Influence of Meteorological Factors on the Characteristics of Volatile Organic Compounds in the Atmosphere at the Surrounding Area of an Oil Storage and Pumping Station

摘要

This study investigated the characteristics of volatile organic compounds (VOCs) in the atmosphere at the surrounding area of an oil storage and pumping station from March to September 2001. The influence of operation condition of storage and pumping station as well as meteorological factors on the distribution of atmospheric VOCs was also investigated. In this study, a sampling network including six sites around the boundary of the storage and pumping station and one site at a nearby village (i.e. sensitive site) was established for the sampling and analysis of VOCs near ground level. VOCs samples were collected by carbontrap 300 multi-bed stainless steel sampling tubes, which were further desorbed by a thermal desorption unit (TDU). The desorbed VOCs were then analyzed quantitatively by a gas chromatography with flame ionization detector (GC/FID). In addition, hydrocarbons (methane and non-methane hydrocarbons) and meteorological condition (wind speed and wind direction) were in-situ monitored automatically in order to correlate with the concentration of VOCs. Results from field measurement indicated that up to twelve VOCs were detected in the atmosphere, which quite consisted with the composition of stored oil including petroleum crude oil, JP-4 aviation jet fuel, 92 and 95 unleaded gasolines, and naphtha. In this study, major VOCs observed were benzene and toluene, however, in some cases high boil-point organic compounds were also detected. It suggested that the nearby village was not only affected by the VOCs emitted from the oil storage tanks but also by other unidentified local sources. Furthermore, meteorological condition played an important role on the distribution of VOCs at the surrounding area. For instance, the concentration of VOCs at the downwind sites were generally higher than that at the upwind sites while northern and northwestem winds blew in late spring. Besides, the toluene to benzene concentration ratios (T/B) ranging from 1.5 to 3.0 during the southwestern winds in summer were higher than those (T/B<1.5) during the northwestem winds in late spring. It suggested that the nearby village could be much more easily affected by local traffics instead of the oil storage and pumping station during the summer time since T/B ratios were approximately 2.0 in the tail gas exhausted from automobiles. Results obtained from health risk analysis indicated that the highest health risk was observed at the floating tank zone, where required much better operation and control strategies for the protection of ambient air quality at the surrounding area.