DIN EN ISO 12782-2:2012-09

This part of ISO 12782 specifies the determination of the content of "reactive" iron in the form of crystalline iron oxides and hydroxides in soil and other materials by extraction with dithionite. As already mentioned in the introduction, materials also include waste. The content of "reactive" iron can be used as input in geochemical models to represent the content of crystalline iron (hydr)oxides. In addition to leaching procedures for subsequent chemical and ecotoxicological testing of soil and other materials including waste, predictive models are becoming indispensable tools in the environmental risk assessment of these materials. Models are particularly required when the results of laboratory leaching tests are to be translated to specific scenarios in the field, with regard to assessing the risks of both contaminant migration and bioavailability. In the past few years, geochemical models have been shown to be valuable tools to be combined with the data obtained from characterization leaching standards, such as pH-dependence and percolation tests. These models have the advantage of being based on fundamental thermodynamic parameters that have general validity. In order to enable extrapolation of laboratory leaching data to the mobility and/or bioavailability of a constituent in a specific field scenario, these models require additional input parameters for specific soil properties. The major reactive surfaces that control the binding of constituents by sorption processes to the soil matrix are particulate organic matter and iron and aluminium (hydr)oxides. It is generally accepted that the reactivity of these mineral and organic surfaces can strongly vary as a function of their specific surface area/crystallinity (iron and aluminium (hydr)oxides) and composition (organic matter). When the results are intended to be used for the above-described purposes of geochemical modelling in conjunction with leaching tests, it is important that the methods be selective for reactive surfaces for which generic thermodynamic adsorption parameters are also available for the most important major and trace elements. These reactive surfaces have been identified in soils as well as in a variety of other materials for which the leaching of constituents is of relevance. It has been shown that the binding properties of these surfaces play a generic role in the speciation and leaching of constituents among these different materials. As an example, a similar geochemical modelling approach, using model input from the partial or complete ISO 12782 series, has been successfully applied to different soils, amended soils, municipal incinerator bottom ash, steel slag, bauxite residues, and recycled concrete aggregate. Hence, the scope of the ISO12782 series extends from soils to materials including soil amendments and waste materials. This standard has been prepared by ISO/TC 190 "Soil quality", in collaboration with CEN/TC 345 "Characterization of soils". The committee responsible for this standard is NA 119-01-02-05 UA "Eluierungsverfahren" ("Leaching test procedures") at DIN.