Rate of diffuse carbon dioxide Earth degassing estimated from carbon balance of regional aquifers : The case of central Apennine, Italy

Central Italy is characterized by an anomalous flux of deeply derived CO2. In the western Tyrrhenian sector of central Italy, CO2 degassing occurs mainly from focused emissions (vents and strong diffuse degassing) and thermal springs, whereas in the eastern Apennine area, deep CO2 is dissolved in “cold” groundwaters of regional aquifers hosted by Mesozoic carbonate-evaporite formations. Influx of deep CO2 into 12 carbonate aquifers (12,500 km2) of the central Apennine is computed through a carbon mass balance that couples aquifer geochemistry with isotopic and hydrogeological data. Mass balance calculations estimate that 6.5×1010 mol yr−1 of inorganic carbon are dissolved in the studied aquifers. Approximately 23% of this amount derives from biological sources active during the infiltration of the recharge waters, 36% comes from carbonate dissolution, while 41% is representative of deep carbon sources characterized by a common isotopic signature (δ13C ≅ −3‰). The calculated deep CO2 influx rate ranges from 105 to 107 mol yr−1 km−2, increasing regionally from east to west in the study area.

[1]  Giovanni Chiodini,et al.  Quantification of deep CO2 fluxes from Central Italy. Examples of carbon balance for regional aquifers and of soil diffuse degassing , 1999 .

[2]  William C. Evans,et al.  Carbon dioxide and helium emissions from a reservoir of magmatic gas beneath Mammoth Mountain, California , 1998 .

[3]  B. Marty,et al.  CO2 FLUXES FROM MID-OCEAN RIDGES, ARCS AND PLUMES , 1998 .

[4]  F. Parello,et al.  Chemical and isotopic characterization of the gases of Mount Etna (Italy) , 1997 .

[5]  C. Fléhoc,et al.  Mantle-derived helium and carbon in groundwaters and gases of Mount Etna, Italy , 1997 .

[6]  F. Stoppa,et al.  The Italian carbonatites: Field occurrence, petrology and regional significance , 1997 .

[7]  T. Rose,et al.  Radiocarbon in Hydrologic Systems Containing Dissolved Magmatic Carbon Dioxide , 1996, Science.

[8]  D. Kerrick,et al.  Hydrothermal CO2 emission from the Taupo Volcanic Zone, New Zealand , 1996 .

[9]  Ken Caldeira,et al.  Convective hydrothermal C02 emission from high heat flow regions , 1995 .

[10]  Giovanni Chiodini,et al.  Deep structures and carbon dioxide degassing in Central Italy , 1995 .

[11]  J. Lupton,et al.  Helium isotopes in some historical lavas from Mount Vesuvius , 1993 .

[12]  F. Innocenti,et al.  Geochemical and petrological evidence of the subduction of delaminated Adriatic continental lithosphere in the genesis of the Neogene-Quaternary magmatism of central Italy , 1993 .

[13]  P. Allard.  Correction to “Global emissions of helium‐3 by subaerial volcanism” , 1992 .

[14]  P. Allard.  Global emissions of helium‐3 by subaerial volcanism , 1992 .

[15]  S. J. Schaefer,et al.  Global carbon dioxide emission to the atmosphere by volcanoes , 1992 .

[16]  T. Gerlach.  Present-day CO2 emissions from volcanos , 1991 .

[17]  P. Zettwoog,et al.  Eruptive and diffuse emissions of CO2 from Mount Etna , 1991, Nature.

[18]  J. Quade,et al.  Systematic variations in the carbon and oxygen isotopic composition of pedogenic carbonate along elevation transects in the southern Great Basin, United States , 1989 .

[19]  Robert A. Berner,et al.  Modeling the geochemical carbon cycle , 1989 .

[20]  F.Arisi Rota,et al.  Magnetic interpretation related to geo-magnetic provinces: the Italian case history , 1987 .

[21]  F. D'amore,et al.  Gas Geothermometry Based on CO Content--Application in Italian Geothermal Fields , 1987 .

[22]  J. Valley.  Chapter 13. STABLE ISOTOPE GEOCHEMISTRY of METAMORPHIC ROCKS , 1986 .

[23]  J. M. Martín,et al.  Influence of Saharan dust on the rain acidity and atmospheric input to the Mediterranean , 1986, Nature.

[24]  J. R. O'neil,et al.  Contrasting fluid/rock interaction between the Notch Peak granitic intrusion and argillites and limestones in western Utah: evidence from stable isotopes and phase assemblages , 1984 .

[25]  G. Pellis,et al.  Geothermal structure of the Tyrrhenian Sea , 1984 .

[26]  R. Garrels,et al.  The carbonate-silicate geochemical cycle and its effect on atmospheric carbon dioxide over the past 100 million years , 1983 .

[27]  D. Rumble.  Chapter 8. STABLE ISOTOPE FRACTIONATION during METAMORPHIC DEVOLATILIZATION REACTIONS , 1982 .

[28]  Claude J. Allègre,et al.  Carbon geodynamic cycle , 1982, Nature.

[29]  F. J. Pearson,et al.  Mass transfer and carbon isotope evolution in natural water systems , 1978 .

[30]  L. N. Plummer,et al.  Defining reactions and mass transfer in part of the Floridan aquifer , 1977 .

[31]  R. Harmon,et al.  Stable carbon isotope ratios and the existence of a gas phase in the evolution of carbonate ground waters , 1974 .

[32]  F. J. Pearson,et al.  Sources of Dissolved Carbonate in an Aquifer Free of Carbonate Minerals , 1970 .

[33]  David L. Parkhurst,et al.  USER'S GUIDE TO PHREEQC A COMPUTER PROGRAM FOR SPECIATION, REACTION-PATH, ADVECTIVE-TRANSPORT, AND INVERSE GEOCHEMICAL CALCULATIONS , 1995 .

[34]  B. Marty,et al.  Volatile fluxes from volcanoes , 1991 .

[35]  Donald E. White,et al.  Global distribution of carbon dioxide discharges, and major zones of seismicity , 1978 .