Assessment of isotopically exchangeable Al in soil materials using Al-26 tracer
2005 (English)In: Geochimica et Cosmochimica Acta, ISSN 0016-7037, E-ISSN 0016-1258, Vol. 69, no 22, 5263-5277 p.Article in journal (Refereed) Published
The solubility of aluminium (Al) in many acidic soils is controlled by complexation reactions with soil organic matter. In such soils, Al solubility is theoretically a function of the pool size of active Al, i.e., the total amount of Al that equilibrates with the sod solution within a defined period of time. To date, no reliable measurements of active Al in soil materials exist. In this study, we determined the isotopically exchangeable pool of Al (E-A1) as an operationally defined assessment of active Al in acidic mineral soils. The suitability of CuCl2 and pyrophosphate (Na4P2O7) as extractants for active Al was also evaluated. Eleven samples, mostly from spodic B horizons, were spiked with carrier-free Al-26 and equilibrated for different time periods (1-756 h). The size of the Al pool with which the Al-26 tracer exchanged increased with time during the whole experimental period. Thus, contact time between solid and solution phases needs to be defined when assessing the active Al pool. Values of E-A1 obtained after I to 5 d of equilibration were equal to the amount of CuCl2 extractable Al, but considerably smaller than the Na4P2O7-extractable pool. Equilibration times greater than 5 d resulted in CuCl2 extractable Al concentrations that under-estimated the active Al pool. Three of the investigated samples were rich in imogolite-type materials (ITM). In these samples, 30-50 % of the added Al-26 rapidly became associated with soil constituents in forms that could not be extracted by Na4P2O7, indicating that a part of ITM may be in a dynamic state.
Place, publisher, year, edition, pages
2005. Vol. 69, no 22, 5263-5277 p.
accelerator mass-spectrometry, aluminum solubility mechanisms, quickly reacting aluminum, podzol bs horizon, organic-matter, humic substances, forest soils, equilibrium-model, aqueous-solution, acid soils
IdentifiersURN: urn:nbn:se:kth:diva-15303DOI: 10.1016/j.gca.2005.06.010ISI: 000234417400007ScopusID: 2-s2.0-29444444890OAI: oai:DiVA.org:kth-15303DiVA: diva2:333344
QC 201005252010-08-052010-08-05Bibliographically approved