TRAFFIC - RELATED CONCENTRATIONS OF BTEX, FORMALDEHYDE AND ACETALDEHYDE IN TEHRAN; CONCENTRATIONS AND SPATIAL VARIABILITY

Traffic and mobile sources are possibly responsible to the most of the ambient volatile organic compounds (VOCs) in urban areas. This study aimed to measure and determine the traffic - related concentrations of benzene, toluene, ethylbenzene, xylenes, formaldehyde, and acetaldehyde at the main streets of Tehran, Iran.
The samples were taken from highly populated streets or main roads with heavy traffic in Central, Northern, Eastern, Southern, and Western areas of Tehran. In total, 33 points for BTEX and 23 points for formaldehyde and acetaldehyde were selected for sampling. The sampling and analysis were performed according to NIOSH methods 1501 and 2016.
The averages (± SD) of benzene, toluene, ethylbenzene, xylenes, formaldehyde and acetaldehyde concentrations in Tehran were 15.04 (± 9.18), 23.42 (± 8.73), 4.97 (± 2.55), 11.81 (± 4.46), 107.11 (± 30.58) and 57.10 (± 18.28) ppbv, respectively. Benzene concentrations were 3.30 to 26.00 times higher than air quality standard of European Union (5 μg / m3). High concentrations of BTEX and formaldehyde / acetaldehyde were found in central and eastern areas, respectively. High correlation coefficients were found between BTEX species (r = 0.77-0.95) and also formaldehyde and acetaldehyde (r = 0.98). The highest coefficient of variation (CoV) as a measure of spatial variability was observed for benzene (54.5 %).
The high outdoor concentrations observed in this study needs to be decreased immediately, especially in case of benzene.