Monitoring of BTX by passive sampling in Hat Yai
Chongdee Thammakhet, Tomah Villeneuve, Vilailuk Munisawang, Panote Thavarungkul, and Proespichaya Kanatharana
pp. 151 - 160
Abstract
Laboratory-built passive samplers were used for monitoring of trace benzene, toluene and xylene
(BTX) in Hat Yai from 28 July to 12 August, 2003. Sampler bottles contained activated Tenax TA 60/80 mesh
and a lab-built thermal well were developed and evaluated for the sampling and analysis of BTX. The
sampling was carried out for two weeks before the passive samplers were thermally desorbed, trapped in
a sampling loop by a laboratory built purge and trap system and analysed by gas chromatography (GC)
equipped with a flame ionization detector. After optimization and calibration, the developed method showed
high selectivity, a good sensitivity with detection limits for BTX of 0.8, 1.1 and 13.0 µg/m3 respectively and
an acceptable precision.
Ambient BTX measurements were conducted at many monitoring site i.e. hot spots (high exposure),
residential areas/work places (common exposure) and park (low exposure). The concentration at hot spots
range from 3.2 to 5.4 µg/m3 for benzene, 38.0 to 80.3 µg/m3 for toluene and 29.7 to 66.7 µg/m3 for xylene.
The low BTX were found at the city periphery (Tesco-Lotus billboard sampling stations, roof level) and in
Hat Yai Municipal Park but no absolute background concentration could be defined. The monitoring results
showed that at higher level from the street surface, the level of BTX tended to decrease and the BTX pollution built up along a street canyon (Sanehanuson Road) according to the wind direction. The highest BTX were
found at the underground parking, 23.5 725.1 and 267.9 µg/m3 respectively where both WHO guideline
for Benzene (16.3 µg/m3) and Toluene (260 µg/m3) were exceeded.
