Levels and sources of BTEX in ambient air of Ahvaz metropolitan city

The benzene, toluene, ethylbenzene, and xylene (BTEX) compounds are categorized as volatile organic compounds (VOCs) that may contribute to the formation of ground-level ozone and photochemical smog, which can cause damage to plants and materials as well as pose human health concerns. BTEX compounds are considered harmful to aquatic organisms. Benzene, toluene, ethylbenzene, and xylenes can enter the environment during manufacture or use of these substances or products containing them. Due to the high volatility of BTEX compounds, emissions are expected to occur principally to air by industries and transportation. Ambient concentrations of BTEX were measured by means of active sampling at 12 sampling points in Ahvaz, capital city of Khuzestan province, from July to September 2012 and January to March 2013. BTEX were analyzed by chemical desorption followed by gas chromatography/flame ionization detector (GC-FID). Mean concentrations of benzene, toluene, ethylbenzene, xylenes, and BTEX were 1.78, 5.19, 0.51, 1.13, and 8.61 mu g m(-3), respectively, and found to be highly correlated. The results of this study showed distinct seasonal and spatial variability in atmospheric BTEX concentrations at sampling sites. Their spatial distribution showed high differences between high-traffic and residential areas and also pointed to traffic as the main emission source of these compounds. The lowest levels of BTEX occurred during summer due to increases in solar radiation and photochemical reactions. Mean concentrations of benzene did not exceed the European limits at any of the monitored points. Based on BTEX levels, distribution maps were depicted to help urban air pollution authorities understand hotspots, spatial variations, future layout of industries, and their possible displacements for mitigation of BTEX levels.