Continuous monitoring of volatile organic compounds through sensorization. Automatic sampling during pollution/odour/nuisance episodic events

• Published in: Atmospheric environment (1994) 2023-04, Vol.299, p.119657, Article 119657
• Main Authors: Gallego, Eva, Perales, José Francisco, Calaf, Josep Maria
• Format: Article
• Language: English
• Subjects: Active sampling; Continuous monitoring; Outdoor air quality; TD-GC/MS; VOC sensor; Volatile organic compounds
• ISSN: 1352-2310; 1873-2844
• DOI: 10.1016/j.atmosenv.2023.119657

Volatile organic compounds (VOCs) are a highly diverse class of chemical contaminants and between 50 and 300 of them may be found in ambient air. In urbanized areas, VOCs are emitted from industrial activities, as well as from vehicle-related and combustion sources. VOCs outdoors can be detected in a broad range of concentrations, usually varying seasonally. The presence of VOCs at relatively high concentrations has been related to poor air quality, discomfort and odorous nuisances. Additionally, they can have negative health effects to the human organism. Hence, in locations where recurrent sporadic situations of high VOCs levels take place, episodic samples' evaluation is necessary instead of 24 h or longer sampling period's evaluations. The use of commercially available metal oxide semiconductor gas sensors for a continuous monitoring of VOCs concentrations in outdoor air is an interesting and innovative technology. Additionally, the use of these sensors for the activation of a VOCs sampler when episodic events of nuisance/odorous annoyance occur was successfully evaluated. The sensor activation is induced by higher VOCs concentrations from a wide number of VOC chemical families. Two sensor stations, developed at our laboratory and provided with sampling pumps, were located in the municipality of Santa Margarida i els Monjos (Catalunya, Spain) in January 2021. The stations started recording data continuously from two different types of VOCs sensors, temperature, relative humidity and pressure in 1.5-min periods. Automatic VOCs sampling was conducted, using multi-sorbent bed tubes, during the months of June–July when the sensors electronic values exceeded a set point value. Samples were analysed through TD-GC/MS. TVOC concentrations in episode samples ranged between 78-669 and 12–159 μg m−3 in Site 1 and Site 2, respectively. Although TVOC concentrations were not high in all cases, relevant concentrations of chloroform were observed, especially in Site 1, with concentrations ranging from 19 to 159 μg m−3. [Display omitted] •Stations record data from VOC, temperature, relative humidity and pressure sensors.•Automatic VOC sampling during odour/nuisance episodic events.•TVOC levels were not high always but relevant concentrations of chloroform were found.•Several industrial sites were identified as possible origins of the episodic events.•VOC sensor monitoring can promote a dynamic of continuous improvement of air quality.