"NO GAS" PROJECT: EXHAUSTED DUMP EMISSIONS

Summary Two in-field campaigns have been carried out in Calabria region, Southern Italy, aimed at characterizing the release of volatile hydrocarbons (VOCs) from exhausted dumps. The former experiment was conducted at two landfills (San Giovanni in Fiore-SGF and San Martino di Finita-SMF), while the latter was performed at one only site (SGF). Volatile hydrocarbons were collected from air by means of both active and diffusive sampling methods. Nitrogen dioxide, ozone, ammonia and sulphur dioxide were collected in parallel. During the summer campaign, concentrations of NO2, SO2, and NH3 ranging from 2 µg/m3 to 6 µg/m3 were detected both inside and outside of the two dumps, while O3 reached ~120 µg/m3. Unlike other toxicants, NO2 was more in dumps than outside. As for VOCs, usually both benzene and toluene were more out of dumps whilst other substances were roughly equal or less; nevertheless, at one point inside SGF the concentrations of compounds apart from benzene were higher. Similarly at SMF most VOCs were higher at a location rich in H2S release from soil. High levels of isoprene and chlorofluorocarbons were estimated at all locations. Introduction A lot of air contaminants are released by dumps; in particular, important emission of volatile hydrocarbons takes place up to several years after their run off. This phenomenon is somewhere exploited for production of methane as alternative fuel, which allows reducing the global budget of green house gases emission. Nevertheless, the control of emission during and after the dump life is mandatory to understand their long-term impact on environment and implement measures aimed at optimizing the landfill management and preventing pollution. Two in-field campaigns were conducted at SGF and SMF landfills during 2015, in June and October. Focus was on volatile hydrocarbons VOCs, however regulated toxicants (i.e. NO2, SO2, O3 and NH3) were measured in parallel, to gain a more complete overview of air composition at the two sites. In SGF, diffusive sampling devices were located at three points, while active sampling (pump + cartridge) was applied occasionally at three further points (Fig. 1). Point No. 3 was outside landfill. In SMF two points were chosen inside and outside the site, and a third point rich of H2S was analyzed with active sampling. Methodology and Results Air toxicants and VOCs were determined using Analyst® passive samplers, allowing to collect compounds over some weeks. Inorganic species were solvent extracted and analyzed through ion chromatography (IC). VOCs were extracted with benzyl alcohol and analyzed through gas chromatography coupled with mass spectrometry (GC-MS). Cartridges for active sampling were thermally desorbed and characterized through GC-MS. Figure 2 provides a synthesis of VOC measurements performed with active sampling during the first campaign (June 2015). Compounds were usually more abundant outside of dumps, the sole important exception consisting in toluene at SMF (H2S rich location). Toxic butadiene was ca. 3 times more outside of landfills than inside (~ 0.3-0.5 µg/m3 vs. 0.1-0.2 µg/m3, respectively). Fig. 2. Mean VOC concentrations at SGF and SMF landfills. EX = external locations; IN = internal locations (mean). As for the inorganic toxicants, the two landfills showed different trends. At SGF (still active with regards to biogas release) SO2 and NH3 were more inside (4.2 vs. 2.1 µg/m3 and 6.0 vs. 3.5 µg/m3, respectively), while the reverse was observed at SMF (1.7 vs. 2.3 µg/m3 and 2.6 vs. 3.9 µg/m3) in active for some 10 years now. NO2 was everywhere more inside than outside of landfills (4.7 vs. 4.2 µg/m3 at SGF and 3.6 vs. 2.5 µg/m3 at SMF). Conclusions Two closed dumps were investigated for the release of VOCs and inorganic toxicants into the atmosphere in Calabria, Southern Italy. The emission of aromatic compounds could be identified at one landfill, that of SO2 and NH3 at the other one; NO2 seemed to be released by both of them.