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At a glance 
The issue Acid water and heavy metal pollution, caused by the disturbance of acid sulphate soils, is a major environmental issue for the management of coastal regions around Australia. A Natural Heritage Trust funded report has confirmed the presence of acid sulphate soils in Tasmania, and has identified that acid is being released from some sites which host acid sulphate soils (Gurung 2001). The report is available from Mineral Resources Tasmania. The disturbance and exposure of acid sulphate soils by earth moving practices and fluctuations in groundwater levels can result in the oxidation of pyrite which, in turn, produces sulphuric acid (the issue of Acid Mine Drainage is examined separately). Implications relate to the direct impact of acid on the receiving environment and the indirect impact of acid in mobilising toxic metals. Elevated levels of mobilised trace heavy metals in soil and water can be toxic to aquatic life if released into the drainage system during high flow events or a rise in the groundwater table. Land areas impacted by exposed acid sulphate soils have poor fertility, high vegetation dieback and are prone to surface scalding and erosion. Although not strictly acid sulphate soil, pyritic tailings sediments deposited in the King River delta area are commonly of acid producing types. There is an opportunity to adapt land management practices to mitigate the risk to the environment and to downstream users arising from the disturbance of acid sulphate soils. This will help to avoid costly and potentially irreversible environmental damage. This 'At a glance' section provides an overview of the issue of acid sulphate soils. Key findings of the survey and report by Shivaraj Gurung (2001) are included in the Disturbance of Acid Sulphate Soils Issue Report. A recommendation relating to Disturbance of Acid Sulphate Soils is also provided. Favourable news - Understanding of the scope of the problem of acid sulphate soils has improved considerably due to the survey, mapping and report prepared on acid sulphate soils in Tasmania by Shivaraj Gurung (2001).
- In south-east Tasmania, the survey identified that the likelihood of sediments occurring with the potential to host acid sulphate soils is minimal. The distribution of potential acid sulphate soils is limited to small patches in low-lying flats in the Scamander, Bicheno, Swansea and Dodges Ferry areas (Gurung 2001).
- In south-west Tasmania, except for the Henty dunes in the Strahan area, the survey showed that very few potential acid sulphate soils occur along the coast.
Unfavourable news - With increasing demand for land development and intensive agricultural practices in coastal areas, the likelihood of greater exposure of acid sulphate soils poses a serious pollution problem in receiving waters adjoining heavily drained areas. Considerable disturbance has already occurred in areas of Tasmania that are now recognised as having the potential to host acid sulphate soils.
- The survey identified parts of north-west Tasmania as a particular 'hot-spot'. Holocene sediments with the potential to host acid sulphate soils occur mostly in the Smithton and Woolnorth areas. These areas also contain a number of backswamps such as the Mowbray (Mella), Montagu and Brittons swamps which have been extensively drained for dairying. Acid drainage from the disturbance of acid sulphate soils was evident at a number of localities in north-west Tasmania. A conservative estimate shows that at Mella, about 1,000 ha of acid sulphate soils may be contributing acid drainage to Scopus Creek during periods of peak drainage flow. Swamp environments similar to Mella also occur at Togari, Montagu and Brittons.
- King Island, north-east Tasmania, and Flinders Island showed some indications of potential problems. On King Island, iron-rich sediments occur in the underlying coastal marine sediments with the potential to host acid sulphate soils. In north-east Tasmania, extensive coastal sand dunes and barriers, as well as saltwater lagoons, occur along the Bass Strait coastline east of George Town. These have the potential to host acid sulphate soils. Extensive agricultural drainage has also occurred.
- The survey did not locate significant areas of potential acid sulphate soil on Flinders Island, although indications of potential problems were shown by the presence of iron and sulphate-rich groundwater in the Memana and Lady Barron areas. Arsenic and aluminium in the water were the dominant contaminants of concern.
- There is no evidence that land management practices are being modified in areas which have the potential to host acid sulphate soils.
Uncertain news - Insufficient information is available from the survey to identify priority areas for remediation and other management intervention. There is no systematic mapping of acid sulphate soils to identify areas with the potential to give rise to acid drainage from disturbance or land development activity.
- The existing environmental impacts from disturbed acid sulphate soils are unknown, and there is limited monitoring of key water quality parameters in coastal waters in the north of the State. There is at present no monitoring and assessment of land use changes in areas hosting acid sulphate soils. These areas are not systematically monitored for disturbance from land management activities. However, the recent preparation of a land use map of Tasmania could be applied to support this work.
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