title: Correlations between short-term mobile monitoring and long-term passive sampler measurements of traffic-related air pollution.
abstract: Mobile monitoring has provided a means for broad spatial measurements of air pollutants that are otherwise impractical to measure with multiple fixed site sampling strategies. However, the larger the mobile monitoring route the less temporally dense measurements become, which may limit the usefulness of short-term mobile monitoring for applications that require long-term averages. To investigate the stationarity of short-term mobile monitoring measurements, we calculated long term medians derived from a mobile monitoring campaign that also employed 2-week integrated passive sampler detectors (PSD) for NOx, Ozone, and nine volatile organic compounds at 43 intersections distributed across the entire city of Baltimore, MD. This is one of the largest mobile monitoring campaigns in terms of spatial extent undertaken at this time. The mobile platform made repeat measurements every third day at each intersection for 6-10 minutes at a resolution of 10 s. In two-week periods in both summer and winter seasons, each site was visited 3-4 times, and a temporal adjustment was applied to each dataset. We present the correlations between eight species measured using mobile monitoring and the 2-week PSD data and observe correlations between mobile NOxmeasurements and PSD NOxmeasurements in both summer and winter (Pearson's r = 0.84 and 0.48, respectively). The summer season exhibited the strongest correlations between multiple pollutants, whereas the winter had comparatively few statistically significant correlations. In the summer CO was correlated with PSD pentanes (r = 0.81), and PSD NOxwas correlated with mobile measurements of black carbon (r = 0.83), two ultrafine particle count measures (r =0.8), and intermodal (1-3 μm) particle counts (r = 0.73). Principal Component Analysis of the combined PSD and mobile monitoring data revealed multipollutant features consistent with light duty vehicle traffic, diesel exhaust and crankcase blow by. These features were more consistent with published source profiles traffic-related air pollutants than features based on the PSD data alone. Short-term mobile monitoring shows promise for capturing long-term spatial patterns of traffic-related air pollution, and is complementary to PSD sampling strategies.
authors.affiliation: University of Washington Department of Environmental and Occupational Health Sciences, Box 357234, Seattle, WA, 98198. +1 (206) 543-3222.
authors.forename: Erin A
authors.initials: EA
authors.lastname: Riley
authors.affiliation: University of Washington Department of Biostatistics, Box 357232 Seattle, WA, 98198.
authors.forename: LaNae
authors.initials: L
authors.lastname: Schaal
authors.affiliation: University of Washington Department of Environmental and Occupational Health Sciences, Box 357234, Seattle, WA, 98198. +1 (206) 543-3222.
authors.forename: Miyoko
authors.initials: M
authors.lastname: Sasakura
authors.affiliation: University of Washington Department of Environmental and Occupational Health Sciences, Box 357234, Seattle, WA, 98198. +1 (206) 543-3222.
authors.forename: Robert
authors.initials: R
authors.lastname: Crampton
authors.affiliation: University of Washington Department of Civil & Environmental Engineering, Box 352700 Seattle, WA, 98198.
authors.forename: Timothy R
authors.initials: TR
authors.lastname: Gould
authors.affiliation: University of Washington Department of Environmental and Occupational Health Sciences, Box 357234, Seattle, WA, 98198. +1 (206) 543-3222.
authors.forename: Kris
authors.initials: K
authors.lastname: Hartin
authors.affiliation: University of Washington Department of Environmental and Occupational Health Sciences, Box 357234, Seattle, WA, 98198. +1 (206) 543-3222; University of Washington Department of Biostatistics, Box 357232 Seattle, WA, 98198.
authors.forename: Lianne
authors.initials: L
authors.lastname: Sheppard
authors.affiliation: University of Washington Department of Environmental and Occupational Health Sciences, Box 357234, Seattle, WA, 98198. +1 (206) 543-3222; University of Washington Department of Civil & Environmental Engineering, Box 352700 Seattle, WA, 98198.
authors.forename: Timothy
authors.initials: T
authors.lastname: Larson
authors.affiliation: University of Washington Department of Environmental and Occupational Health Sciences, Box 357234, Seattle, WA, 98198. +1 (206) 543-3222.
authors.forename: Christopher D
authors.initials: CD
authors.lastname: Simpson
authors.affiliation: University of Washington Department of Environmental and Occupational Health Sciences, Box 357234, Seattle, WA, 98198. +1 (206) 543-3222.
authors.forename: Michael G
authors.initials: MG
authors.lastname: Yost
keywords: Traffic-related air pollution; black carbon; mobile monitoring; ozone; ultrafine particles