Iron distribution in the clay fraction of Cambisols as determined by Mössbauer spectroscopy,X-ray diffractometry and selective dissolution

Iron forms which characterize the clay fraction of four Cambisols from granite and the distribution of iron oxides in the soil profiles are studied by Mössbauer spectroscopy, X-ray diffractometry and selected chemical methods. The results obtained show that about 50 % of the Fe_t(6–10 % Fe) is not extracted by dithionite. The Fe_o/Fe_d ranges between 0.15 and 0.35. Oxalate dissolves goethite in different amounts, probably depending on the particle size and the Al-substitution level. The highest amount of hematite is found in the samples characterized by the lowest internal magnetic fields, suggesting that the soil distribution of hematite and goethite is related to environmental factors favouring or disfavouring Al-for-Fe substitution and crystallinity of the oxides.