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Ways to Prevent Acid Sulphate Soils From Causing Environmental Problem

Acid sulfate soils (ASS) are the soils that contain sulfidic mineral pyrite. When these soils are not disturbed, they cause no harm to the surrounding environment and are termed potential ASS. However, when the soils are exposed to air by soil excavation, soil uplifting, sea level falling or drainage, their sulfidic mineral pyrite will be oxidized to form sulfuric acid. If the generated acidity exceeds the soil’s neutralizing capacity, then the exposed soils are termed actual ASS and usually have a pH below 4. Actual ASS cause both environmental and economic problems.

ASS are nasty soils that, globally, exert impacts on as many as 17 million hectares of land. In Australia’s Queensland State alone, 666,000 hectares are affected by ASS. ASS are a both land and water management issue because, through their accompanying processes of acidification, toxic metal release, ion precipitation and oxygen depletion, they can degrade lowland environment, contaminate ground- and surface water, and impact on adjacent aquatic ecosystems. ASS assessment is a complex process that comprises different steps from field survey, soil sampling, laboratory analysis, to data interpretation; therefore, it is usually costly to do ASS assessment for a development project.

In order to manage potential and actual ASS the followings should be implemented:

  • Implement programs on raising awareness, education and training on ASS problem
  • Develop policy and regulation on ASS management
  • Encourage participation of local communities
  • Implement mapping and assessment of ASS
  • Avoid disturbing potential ASS if there is any alternative for the development project
  • Rebury or encapsulate the potential ASS that are unavoidably removed for the development project in order to always keep the soil in reduced condition, in which they are harmless. For drainage system design in an ASS area, the dug drains should not disturb the potential ASS
  • Treat actual ASS by liming to neutralize acidity (move pH up to 5.5)

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