ABSTRACT
The dissolution methods for extracting Al, Fe, Mn, and Si are valuable tools to help
determine the chemical forms of these elements in soils. The results are useful in studies
of soil classification, soil genesis, soil reactivity, and metal mobility or bioavailability in
soils. For example, the nature and amounts of extractable organic and inorganic Al and Fe
may reflect the pathway of soil genesis. Also, extractable soil constituents are generally fine
grained with large specific surface area and therefore, have a marked effect on physical and
chemical soil properties and behavior. For these reasons, extraction data, notably for Al and
Fe, are commonly used as chemical criteria for soil classification. Moreover, extractions are
often performed to establish the mechanisms of metal retention and fractionation in con-
taminated soils. A variety of chemical extractants are used to approximate the amounts and
forms of Al, Fe, Mn, and Si in soils. Five of the most commonly used extractions are
discussed here and four methods are presented.
