Viveiros Fátima, Ferreira Teresa, Silva Catarina, Gaspar João L
Centro de Vulcanologia e Avaliação de Riscos Geológicos, University of the Azores, Rua Mãe de Deus, 9500-801 Ponta Delgada, Azores, Portugal.
Sci Total Environ. 2009 Feb 1;407(4):1362-72. doi: 10.1016/j.scitotenv.2008.10.009. Epub 2008 Nov 8.
Furnas volcano is one of the three quiescent central volcanoes of São Miguel Island (Azores Archipelago, Portugal). Its present activity is marked by several degassing manifestations, including fumarolic fields, thermal and cold CO2 springs and soil diffuse degassing areas. One of the most important soil diffuse degassing areas extends below Furnas village, located inside the volcano caldera. A continuous gas geochemistry programme was started at Furnas volcano in October 2001 with the installation of a permanent soil CO2 efflux station that has coupled meteorological sensors to measure barometric pressure, rain, air and soil temperature, air humidity, soil water content and wind speed and direction. Spike-like oscillations are observed on the soil CO2 efflux time series and are correlated with low barometric pressure and heavy rainfall periods. Stepwise multiple regression analysis, applied to the time series obtained, verified that the meteorological variables explain 43.3% of the gas efflux variations. To assess the impact of these influences in inhabited zones a monitoring test was conducted in a Furnas village dwelling placed where soil CO2 concentration is higher than 25 vol.%. Indoor CO2 air concentration measurements at the floor level reached values as higher as 20.8 vol.% during stormy weather periods. A similar test was performed in another degassing area, Mosteiros village, located on the flank of Sete Cidades volcano (S. Miguel Island), showing the same kind of relation between indoor CO2 concentrations and barometric pressure. This work shows that meteorological conditions alone increase the gas exposure risk for populations living in degassing areas.
富尔纳斯火山是圣米格尔岛（葡萄牙亚速尔群岛）三座休眠的中心火山之一。其目前的活动以多种脱气表现为特征，包括喷气田、热和冷的二氧化碳泉以及土壤扩散脱气区。最重要且土壤扩散脱气区之一位于火山口内的富尔纳斯村下方。2001年10月，在富尔纳斯火山启动了一项持续的气体地球化学计划，安装了一个永久性的土壤二氧化碳排放站，该站配备了气象传感器，用于测量气压、降雨、空气和土壤温度、空气湿度、土壤含水量以及风速和风向。在土壤二氧化碳排放时间序列上观察到尖峰状振荡，并且与低气压和强降雨期相关。对所获得的时间序列进行逐步多元回归分析，证实气象变量解释了43.3%的气体排放变化。为了评估这些影响在居民区的作用，在土壤二氧化碳浓度高于25%（体积）的富尔纳斯村一处住宅中进行了监测测试。在暴风雨天气期间，室内地面水平的二氧化碳空气浓度测量值高达20.8%（体积）。在位于七城火山（圣米格尔岛）侧翼的另一个脱气区莫斯特罗斯村进行了类似测试，结果显示室内二氧化碳浓度与气压之间存在相同类型的关系。这项工作表明，仅气象条件就会增加生活在脱气区人群的气体暴露风险。
