Hydrologic and geochemical survey of the lake “Specchio di Venere” (Pantelleria island,Southern Italy) |
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| Authors: | A Aiuppa W D’Alessandro S Gurrieri P Madonia F Parello |
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| Institution: | (1) Dipartimento CFTA, Università di Palermo, via Archirafi 36, 90123 Palermo, Italy;(2) Istituto Nazionale di Geofisica e Vulcanologia, Sezione di Palermo, via U. La Malfa 153, 90146 Palermo, Italy |
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| Abstract: | Hydrological and geochemical studies performed on Lake Specchio di Venere on Pantelleria island (Italy) indicate that this
endorheic basin has been formed through upwelling of the water table, and that it is continuously fed by the thermal springs
situated on its shores. The lake is periodically stratified both thermally and in salinity, albeit this stratification is
rather unstable over time, since meteorological events such as strong rain or wind can determine the mixing of its waters.
Periodical analyses of the lake water chemistry show large variations of the salt content due to the yearly evaporation-rain
dilution cycle. These processes are also responsible for the saline stratification during steady meteorological conditions.
The mineralogical characterisation of the bottom sediments shows the almost exclusive presence of neoformation minerals, mainly
carbonates, formed in response to the pH gradient between spring- (pH ≈ 6) and lake-waters (pH ≈ 9). Finally, the CO2 partial pressures in the lake water slightly exceeding the atmospheric one, are due to the large amounts of CO2 brought to the lake through the bubbling free gas phase of the thermal springs. Nevertheless the high pH value of the lake
water, its small volume and its periodical mixing prevent dangerous built up of this gas. |
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| Keywords: | Pantelleria island Volcanic lake Gas hazard |
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