Resumen de Variación espacial de la movilidad de Fe, Mn, Cu y Zn

M.T. Taboada-Castro, M. J. Gómez Suárez, Antonio Paz González

• To investigate the spatial behavior of topsoil Fe, Mn, Cu and Zn in a small (1,8 ha) field 53 samples were taken acording to a nested sampling pattern. Metal contents extracted by 0.05 EDTA, both at pH = 5 and pH = 7 were analyzed and the Fe, Mn, Cu and Zn degree of binding was assessed by a mobility index, calculated as the difference between the concentrations released at pH = 5 and at pH = 7.

  Both the extractable content and the mobility index of these four metals displayed a wide range of variability. As expected, at the pHs range studied, field-averaged solubility was constant for Fe and increased for the other metals following the rank Zn ≈ Cu < Mn.

  Mobility index data analyzed by geostatistical techniques,specifically variogram computation, were found to have a spatial structure. Block-kriged contour maps allowed to identify microregions with significantly increased risk of Mn, Cu and Zn mobilization.

  Organic matter content, exchangeable cation capacity and silt content appeared to be the main factors responsible for the observed distribution of metals extractability and mobility index within the studied field.