Identification of the origin of odour episodes through social participation, chemical control and numerical modelling E. Gallego a, * , C. Soriano b,1 , F.X. Roca a , J.F. Perales a , M. Alarco ´n c, 2 , X. Guardino d, 3 a Laboratori del Centre de Medi Ambient, Universitat Polite`cnica de Catalunya (LCMA-UPC), Avda. Diagonal, 647, E 08028 Barcelona, Spain b TECNOMA (Typsa Group), Atmospheric Projects Group, C/Mallorca 272-276, E 08037 Barcelona, Spain c Departament de Fı ´sica i Enginyeria Nuclear, Universitat Polite`cnica de Catalunya, Av. Vı ´ctor Balaguer, s/n, E 08800 Vilanova i la Geltru ´, Spain d Centro Nacional de Condiciones de Trabajo, INSHT, C/Dulcet, 2-10, E 08034 Barcelona, Spain article info Article history: Received 19 February 2008 Received in revised form 29 July 2008 Accepted 4 August 2008 Keywords: Odour episodes Volatile organic compounds Thermal desorption Gas chromatography/mass spectrometry Back trajectories Social participation abstract Odour episodes and environmental air quality are topics of worldwide concern, mainly due to the fact that industrial facilities are often located very close to inhabited areas. Several atmospheric pollutants, mainly volatile organic compounds (VOCs), are responsible for odour episodes of varying degrees of annoyance. A methodology based on the simulta- neous application of social participation (by building databases of odour episodes and acquiring air samples), chemical control and the computation of back trajectories allows us to identify the origin of odour episodes. A validated analytical method, based on thermal desorption (TD) coupled with gas chromatography (GC) and mass spectrometry (MS), is used to identify and determine a wide range of VOCs that cause odour nuisance and affect air quality in outdoor air. Back-trajectory modelling is used to track the origin of the air mass responsible for the discomfort backwards in time, mainly to find possible VOC sources outside the urban area. The procedure combines, on one hand, an analytical approach based on the acquisition of samples, which requires the participation of the affected population (which means that social participation is used as a scientific tool), and on the other hand, a modelling approach. Three examples are described to illustrate the methodology. Ó 2008 Elsevier Ltd. All rights reserved. 1. Introduction In urban areas, odour nuisance can be caused by volatile organic compounds (VOCs) whose precise origin and emission strength are seldom known. Several atmospheric pollutants, but mainly VOCs, are responsible for the occurrence of odour episodes of varying degrees of annoyance. Detectable odours have a considerable impact on people’s daily lives, as they can affect moods and have psychological and physiological impacts. Interest in deter- mining VOC concentrations in outdoor air has increased over the last few decades, since VOCs have been identified as major cancer risk factors in the urban environment (Belpomme et al., 2007; Irigaray et al., 2007); are known precursors of photochemical smog formation (Derwent et al., 1996; Chang et al., 1999; Atkinson, 2000; Peng et al., 2006; Vautard et al., 2007); can have short- and long-term adverse effects on human health (irritation of mucous membranes, psychological stress and long-term toxic reactions) (ECA-IAQ, 1997; Hutter et al., 2006; Liang and Liao, 2007); and can cause discomfort (bad odours) (Wolkoff and Nielsen, 2001; Zuraimi et al., 2006). In urban and industrial areas, most VOC emissions come from anthro- pogenic sources, such as transportation, fossil-fuel-burning * Corresponding author. Tel.: þ34 934016683; fax: þ34 934017150. E-mail addresses: lcma.info@upc.edu (E. Gallego), catalunya@tecnoma. es (C. Soriano), marta.alarcon@upc.edu (M. Alarco ´ n), cnctinsht@mtas.es (X. Guardino). 1 Tel.: þ34 934879199. 2 Tel.: þ34 938967739. 3 Tel.: þ34 932800102; fax: þ34 932803642. Contents lists available at ScienceDirect Atmospheric Environment journal homepage: www.elsevier.com/locate/atmosenv 1352-2310/$ – see front matter Ó 2008 Elsevier Ltd. All rights reserved. doi:10.1016/j.atmosenv.2008.08.004 Atmospheric Environment 42 (2008) 8150–8160