Source apportionment of BTEX compounds in Tehran, Iran using UNMIX receptor model

Understanding the distribution levels and sources of volatile organic compounds (VOC), mainly benzene, toluene, ethylbenzene and xylenes (BTEX), in the ambient atmosphere is important for efficiently managing and implementing the associated control strategies. We measured BTEX compounds at an industrial location in the west Tehran city (Iran), which is highly influenced by industrial activities and traffic during the winter and spring seasons during 2014-2015. A multivariate receptor model, UNMIX, was applied on the measured data for the identification of the sources and their contributions to BTEX compounds in a highly industrialised and trafficked atmospheric environment of Tehran city. Three main groups of sources were identified. These included solvent and painting sources (e.g. vehicle manufacturing), motorised road vehicles and mixed origin sources. While the solvent and painting sources and vehicle exhaust emissions contributed to about 5 and 29% of total BTEX mass, respectively, the mixed origin source contributed to about two-third (~66%) of the remaining mass. These mixed origin sources included rubber and plastic manufacturing (39%), leather industries (28%) and the unknown sources (33%). The mean concentrations of benzene, toluene, ethylbenzene and average xylene(o, p,m) compounds were measured as 28.96±9.12 µg m –3 , 29.55±9.73 µg m –3 , 28.61±12.2 µg/m-3 and 25.68±10.58 µg m–3 , respectively. A high correlation coefficient (R 2 >0.94) was also found between predicted (modelled) and measured concentrations for each sample. Further analyses from UNMIX receptor model showed that the average weekday contributions of BTEX compounds were significantly higher during winter compared with those during spring. This higher concentration during winter may be attributed to calm wind conditions and high stability of the atmosphere, along with the after effect of government policies on the use of cleaner fuel in refineries that became operational in winter 201