Year: 1994
Type: article
Abstract: Aluminum release rates were studied for subsoil horizons of allophanic and nonallophanic Andosols and for imogolite gel films. Release rates were determined using a stirred, flow-through reaction vessel with a 10−3 M acetate buffer adjusted to pH 3.3, 3.8, or 4.2. To determine the sources of dissolved AI, soils were pretreated with Kel, Na-pyrophosphate, citrate-bicarbonate-dithionite, and acid oxalate to remove various solid-phase pools of active AI. Rates of Al release for imogolite gel films during the first minute of reaction ranged from 74.8 nmol/gls at pH 4.2 to 113.3 nmol/g/s at pH 3.3. Rates of AI release for nonallophanic Andosols were greater than for allophanic Andosols due to the rapid release of exchangeable Al from nonallophanic Andosols. Aluminum release rates showed fractional order H+ -dependence ranging from 0.23 to 0.54. The primary source of dissolved Al in allophanic Andosols was from AI-humus complexes and allophane/imogolite. In nonallophanic Andosols, exchangeable Al and AI-humus complexes were the primary sources of dissolved AI. Treatment with KCl increased Al release rates for allophanic Andosols, possibly due to precipitation of polymeric-AI on soil surfaces. Iron oxyhydroxide coatings substantially attenuated Al release rates from allophane and imogolite in allophanic Andosols.
Source: Soil Science & Plant Nutrition
Authors: Randy A. Dahlgren, Masahiko Saigusa
Institutions: University of California, Davis, Tohoku University
Language: English
Subfield: Geochemistry and Petrology
Field: Earth and Planetary Sciences
Domain: Physical Sciences
Open Access status: bronze
OpenAlex ID: W2071918617