By Vo Thi Quynh Truc and Nguyen Thi Kim Oanh (to appear in Atmospheric Environment).
Hourly concentrations of benzene, toluene, ethylbenzene, m,p-xylenes, and o-xylene (BTEX) plus CO, NOx, SO2 were monitored at roadsides simultaneously with the traffic
volume during the dry season of 2004, in Hanoi, Vietnam. The selected three streets included Truong Chinh with a high traffic volume (TC), Dien Bien Phu with low traffic volume (DBP), and Nguyen Trai (NT) with high traffic volume running through an industrial estate. BTEX were sampled by SKC charcoal tubes and analyzed by GC-FID. Geometric means of hourly benzene, toluene, ethylbenzene, m,p-xylenes and o-xylene are, respectively, 65, 62, 15, 43, and 22 ìg m-3 in TC; 30, 38, 9, 26 and 13 ìg m-3 in DBP street; and 123, 87, 24, 56, and 30ìg m-3 in NT street. Levels of other gaseous pollutants including CO, NOx and SO2, measured by automatic instruments, were low and not exceeding the Vietnam national ambient air quality standards. BTEX levels were comparatively analyzed for different downwind distances (3m-50m) from the street, between peak hours and off-peak hours, as well as between weekdays and weekend. Results of principal component analysis suggest that the gaseous pollutants are associated with different vehicle types.