Unsaturated Characteristics of Acid Sulfate Soils before and after Neutralization Treatment
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pISSN 1226-7988, eISSN 1976-3808 www.springer.com/12205
DOI 10.1007/s12205-020-0630-0
Geotechnical Engineering
Unsaturated Characteristics of Acid Sulfate Soils before and after Neutralization Treatment Young-Suk Song
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Member, Geologic Environment Division, Korea Institute of Geoscience and Mineral Resources, Daejeon 34132, Korea
ARTICLE HISTORY
ABSTRACT
Received 16 April 2020 Revised 19 June 2020 Accepted 28 July 2020 Published Online 14 October 2020
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 dryingwetting 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.
KEYWORDS Acid sulfate soils Unsaturated characteristics Soil water characteristic curves Hydraulic conductivity function Neutralization treatment Soil aggregation
1. Introduction Acid sulfate soils (ASSs) are naturally formed soils or sediments that are produced under waterlogged and poorly drained conditions near river mouths or coastal areas (Braungardt et al., 2003; Fitzpatric et al., 2009; Nyberg et al., 2012). These soils may have a high sulfate content due to the oxidation of pyrite (Berner, 1984; Sullivan et al., 2009). ASSs have been acid as long as the pyrite or other sulfides is still intact, and the sulphur is still bound in the mineral under undisturbed condition below the water table, and do not cause environmental problems. Generally, ASSs under the aforementioned conditions are defined as potential ASSs (Naylor et al., 1998; van Mensvoort and Dnet, 1998). However, if the soils are drained and exposed to the atmosphere due to excavation for construction projects, the sulfide
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