Acid Mine Drainage (AMD) and Acid Sulfate Soils (ASS) are two very similar problems. They are caused by the oxidation of sulfides, predominantly pyrite, and result in acidic water and soil conditions. Fish kills and blighted vegetation are the commonly reported consequences. Typically, they manifest at different magnitudes, which is to be expected as ASS are predominantly coastal, to be encountered by civil works, while AMD occurs on mine sites. Treatment of ASS currently involves mixing lime with the affected soil, and utilising engineered covers over the remaining acidic area. Treatment of AMD consists of the same process, in addition to landscaping the disturbed land.
The Department of Natural Resources (AMD) and the QASSIT task force (ASS) write legislation pertaining to their expertise. Due largely to two separate bodies undertaking to provide and enforce their own guidelines, there is a significant disparity in identification and remediation practices adopted by the various industries. Different designations are given to the same effect, which can lead to misinformation and confusion. There has been little previous work done to align the testing and treatment of both problems, in order to better understand and address the problems of metal sulfide oxidation.
Economies of scale, size and sensitivity reveal that the high apparent cost of ASS treatment and protection may be warranted, because of the higher import placed upon failure. A mining operation is by and large self-correcting, as it deals with large quantities and is able to treat en masse its acid problems. ASS is confined to the coastal regions, and flood plains and nearby infrastructure and development may influence the necessity and intensity of treatment required.
Three topics have been recommended for further investigation. They are:
→ Streamlining of testing methods and requirements,
→ Standardisation and improvement of liming neutralisation and application rates, and
→ A cost comparison between typical AMD and ASS treatment options.