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Aluminum Fractionation of Soil Solutions from Unperturbed and Tephra‐Treated Spodosols, Cascade Range, Washington, USA
Author(s) -
Dahlgren R. A.,
Ugolini F. C.
Publication year - 1989
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/sssaj1989.03615995005300020043x
Subject(s) - podzol , fractionation , tephra , chemistry , lysimeter , aqueous solution , environmental chemistry , isotope fractionation , organic matter , soil water , mineralogy , inorganic chemistry , geology , chromatography , soil science , organic chemistry , geochemistry , volcano
Fractionation of aqueous Al was investigated in leachates from a subalpine Spodosol (Typic Cryohumod) located in the Cascade Range of Washington state. Leachates were collected from major genetic horizons with tension lysimeters during the fall, winter, and spring seasons. Solutions were collected from unperturbed profiles and from profiles that had received artificial additions of Mt. St. Helens tephra 4 yr prior to this study. Fractionation of Al was performed by a column cation exchange technique that minimized alterations in pH and ionic strength during the fractionation procedure. Organically complexed Al was the dominant form of soluble Al in the Oa, E, and Bhs horizons, while organically complexed and inorganic forms were nearly equal in the Bs horizon. These results are consistent with the metal‐fulvate theory of podzolization. The effects of tephra deposition were only apparent in the Bs horizon, where inorganic Al concentrations were twice the concentrations measured in nondisturbed profiles. Laboratory experiments showed that the ability of natural organic acids in soil solutions to complex Al increased as the pH was increased from 3.8 to 5.0. Aqueous Al 3+ , added as AlCl 3 to solutions at pH = 4.5, was found primarily as organic complexes when organic C/metal atomic ratios were >50. At organic C/metal ratios <50, the additional Al was found primarily in inorganic forms.