Aluminum solubility and release rates from soil horizons dominated by aluminum-humes complexes
Open Access
- 1 March 1995
- journal article
- research article
- Published by Taylor & Francis in Soil Science and Plant Nutrition
- Vol. 41 (1), 119-131
- https://doi.org/10.1080/00380768.1995.10419565
Abstract
Aluminum solubility and release rates were studied for A horizons of three nonallophanic Andosols and for a Bhs horizon of one Spodosol that had active Al fractions dominated by Al-humus complexes. The A horizon of one allophanic Andosol was also used for comparison. Aluminum solubility relationships over the pH range 3–5 were determined in a 30-d equilibration study. Aluminum release rates were measured using a stirred, flow-through reaction vessel with a 10-3 M acetate buffer adjusted to pH 3.5, 4.0, and 4.5. The effect of ionic strength on Al release was determined using different concentrations of CaCl2 adjusted to pH 4.0. To determine the source of the dissolved Al, soils were pretreated with KC1, Na-pyrophosphate, and acid oxalate to remove various solid-phase pools of active Al. The nonallophanic Andosol and Spodosol samples displayed pAl versus pH slopes of 2.0–2.4 and solubilities considerably lower than those of common A1(OH)3 phases. In contrast, the allophanic Andosol exhibited a pAl versus pH slope of 2.9 and a solubility virtually equal to that of synthetic gibbsite. All the soils showed very rapid Al release rates at t = 0 ranging from 16–44 nmol g-1 s-1 at pH 3.5 to 4–8 nmol g-1 s-1 at pH 4.5. The H+-dependence at t = 0 ranged between 0.64–0.86 for the nonallophanic Andosols and Spodosol to 0.46 for the allophanic Andosol. The ionic strength dependence was generally greater for the nonallophanic Andosols and Spodosol than for the allophanic Andosol. Pyrophosphate treatment of the nonallophanic Andosols and Spodosol reduced Al release rates to very low levels indicating that Al-humus complexes were the primary source of dissolved Al For the allophanic Andosol, both pyrophosphate and acid oxalate treatments resulted in reductions of Al release rates indicating that the dissolved Al fraction was derived from both Al-humus complexes (approximately 20% of the total dissolved Al) and allophanic materials (80%).Keywords
This publication has 32 references indexed in Scilit:
- Solubility control of KCl extractable aluminum in soils with variable chargeCommunications in Soil Science and Plant Analysis, 1994
- Aluminum release rates from allophanic and nonallophanic AndosolsSoil Science and Plant Nutrition, 1994
- Aluminum Solubility in Organic Soil Horizons from Northern and Southern Forested WatershedsSoil Science Society of America Journal, 1990
- Hydrologic control of aluminum chemistry in an acidic headwater streamWater Resources Research, 1988
- Effect of Solution Composition on the Rate and Mechanism of Gibbsite Dissolution in Acid SolutionsSoil Science Society of America Journal, 1987
- PROPERTIES OF NONALLOPHANIC ANDOSOLS FROM JAPANSoil Science, 1985
- The Kinetics of Gibbsite Dissolution in Nitric AcidSoil Science Society of America Journal, 1983
- Chemical and colloidal stability of sols in the Al2O3‐Fe2O3‐SiO2‐H2O system: their role in podzolizationEuropean Journal of Soil Science, 1982
- Extraction of Aluminum from Aluminum-Organic Matter Complexes1Soil Science Society of America Journal, 1981
- Copper Chloride as an Extractant for Estimating the Potentially Reactive Aluminum Pool in Acid SoilsSoil Science Society of America Journal, 1979