An examination of 7:00-9:00 PM ambient air volatile organics in different seasons of Kaohsiung city, southern Taiwan

This study presents annual data (2000) of non-methane hydrocarbons (NMHC) monitored at dusk hours in ambient air of Kaohsiung by near time sampling at 20 different locations (road-side and industrial) between 7 and 9 PM. A 16-canister automatic introducing system was applied to inject the air sample into a sample pre-concentration trap (SPT) that cryo-focused the sample, followed by desorption from SPT by heating to 160degreesC, and analyzed by a GC system coupled with FID or MSD. The highest levels of non-methane hydrocarbons were detected in industrial zones and were two times greater than those in non-industrial areas in June and about 1.4-1.7 times greater during the rest of the year. Ethylene, 2-methyl butene and toluene were found to be the most abundant occurring analytes in the four seasons. Ethylene was mainly emitted from petroleum plants and to a lesser extent from vehicles. The major source of toluene is identified as emissions from mobile vehicles and partly from vaporization of organic solvents used in petroleum industries. n-Butane at the non-industrial sites is mainly emitted from liquefied petroleum gas (LPG)-fuelled vehicles. A 24 h monitoring in December 1999 at non-industrial sites revealed a comparatively higher ratio of toluene/benzene and toluene/ethylene at night. The estimated reactivity's with OH and NO3 radicals is greater in November and least in March and ozone formation potential appears greater in January and the least in March. A comparison of this data set with that obtained in 2003 from two specific sampling sites indicates a 5-10% reduction in emissions of alkenes and an increase of 7-10% of alkanes. (C) 2004 Elsevier Ltd. All rights reserved.