The island of Gran Canaria is located in the eastern Atlantic, to the west of the Saharan Desert, and, as a result of its proximity, is regularly affected by Saharan dust. When this weather condition occurs (haze conditions) the particulate/aerosol accumulation rate was lightly higher than under nonhaze conditions (5.473.8 mg m À2 h À1 versus 4.372.1 mg m À2 h À1). To quantify the contribution of airborne Saharan dust to soil development in northeastern Gran Canaria, aeolian dust was collected weekly at different altitudes and distances from the coast during a year in a series of collection plots. Mean values of dust accumulation rates decreased with increasing altitude (from 79 to 17 g m À2 yr À1 ). The mineralogy of airborne dust, identified by XRD, was quartz, Mg-calcite, calcite, feldspars, dolomite, magnetite, aragonite, halite, and minor amounts of illite, kaolinite-chlorite and palygorskite. Quartz is considered allochthonous because it is not present in the volcanic substrate of the island. However, the difference in quartz concentration from haze to non-haze conditions was only 10% higher. This suggests an external source, but does not preclude a recycled origin. The recognition of well shaped dolomites, observed by SEM-EDX in collected dust samples and in soils samples of the lowest altitude plot, indicate an edaphic origin, but are later recycled as an airborne component. r

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The preparation of ZrO2 by alkaline hydrolysis of ZrOCl2·8H2O, leads to an amorphous oxohydroxide precursor that upon calcination at temperatures higher than 350 °C produces a system with mixed crystallographic phases (monoclinic and tetragonal). Preparation of this material by the same procedure but adding different molar ratios of H2O2 produces amorphous precursors (ZHPn) developing, mainly, the tetragonal crystal phase at the same calcination temperatures. The molar fraction of the phases seems to be dependent on the H2O2 molar ratio, thus indicating a direct relationship of this parameter with the crystallization behavior. At a surface level, preparation with H2O2 seems to retain NH4 + from the alkaline medium even after calcination at 500 °C for 2 h. The sulfation process of these ZHPn samples also modifies the structural properties; in this case, the crystallization process is delayed at higher temperatures, but with the same crystallographic features of the nonsulfated series, the tetragonal phase becoming stable for temperatures up to 800 °C.