Soil chemistry and acidification risk of acid sulfate soils on a temperate estuarine floodplain in southern Australia

Abstract

The distribution and geochemical characterisation of coastal acid sulfate soils (CASS) in Victoria in southern Australia is relatively poorly understood. This study investigated and characterised CASS and sulfidic material at four sites (wetland (WE), swamp scrub (SS), woodland (WO) and coastal tussock saltmarsh (CTS)) on the estuarine floodplain of the Anglesea River in southern Australia. Shell material and seawater buffered acidity generated and provided acid-neutralising capacity (up to 10.65% CaCO3-equivalent) at the sites located on the lower estuarine floodplain (WO and CTS). The SS site, located on the upper estuarine floodplain, can potentially acidify soil and water due to high positive net acidity (>200molH+t–1) and a limited acid-neutralising capacity. High titratable actual acidity in the SS and WO profiles (>270molH+t–1) were the result of high organic matter in peat-like layers that can potentially contribute organic acids in addition to acidity formed from oxidation of sulfidic sediments. The results of the present study suggest that the environments and chemistry of acid sulfate soils in southern Australia are distinct from those located in eastern Australia; this may be related to differences in estuarine processes that affect formation of acid sulfate soils, as well as the geomorphology and geology of the catchment.