TEMPORAL PROFILE OF BTEX AT THE AREA OF PETROL STATION

Abstract

This study aims to investigate temporal variation of BTEX during a day at petrol station, by collecting BTEX in ambient air at back of the station, near filling nozzle, and roadside. The study of comparison between BTEX variation at the petrol station in urban and suburban area was conducted in 2012, and the study between their variation in wet (July – August 2013) and dry (November 2013) season at suburban station. BTEX was collected by a charcoal glass tube connected to a personal air pump with flow rate 100 ml/min during 6 a.m. to 10 p.m. In 2012, each sample was collected for every 4-hr, while 2-hr interval sampling was done in 2013. After finish the sampling, a charcoal tube was extracted by carbon disulfide and BTEX was analyzed by GC/FID. The study found that BTEX had high concentration in rush hour because of traffic congestion and lot of customers. Moreover, BTEX concentration nearby refueling nozzles had the highest concentration among 3 sampling points, about 6 times of roadside. The averaged tBTEX obtained from the refueling nozzles and roadside were 15,866.65±7,248.41 and 2,536.31±2,018.34 µg/m3, respectively. The ratio of benzene concentration between 3 sampling points was the lowest among BTEX, because the amount of benzene is not diminished by distance from the main point source as much as toluene, ethylbenzene and xylene. BTEX in a station which was smaller and surrounding with trees and buildings tended to have well dispersion inside station more than the bigger one. BTEX concentration at urban station was extremely higher than at suburban station and BTEX in wet season was significantly lower than in dry season (p<0.005). From statistical analysis, wind speed was a strongest affecting factor on diurnal variation of BTEX especially benzene and ethylbenzene nearby refueling nozzles.