Overview of acid sulfate soil properties, environmental hazards, risk mapping and policy development in Australia

This paper presents information on the nature, distribution and impacts of both coastal and inland acid sulfate soils (ASS) in Australia. It overviews factors associated with formation of pyrite and sulfuric acid in these complex soils and the key impacts this has on a wide range of environments. Three case studies have been selected to illustrate the properties and impacts of ASS, ranging from two characterized sites in coastal tropical north Queensland and temperate (Mediterranean) South Australia to an inland ASS site in the Mount Lofty Ranges, SA. The paper outlines the National Strategy (National Working Party on Acid Sulfate Soils, 2000) to manage coastal ASS around Australia and the priorities for future research that has been identified by the National Committee on Acid Sulfate Soils (NatCASS). Acid sulfate soils and sediments (ASS) containing sulfidic materials (pH> 4 with pyrites), sulfuric horizons (pH < 4 with oxyhydroxysulfates of Fe and Al) and monosulfidic black ooze (pH> 4 with monosulfides) are currently developing in a wide range of landscapes across Australia, often in association with areas undergoing salinisation. Oxidation of sulfidic materials and monosulfidic black ooze following the lowering of water tables or soil disturbance is contributing to degraded saline seepages and poor stream water quality. PROPERTIES AND ENVIRONMENTAL HAZARDS Acid sulfate soils are saline soils or sediments containing pyrite, which once drained (as part of lan