Vehicular fuel composition and atmospheric emissions in South China : Hong Kong, Macau, Guangzhou, and Zhuhai

Abstract

Vehicular emission is an important source of air pollutants in urban cities in the Pearl River Delta (PRD) region of South China. In order to study the impact of evaporative loss of vehicular fuel on air quality, several commonly used fuel samples were collected in four main cities in the PRD region – Hong Kong, Guangzhou, Macau and Zhuhai, and analyzed for their volatile organic compounds (VOCs) composition. Source profiles of vapors of the vehicular fuels used in these cities were constructed and are believed to be the first reported for the PRD region. The C₈-C₁₀ hydrocarbons were the main constituents of diesel. Different from diesel, gasoline used in the PRD region was mainly comprised of lighter C₄-C₇ hydrocarbons, with toluene and i-pentane being the two most abundant species. The toluene content in the Hong Kong and Macau gasoline samples were higher than that in Guangzhou and Zhuhai, while the reverse was true for the benzene content. The benzene levels in Guangzhou and Zhuhai exceeded the maximum allowable benzene levels for Mainland China unleaded gasoline. Liquefied Petroleum Gas (LPG) samples were collected only in Hong Kong and were comprised mainly of n-butane, propane and i-butane. Traffic samples indicated that evaporative loss and vehicular combustion were the primary contributors to elevated VOC levels in roadside atmospheres. Significant i-pentane and toluene concentrations were observed in roadside atmospheres in all four cities. Ratio of i-pentane in gasoline vapors to that in roadside samples were calculated and this showed that the degree of evaporative loss were higher in Guangzhou and Zhuhai than that in Hong Kong and Macau. We suggest the difference is due to the better maintenance and more new cars in Hong Kong and Macau. From tunnel samples collected in Hong Kong in two different years, we found that the relative amount of propane, i-butane, and n-butane increased between 2001 to 2003, consistent with the 40% increase in LPG fueled vehicles. Propane to butanes ratios were calculated for LPG samples and tunnels samples, and the comparable ratios illustrated the LPG leakages from LPG fueled vehicles crossing the tunnel.