Assessment of Acid Sulphate Soil both on surface and in subsurface using hyperspectral data

Abstract

Acid sulphate soils (ASS) are widely spread around the world and are potentially harmful to the environment due to their strong acidity producing ability and their capability to release trace metals. Secondary iron-bearing minerals produced by ASS, have diagnostic spectral features in the visible-near infrared to short-wave infrared spectral range and can be good indicators to the severity of the effects of ASS. Therefore, it is possible to detect ASS using hyperspectral sensing by mapping these indicative iron-bearing minerals. Iron oxides, hydroxides, hydroxysulphates, as well as noniron-bearing minerals, were mapped using airborne Hyperspectral Mapper data. Subsequently, a soil pH map of the surface was deduced according to the relationship between the indicative mineral species and measured pH values. Furthermore, this study investigated the presence of ASS in the subsurface by the proximal hyperspectral sensing HyLogger system, together with soil coring and soil property measurements. This allowed the acquisition of mineralogy, pH, and other soil properties at different subsurface depths. Thus, comprehensive understanding and estimation of ASS, both on the surface and in the subsurface, were attained.