ODOR-GC: development of a new instrument for the analysis of olfactory nuisances

In the last years, the increasing number of plants capable of releasing odorous emissions in urban areas has led to a rise in unpleasant emissions, generating growing concern about olfactory pollution and causing discomfort, partly because of increasing attention to environmental and health protection. The need to monitor odorous emissions is becoming increasingly important following the enactment of Legislative Decree n° 183 of 2017, which allows the relevant authorities to set limit values for odorous emissions and to impose the implementation of measures to contain them. ODOR-GC is a project which has the purpose of developing an innovative instrumental and modeling infrastructure for rapid and integrated monitoring of odor nuisance generated by various types of sources (e.g. landfills, industrial plants, biodigesters, water treatment plants). The heart of the project is a miniaturized instrument for gas chromatography analysis (based on the architecture “Compact-GC” previously developed at CNR-ISMN Bologna), designed for use in-situ in two versions: fixed installations and inside a portable case. The first type is used for continuous monitoring at known sources of odor nuisance, while the second is used for occasional monitoring of transient phenomena. For the development of this system, measurement campaigns were carried out at companies, comparing the results with established instruments such as GC-MS (comparing the quantifications of some previously selected target compounds) and dynamic olfactometry. Samples were taken, simultaneously for the three types of analysis to be compared, at four different points on two industrial sites: a plastics factory and an agricultural company with livestock farms and biogas digesters. The analyses with mass spectrometry were performed using the thermal desorption technique through one-dimensional and comprehensive two-dimensional gas chromatography (TD-GC(×GC)-TOFMS). This technique uses packed tubes that act as traps for air sampling. Tenax-TA and Carbotrap 300 tubes were used in this study. 1 L of air was sampled for each sampling tube, and these tubes were then inserted into the GC injector so that the analytes could be desorbed directly at the top of the column. Thanks to the concentration of analytes achieved by using packed tubes during sampling and the use of GC×GC, it was possible to detect traces of target compounds. In addition, different compounds were found that were not among the targets and could be linked to olfactory nuisances.