Seasonal and Spatial Variation of BTEX in Ambient Air of Delhi

Abstract

The present study aims to provide an indication of ambient levels of BTEX in the immediate vicinity of petrol filling stations in Delhi & other road side corridors of Delhi. In this study spatial and seasonal variation of BTEX has been measured at different locations in Delhi. For the measurement of VOCs, passive based diffusion methodology was adopted for the adsorption of BTEX over the activated charcoal. Four categories of sampling sites were chosen (residential, traffic junctions, road side corridors and petrol pumps). The result confirms that the aromatic concentrations in the ambient air of gas stations are appreciably higher than the average values in locations with high vehicular flux. The mean concentration of BTEX at all the locations was 0.622μg/m 3 , 0.361 μg/m 3 , 1.037 μg/m 3 and 0.122 μg/m 3. The average concentration of benzene was highest at petrol pump 3.5 μg/m 3 however at all other sampling sites it was in the range of 0.294 to 0.712 μg/m 3. The mean concentration value shows that the xylene concentration dominates more in Delhi as compared to benzene. The total average BTEX concentration at road side corridors was 0.594 μg•m −3 , at residential corridors was 0.262 μg•m −3 , at intersections it was 0.649 μg•m −3 and at petrol filling stations it was 1.457 μg•m −3. The concentration was in the order of petrol filling stations > intersections > road side corridors > residence. These data show the predominance of diesel driven vehicles in Delhi since xylene mainly comes from diesel exhausts. The influential VOC species in case of diesel engine exhaust are benzene, ethylbenzene, xylenes, propane, n-decane and undecane and in case of gasoline vehicle exhaust influential species are benzene, ethylbenzene, 1,2,4-methylbenzene, 1,3,5-methylbenzene, n-hexane and 2-methylhexane. So xylene is mainly coming from diesel exhaust since gasoline vehicle exhaust doesn't show this species.

Investigation of BTX Concentrations and Effects of Meteorological Parameters in the Steelpoort Area of Limpopo Province, South Africa

“…The results are in agreement with those obtained by other studies in which toluene was reported to have the highest concentrations of BTX [38][39][40]. For example, the values of benzene, toluene and m,p-xylene reported by [40] are 598.34 µg/m 3 , 1054.32 µg/m 3 and 1076.29 µg/m 3 , respectively. The concentrations of benzene and toluene were lower than the world governing bodies' annual exposure limits, which are 5 µg/m 3 (annually) and 260 µg/m 3 (weekly) for benzene and toluene, respectively.…”

“…It has also been reported that a lower average ambient temperature aids the accumulation of pollutants in the atmosphere, due to the limited movement of air masses in the vertical plane [37]. The results are in agreement with those obtained by other studies in which toluene was reported to have the highest concentrations of BTX [38][39][40]. For example, the values of benzene, toluene and m,p-xylene reported by [40] are 598.34 µg/m 3 , 1054.32 µg/m 3 and 1076.29 µg/m 3 , respectively.…”

Seasonal and diurnal measurement of ambient benzene at a high traffic inflation site in Delhi: Health risk assessment and its possible role in ozone formation pathways

“…The production of OH radicals could also increase from the reaction of terpenes with O3 [ 47 ]. Similar seasonal concentration trends for benzene were observed in Delhi [ 39 , 48 ]. The level of benzene during the summer and monsoon seasons was relatively low as compared to the winter season, as supported by the literature [ 49 ].…”

Risk assessment of workers’ exposure to BTEX and hazardous area classification at gasoline stations

“…BTEX concentrations in the ambient air of working surroundings throughout the period spent at dispensing areas were lower than in previous studies in Bangkok, Thailand [11], but benzene and toluene concentrations were higher than those of other countries [13,14] and in excess of the NIOSH standard level (100 ppb), like in the study of gasoline station workers in Kuwait [15]. A study of a gasoline station in Malaysia [9] found that concentrations were quite lower or close to the range in our study.…”

“…The mean concentration of benzene was found to be 45.36 ppb at the gasoline stations in the northeast of Thailand [ 12 ]. With regard to other countries [ 13 , 14 ], the concentrations found there were lower compared to Thai gasoline stations, such as in the gasoline stations of Brazil, where BTEX concentrations were 9.30, 12.7, 5.4 and 11.42 ppb for benzene, toluene, ethylbenzene and xylene, respectively [ 14 ]. Gasoline station workers in Kuwait were exposed to concentrations in excess of the NIOSH exposure limits [ 15 ].…”