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Solution/Soil Ratio and Release of Cations and Acidity from Spodosol Horizons
Author(s) -
Skyllberg Ulf
Publication year - 1995
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj1995.03615995005900030022x
Subject(s) - chemistry , cation exchange capacity , distilled water , soil water , soil ph , ionic strength , horizon , inorganic chemistry , electrolyte , ion , analytical chemistry (journal) , chromatography , soil science , geology , aqueous solution , mathematics , geometry , organic chemistry , electrode
The pH value, exchangeable acidity, and effective cation‐exchange capacity (CEC e ) are often used to characterize soils. In addition to properties of the soil itself, these parameters are highly attributed to electrolytes and ionic strength in extraction solutions, as well as to the solution/soil ratio (s/s ratio, liters per kilogram). The influence of the s/s ratio on pH, exchangeable acidity, and cations were studied in soil suspensions of Spodosol O, E, and Bs horizon soil samples in distilled water, 0.01 M CaCl 2 , 1.0 M KCl, and 0.5 M CuCl 2 . An enhanced s/s ratio resulted in a release of H ions from O and E horizon soil samples in agreement with a weak acid equilibrium, whereas the Bs horizon samples showed a higher buffer intensity of pH. A simultaneous release of organic acids and Al and the fact that samples from the spodic horizons were close to the point of zero charge indicate a more complicated pH buffering mechanism in these horizons. The amount of Al ions released from O and E horizon samples in 1.0 M KCl (Al e ) were simply diluted when the s/s ratio was increased. Therefore, Al e is suggested to be a quite finite subpool of totally bound Al (Al t ; extracted in 0.5 M CuCl 2 ). A solution of 0.5 M CuCl 2 extracted all exchangeable K + , Na + , Mg 2+ , Mn 2+ , Fe 3+ , and Al 3+ in O horizon samples, independent of s/s ratio, whereas the release of Ca 2+ was slightly enhanced with increased s/s ratio. Hydrogen ions exchangeable in 1.0 M KCl (H e , centimoles of charge per kilogram) increased by 17 to 22% in O and E horizons and by 32 to 33% in Bs horizons when the s/s ratio increased from 100 to 150. Consequently, estimated H e and CEC e pertaining to different samples can only be accurately compared if they are obtained at the same s/s ratio or corrected for differences in the s/s ratio by specific functions for different soil horizons.