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FHWA and EPA National Near-Road Study Las Vegas

2 Background

The objective of the study was to determine MSAT concentrations and variations in concentrations as a function of distance from the highway and to establish relationships between MSAT concentrations as related to highway traffic flows including traffic count, vehicle types, and speed; and meteorological conditions such as wind speed and wind direction.2

Studies have demonstrated that spatial gradients of several traffic-emitted air pollutants (e.g., NOx, CO, elemental or black carbon, ultrafine and coarse particles, and mobile source air toxics) decrease with distance from the road, generally returning to levels comparable to concentrations upwind of the road within a few hundred meters downwind5,6. Some studies show that fine particulate matter (PM2.5) is only moderately impacted by traffic with greater contributions of ultrafine and coarse particles5,6. The extent of the spatial impacts of traffic related air pollutants is related to factors including the type of roadway, traffic volume and intensity, and meteorology5,6,7,8. The areal extent of traffic generated particles, especially ultrafine particles, has been shown to vary diurnally and seasonally with the greatest spatial extent of the roadway plume occurring at night and during winter9,10. The composition of PM near roads is also impacted by traffic emissions with greater quantities of a number of metals including copper, iron, and antimony11,12. While most studies have focused on the criteria air pollutants PM, CO, and NOx, less information exists concerning the spatial distribution of MSATs near-roadways1,7,13.

This report describes the methods and initial results from research conducted to evaluate mobile source contributions to criteria, air toxics and PM2.5 pollutant concentrations, and their dispersion patterns near a highway in Las Vegas, Nevada.2

Updated: 5/21/2013
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