Soil acidity/Acid Sulfate Soils - 2008Home | Land | Land Use & Management | Soil Acidity/Acid Sulfate Soils | 2008 What does the Data tell us for 2008Acid Sulfate Soils Acid sulfate soil is the common name given to soils containing iron sulfides. When the sea level rose 10 000 years ago, it inundated the land and sulfate from the sea water mixed with land sediments containing iron oxide and organic matter. The subsequent chemical reaction produced large amounts of iron sulfides in the waterlogged sediments. When these sediments are exposed to air, the sulfides in them oxidise to produce sulfuric acid and then acid sulfate soils. The figure below illustrates how acid sulfate soils develop when land is modified, particularly through artificial drainage.
Natural Setting - low frequency, low magnitude, short duration
acidity Post Drainage - High frequency, high magnitude, persistent acidity
Sourced from NSW Department of Primary Industrieshttp://www.ricecrc.org/reader/soil-acidss/acid-intro.htm
Extensive areas of Acid Sulfate Soils exist on the Shoalhaven River, Crookhaven and Broughton Creek floodplains. There is a need for a suite of measures to deal with acid sulphate soils and current approaches are concentrating on the manipulation of flood gates to provide buffering of acid drainage with seawater, as well as strategies to deal with the lower areas that would be flooded if floodgates were manipulated. The approaches seek to ensure that strategies to improve acid drainage do not have unacceptable impacts on agricultural production. A map illustrating the distribution of acid sulfate soils can be viewed at http://gis.shoalhaven.nsw.gov.au/soemaps Acid Sulfate Soils Hot Spots Program The Acid Sulfate Soils Hot Spots Program is nearing completion with the Management Plan Completed in November 2002 and design and installation well underway. It is anticipated that all capital works will be completed by December 2003 and monitoring will continue into 2004. The capital works include four 'smartgates' to replace existing floodgates, two self regulation tilting weirs (SRTW's) and two lime injection trials. The 'smartgates' provide for two way flow through the floodgates to permit saltwater to backflow up the drains at suitable times to neutralise the acid in the drain in the vicinity of the floodgate as well as helping to raise the water level in the drain to reduce acid formation and transport to the drain. The SRTW's are installed upstream of the floodgates to regulate the groundwater level in close vicinity to the flood mitigation drain to help reduce the oxidation of potential and actual acid sulfate soils as well as reducing the hydraulic gradient of acidic groundwater entering the drains. The lime injection trials are providing the opportunity to install and monitor two strategies that may be very beneficial for utilisation in lower areas of the floodplain. One method is for a lime/fly ash impermeable horizontal barrier to attempt to seal off the acid sulfate layer to reduce the vertical migration of acid to the upper layer for transport to the drains. The other method being trialled is to inject lime slurry into the upper layers of the soil in close vicinity to the drains to neutralise the acid store that exists from years of acid generation to prevent it from being flushed into the drains. The evaluation of these new strategies will determine if they will be used more extensively across the floodplain. For full details of the Hot Spot Project see the Broughton Creek ASS Management Plan 2003 (1.1Mb pdf)
Home | Land | Land Use & Management | Soil Acidity/Acid Sulfate Soils | 2008 |
