MOSSBAUER STUDIES ON SOME ARGENTINEAN SOIL - MOLLISOLS FROM BAHIA-BLANCA

Clay fractions of a Mollisol sample as is, treated with ammonium oxala te (AO), with dithionite-citrate-bicarbonate (DCB) and with dithionite -ethilene-diamine- tetraacetic acid (D-EDTA) methods, were studied. Il lite-montmorillonites together with hematites, goethites and maghemite s, all of the Al-substituted and with a wide range of sizes, were iden tified. It is found that the AO attack extracts little iron, whereas t he other two attacks extract the magnetic signal. Furthermore, the DCB attack facilitates the reduction of the Fe3+ ions, while the D-EDTA m ethod does not. Instead, this attack extracts more clay mineral Fe ion s. A comparison with large grain soil samples is made.