Open AccessPreliminary geochemical characterization of the Mts. Simbruini karst aquifer (Central Italy)
Author(s) -
Massimo Ranaldi,
Marianna Cangemi,
Maria Luisa Carapezza,
Marco Vinci,
Paolo Madonia
Publication year - 2021
Publication title -
annals of geophysics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.394
H-Index - 60
eISSN - 2037-416X
pISSN - 1593-5213
DOI - 10.4401/ag-8698
Subject(s) - aquifer , karst , geology , groundwater , alkalinity , meteoric water , groundwater recharge , weathering , carbonate , geochemistry , δ18o , hydrology (agriculture) , mineralogy , stable isotope ratio , chemistry , paleontology , physics , geotechnical engineering , organic chemistry , quantum mechanics
Mts. Simbruini karst aquifer feeds important springs whose capture contributes to the water supply of Rome City. To improve the geochemical characterization of this aquifer, we analyzed 36 groundwater samples, 29 from springs and 7 from shallow wells, collected in 1996 and 2019. Atomic adsorption spectroscopy, tritration, ionic chromatography and mass spectrometry were the used analytical methods. Ground waters are bicarbonate alkaline-earth type and HCO3 dominance confirms that the aquifer is hosted in carbonate rocks. Total alkalinity vs. cations plot indicates that CO2 driven weathering controls the water chemistry. The probability plots of HCO3, cations and Ca2+ +Mg2+ indicate four groundwater populations with the less represented one (9 samples) characterized by the highest PCO2 values (>0.3 atm). Most anomalous values of the dissolved PCO2 are from springs located near the center of the studied area. Four samples have negative values of d13CCO2 (about -22‰ vs. PDB), indicating its organic origin, but two other samples have positive values (1.6 and 2.6 ‰ vs. PDB), similar to those observed in the CO2 of deep origin discharged at the close Colli Albani volcano. Therefore, geochemical evidence indicates that the Mts. Simbruini aquifer is locally affected by the input of deep originated CO2, likely rising up along fractures, interacting with a recharge of meteoric origin, as evidenced by its d2H and d18O isotopic signatures.