Hydrogen Sulfide Study Near Petroleum Asphalt Plants

摘要

An ambient air monitoring study along with emission tests were conducted to estimate concentrations of several toxic pollutants in a residential suburban area adjacent to a liquid asphalt distribution terminal and a hot mix asphalt plant. Data were collected at three monitoring sites from May to September 2001 for hydrogen sulfide (H2S), volatile organic compounds (VOCs), and meteorological conditions. In addition, data were collected to characterize key parameters for process operations from both paving asphalt plants, nearby road traffic, and odor complaints. These data were analyzed to evaluate relationships between H2S concentrations, both asphalt plants' process operations, wind direction, and odor complaints. Integral to the study were source H2S emission measurements, one using EPA Method 15 on the liquid asphalt terminal and the other using an electrochemical monitor on the hot mix asphalt plant. Dispersion modeling using the recent emission data was performed to determine compliance with NC regulatory acceptable ambient levels. Finally, a careful comparison was made between measured and known health effect levels for H2S to evaluate whether local exposures may be cause for concern. Notable outcomes from this and related efforts include the following: 1. Discovery that H2S is the most emissive toxic compound from liquid asphalt terminals and appears to be the same for hot mix asphalt plants. 2. H2S emission control practice in the asphalt industry in NC is largely non-existent. 3. Monitoring data, process data, citizen odor complaints, and dispersion modeling argue strongly that the liquid asphalt terminal is the primary contributor to H2S levels above the odor threshold in the nearby area. Human exposure to H2S at the levels measured in our study might result in physiological or psychological reactions to the detection of unpleasant odors, but it is considered unlikely that any direct toxicity would result from such exposures.