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Sulfate Adsorption and Desorption Reversibility in a Variety of Forest Soils
Author(s) -
Harrison Robert B.,
Johnson Dale W.,
Todd Don E.
Publication year - 1989
Publication title -
journal of environmental quality
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.888
H-Index - 171
eISSN - 1537-2537
pISSN - 0047-2425
DOI - 10.2134/jeq1989.00472425001800040004x
Subject(s) - adsorption , soil water , desorption , saturation (graph theory) , sulfate , chemistry , leaching (pedology) , environmental chemistry , phosphate , soil test , soil science , geology , organic chemistry , mathematics , combinatorics
Subsurface soil samples were collected from 20 forest sites of differing soil and cover type, atmospheric deposition history and physiographic location. Samples were analyzed for S pools, sulfate adsorption capacity, adsorption reversibility, and associated soil properties in order to compare the relative S chemistry and SO 4 retention capacities of the sites. The SO 4 adsorption capacity was determined by sequential equilibration of air‐dried soil samples with a percolating solution of 0.25 m M CaSO 4 , and adsorption reversibility by leaching both SO 4 saturated and untreated soil samples with deionzed water. Phosphate extractable SO 4 was measured at the end of each series of equilibrations as a means of estimating irreversibly adsorbed SO 4 . A total of 32 out of 36 soil horizons studied showed net SO 4 adsorption, ranging from a desorption of 0.4 to an adsorption of 7.2 mmol SO 4 kg −1 . Thus, most of these soils were not yet saturated with respect to a solution concentration of 0.25 m M SO 4 . Most soil horizons showed irreversible SO 4 adsorption (an average of 36% of adsorbed SO 4 was retained irreversibly) as evidenced both by changes in phosphate extractable SO 4 and by a comparison of desorption of SO 4 before and after saturation by the 0.25 m M SO 4 solution. When adsorption and adsorption reversibility observations were compared with measured soil properties, the presence of hydrous oxides of Al and native SO 4 were the best indicators of SO 4 adsorption potential. Most adsorption/desorption/extraction sequences showed mass conservation of SO 4 , indicating inorganic SO 4 adsorption appeared to be far more important in these procdures than organic S incorporation or mineralization. It is unclear how much air‐drying, sample treatment, and the procedures followed might have changed the inorganic and organic S pools of these soils.