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Acid Sulfate Soils (ASS)

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To see more online publications, go to CSIRO Land and Water's publications database and type 'acid sulfate soils' into the Search in Title/Abstract field. Also tick 'View online publications only'.


Housing, marina, infrastructure and farming developments frequently disturb soils and sediments, sometimes with dramatic consequences. To assist land managers and developers, CSIRO is leading the Atlas of Australian Acid Sulfate Soils (AASS) project, under the auspices of National Committee for Acid Sulfate Soils (NatCASS), to identify the extent and severity of ASS in coastal, River Murray and other inland environments.

The problem with acid sulfate soils

Acid Sulfate Soils occur naturally in both coastal (tidal) and inland or upland (freshwater) settings. Left undisturbed, these soils are harmless, but when excavated or drained, the sulfides within the soil react with the oxygen in the air, forming sulfuric acid. This acid, together with associated toxic elements (heavy metals and other contaminants), can kill plants and animals, contaminate drinking water and food such as oysters, and corrode concrete and steel.

Land managers need to be able to identify those areas where development is either best avoided, or is going to need some special treatment. Already, there are many examples of costly mistakes in Australia (particularly in NSW, Queensland and South Australia), involving considerable damage to land, buildings and waterways.

The research

For decades Dr Rob Fitzpatrick and the team at CSIRO Land and Water have investigated a wide variety of coastal, inland and other (e.g. minesite waste rock dumps) acid sulfate soils - and have been challenged and fascinated by their many, varied forms, yet determined to identify, characterise, map and monitor them.

Field studies have taken place at some 900 degraded sites across Australia and overseas (China, Iraq). More than 8,000 samples have been retrieved, representing the wide range of acid sulfate soils and sediments, including sulfidic materials, sulfuric materials, gels, salt efflorescences, salt crusts, iron-rich crusts and monosulfidic black ooze (MBO).

Analytical techniques

In the laboratory, CSIRO Land and Water researchers have developed and applied various techniques to improve the reliability, accuracy and speed of analysis of acid sulfate soils. These include geochemical, mineralogical (particularly x-ray diffraction and electron microscopy), wet chemical, geophysical and isotopic methods (S and Pb). They have also designed experiments to synthesise several minerals under conditions approaching those found in nature.

The team learned to identify and characterise acid sulfate soils in field situations in many different environments (e.g. across Australia, Iraq, Vietnam, Brunei and southern Africa), using specially adapted tools and techniques, modelling risk potential and predicting responses to future land management scenarios.

Risk mapping

While some risk mapping had been undertaken in various locations around Australia, there was a lack of consistency and many large gaps. In collaboration with the National Committee for Acid Sulfate Soils (NatCASS), CSIRO has developed the Atlas of Australian Acid Sulfate Soils which is available on online at www.asris.csiro.au.

Also, in collaboration with the National Heritage Trust and the Coastal Protection Branch of the South Australian Department for Environment and Heritage, the CSIRO team has produced risk maps of the South Australian coast (2002-03). The results are freely available, online at www.asris.csiro.au and www.atlas.sa.gov.au.


Local and state governments around Australia are beginning to respond, producing planning policies and guidelines mindful of the risks associated with acid sulfate soils. Some are more developed than others.

It is hoped that the Atlas of Australian Acid Sulfate Soils will enable informed risk management, both in terms of the maintenance of existing development and the assessment of future development proposals.

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