Temporal Variability of Major and Trace Element Concentrations in the Groundwaters of Mt. Etna (Italy): Effects of Transient Input of Magmatic Fluids Highlighted by Means of Cluster Analysis |
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Authors: | Salvatore Giammanco Massimo Ottaviani Enrico Veschetti |
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Institution: | (1) Istituto Nazionale di Geofisica e Vulcanologia – Sezione di Catania, Piazza Roma 2, Catania, 95123, Italy;(2) Istituto Superiore di Sanità, Viale Regina Elena 299, Roma, 00161, Italy |
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Abstract: | Data for major, minor and trace elements in groundwaters from Mt. Etna volcano collected in 1994, 1995 and 1997 were analyzed
using Cluster Analysis (CA). Two groups of sampling sites were identified (named clusters A and B), mainly on the basis of
their different salinity and content of dissolved CO2. The highest levels of both of these parameters were observed in the sites of cluster A, located in the lower south-western
and central eastern flanks of the volcano. For both of the statistical groups CA was repeated, taking into account the mean
values of each parameter in time, and the results allowed us to recognize four distinct groups of parameters for each group
of sites on the basis of their temporal patterns. Four different types of temporal patterns were recognized: concave, convex,
increasing, decreasing. The observed changes were basically interpreted as a result of the different response of dissolved
chemical elements to changes in the aqueous environment and/or in their solubility/mobility in water due to different rates
of input of magmatic gases to Etna’s aquifers. The main changes occurred in 1995, when Etna’s volcanic activity resumed after
a two-year period of rest. The temporal changes of the majority of the studied parameters (water temperature, water conductivity,
Eh, pH, Al, Mg, B, Ca, Cl−, Hg, Mn, Mo, Na, Ni, Se, Si, Sr, Cr Zn and pCO2) were not cluster-dependent, therefore they were not apparently affected by differences in water salinity between the two
groups of sampling sites. A limited number of parameters (Ti, K, Li, HCO3−, As, Fe, SO42−, Cu and V), however, manifested different behaviors, depending on the cluster of sites to which they belonged, thus suggesting
their apparent dependency on water salinity. |
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Keywords: | Trace elements groundwater Mount Etna cluster analysis volcanic activity |
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