Submitted to: Soil Science Society of America Special Publication Book Chapter
Publication Type: Book / Chapter
Publication Acceptance Date: January 21, 2004
Publication Date: June 24, 2005
Citation: Suarez, D.L. 2005. Chemistry of salt-affected soils. In: Chemical Processes in Soils. M.A. Tabatabai and D.L. Sparks (eds.) Soil Science Society of America Special Publication Book Series. Madison, WI. Chapter 15 pp:689-705. Interpretive Summary: Chemical processes exert a strong influence on the composition of saline soils. This book chapter covers the major chemical processes of importance to saline soils, including activity and solubility calculations, precipitation and cation exchange. Discussion includes the different approaches to calculating ion activities and their limitations. Various methods are available to characterize soil salinity; these are defined and described in terms of their utility. The development of different chemical compositions of saline waters is outlined in relation to the concentrating process of evaporation and precipitation of mineral phases.
Technical Abstract: The chemistry of saline soils differs significantly from that present in non saline, predominantly humid environments. Among the differences are the importance in saline soils of the process of evapotranspiration, soil mineralogy, with predominance of smectites over kaolinite, elevated pH and base cation saturation of exchange sites. Calculation of solution activities in saline soils is essential for all solution speciation and solubility calculations. Discussion is presented of the different approaches to activity corrections and the implications for calculation of saturation status and controlling phases. Major solid phases controlling solution composition are reviewed including calcite, gypsum and dolomite. Other phases such as mirabilite, sepiolite and highly soluble salts control solution composition under yet more saline conditions. A chemical evolution scheme is presented outlining the development of different chemical end member compositions upon concentration of the solution.