VIVEIROS, F., FERREIRA, T., GASPAR, J.L., SILVA, C. (2016) – Anomalous volcanic CO2 exposure maps – a first approach. ICUR2016 Proceedings, Centro Europeu de Riscos Urbano, Lisboa: 493-500.

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Artigos em livros de atas ► Internacionais

Referência Bibliográfica

VIVEIROS, F., FERREIRA, T., GASPAR, J.L., SILVA, C. (2016) – Anomalous volcanic CO₂ exposure maps – a first approach. ICUR2016 Proceedings, Centro Europeu de Riscos Urbanos, Lisboa: 493-500.

Resumo

Several secondary manifestations of volcanism can be found in the Azores archipelago as fumaroles, thermal and cold CO₂-rich springs and soil diffuse degassing areas. Carbon dioxide (CO₂) and the radioactive gas radon (²²²Rn) are the main gases permanently and silently released by the soils in the diffuse degassing sites of the Azores. Studies developed in the last decades highlight that some villages are placed on these anomalous degassing areas and, considering that CO₂ acts as asphyxiant, some persons were even removed from their houses due to the high indoor CO₂ concentrations. Furnas and Ribeira Quente villages are located, respectively, inside the caldera and in the south flank of Furnas Volcano, a quiescent central volcano located in the eastern part of S. Miguel Island (Azores archipelago). Two volcanic eruptions occurred in this volcanic system since the settlement of the archipelago in the 15^th Century and nowadays its activity is characterized by low magnitude seismicity and the existence of permanent gas emissions. Soil CO₂degassing maps performedin the last years, based on the accumulation chamber method, showed that both Furnas and Ribeira Quente villages are placed over significant CO₂ diffuse degassing areas. Based on CO₂ degassing susceptibility and vulnerability maps this work proposes a methodology to produce the first anomalous air CO₂ exposure risk maps for these two villages. CO₂ degassing susceptibility classes were defined based on the soil CO₂ flux biogenic limit (25 g m^-2d^-1 ) and on the CO₂ flux threshold selected to define the Diffuse Degassing Structures (50 g m^-2 d^-1). The criteria defined for the vulnerability concerning human exposure to anomalous air CO₂ concentrations were based on the differences of exposure in indoor and outdoor environments and in underground structures (basements, pits, confined depressions). Based on the CO₂ susceptibility maps produced, ~ 56% and ~ 98% of the sampled area at Furnas caldera and Ribeira Quente village, respectively, are classified as high soil CO₂ degassing susceptibility zones. The risk of exposure to anomalous air CO₂ concentration is considered high in 58% and 98% of the buildings of Furnas and Ribeira Quente villages, respectively. These high percentages of buildings in anomalous diffuse degassing zones show the importance of these maps for land-use planning, in volcanic regions or in soil degassing prone areas resulting from other sources, since the CO₂gas can easily introducein buildings, as it was already showed in several works.

Observações

Anexos

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