Acid Sulfate Soils

Abstract

The term acid sulfate soils was introduced by L.J. Pons and others prior to the first international acid sulfate soils symposium at Wageningen, the Netherlands, in 1972. According to Pons, these soils were known for centuries and were recognized with terms such as argilla vitriolacea, meaning “clay with sulfuric acid” by Linnaeus in the 18th century. They were recognized prior to the acid sulfate soils terminology by colloquial terms such as the Dutch Kattekleigronden or Katte Klei, or the English cat clay soils, or the German Maibolt to imply hayfields affected by an evil spirit, or Gifterde for poison earth, to connote mysterious and evil circumstances surrounding the difficulty in producing crops on them. Five subsequent international?symposia/conferences, held in Thailand/Malaysia in 1981, West Africa (Senegal, Gambia, Guine Bissau) in 1986, Vietnam in 1992, Australia in 2002, and China in 2008, with a seventh planned for Finland in 2012, show the wide geographic distribution of these environmentally sensitive soils in coastal regions of the world; however, sulfidic materials lurk in the unoxidized zone of the soil‐geologic columns, ready to give rise to active acid sulfate soils upon exposure by land disturbance, in many inland/upland regions of the earth over sediments and sedimentary rocks influenced by sulfidization during their deposition under marine or estuarine environments in the geologic past. This entry references nomenclature schemes for these soils based on current soil taxonomy definitions (provided) of sulfidic materials (potential acid sulfate soil materials) and the sulfuric horizon (active acid sulfate soil materials) and discusses potential, active, and postactive acid sulfate soils utilizing soil taxonomy terms and concepts and references some taxonomic great group and subgroup classes that represent the genetic stages of development. The Australian soil classification system and the WRB (World Reference Base) system of IUSS (International Union of Soil Science) define sulfidic materials (Australia) or sulphidic materials (WRB) and sulfuric materials (Australia) or the thionic horizon (WRB) in ways similar to the equivalent soil taxonomy terms. Also, the geographic distinction between Coastal as opposed to Inland/Upland acid sulfate soils is briefly explained.