Australian Government

Australian Government

Basin wetlands checked for acid sulfate soils


Source: Australian Government

More than 1000 wetlands throughout the Murray-Darling Basin are being assessed to determine the risk posed to them by acid sulfate soils, the Murray-Darling Basin Commission (MDBC) announced today.

Chief Executive Dr Wendy Craik AM said the MDBC was funding the project which is being carried out by State agencies, the Murray-Darling Freshwater Research Centre, CSIRO, Southern Cross University and several catchment management authorities.

“The Murray-Darling Basin Ministerial Council established this project at its March 2008 meeting and the project began immediately,” Dr Craik said.

“The project has been given a high priority, particularly given the scale of this issue and nature of the threats in South Australia's Lower Lakes. An interim report will be presented to the Ministerial Council at their next meeting.”

Dr Craik said the project was assessing the extent of, and risk posed by, acid sulfate soils at key wetlands in Queensland, News South Wales, Victoria and South Australia.

“The sites have been selected because of their environmental significance. They include the sixteen Ramsar listed wetlands in the Basin, as well as those listed on the Directory of Important Wetlands in Australia and other environmentally significant wetlands.

“Other sites have been chosen where there is an increased likelihood of acid sulfate soils developing which could impact on the surrounding environment and water supplies.

“Because of the recent drought, river levels have dropped and many wetlands have dried out.

“Long-submerged soils and sediments are being exposed to the air creating the potential for sulfuric acid production and other risks,” Dr Craik said.

Acid sulfate soils are soils containing iron sulfide minerals. These soils form naturally when saline groundwater or other water containing sulfate mix with sediments which contain iron oxides and organic matter.

When undisturbed and not exposed to air these soils pose little threat. However when exposed to oxygen these sediments have the potential to form sulfuric acid, cause deoxygenation and release contaminants such as heavy metals.

“This can cause significant harm to fish and other aquatic organisms, impact on water quality for potable water supplies, and in some cases corrode metal, concrete and other structures,” Dr Craik said. “The program will also identify management options for wetlands considered at high risk from acid sulfate soils.”

Dr Craik said the problem has been identified as an issue for decades in coastal areas but the risk has only recently become apparent in inland wetlands and rivers.

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