Characteristics of atmospheric non-methane hydrocarbons in Foshan City, China.

Foshan is the most air-polluted city in Pearl River Delta. Non-methane hydrocarbons (NMHCs) were investigated for the first time in Foshan in winter 2008. Ethene, ethane, ethyne, propane, i-pentane, and toluene were the most abundant hydrocarbons and observed to be higher in Foshan than those in many other cities in China. Different from other cities, ethene and ethane were observed to be the two highest compounds in Foshan. Generally, the most abundant hydrocarbons showed high mixing ratios in the morning (0930-1030 hours), decreased to the lowest level in the afternoon (1430-1530 hours), and increased to higher value in the evening (1930-2030 hours). But i-pentane exhibited a different diurnal pattern with the highest level (13.4 ± 5.8 ppbv) in the afternoon, implying the acceleration of solvent evaporation resulting from higher temperature. Correlation coefficients (R(2) = 66% for n = 6 at 95% confidence level) of the individual hydrocarbons with ethyne and i-pentane indicated vehicular emissions were the main sources of ethene, propene, i-butene, isoprene, benzene and toluene, while gasoline evaporation was responsible for n-pentane, n-hexane, and n-heptane. The good correlation of most of the hydrocarbons with ethyne, indicating vehicular emissions, were the main sources of NMHCs. B/T ratio was 0.36 ± 0.06, implying vehicular emissions acted as the major contributors as well as additional emissions of toluene emitted from solvent usage. According to investigation, it also suggested that LPG leakage was the main source of propane, while NG leakage was responsible for ethane in Foshan City.