the usual case). This calculation may or may not be performed by commercial labs before they present the ABA results to the client. Retained Acidity is a very recalcitrant pool of acidity in that it is slow to release and not easily neutralised. Therefore, soils with high amounts of Retained Acidity may require special management considerations to mitigate gradual acidification over tens to hundreds of years. Preservation of Acid Sulfate Soil Samples Oxidation of RIS occurs rapidly under ambient conditions This is especially true for iron monosulfides, which have a higher surface area than iron disulfides. Monosulfidic material will change from pitch black to light brown within minutes of being exposed to air (see images below). Consequently, acid sulfate soil samples should be immediately cooled to < 4°C to slow oxidation; and samples containing monosulfidic material should be immediately frozen (e.g., using a portable freezer or liquid nitrogen). The use of dry ice is recommended as the gaseous carbon dioxide should further hinder oxidation. Samples should be tested for ABA within 24 h of sampling. Otherwise, additional preservation techniques (e.g., freezing or drying at > 85°C) should be used. See also Acid mine drainage Estuarine acidification Soil pH References Further reading External links Australian Department of Environment & Heritage National Coastal Acid Sulfate Soil website Western Australian Department of Environment Acid Sulfate Soils website New South Wales Office of Environment and Heritage acid sulfate soils website Frequently asked questions, question 3: documentation on acid sulfate soils Soil chemistry Types of soil