AAAR 35th Annual Conference October 17 - October 21, 2016 Oregon Convention Center Portland, Oregon, USA
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Ultrafine Particle Measurements at Schools Next to a Freeway in Las Vegas and in the Greater Salt Lake City Area
STEVEN G. BROWN, Jennifer DeWinter, Paul Roberts, Sonoma Technology, Inc
Abstract Number: 389 Working Group: Urban Aerosols
Abstract We report on ultrafine particle (UFP) concentrations at two schools: (1) Hunter High School in West Valley City, Utah (a suburb of Salt Lake City), which is located in an urban center away from major roadways; and (2) Adcock Elementary School in Las Vegas, Nevada, which is 20 m from the U.S. 95 freeway. Data were collected at Hunter in winter 2012, and at Adcock in spring 2013. UFP concentrations were higher at Adcock than at Hunter due to Adcock’s proximity to the freeway. At Adcock, the mean hourly value was 11,022 particles/cm3; at Hunter, the mean hourly value was 6,755 particles/cm3. Both locations showed a strong morning peak in particle concentrations and similar morning peaks in black carbon (BC) concentrations. On roughly 40% of days at Adcock, UFP had a midday peak with no corresponding BC peak, likely due to new particle formation. UFP and BC concentrations were significantly higher at Adcock when wind speeds were low, while at Hunter the UFP concentrations were invariant with wind speed and BC was only slightly lower at higher wind speeds. We attribute this difference to the impact of emissions on U.S. 95 next to Adcock, where concentrations are higher under lower wind speeds regardless of wind direction. BC and UFP had no correlation at Adcock, and a low correlation (r = 0.35) at Hunter. Other studies have found that BC and particle count is only correlated with larger particles (greater than 200 nm diameter). Since Adcock is next to U.S. 95 and fresh vehicle emissions, UFP count measurements are likely dominated by particles less than 100 nm in diameter, leading to a low correlation with BC. At Hunter, particles are likely more aged and thus larger, leading to a higher correlation between UFP and BC.