamide (PAM) which is a soil stabilizer, were mixed with the ASS in the neutralization treatment. The soil-water characteristics curves (SWCCs) and hydraulic conductivity functions (HCFs) of the drying-wetting processes of the ASS before and after the neutralization treatment were measured and assessed using the van Genuchten model. According to the assessment results of the SWCCs and HCFs, the matric suction of the ASS after the treatment was smaller than that before the treatment at the same volumetric water content (VWC). Additionally, the hydraulic conductivity of the ASS after treatment was larger than that before treatment at the same effective degree of saturation because the effective particle size of the ASS increased and the pore size among particles increased due to soil aggregation. It was confirmed that the neutralization treatment improved the hydrological properties of the ASS and the ASS after treatment may be utilized as sound materials for various fields.