Abstract
The University of Tennessee and Oak Ridge National Laboratory conducted a 5-month long air monitoring study at the Watt Road interchange on I-40 in Knoxville Tennessee where there are 20,000 heavy-duty trucks per day traveling the interstate. In addition, there are 3 large truck stops at this interchange where as many as 400 trucks idle engines at night. As a result, high levels of PM2.5 were measured near the interchange often exceeding National Ambient Air Quality Standards. This paper presents the results of the air monitoring study illustrating the hourly, day-of-week, and seasonal patterns of PM2.5 resulting from diesel truck emissions on the interstate and at the truck stops. Surprisingly, most of the PM2.5 concentrations occurred during the night when the largest contribution of emissions was from idling trucks rather than trucks on the interstate. A nearby background air monitoring site was used to identify the contribution of regional PM2.5 emissions which also contribute significantly to the concentrations measured at the site. The relative contributions of regional background, local truck idling and trucks on the interstate to local PM2.5 concentrations are presented and discussed in the paper. The results indicate the potential significance of diesel truck idling emissions to the occurrence of hot-spots of high PM2.5 concentrations near large truck stops, ports or border crossings.
