Acid Sulphate Soils (ASS)
Acid sulphate soils (ASS) refer to naturally occurring soils, sediments or organic substrates which contain high amounts of iron sulfides and are formed under waterlogged conditions. When exposed to air due to drainage or disturbance, these soils produce sulfuric acid, often releasing toxic quantities of iron, aluminium and heavy metals. ASS commonly occurs on coastal wetlands as layers of marine muds and sands deposited in protected low-energy environments such as barrier estuaries and coastal lakes.
Acid sulfate soils are formed in the absence of oxygen when seawater or sulfate-rich water mixes with land sediments containing iron oxides and organic matter in a waterlogged situation. When ASS are exposed to air, the iron sulfides in the soil react with oxygen and water to produce a variety of iron compounds and sulfuric acid. The ASS problem is worsened as the generated acid destroys the fine clay particles present in the soil and releases soluble forms of aluminium (Al) which can then move into groundwater and water bodies. The acid can also solubilise manganese and other heavy metals, resulting in metals being released into the environment.
It should be noted, the term acid sulphate soil generally includes both actual and potential acid sulphate soils. Actual and potential acid sulphate soils are often found in the same soil profile, with actual acid sulphate soils generally overlying potential acid sulphate soil horizons.
1. Preliminary Assessment
- To determine if ASS are present and if any planned works will possibly disturb these soils. .
- If ASS are present whether or not a management plan is required.
- Provide information to assist in further decision making.
2. ASS Management plan.
- To help clients ascertain the degree and make up of ASS on a specific site.
- What impacts any intended activity could have on these soils.
- Propose measures to minimise environmental impact from an intended activity or non action.
3. Treatment Solutions
- Treatment options for acid sulphate soils include excavating and treating soil to reduce acidity, re-flooding the soils to prevent the formation of fresh acid and minimising or treating acid run-off.
Please contact Australian Enviro Services for further information & assistance.