Chemical composition of headspace vapor from volatilization of ten petroleum samples

The volatilization potential and vapor composition of crude oil and refine products is critical for volatile organic compounds (VOCs) emission control and risk assessment at petroleum spill sites. This study investigated the weight loss and headspace vapor molecular composition of 10 petroleum samples (including 5 crude oils, 1 naphtha, 1 lighter fuel, 1 gasoline, 1 jet fuel, and 1 diesel) during their 90-day volatilization (evaporation). The gasoline and lighter fuel showed the highest volatilization potential with high initial headspace vapor concentrations (>620 g m(-3)) and high weight loss fractions (>99.5%). The volatilization-induced weight loss fractions of the crude oils ranged from 3.3% to 29.3%. The initial headspace vapor concentrations of naphtha and most crude oils were high (60-380 g m(-3)). Volatilization is an important natural attenuation mechanism at recently-released gasoline, naphtha, and light crude oil sites, which may also present a significant risk of vapor exposure. The volatilization-induced weight loss and headspace vapor concentration of the jet fuel and diesel were relatively low. During the volatilization of most of the 10 petroleum samples, the concentration of <C7 hydrocarbons consistently decreased with time. The concentrations of C8-C10 hydrocarbons were generally low during the entire 90-day volatilization. Alkanes were the most abundant group in the headspace vapors of crude oil and fuel oil at the beginning of volatilization. The role of alkanes should be highlighted during risk assessment of vapor exposure. As volatilization proceeded, the weight fraction of aromatics in the headspace vapor generally increased. This study provides valuable data for estimating the VOCs emission, vapor exposure risk, and the natural attenuation loss of volatilization at petroleum spill sites.