Consequences of Microbial Pyrite Oxidation in Acid Sulfate Soils

抄録

Thai (Munoh and Kab Daeng), Japanese (Tomikura and Sagata) and Ghanaian (Ada) soils were analyzed for iron and sulfur bacteria to study their contribution to the formation of acidity in these soils. Acid sulfate potentiality was also tested for the soils (Sagata and Ada). High numbers of iron bacteria (>10⁶) and sulfur bacteria (>10⁵) were found in Tomikura and Kab Daeng soils, respectively. In addition to the high iron and sulfur bacterial numbers, these soils have high sulfate contents and high acidity (<pH 4). These properties qualify them as acid sulfate soils. In addition, Kab Daeng soil has high organic matter content and is regarded as a peat/acid sulfate soil. Munoh soil has also been classified as an acid sulfate soil since it also shows the presence of enough iron and sulfur bacteria coupled with low pH. Sagata soil has been classified as a typical potential acid sulfate soil because its pH drops sharply from 5.44 to 3.21 within 30 days of incubation. Ada soil is regarded as neither an acid sulfate soil nor a potential one, since it requires as long as 60 days for its pH to drop from 5.46 to 4.65.