Boron Sorption and Desorption in Soils

Abstract Boron (B) sorption and desorption reactions in 10 soil samples from New Mexico were investigated. Boron sorption in seven of the 10 soils conformed to the Langmuir adsorption isotherm, but only over limited concentration ranges. On the other hand, the Freundlich adsorption isotherm was applicable over the entire B concentration range (0 to 100 µg/ml) for all 10 soils. Simple and multiple regression models allowed various B sorption parameters to be predicted from selected soil properties. For example, a multiple regression equation including Fe 2 O 3 %, organic carbon (OC) %, and specific surface predicted 98% of the variance in Freundlich K values. Boron desorption data could also be expressed by the Freundlich isotherm. Two types of B desorption reactions were present in the soils investigated (reversible and hysteretic). Boron desorption was strongly hysteretic in six soils, but was reversible in the other four soils. The tendency for desorption to be hysteretic was not significantly correlated to any soil property measured, nor was it explainable in terms of existing literature.