Potential hazards of CO2 leakage in storage systems : learning from natural systems

The aim of this chapter is to focus on the effects of increasing global atmospheric CO2 concentrations on plants and marine ecosystems, less is known about the effects of high, but very localized, CO2 concentrations originating from depth. It summarizes some of the findings from the EC-funded natural analogues for the storage of CO2 in the geological environment project (NASCENT) project, which studied a number of natural CO2 seeps throughout Europe. Of these, four sites were chosen for this chapter which, allowed different leakage processes and impacts to be assessed. One site was located in northern Greece, around the commercially producing florina CO2 gas field. The other three sites were in central Italy, including: a selected area of the latera geothermal complex, where natural deep CO2 migrates upwards along faults and is emitted to the atmosphere, the San Vittorino intermontane basin where CO2-charged ground waters cause extensive dissolution of limestone to form large sinkholes, and the Ciampino area to the southeast of Rome, where CO2 derived from deep-seated volcanism within the Alban hills complex migrates along faults in a residential area. Results indicate modifications in groundwater chemistry, sinkhole formation, and elevated toxic gas exposure risks in these areas caused by the occurrence of numerous active CO2 vents, however data also show that effects can be spatially restricted, and that health risks can be minimized with simple and inexpensive approaches and regulations.