2.2. Analytical methods
Soil particle size distribution was assessed by sieving and sedimentation, according to the hydrometer method (Gee and Bauder, 1986). The mineralogical composition was determined by XRD with a XR-PW3040 Phillips Diffractometer, interpreting the diagrams with Phillips X’Pert Graphics and Identify software. A semi-quantitative analysis of the soil was made using the diffraction intensities and values for the same phases given in the literature (García-Rizo et al., 1999).