Health Hazard From Endogenous Gas Emissions In Alban Hills (Rome, Italy)

Abstract

The quiescent volcano of Alban Hills, near Rome, is characterized by strong emission of endogenous gas (mostly CO2 with minor H2S) from zones where excavation removed the superficial impervious cover. These gases –denser than air- accumulate in morphological depressions and many lethal accidents to animals and also to one person have occurred in the last years. At Cava dei Selci and Solforata sites, the CO2 flux has been estimated to 95 and 200 tons/day respectively from 0,6 and 5 hectares. Dangerous accidental gas blowouts also occurred from boreholes that reached gas pressurized shallow aquifers. In order to evaluate the gas hazard, several geochemical surveys were performed to estimate the CO2 and H2S soil flux and air concentration. In the urbanized area of Vigna Fiorita, dangerous indoor conditions were found with [CO2] up to 10 % and [H2S] up to 30 ppm and lethal indoor [CO2] (up to 22%) persisted within a non-ventilated house. Results will help in suggesting appropriate prevention measures to be adopted by residents. An important discovery was found measuring CO2 and H2S air concentration (by TDL at 30 cm from the ground). In periods of very low or no wind (generally in night-time) lethal concentrations were reached by H2S (up to 400 ppm), whereas [CO2] remained at tolerable values. These data indicate that the many animal deaths occurred in these years and previously attributed to CO2 where instead caused by H2S and a specific study on the health effects of this gas on man and on different animal species is presently under progress. Alban Hills test site provides useful methodological indications on how to assess the insidious hazard associated to soil gas release in inhabited zones of quiescent or recent volcanoes.