Acid Sulfate Soils Specialists

Acid sulfate soils (ASS) are naturally occurring soils and sediments containing iron sulfides, most commonly pyrite. When ASS are exposed to air the iron sulfides in the soil react with oxygen and water to produce a variety of iron compounds and sulfuric acid. Therefore, projects involving the disturbance of ASS must assess the risk associated with disturbance through the consideration of potential impacts.

Our team has extensive experience in undertaking ASS investigations. Firstly, these investigations rely on in-situ field pH (pHf) and oxidised field pH (pHfox) testing as a screen to identify actual acidity (pH) and potential acidity by oxidised pH of a 1:5 soil extract. Visual fizzyness is a coarse indicator of the rate of reaction. Secondly, laboratory analysis is conducted using SPOCAS (suspension peroxide oxidation – combined acidity and sulfate) and/or Chromium suites. The SPOCAS suite measures both the ‘acid trail’ and the ‘sulfur trail’. The Chromium suite measures the required components of the Acid Base Account. Only acidity (H+) or sulfur (%S) is measured at each step.

Successful management of ASS depends on investigation results and the site conditions to determine the most appropriate management strategy for a site.

Our specialists offer services for the management of ASS including aglime treatment, storage, transportation and disposal.