Spatial Distribution of Field Physico-Chemical Parameters in the Vulcano Island (Italy) Coastal Aquifer: Volcanological and Hydrogeological Implications

Abstract

Vulcano, the southernmost of the Aeolian island arc (Italy), is characterized by a shallow coastal aquifer resulting from the mixing of seawater, meteoric recharge and volcanogenic fluids. The aquifer has been intensively studied during the last decades, but a comprehensive hydrogeological model has never been developed due to the lack of direct information about the litho-stratigraphic columns of the wells and the depth of water bearing levels. We present and discuss here the time and spatial analysis of water table elevation, temperature and electric conductivity data, acquired during the last 20 years in 33 wells located at Vulcano Island, with the aim of developing a groundwater circulation scheme able to fit the field observations. We retrieved a circulation scheme characterized by an intricate geometry of flow paths driven by horizontal and vertical permeability variations, accounting for the strong variability of geochemical data evidenced in this area by the related scientific literature. Extending these results to a general context, particular care must be taken in approaching the study of aquifers in volcanic islands, because a strong, small spatial scale variability of the hydrogeochemical parameters is expected, and a reliable knowledge of the local conditions is required for developing successful groundwater circulation schemes. OPEN ACCESSWater 2015, 7 3207

Fractionation processes affecting the stable carbon isotope signature of thermal waters from hydrothermal/volcanic systems: The examples of Campi Flegrei and Vulcano Island (southern Italy)

“…Although such process is not expected to occur only along the Tindari-Letojanni fault, local conditions may play a key role in determining the isotopic composition of dissolved carbon species in thermal waters. In particular, (i) decreasing temperature and salinity (Madonia et al, 2015) at increasing distance from the volcanic edifice and (ii) absence of CO 2 soil degassing anomalies in this area (Inguaggiato et al, 2012) revealed a less intense supply of volcanic/hydrothermal fluids into shallow ground waters, which, consistently with what observed at the Campi Flegrei, likely allowed secondary isotopic fractionation processes to overwhelm the typical signature of the deep-derived carbon.…”

“…A relevant contribution from volcanic condensates was recognized in #27 well, where temporal variations in PCO 2 values were found to be strikingly related to changes in La Fossa crater fumarolic activity (Capasso et al, 1999(Capasso et al, , 2000. Accordingly, the supply of volcanic fluids was highlighted by the presence of a piezometric high (Madonia et al, 2015) and anomalous CO 2 soil degassing (Capasso et al, 2000) in this area. Similarly, the relatively high temperature, the TDS values of Cl-and SO 4 -rich waters from Baia di Levante (#23, #25, #26) and the peculiarly high HCO 3 contents measured in the #28 water (Table 1; Capasso et al, 2000Capasso et al, , 2001Boschetti et al, 2003) were likely originated by interaction processes with volcanic condensates or CO 2 -rich steam phase.…”

“…1b; Billi et al, 2006), i.e. the main tectonic discontinuity in this region, where an upflow of volcanogenic fluids was inferred on the basis of an anomalous elevation of the water table recognized in this area (Inguaggiato et al, 2012;Madonia et al, 2015). The remaining C waters (#30 and #33), characterized by high Cl, Br, NH 4 and Li contents (Table 1) and Na/Cl and Cl/Br mass ratios (0.51 and 302 in #30 and 0.57 and 313 in #33, respectively) similar to those of seawater (Na/Cl = 0.56, Cl/Br = 292), likely intercepted a seawater-contaminated water body affected by hydrothermal contribution (Federico et al, 2010).…”

“…The hydrogeological setting in Vulcano Island is characterized by discontinuous shallow aquifers, complex vertical and horizontal flow paths and different fluid sources (meteoric water, seawater, uprising geothermal waters and volcanic steam) (e.g. Capasso et al, 1999Capasso et al, , 2001Boschetti et al, 2003;Federico et al, 2010;Madonia et al, 2015), producing strongly differing geochemical features in the well waters (Table 1).…”

Hydrogeological and Geochemical Characteristics of the Coastal Aquifer of Stromboli Volcanic Island (Italy)

“…However, the main focus of this research has been concentrated on volcano monitoring implications. This is the case for Vulcano Island (Aeolian Archipelago, Italy), where tens of geochemical papers have described its shallow hydrothermal aquifer since 1988 [4], but the of geochemical papers have described its shallow hydrothermal aquifer since 1988 [4], but the first hydrogeological model was proposed only in 2015 [5]. An analogous fate concerned the close volcanic island of Stromboli (Figure 1), permanently active during the last 1500 years [6].…”