The measurements of 31 kinds of VOCs in the ambient air of a site were carried out in the downtown of Guangzhou by online method from November 5, 2009 to November 9, 2009. The ambient level and composition characteristics, temporal variation characteristics, sources identification, and chemical reactivity of VOCs were studied, and the health risk of VOCs in the ambient air in the study area was assessed by using the international recognized health risk assessment method. Results showed that the mean and the range of the mass concentrations of 31 VOCs were 114.51 microg x m(-3) and 29.42-546.06 microg x m(-3), respectively. The mass concentrations of 31 VOCs, and those of
alkanes,
alkenes, and aromatics all showed a changing trend of higher in the morning and in the evening, and lower at noontime. Vehicular exhaust,
gasoline and liquefied
petroleum gas evaporates were the main sources of VOCs with the volatilization of paints and
solvents being important emission sources.
Toluene, trans-2-butene, m/
p-xylene, i-
butane, and
1,3,5-trimethylbenzene were the key reactive species among the 31 VOCs. Vehicular exhaust and
gasoline evaporation were the main sources of VOCs leading to the formation of
ozone. Health risk assessment showed that
n-hexane,
1,3-butadiene,
benzene,
toluene,
ethylbenzene, m/
p-xylene and
o-xylene had no appreciable risk of adverse non-
cancer health effect on the exposed population, but 1, 3-butadiene and
benzene had potential
cancer risk. By comparing the corresponding data about health risk assessment of
benzene compounds in some cities in China, it is concluded that
benzene can impose relatively high
cancer risk to the exposed populations in the ambient air of some cities in China. Therefore, strict countermeasures should be taken to further control the pollution of
benzene in the ambient air of cities, and it is imperative to start the related studies and develop the atmospheric environmental health criteria and national ambient air quality standard for
benzene in China.