Publication Date:
2022-03-07
Description:
Comprehensive hydrogeochemical studies have been conducted in the Campi Flegrei volcanic aquifer since late
20th century due to the volcanic unrest. In the last decade, groundwater samples were grouped based on the
dominant anion species (i.e. bicarbonate, sulfate and chloride) to explain the general hydrogeochemical processes.
In this article, 44 groundwater samples are collected from Campi Flegrei aquifer to geochemically and
spatially capture the main characteristics of the groundwater body. The hierarchical clustering algorithm is then
performed on proportion of bicarbonate, sulfate and chloride, and the optimum number of clusters are determined
regarding the results of deep hydrogeochemical investigations published in the past. The collected samples
are categorized in the following groups: (1) bicarbonate-rich groundwater; (2) chlorine-rich groundwater;
(3) sulfate-rich groundwater; and (4) mixed groundwater. The first group (As = 158.2 ± 169 μg/l, electric
conductivity = 1,732.1 ± 1,086 μS/cm and temperature = 25.6 ± 8 ◦C) is mainly derived from poor arsenic
meteoric water, but there is significant thermal/seawater contribution in the second one (As = 1,457.8 ± 2,210
μg/l, electric conductivity = 20,118.3 ± 11,139 μS/cm and temperature = 37.1 ± 20 ◦C). Interaction of the
bicarbonate-rich groundwater and hydrothermal vapors gives rise to the sulfate-rich groundwater (As = 847.2 ±
679 μg/l, electric conductivity = 3,940.0 ± 540 μS/cm and temperature = 82.8 ± 3 ◦C) around Solfatara volcano.
The mixed groundwater (As = 451.4 ± 388 μg/l, electric conductivity = 4,482.9 ± 4,027 μS/cm and
temperature = 37.1 ± 16 ◦C) is observed where the three main groundwater groups undergo a mixing process,
depending on the hydrogeology of the volcanic aquifer. Contrary to the bicarbonate- and sulfate-rich groundwater,
the chlorine-rich and mixed groundwater generally occurs at low piezometric levels (approximately 〈1 m
above sea level) near the coastline. The hierarchical cluster analysis provides more information about the volcanic
aquifer, particularly when compositional data analysis is applied to study hydrogeochemistry of the homogeneous
groundwater groups and to uncover the relationships between variables. Addressing compositional
nature of data is recommended in the future studies for developing new tools that help deeper understanding of
groundwater evolution in volcanic aquifers and identifying promising precursors of volcanic eruption.
Description:
Published
Description:
106922
Description:
4V. Processi pre-eruttivi
Description:
2IT. Laboratori analitici e sperimentali
Description:
JCR Journal
Keywords:
Hierarchical cluster analysis
;
Groundwater evolution
;
Hydrothermal system
;
Precursors of volcanic eruption
;
03.02. Hydrology
Repository Name:
Istituto Nazionale di Geofisica e Vulcanologia (INGV)
Type:
article
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