Abstract
Mobile Source Air Toxics (MSATs) are of growing concern due to recent studies linking health risk to residency near heavily traveled roadways. Few research studies on MSAT emissions have been performed due to several factors; those factors include: the difficulty of measuring MSATs due to their semi-volatile nature, lower relative concentration in comparison to NOx and other criteria emissions, and fewer regulations on MSATs. In this paper, measurements of MSATs at a "hot spot" of poor air quality created by a high population of idling heavy-duty trucks are presented. The study area was the Watt Road-Interstate-40/75 interchange just west of Knoxville, TN where approximately 20,000 heavy-duty trucks travel along the interstate each day and hundreds of heavy-duty trucks idle at three large truck stops near the interchange. The air quality in the local area surrounding the interchange is affected negatively by the high number of mobile sources as well as geographic and meteorological conditions; the interchange lies in a valley between two ridges which slows long range transport of pollutants especially in winter months when temperature inversion occurs frequently. Ambient air quality was measured during summer and winter months of two separate years at three sites: a site in one of the truckstops, a site near the interstate roadway, and a site on top of one of the surrounding ridges chosen as a background site for comparison. Results of criteria pollutants measured at these sites are reported in a companion paper by Miller et. al.; the results presented here include measurements of MSATs such as formaldehyde, acetaldehyde, acrolein, and other species obtained via collection on di-nitrophenyl hydrazine (DNPH) filters. Also, preliminary measurements of poly-aromatic hydrocarbons are presented. The results indicate that emissions from idling heavy-duty trucks are a primary contributor of MSATs to local air quality near areas of high static truck traffic; furthermore, higher levels of MSATs were detected in winter months indicating the meteorological effects on engine emissions and pollution transport.
