Ambient BTX measurements in Suzhou, China.

Within the Sino-Italian environmental protection cooperation framework established in 2002, a comprehensive air quality monitoring network has been developed in urban Suzhou, a medium-sized Chinese city, in compliance with European standards (Directive 96/62/EC). This paper is among the first attempts to present a systematic and scientific analysis of benzene, toluene, and xylenes (BTX) pollution in China. It presents our analysis of BTX space-related and time-related measurement results. Background BTX concentrations were investigated by passive sampler Analyst(R) in 2003. We depicted the spatial distribution of average BTX concentrations collected from three 15-day campaigns on isoconcentration maps. This is the first time such detailed BTX concentration maps have been developed in China in a city scale. Continuous measurement of BTX by automatic gas chromatography was carried out at two fixed monitoring stations, one in an urban residential zone and one in a heavy traffic zone, from April to December 2005. The results show similar seasonal trends at both sites, the similarities reaching their greatest level in December and their lowest level in August. The average daily profile of BTX shows greater fluctuation in spring and winter with clear morning and evening peaks. Daily average benzene, toluene, and m,p-xylenes concentrations for the study period were 2.64, 11.52, and 3.52 microg m(-3), respectively. The benzene/toluene ratio we found was lower in Suzhou than those published in studies of other worldwide cities, which indicates serious levels of toluene pollution from local stationary sources. The similarities in seasonal trend and spatial distribution in these manual and automatic measurement results were compared with each other, though the concentration values differed.