| Advances in research on volatile organic compounds (VOCs) in the ambient air are reviewed with 97 references. The general situation of VOCs' survey in the ambient air and the origins of VOCs in the pollution of indoor and outdoor air are discussed emphatically. The sampling, clean-up and analytical methods of VOCs are described in brief. The indicators of personal exposures to VOCs and risk assessment of VOCs in the ambient air are particularly evaluated.An analytical method by gas chromatography (GC) for monitoring benzene and its alkyl derivatives in ambient air is proposed. This method consists of a little volume and low noise air sampling pump, solvent extraction and capillary gas chromatographic determination. Sampling of the benzene and its alkyl derivatives was carried out at a flow rate of 0.5L/min for 3 hours using a small low noise sampler, which was composed of an activated charcoal sampling tube (250mg in each layer). The benzene and its alkylbenzenes collected hi the activated charcoal were extracted with carbon disulfide by mechanical shaking for 20 min. The extract was then analyzed by capillary GC/FID, which was carried out at a flow rate of 30mL/min by highly pure nitrogen. The detector gas is hydrogen and air. The relative standard deviations (n=10) of the retention time and peak area were in the range of 0.36-0.81% and 1.14-3.23%, respectively, which were at BTEX concentration levels of 8.6-8.8 ug/mL with the linearly regressively factors being over 0.99. The detection limits ranged from 1.09~4.15ng when the maximum sampling measure was 180L. The recoveries of BTEX were 91.64?5.60%. Reproducibility and reliability of this method was proved to be excellent. Extraction procedure is simple and easy, and BTEX in many samples can be extracted in a short time. Separation and determination procedures by capillary gaschromatography and data processing system can operate routinely and automatically. The simple, easy, highly sensitive and reliable analytical method for BTEX can be applied to indoor and outdoor air pollution survey.The present situation of BTEX pollution in the indoor air of eight families, which were decorated recently, was investigated. The BTEX samples were collected from eight families, which BTEX pollution in the indoor air was more serious, and analyzed by GC in June 2000. The levels of total BTEX in the indoor air ranged from 0.11~2.57mg/m3, and the concentration of the benzene, toluene, o-, m- and p-ethyltoluenes was in the range of 0.05-0.77 mg/m3, 0.01-1.19 mg/m3, 0.02-0.61 mg/m3, respectively. And mean concentration of benzene which can cause human cancer was up to 0.24 mg/m3. The BTEX pollution was very serious and the concentration was much higher than Europe and Japan. More than 50% percent of the total BTEX was the toluene. As far as toluene was concerned, the main source was gooey used in indoor decorating. Benzene and o-, m- and p-ethyltoluenes originated from chemical compounds such as coating and paints.In order to study the seasonal variation of BTEX in the urban air of Hangzhou, the samples were collected in five sites from June 2000 to October 2001. In July 2001, the mean concentrations of BTEX were between 37.96-222.55 Mg/m3. It was much higher than that in June 2000 (30.78-196.54 Mg/m3). The total content of BTEX in the air in July 2001 was 104.72 Mg/m3, which was almost 1.5 higher than that in June 2000 (70.79 Mg/m3). And the concentrations of BTEX in ambient air show a distinct variation (summer>autumn), Consisting with temperature variation. The concentration of toluene in each site was higher than benzene and it was the highest. So the results indicated that exhaust gas letting off from motor vehicles was the main source of BTEX in ambient air in Hangzhou.
|
PDF Full Text Request