MAJOR AND TRACE ELEMENTS GEOCHEMISTRY IN THE GROUND WATERS OF A VOLCANIC AREA: MOUNT ETNA (SICILY, ITALY)

Abstract

Thirty-five ground-water samples have been collected from wells, springs and drainage galleries on Mt Etna volcano for the determination of major, minor and trace elements in solution. Attention has been focused in particular on dissolved minor and trace elements, for most of which no data were available in the studied area. In general, dissolution of solids into Etna's ground waters follows from strong interaction between water of meteoric origin, CO 2 gas of magmatic origin and the volcanic rocks of the aquifers. However, the R-mode analysis allowed to distinguish several sources of solutes: Al, Co, Ni, Fe, Si, As would derive mainly from alteration of the volcanic rocks of Etna; SO 4 =, K, Na, V, Sr, Mo, Cr and calculated p(CO 2) would instead indicate a major contribution of volcanic gases (mostly CO 2 and SO 2); and TDS, HCO 3 =, Li Mg, B and Cl − would indicate a derivation from both these sources. Se, Hg, Cu and Mn would derive from hydrothermal fluids, and Ca would derive both from this latter contribution and from rock alteration. The comparison between trace elements abundance in Etna's ground waters and that in the ground waters of other areas of Italy showed that, in general, Etna's waters, like other volcanic ground waters, are enriched in Li, Mn, Si, V, As and Mo. Furthermore, in the areas of Mt Etna where the contribution of volcanic gas to the aquifers is greatest, ground waters are also enriched in B, Se, Co, Hg, Al, Fe and Ni. The obtained results show clearly that, in active volcanic areas, many dissolved elements can attain levels that can be appreciably different from those indicated by WHO for drinking water. Therefore, the local geological factors which can influence the geochemical behavior of these elements in solution should be taken into account when establishing national standards for drinking-water quality. In consideration of the local natural background values, concentrations of dissolved elements that differ from the guideline values should be accepted in areas with peculiar geological characteristics, provided that the elements under consideration do not have a direct influence on health. © 1998 Elsevier Science Ltd. All rights reserved