Abstract

A method using isotopic dilution of carrier-free sulfur (S-35) for determining adsorbed sulfate (SO42-) in soil samples from B horizons of podsolized soils was compared with an extraction of SO42- by 10 mM calcium dihydrogen phosphate [Ca(H2PO4)2]. The two methods gave comparable results for flesh soil samples while the extraction method resulted in significantly higher amounts of adsorbed SO42- when using air-dried samples. Since the S-35 method assumes equilibrium between adsorbed SO42- and SO42- in solution, these results are evidence of complete exchangeability of adsorbed SO42- extracted with Ca(H2PO4)2 in fresh soil samples. It was thus concluded that the extraction method is a useful method when determining adsorbed SO42- in equilibrium with the soil solution in these soils. The S-35 reached equilibrium with the soil solution within 2 h. The difference between the methods when using air-dried samples indicates that part of the adsorbed SO42- is irreversibly bound to the soil during air-drying. Furthermore, it is recommended that the amount of SO42- determined in an extraction with water should be expressed as an intensity variable, i.e., SO42- activity, rather than a capacity variable.

Published in

Communications in Soil Science and Plant Analysis
1994, Volume: 25, number: 3-4, pages: 207-214

SLU Authors

• Karltun, Erik

  • Department of Soil Sciences, Swedish University of Agricultural Sciences
    

UKÄ Subject classification

Soil Science


Publication identifier

DOI: https://doi.org/10.1080/00103629409369031

Permanent link to this page (URI)

https://res.slu.se/id/publ/89789