Surfacial mineralogy of coastal acid sulfate soils in urbanization area of Pinjarra, Western Australia

Acid sulfate soils in Western Australia commonly occur in coastal regions. One of the greatest threats to coastal environment is the disturbance of acid sulfate soils due to urban development which can lead to widespread acidification of lands and streams and subsequent economic losses onsite or in adjacent areas. Surface sampling from different landforms of the study area and analytical results of XRD, SEM and VNIR indicate that morphological and surfacial minerals variations, due to oxidative sulfide weathering processes in affected landscape. In dry season, the surface mineralogy of salt affected zone is dominated by halite, gypsum, barite and importantly, iron oxyhydroxides crusts (ferrihydrite, schwertmannite). The oxidative weathering of the jarosite with rapid oxidation of Fe2+, can generate iron oxyhydroxides and acid. The visible near infra-red (VNIR) reflectance spectra of the surface minerals from salt affected zone and acid sulfate soils horizon, showed spectral differences expressed in the VNIR region due to absorption bands of iron oxides and hydroxides. The spectral difference can be utilized for regional scale mapping of coastal acid sulfate soils disturbance due to urbanization in Pinjarra area via hyperspectral and multispectral remote sensing.