Volatile organic compounds in 43 Chinese cities

Whole air samples were collected in 43 Chinese cities in January and February 2001, and methane and nonmethane hydrocarbon (NMHC) concentrations for those samples are here discussed. In order to identify the main sources of the hydrocarbons in these cities, cross-correlations with the general combustion tracer ethyne and the gasoline marker i-pentane were investigated. Most of the identified NMHCs correlated with ethyne or i-pentane suggesting that their primary source is combustion or gasoline evaporation. To differentiate between vehicular and other combustion sources, the benzene to toluene ratio characteristic of the Chinese vehicular fleet was calculated using roadside samples (collected in 25 cities). Cities where the main source of the NMHCs was traffic related were identified. The slope resulting from the correlation of selected gases was used to identify the likely sources of the NMHCs measured. Vehicular emissions were found to be an important source of isoprene in some cities. Different VOC mixing ratio distributions throughout the country were also investigated. This paper gives a general overview of urban VOCs in many Chinese cities. Future more rigorous studies will be necessary to further characterize VOC sources in China.