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Ultrafine particles near a major roadway in Raleigh, North Carolina: downwind attenuation and correlation with traffic-related pollutants
Citation:
HAGLER, G., R. W. BALDAUF, E. D. THOMA, THOMAS LONG, R. SNOW, J. KINSEY, L. OUDEJANS, AND B. K. GULLETT. Ultrafine particles near a major roadway in Raleigh, North Carolina: downwind attenuation and correlation with traffic-related pollutants. ATMOSPHERIC ENVIRONMENT. Elsevier Science Ltd, New York, NY, 43(6):1229-1234, (2009).
Impact/Purpose:
journal article
Description:
Ultrafine particles (UFPs, diameter <100 run) emitted by traffic are a potential direct health threat to nearby populations and may additionally act as a tracer for co-emitted pollutants. During summertime in Raleigh, North Carolina, UFPs were simultaneously measured upwind and downwind of a major roadway using a spatial matrix of five portable industrial hygiene samplers (measuring total counts of 20-1000 nm particles). While the upper sampling range of the portable samplers extends past the defined "ultrafine" upper limit (100 run), the 20-1000 nm number counts had high correlation (Pearson R = 0.7-0.9) with ultrafine particles (10-65 nm) measured by a co-located research-grade analyzer and thus appear to be driven by the ultrafine range. Highest UFP concentrations were observed during weekday morning work commutes, with levels at 20 m downwind from the road nearly 5-fold higher than at an upwind station. A strong downwind spatial gradient was observed, linearly approximated over the first 100 m as an 8% drop in UFP counts per 10 m distance. This result agreed well with UFP spatial gradients estimated from past studies (ranging 5-12% drop per 10 m). Linear regression of other vehicle-related air pollutants measured in near real-time (10-min averages) against UFPs yielded moderate to high correlation with benzene (R2 = 0.76), toluene (R2 = 0.49), carbon monoxide (R2 = 0.74), nitric oxide (R2 = 0.80), and black carbon (R2 = 0.65). Overall, these results support the notion that near-road levels of ultra fine particles are heavily influenced by traffic emissions and well represent patterns of other vehicle produced pollutants, including certain air toxics.
