Aluminio y estabilidad mineral en suelos del entorno de As Pontes

Resumo

Al fractions susceptible to be liberated from the solid phase, Al forms in soil solutions and the saturation indexes for certain Al-minerals (gibbsite, microcristaline gibbsite, kaolinite, alunite, jurbanite and basalunite) are studied in the A and B horizonts of soils derived from different parent materials representative of the studied area (granitic rocks, gneisses, schists, phyllites, quarzous sediments and metabasic rocks). The results show that the soils from granite, phyllite and gneiss had the highest levels of exchangeable, labile potential, maximun potential Al in the solid phase and total Al in soil solution; the soils derived from metabasic rocks showed high quantities of maximun potential Al and low levels of the most labile forms and total Al in solution. The schist displayed intermediate values for these Al forms. The mineral saturation indexes indicate that many samples, independently of the parent material and horizon type, are situated in the disolution field for the minerals considered. When oversaturation conditions are produced, kaolinite is the most stable mineral and gibbsite the one that, most frequendy, controls Al3+ activity in solution.