Carbon Dioxide Discharged through the Las Cañadas Aquifer, Tenerife, Canary Islands

Abstract

Carbon dioxide is one of the first gases to escape the magmatic environment due to its low solubility in basaltic magmas at low pressures. The exsolved CO 2 gas migrates towards the surface through rock fractures and high permeability paths. If an aquifer is located between the magmatic environment and the surface, a fraction of the CO 2 emitted is dissolved in the aquifer. In this paper, an estimation of the water mass balance and the CO 2 budget in Las Cañadas aquifer, Tenerife, Canary Islands, is presented. Magmatic CO 2 is transported by groundwater and discharged through man-made sub-horizontal drains or galleries that exist in this island, and by the flow of groundwater discharged laterally towards other aquifers or to the ocean. In addition, the pCO 2 at the gallery mouth (or entrance) and at the gallery bottom (internal and deepest discharge point where the gallery starts) are calculated and mapped. The total CO 2 advectively transported by groundwater is estimated to range from 143 to 211 t CO 2 d -1 . Considering that the diffuse soil emission of CO 2 for the same area is 437 t d -1 , the diffuse/dissolved CO 2 flux ratio varies between 2 and 3. The high dissolved inorganic carbon content of groundwater explains the ability of this low temperature hydrothermal water to dissolve and transfer magmatic CO 2 at volcanoes, even during quiescence periods.

Mantle CO2 degassing at Mt. Vulture volcano (Italy): Relationship between CO2 outgassing of volcanoes and the time of their last eruption

“…(Martelli et al, 2008). In fact, the low 3 He/ 4 He ratios for both gas emissions and fluid inclusions in volcanoes of central-southern Italy, coupled to the low 3 He/CO 2 ratios and the generally high δ 13 C CO2 values, are consistent with a partial derivation of the gas from the subducted slab, which might be rich in carbonate lithologies (e.g., Chiodini et al, 2011;Frezzotti et al, 2009;Martelli et al, 2004;Peccerillo, 1999).…”

Diffuse surface emanations as indicator of structural permeability in fault-controlled geothermal systems

“…Large amounts of carbon dioxide that is released from magmatic bodies can also be dissolved in aquifers and carried away from major upflow zones (Marrero et al, 2008). This characteristic can provide additional information on the direction of geothermal fluid migration through structural elements and indicate potential outflow zones.…”

The effect of regional groundwater on carbon dioxide and methane emissions from a lowland rainforest stream in Costa Rica

“…In addition to biogenic contributions from the surface, dissolved CO 2 and CH 4 in regional groundwater can originate from volcanic degassing, nonvolcanic escape of gases from the upper mantle, intrusive magma chambers, carbonate‐bearing rocks in the crust, hydrocarbon accumulations [ Mörner and Etiope , ], and remineralization of ancient sedimentary organic matter [ Lovley and Anderson , ; Park et al ., ; Liu et al ., ]. Aquifers transporting high concentrations of dissolved C have been identified in numerous places around the world, for example, Portugal [ Cruz and Amaral , ], the Canary Islands [ Marrero et al ., ], the United States [ Evans et al ., ; Kampman et al ., ], Japan [ Yamada et al ., ], Canada, Costa Rica, Italy [ Genereux et al ., , and references therein], the Lesser Antilles [ Rivé et al ., ], and the Slovak Republic [ Kucharič et al ., ]. However, little is known about the fate of that C once it discharges into surface waters and its effects on C balances of the aquatic and surrounding terrestrial ecosystems.…”