Geochemistry of high-pH waters from serpentinites of the Gruppo di Voltri (Genova, Italy) and reaction path modeling of CO2 sequestration in serpentinite aquifers

The large number of geochemical data gathered on the Gruppo di Voltri springs confirm that progressive interaction of meteoric waters with ultramafic rocks variably affected by serpentinization leads initially to the formation of Mg-HCO3 waters when the system is open to CO2, and Na-HCO3 and Ca-OH type water upon further interaction with the rock, under highly reducing closed-system conditions with respect to CO2. As indicated by H-3 data, these high-pH waters have had long residence times underground in deep aquifers hosted by serpentinitic rocks. These waters are the only available evidence of the presence of such deep aquifers. High-pressure injection Of CO2 into these deep aquifers was simulated by reaction path modeling. Results indicate that this is a feasible methodology to reduce the inputs of anthropogenic CO2 into the atmosphere. Serpentinitic rocks have a high capacity for CO2 sequestration, mainly through formation of carbonate minerals. Dissolution of serpentinitic rocks and precipitation of magnesite and silica minerals occurs naturally in areas of high terrestrial CO2 fluxes such as in southern Tuscany, corroborating the feasibility of this methodology Of CO2 sequestration. However, this process causes a progressive decrease in the porosity of the aquifer, at least under closed-system conditions. These side effects must be carefully evaluated by means of further laboratory tests and field activities. (C) 2003 Elsevier Ltd. All rights reserved.