Physical transformation of ultrafine particles near three Texas roadways

A systematic evaluation of vehicular emitted air pollutants in the vicinity of three Texas roadways, i.e., a heavily traveled arterial highway, dominated by passenger vehicles, a limited access highway, and a heavily traveled surface highway dominated by truck traffic, was carried out. Under inconsistent wind conditions, distances along wind trajectory from the roadway to the sampling points were better metrics for ultrafine particle (UFP) spatial profiles than physical perpendicular distances from the roadway to the sampling points. Under perpendicular wind conditions, for all studied roadway type, particle number concentrations increased when one moves from the upwind side to the downwind side of the roadways and decayed exponentially with increasing distances with sharp concentrations gradient observed within 100-150 m from the roadway. A single exponential decay curve fitted the data collected from all three roadways very well under perpendicular wind conditions. Although no consistent pattern was observed for UFP under parallel wind conditions, for virtually every roadway type, and independent of whether air flow was parallel to or perpendicular to the roadway, particle concentrations returned to background levels within a few hundred meters of the roadway. This is an abstract of a paper presented at the 101st AWMA Annual Conference and Exhibition (Portland, OR 6/24-27/2008).