ORGANOMINERAL COMPLEXES IN LACUSTRINE SOILS FROM XOCHIMILCO (MEXICO). Amada Laura Reyes Ortigoza¹, Nicolas Aguilera Herrera¹, Norma García Calderón¹, Jaqueline Cañetas Ortega², ¹Facultad de Ciencias, ²Instituto de Física, Universidad Nacional Autónoma de México

Introduction. The most important organominerals (OM)) in soils have a union between simple or complex minerals (clays) and organic material as humic acids (HA), fulvic acids (FA). The stability of OM complexes and its resistence to degradation give a wide utility in vegetal nutrition. These complexes establish the modern organic agriculture in high productivity groups.(1). This investigation in order to characterise some OM crystals in soils.

Materials and Methods. Three soil samples from lacustrine sities Xochimilco with different pHs (acid, neutral and alcaline) were separated in particle sizes in order to investigate the clay fraction (with and without organic matter) and the organic fractions HA, FA. All samples were characterised with X ray diffraction (XRD), infrared spectroscopy (IR), microsonde, atomic plasma spectrochemical analysis, transmission electron microscopy (TEM), and scanning electron microscopy (SEM).

Results and Discussion. Clay-OM complexes (with and without organic matter), HA and FA originated of samples from the soils pH alcaline and acid showed differences defined by IR spectra, TEM, SEM and the total metal contents. The OM did not show any difference in pHs acid and neutral. The values d/N of XRD, TEM, SEM and IR indicated presence for the following crystaline minerals feldespars, quartz, micas, pyroxenes, smectites, halloysite, amphiboles, allophane and cristobalite.

References:

1.Newman,A.C. 1987. Chemistry of clays and clays minerals, Longam Scientific & Technical. Mineralogical Society. Monograph No. 6 480 pp.