Fitzpatrick and Shand (2008) Inland acid sulfate soil systems across Australia: CRC LEME Open File Report 249 (Fitzpatrick and Shand, 2008) provides a comprehensive introduction to the subject as well as more detailed discussion on select aspects such as the mineralogy of and toxic gas emissions from acid sulfate soils. The report also contains a range of Australian case studies that demonstrate environmental and community health hazards posed by acid sulfate soils, and how these hazards were or were not effectively managed. Acid Base Accounting Overview Acid Base Accounting (ABA), namely, the practice of quantifying sources of acidity and alkalinity, is a critical aspect of managing acid sulfate soils. For example, ABA is used to calculate the amount of neutralising agent (e.g., lime) required to neutralise stockpiled sulfidic material generated from excavation or dredging activities. The standard Australian ABA system describes three operationally defined pools of acidity (mol H+ per tonne dry soil). Potential Sulfidic Acidity (PSA) is a measure of the ‘oxidisable sulfur’ associated with Reduced Inorganic Sulfur (RIS) (e.g., iron sulfides and elemental sulfur) that may oxidise to produce sulfuric acid. Titratable Actual Acidity (TAA) is a measure of soluble and exchangeable acidity associated with organic acids and loosely bound Al3+ and Fe3+ ions – which react with water to produce H+ (i.e., hydrolysis). Retained Acidity (RA) is a measure of sparingly soluble sulfates such as jarosite and schwertmannite, which slowly generate acidity via the release and hydrolysis of Al3+ and Fe3+. The Acid Neutralising Capacity (ANC) of the soil sample is subtracted from the sum of the PSA, TAA and RA to calculate the net acidity. ANC is typically associated with carbonates and, to a lesser extent, organic matter. In Australia, net acidity is used in combination with the texture or clay content of the sample and the weight of acid sulfate soil to be disturbed (e.g., excavated for construction) to determine whether or not an Acid Sulfate Soil Management Plan (ASSMP) is required as part of statutory environmental management protocols. Estimation of Potential Sulfidic Acidity: SCR and SPOS Potential Sulfidic Acidity (PSA) is a function of the concentration of Reduced Inorganic Sulfur (RIS) in a soil sample. If RIS were the only pool of sulfur present in a sample, PSA could be directly estimated from the total concentration of sulfur. In some cases this may possible. However, sulfate minerals (e.g., gypsum, epsomite, and jarosite) and organic