1. Gas Hazard Assessment In The Roman Province By TDL And Accumulation Chamber

Abstract

The city of Rome lies between the two Quaternary volcanic complexes of Mts. Sabatini, to the North, and of Alban Hills to the South. Both these volcanic areas are characterized by zones with a huge endogenous degassing and several accidents have occurred to people and animals in the last 20 years. CO2 is the main component (up to 98 vol.%) of the gas emissions followed by H2S (1-2 vol.%), and N2. The Caldara di Manziana depression hosts the main gas manifestation of Mts. Sabatini. Here a total (diffusive and viscous) CO2 release of ca. 160 tons/day from 0.15 Km2 has been measured. The Colli Albani edifice extends to the south-eastern periphery of Rome. Its main gas emission zones are Cava dei Selci and Solforata di Pomezia. Cava dei Selci is an area located in the suburb of the homonymous village. CO2 diffusive flux from the soil (from 6000 m2) ranged between 25 and 5 tons/day in the last 7 years. The continuous monitoring of CO2 and H2S in air (1m) in the confining village has shown the frequent overcome of the (TWA and STEL) threshold limits for both gases. At Solforata di Pomezia a 44 tons/day CO2 diffusive flux has been estimated from 1.9 hectares, with 0.5 tons/day of H2S. On 2007, two multi-technique surveys have been carried out to estimate the total gas output of these three degassing sites, by measuring CO2 and H2S fluxes from the soil (by accumulation chambers) and the gas flux from bubbling pools. Moreover the CO2 and H2S concentration in air were measured by several TDL profiles. Results confirm the high gas hazard of these areas. Particularly in late afternoon and night, when wind strongly lowers, lethal concentrations are frequently reached by H2S, whereas CO2 remains at high but tolerable values.