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Referência Bibliográfica

PASQUIER-CARDIN, A., ALLARD, P., FERREIRA, T., HATE, C., COUTINHO, R., FONTUGNE, M., JAUDON, M. (1999) - Magma-derived CO2 emissions recorded in 14C and 13C content of plants growing in Furnas caldera, Azores. Journal of Volcanology and Geothermal Research, 92, 195-208.


​The environmental impact of fumarolic and soil emanations of magma-derived carbon dioxide across Furnas caldera has been investigated by measuring the 14C and 13C content of 40 specimens of different C3 plants (leaves) growing within and outside the degassing areas. The results demonstrate a significant to large 14C depletion in many of the plants due to assimilation of 14C-free endogenous CO2 during photosynthesis and leading to artificial radiocarbon ageing of up to 4400 years. The extent of 14C ageing broadly correlates with the intensity of gas manifestations at the sampling sites, as inferred from field observations and measurements of excess CO2 concentrations in the volcanic ground. It also provides a time-integrated measure of the amount of volcanic CO2 locally admixed to the ambient air; at several sites this accounts for 15 to 40% of total CO2 (420 to 600 ppm) in enriched air. In some of the plant species (Azalea, Camellia and fern) 14C depletion is correlated with an enrichment of 13C due to assimilation of magma-derived CO with a 4‰ higher ð13C than normal atmosphere. The rate of 13C enrichment averages ca. 0.18‰ by percent of volcanic carbon fixed in the plant and includes enhanced 13C discrimination during photosynthesis as a consequence of increased ambient pCO2 inferred at -0.0306‰ per added ppm of volcanic (CO2) . Furnas is one of the few volcanoes where clear C enrichment in plants due to endogenous degassing has been evidenced. Our results can be used to estimate the local intensity of volcanic soil gas fluxes in the emanating areas of Furnas caldera. They also have implications for radiocarbon dating of past eruptive events in the caldera, since plants artificially aged by previous degassing could be trapped in volcanic deposits.