CO 2 and heat fluxes in the Apennines, Italy Giovanni Chiodini (INGV, sezione di Bologna, Italy) CO 2 Earth degassing and climate changes CO 2 Earth degassing and tectonics CO 2 flux Mt yr 1 Fossil fuels and industry* >30000 Earth degassing <1000 (<3%) * Le Quéré et al. (2016) Tamburello et al., submitted Extensional teconic regimes are characterised by an anomalous emission of deep CO 2
CO 2 and heat fluxes in the Apennines, Italy Giovanni Chiodini (INGV, sezione di Bologna, Italy) Outline 1) Map of CO 2 Earth degassing in Italy 2) Quantification of CO 2 fluxes 3) Origin of the gas 4) CO 2 and heat fluxes 5) Earth degassing and seismicity
1. Map of CO 2 Earth degassing in Italy Stifone springs: CO 2 flux = 1200 t/d TDIC (as CO 2 ) = 0.91 g/l (i.e. CO2 flux = 1200 t d -1 ) Stifone springs (flow rate = 15000 l/s, central Italy) Total flux of dissolved CO2 ~ 1200 t d -1
1. Map of CO 2 Earth degassing in Italy Carbon mass balance of regional aquifers We eliminated from TDIC the contribution from carbonate dissolution, computing for each spring two new variables: C ext = C inf + C deep = TDIC -C carb δ 13 C ext = (δ 13 C TDIC x TDIC - δ 13 C carb x C carb ) / C ext Chiodini et al, 2000
1. Map of CO 2 Earth degassing in Italy Carbon mass balance of regional aquifers For the elaboration of the map we studied the main springs of the region. Data set Carbonate aquifers n Q (l/s) Q mean Apennines 154 231000 1500 Toscana-Umbria-Lazio 52 15600 300 The sampled springs represents the 61% of the total flow rate discharged by Apennine aquifers. Chemical and isotopic analysis of dissolved carbon were used to investigate the origin of the carbon dissolved in the waters by solving the carbon mass balance of each aquifer C ext = C inf + C deep = TDIC -C carb δ 13 C ext = (δ 13 C TDIC x TDIC - δ 13 C carb x C carb ) / C ext
1. Map of CO 2 Earth degassing in Italy Carbon mass balance of regional aquifers C inf C inf + C deep 0.003 Apennine aquifers are affected by the same process occurring in volcanic aquifer: the input of a large amount of deeply derived, inorganic CO 2! Chiodini et al. (2000) C ext = C inf + C deep = TDIC -C carb δ 13 C ext = (δ 13 C TDIC x TDIC - δ 13 C carb x C carb ) / C ext
1. Map of CO 2 Earth degassing in Italy Daily budget of carbon (expressed in tons of CO 2 ) of Stifone Springs TDIC = Carbon from carbonate mineral dissolution C carb + Carbon from organic sources (infiltration) C inf Carbon from deep sources + C deep 1200 t d -1 370 t d -1 190 t d -1 640 t d -1 q = 1.3 10 9 l d -1 C deep = 0.011 mol l -1 = 0.49 g l -1 Deeply derived CO 2 (C deep x q) = 640 t d -1 A (area of the hydrogeological basin) = 740 km 2 Flux of deep CO 2 = 640 / 740 = 0.86 t km -2 d -1 Each spring can be used as a measuring point of the average flux of deep CO2 affecting large areas, typically from tens to hundreds km 2 in the Apennines Stifone springs (flow rate = 15000 l/s, central Italy) Flux of deeply derived CO2 dissolved in the water ~ 638 t d -1
1. Map of CO 2 Earth degassing in Italy CO 2 mass balance of aquifers A Hydrogeological map of Central Italy Boni, Bono, Capelli (1986) Stifone Springs q C deep from geochemical modeling Each spring can be used as a measuring point of the average flux of deep CO2 affecting large areas, typically from tens to hundreds km 2 in the Apennines
1. Map of CO 2 Earth degassing in Italy Each spring can be used as a measuring point of the average flux of deep CO2 affecting large areas, typically from tens to hundreds km 2 in the Apennines
1. Map of CO 2 Earth degassing in Italy
2. Quantification of CO 2 Earth degassing (gas emissions) Quantification of CO 2 flux from deep sources Structure Specific flux Area Total output t km -2 d -1 km 2 t d -1 TRDS 0.45 37800 16900 CDS 0.57 14900 8400 TOTAL 25300 The measurement of Specific deep CO 2 fluxes from aquifers in different tectonic setting could be fundamental for global estimations of CO 2 degassing from diffuse emission..
2. Quantification of CO 2 Earth degassing (gas emissions) An independent observation: the location of gas emissions in Italy Databases of gas emissions ITALY GOOGAS (http://googas.ov.ingv.it/) GLOBAL MAGA (http://www.magadb.net/)
2. Quantification of CO 2 Earth degassing (gas emissions) Measured CO 2 release (24 gas emissions) : > 5700 t/d Estimated CO 2 release (>150 gas emissions) : >> 5700 t/d CO 2 emission forming a gas river at Mefite d Ansanto CO 2 flux ~ 2000 t d -1 (measured using gas concentration, velocity of the river and physical simulation of the gas plume, Chiodini et al., 2010) Mefite d Ansanto
Natural emissions of CO2 in Central Italy and related hazard November 19th, 2003, Mt. Amiata, Siena Killed by the gas escaping from the Earth
2. Quantification of CO 2 Earth degassing CO 2 flux from Tyrrhenian Italy Aquifers Gas emissions > 9.1 Mt/yr >> 2.1 Mt/yr The amount of CO 2 released by TRDS and CDS is larger than the amount released by the active volcanoes of Italy
2. Quantification of CO 2 Earth degassing CO 2 flux from Tyrrhenian Italy Aquifers Gas emissions > 9.1 Mt/yr >> 2.1 Mt/yr Redraw from the original in Barnes et al., 1978 CO 2 release in the studied area is 2%-15% of global volcanic CO 2 flux Burton et al. (2013) Burton et al. (2013) How much CO 2 is globally released by the tectonic areas?
3. Origin of the gas CO2 vent at Palidoro (Rome) Total CO2 output unquantified CO 2, 3 He, 13 C data suggest that the gas is produced mainly by the mixing between a MORB source with fluids deriving from decarbonation of limestone
4. Advective heat transport associated to Earth degassing in Apennine The Tyrrhenian side is hot! high CO 2 flux Apennine belt is apparently cold
Advective heat transport associated to regional Earth degassing in central Apennine (Italy) CO 2 flux of Italy Conductive heat flux of Italy Italy N CO 2 flux (t d -1 km -2) input of deep CO2 0.7 0.6 0.5 0.4 0.3 Roma CO rich gas emission 2 CH rich gas emission 4 0.2 Napoli 0.1 0 50 100km Total CO 2 emission > 25000 t d -1 Modified from Cataldi, R.,Mongelli,F., Squarci,P., Taffi, L.,Zito,G., Calore,C.,1995. Geothermal ranking of Italian territory. Geothermics 24, 115 129 (plate 2)
Advective heat transport associated to regional Earth degassing in central Apennine (Italy) The map of the heat flux of Italy shows a N-S band of low heat fluxes that corresponds to the area of the Apennine aquifers. Meteoric waters deeply circulate in these areas, cooling the crust, transporting an unknown amount of heat and possibly causing the measured low heat flux of the area.
Advective heat transport associated to regional Earth degassing in central Apennine (Italy) Heat flow map of Italy with the main factors influencing the heat flow distribution Deep meteoric water infiltration zone of low heat flux (conductive) Della Vedova et al., 2000
Advective heat transport associated to regional Earth degassing in central Apennine (Italy) At the Earth surface the heat flux is normally conductive and its direction is vertical. The heat flux is estimated based on the data of boreholes (measurements of thermal gradient and of the thermal conductivity of the rocks); In mountainous regions characterised by a high permeability of near-surface rocks and high water recharge rates, groundwater flow makes the estimates of heat flux based on a conductive model unreliable. In these regions, due to the abundant groundwater circulation, the advective heat flow can be the dominant form of heat transfer, and the temperature of the spring water can be used to estimate more realistic values of geothermal heat flux. Mass and energy balances of groundwater circulation has been systematically applied only to the US Cascade Range providing the recognition of the deep thermal sources active in the area (e.g., Ingebritsen et al., 1989; Ingebritsen and Mariner 2010; Manga, 1998) and, more recently, to Apennine (Italy) (Chiodini et al., 2013).
Advective heat transport associated to regional Earth degassing in central Apennine (Italy) Investigated aquifers of central Apennine 46 springs, flow rates from 0.2 to 18 m 3 /s, total sampled flow rate 130 m 3 /s Apennine The sampled springs are from 11 carbonate hydrogeological structures which represent a significant portion of the permeable structures of the central Apennine
Advective heat transport associated to regional Earth degassing in central Apennine (Italy) CO 2 mass balance of aquifers: results Total input of deep CO 2 in the studied aquifer: 3100 t d -1 The water is in each aquifer of meteoric origin In most of the aquifers the carbon mainly derives from the deep source
Advective heat transport associated to regional Earth degassing in central Apennine (Italy) Enthalpy balance of aquifers
Advective heat transport associated to regional Earth degassing in central Apennine (Italy) Enthalpy balance of aquifers The geothermal heat flux affecting the of groundwater has been computed starting from: T = water temperature at discharge water temperature at infiltration and z = difference between the water recharge area and the spring elevations Q C b T = + z w w A q ρ} Geothermal warming g C w } Gravitational potential energy (GPE) dissipation Q b lines computed assuming effective infiltration q/a = 0.02 m 3 km -2 s -1 Where: Q b = geothermal heat flux T = water temperature at discharge water temperature at infiltration z = difference between the water recharge area and the spring elevations g = gravitational acceleration constant ρ w = water density C w =water heat capacity A = areal extension of hydrogeological basin of the spring (based on hydrogeological studies) q = spring flow rate The used equation assumes a negligible effect of the conductive heat transfer from the aquifer to the surface (Manga and Kirchner, 2004) geothermal warming
Advective heat transport associated to regional Earth degassing in central Apennine (Italy) Enthalpy balance of aquifers: results Total input of geothermal energy in the studied aquifer: 2.1 GW In the aquifers not affected by the input of deep CO 2 the mean advective heat flux (25-44 mw/m 2 ) practically coincides with the known, low, conductive heat flux. For the aquifer affected by the input of deep CO 2 the mean advective heat flux (180-370 mw/m 2 ) results up to one order of magnitude higher than the conductive heat flux!
Advective heat transport associated to regional Earth degassing in central Apennine (Italy) Geothermal heat transported by central Italy groundwaters 1.3 10 9 J/s (1.3 GW) (measured) 2.1 10 9 Js -1 (2.1 GW) (estimated extending the computed values to the not sampled portion of groundwater) The amount of geothermal heat transported by central Apennine cold groundwaters is: 1) about the double than the hydrothermal heat discharge of the US Cascade Range (~1 GW, Ingebritsen and Mariner, 2010) 2) about 1/3 of the total heat discharged at Yellowstone, i.e. the largest hydrothermal system of the world (~6 GW; Fournier, 1989; Ingebritsen et al., 2001).
Advective heat transport associated to regional Earth degassing in central Apennine (Italy) Geothermal heat flux and CO 2 flux The geothermal heat is transported from depth by CO 2 - rich fluids!
Advective heat transport associated to regional Earth degassing in central Apennine (Italy) Geothermal heat flux and CO 2 flux Central Italy Torre Alfina Latera The geothermal heat is transported from depth by CO 2 - rich fluids! The fluids entering in the Apennine aquifers have enthalpy - CO 2 ratios close to that measured in the known geothermal systems of Torre Alfina and Latera
Advective heat transport associated to regional Earth degassing in central Apennine (Italy) Geothermal heat flux and CO 2 flux Frondini et al., submitted The geothermal heat is transported from depth by CO 2 - rich fluids! The plot highlights a problem for the development of the geothermal resource in Italy: the very high content of CO 2 (and H 2 S) of the fluids! (e.g. the Italian geothermal fluids are several times richer in CO 2 than those from New Zealand...)
Advective heat transport associated to regional Earth degassing in central Apennine (Italy) Heat and deep fluids source? Thermal and fluid source? Chiodini et al. (2013) The heat anomaly broadly coincides with a low velocity anomaly in the crust which could be associated with a large magmatic intrusion with the top at 10-15 km below the Apennines.
5. Earth degassing and seismicity The anomalous flux of CO 2 suddenly disappears in the Apennine in correspondence with a narrow band where most of the seismicity concentrates. Here, at depth, the gas accumulates in crustal traps originating overpressurised reservoirs that induce seismicity Chiodini et al., 2004
5. Earth degassing and seismicity 1983-2013 Campi Flegrei earthquakes
5. Earth degassing and seismicity 2013-2014 Matese earthquakes 1983-2013 Campi Flegrei earthquakes
5. Earth degassing and seismicity ~ 50000 ton 1989 Colli Albani earthquakes 2013-2014 Matese earthquakes 1983-2013 Campi Flegrei earthquakes
5. Earth degassing and seismicity 1997 Umbria-Marche earthquakes 1989 Colli Albani earthquakes Chiodini et al., 2012 2013-2014 Matese earthquakes 1983-2013 Campi Flegrei earthquakes Chiodini et al., 2012
5. Earth degassing and seismicity 1997 Umbria-Marche earthquakes 2009 L Aquila earthquakes Anomalous emission of deeply derived CO 2 accompanied L Aquila 2009 earthquakes 1989 Colli Albani earthquakes CO 2 transported by the aquifers in the epicentral 2013-2014 Matese area earthquakes (in preparation) Cardellini et al., in preparation 1983-2013 Campi Flegrei earthquakes
5. Earth degassing and seismicity 1997 Umbria-Marche earthquakes 2009 L Aquila earthquakes In the Apennines there are numerous signs of an active role of CO 2 rich fluids in the seismogenesis 1989 Colli Albani earthquakes 2013-2014 Matese earthquakes 1983-2013 Campi Flegrei earthquakes
Conclusions Regional maps and quantitative estimations of CO 2 Earth degassing can be obtained by defining the carbon mass balance of regional aquifers (high flow rate discharges rather than low flow rate anomalous springs!) Central Tyrrhenian Italy, including Apennines, is affected by a CO 2 flux of 0.4-0.6 t km 2 d -1 (total > 9.1 Mt/yr). The flux of other tectonic zone of the Earth is unknown! A large sector of Central Apennines is affected by very high heat fluxes (estimated as high as 300 mw m -2 ). The heat is transported from depth by CO 2 rich fluids. The source of heat and fluids below the Apennine, is likely a broad magmatic intrusion; The thermal regime of tectonically young and active areas of the Earth, where large amount of meteoric waters infiltrate and circulate deeply (such as in the entire Alpine-Himalayan belt) should be revised on the basis of mass and energy balances of the groundwater systems; There are numerous signs of an active role of CO 2 rich fluids in the seismogenesis of the Apennines.
2) Cold CO2 emissions from geothermal systems in central Italy Heat and deep fluids source? CO 2 emission at Latera CO 2 emission at Torre Alfina CO 2 flux = 86 ton/d T = 150 C, CO2 = 0.37 mol/kg CO 2 flux = 1 kg/s geothermal water 61 kg/s Associated heat = 39 MW T = 212 C, CO2 = 0.72 mol/kg CO 2 flux = 4.1 kg/s geothermal water 128 kg/s Associated heat = 117 MW