Mössbauer analysis of Brazilian Oxisols

Three sets of Brazilian Oxisols have been analysed by Mössbauer spectroscopy at 290, 80 and 4.2 K. In most cases two resolved magnetic hyperfine patterns associated with aluminous goethite and hematite are resolved; their ratio is related to soil colour. Samples from a 3 m soil profile show that both oxides become decreasingly aluminium substituted and/or better crystallized with depth. Goethite from surface or deep layers is readily differentiated by its hyperfine parameters. As there is no significant alternate source of iron, the results suggest that both hematite and goethite undergo continuous neoformation throughout the profile in response to the changing pedogenic environment.