title: Time-series analysis to study the impact of an intersection on dispersion along a street canyon.
abstract: This paper presents data analysis from the Brooklyn Traffic Real-Time Ambient Pollutant Penetration and Environmental Dispersion (B-TRAPPED) study to assess the transport of ultrafine particulate matter (PM) across urban intersections. Experiments were performed in a street canyon perpendicular to a highway in Brooklyn, NY, USA. Real-time ultrafine PM samplers were positioned on either side of an intersection at multiple locations along a street to collect time-series number concentration data. Meteorology equipment was positioned within the street canyon and at an upstream background site to measure wind speed and direction. Time-series analysis was performed on the PM data to compute a transport velocity along the direction of the street for the cases where background winds were parallel and perpendicular to the street. The data were analyzed for sampler pairs located (1) on opposite sides of the intersection and (2) on the same block. The time-series analysis demonstrated along-street transport, including across the intersection when background winds were parallel to the street canyon and there was minimal transport and no communication across the intersection when background winds were perpendicular to the street canyon. Low but significant values of the cross-correlation function (CCF) underscore the turbulent nature of plume transport along the street canyon. The low correlations suggest that flow switching around corners or traffic-induced turbulence at the intersection may have aided dilution of the PM plume from the highway. This observation supports similar findings in the literature. Furthermore, the time-series analysis methodology applied in this study is introduced as a technique for studying spatiotemporal variation in the urban microscale environment.
authors.affiliation: National Center for Environmental Assessment, US Environmental Protection Agency, 109 T. W. Alexander Drive, MC B243-01, Research Triangle Park, NC 27711, USA.
authors.forename: Jennifer
authors.initials: J
authors.lastname: Richmond-Bryant
authors.forename: Alfred D
authors.initials: AD
authors.lastname: Eisner
authors.forename: Intaek
authors.initials: I
authors.lastname: Hahn
authors.forename: Christopher R
authors.initials: CR
authors.lastname: Fortune
authors.forename: Zora E
authors.initials: ZE
authors.lastname: Drake-Richman
authors.forename: Laurie A
authors.initials: LA
authors.lastname: Brixey
authors.forename: M
authors.initials: M
authors.lastname: Talih
authors.forename: Russell W
authors.initials: RW
authors.lastname: Wiener
authors.forename: William D
authors.initials: WD
authors.lastname: Ellenson
mesh_terms: D000393:Air Pollutants / Q000032:analysis*; D016902:Air Pollution, Indoor / Q000032:analysis; D001272:Atmosphere / Q000737:chemistry*; D004784:Environmental Monitoring / Q000379:methods*; D007700:Kinetics; D009519:New York City; D052638:Particulate Matter / Q000032:analysis*; D013997:Time Factors; D001335:Vehicle Emissions / Q000032:analysis*; D014919:Wind
chemical_list: D000393:Air Pollutants; D052638:Particulate Matter; D001335:Vehicle Emissions