Elemental geochemistry of soils from the volcanic island of Pantelleria, Sicily: implications for Moscato wine production.

The volcanic island of Pantelleria produces a naturally sweet wine Moscato di Pantelleria DOC obtained from the «Moscato d'Alessandria» (or «Zibibbo»), a grape favoured by hot climate. Geochemical and mineralogical investigations performed on soil profiles devoloped on rocks representative of the major outcropping lithologies (pantellerite, trachyte and alkalic basalt) show that the soils have preserved the parent material imprint. Consistently, values of the chemical index of alteration (CIA) indicate a low to moderate weathering degree for the rocks exposed in the Pantelleria area and consequently a low to moderate soil evolution. Soil-solution chemical analyses highlight that macro- and micronutrient elements are present in forms potentially available to plants. Although the grape ripening capacity is controlled by various factors (climate, pedologic substratum, exposure, morphology), different degrees of weathering, as measured by CIA values, appear to correspond to different grape ripening times. Less weathered soils contain noncrystalline phases, mainly Fe and Al hydroxides, which make them more sensitive to drying effects; these soils are generally related to early sites. In more weathered soils, the presence of clay minerals contributes to increased available water content and, in turn, to conditions of enhanced specific heat, which can delay the grape ripening.