Acid sulfate soils
Much of the acid sulfate soils of concern are those that were formed long ago, underwater. However, iron sulfide layers in soil are still being formed today under tidal conditions. When they are undisturbed and waterlogged these soils are relatively harmless, but when they are disturbed and exposed to oxygen they can produce sulfuric acid in large quantities.
After rain, and particularly following prolonged dry periods, the built up sulfuric acid is released. As the acid moves through the soil profile it releases other pollutants, like heavy metals. This toxic cocktail eventually flows into surrounding waterways and significantly decreases water quality, kills fish and damages sensitive ecosystems.
Acid sulfate soils have long been a problem in coastal areas , and managing the issue in inland wetlands and rivers is now gaining importance. The distribution of acid sulfate soils in inland areas is yet to be fully studied.
Acid sulfate soil runoff affects not only the environment but also the economy and communities. Besides the obvious impact on the environment such as fish kills, acid runoff has been attributed to the decline or failure of fishery and aquaculture industries. It can damage valuable tourist resources like good fishing grounds, swimming areas and other water sports areas. Acid discharges also damage town services and structures like pipes, foundations, drains, bridges and flood controls.
Options for reducing the effects of acid from these soils are; minimising disturbance and maintaining waterlogged conditions, neutralising acid with lime, and reflooding drained land with freshwater.
More information
Projects
- Some water quality hotspots are under pressure due to acid sulfate soils
Publications
- An introduction to acid sulfate soils
- National guidance for the management of acid sulfate soils in inland aquatic ecosystems - 2011
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