The Brooklyn Traffic Real-Time Ambient Pollutant Penetration and Environmental Dispersion (B-TRAPPED) study

Russell W. Wiener

Dr. Russell Wiener is a senior scientist with the National Homeland Security Research Center at the U.S. Environmental Protection Agency (EPA) in Durham, NC. Prior to this position he was Chief of the Atmospheric Methods and Monitoring Branch, National Exposure Research Laboratory, U.S. EPA, where he was responsible for developing the sampling methodology for the 1997 National Ambient Air Quality Standard for Fine Particulate (PM2.5). Dr. Wiener's personal research interest has been focused on studying aerosol transport and sampling to better understand the mechanisms of human and ecosystem exposure to suspended particulate matter.

This issue features a collection of papers presenting the results of the Brooklyn Traffic Real-Time Ambient Pollutant Penetration and Environmental Dispersion (B-TRAPPED) study. The aim of this study was to develop a better understanding of the transport of airborne particulate pollutants in a heavily populated urban neighborhood, from the sources on the streets, down the street canyon, and into and within the adjacent buildings. A growing number of epidemiological studies have identified an increase in occurrence of adverse health effects for populations living near major roads. Exposure to airborne traffic emissions may cause significant health problems, including asthma and other respiratory diseases. Concerns regarding these exposures have resulted in a need to evaluate and improve methods of predicting exposures in the near-road environment. Similarly, concerns about homeland security have resulted in a need to better understand urban dispersion near an accidental or intentional release of hazardous materials on a nearly instantaneous time scale.

This study was designed to help develop a simplified model of urban aerosol transport relevant to human exposure in the near field of a release. Components of the B-TRAPPED study included laboratory evaluations of the sampling technologies, wind tunnel studies of the atmospheric boundary layer flows in a simulated neighborhood, a modest microscale urban field study, and comprehensive theoretical modeling of the major mechanisms of particulate matter (PM) source release, transport, dispersion, surface flux, and infiltration processes.

The B-TRAPPED field study was conducted in the residential Sunset Park neighborhood of Brooklyn, NY, USA, in May 2005. The neighborhood contained the Gowanus Expressway (Interstate 278), a major arterial road (4th Avenue), and residential side streets running perpendicular to the Gowanus Expressway and 4th Avenue. The study site was chosen to represent a typical urban population center where high-density housing is in close proximity to major traffic arteries. The study investigated the dispersion of fine aerosols from the principal roadways and down a transecting street canyon, the flux of particles onto the building surfaces, the infiltration through the building shell, and the circulation within the residential structure. The laboratory portions of the program were conducted at the U.S. EPA facility in Research Triangle Park, NC, between 2004 and 2006.

Contaminant transport is strongly dependent on the direction of air movement with respect to the roadways and the complexity of the topography (number of cross streets, building heights, vegetation, and terrain). If the wind direction is parallel to the road, contaminants at human height may be channeled down the street. Flows may be far more complicated, however, due to the generation of turbulence from structures and other obstructions upwind of the canyon. In this study, special attention was paid to the effects of a single tall building and cross streets on the flow of the pollutants down the street canyon being examined.

Other key areas of interest were developing a physical model of the turbulent flux onto the building surfaces and determining the infiltration flux rate of fine PM into the adjacent buildings. This study sought to measure dispersion in the street canyon, infiltration into the adjacent buildings, and concentration within the structures simultaneously. We have found that urban dispersion, contaminant infiltration, and indoor exposures are closely related phenomena.

The results of this study as presented in the ten following papers intend to accomplish the following:

• Delineate and visualize how a plume that is generated by customary (e.g., traffic), accidental (e.g., spill), or intentional (e.g., terrorist attack) means near or on the major roadway travels downwind and presents potential inhalation hazards at various locations and in both outdoor and indoor environments.

“Overview of the Brooklyn Traffic Real-Time Ambient Pollutant Penetration and Environmental Dispersion (B-TRAPPED) study: theoretical background and model for design of field experiments“ DOI: 10.1039/b907123g

“The Brooklyn Traffic Real-Time Ambient Pollutant Penetration and Environmental Dispersion (B-TRAPPED) field study methodology” DOI: 10.1039/b907126c

“Characterization of traffic-related PM concentration distribution and fluctuation patterns in near-highway urban residential street canyons” DOI: 10.1039/b907130j

“Time-series analysis to study the impact of an intersection on dispersion along a street canyon” DOI: 10.1039/b907134m

• Determine how time-series data of aerosol concentrations measured at a fixed site can be used to discern and describe the characteristic “wave” forms of plumes generated at a source (major roadway) traveling to downwind receptor locations in an urban environment when temporal autocorrelation analysis is applied.

“Establishing a link between vehicular PM sources and PM measurements in urban street canyons” DOI: 10.1039/b907132f

• Determine the infiltration flux rate that can predict the degree of indoor exposure risk for certain harmful material of outdoor origin using cross-correlation analyses of concurrent indoor–outdoor concentration time series.

“Building characterization and aerosol infiltration into a naturally ventilated three-story apartment building” DOI: 10.1039/b907139n

“Parameterization of meteorological variables in the process of infiltration of outdoor ultrafine particles into a residential building” DOI: 10.1039/b907140g

“Analysis of indoor air pollution trends and characterization of infiltration delay time using a cross-correlation method” DOI: 10.1039/b907144j

• Characterize temporal and spatial PM concentration fluctuation and distribution patterns in the urban street canyon and their relationship to reference wind patterns and investigate their potential implications in exposure risk assessment.

“Characterization of traffic-related PM concentration distribution and fluctuation patterns in near-highway urban residential street canyons” DOI: 10.1039/b907130j

“Establishing a link between vehicular PM sources and PM measurements in urban street canyons” DOI: 10.1039/b907132f

“Time-series analysis to study the impact of an intersection on dispersion along a street canyon” DOI: 10.1039/b907134m

• Determine the influence of meteorological variables on the transport, dispersion, and infiltration processes.

“Overview of the Brooklyn Traffic Real-Time Ambient Pollutant Penetration and Environmental Dispersion (B-TRAPPED) study: theoretical background and model for design of field experiments” DOI: 10.1039/b907123g

“Characterization of traffic-related PM concentration distribution and fluctuation patterns in near-highway urban residential street canyons” DOI: 10.1039/b907130j

“Parameterization of meteorological variables in the process of infiltration of outdoor ultrafine particles into a residential building” DOI: 10.1039/b907140g

“Analysis of indoor air pollution trends and characterization of infiltration delay time using a cross-correlation method” DOI: 10.1039/b907144j

• Characterize the relationships between the building parameters and the infiltration mechanisms and identify the dominant mechanisms involved in the infiltration process.

“Building characterization and aerosol infiltration into a naturally ventilated three-story apartment building” DOI: 10.1039/b907139n

“Parameterization of meteorological variables in the process of infiltration of outdoor ultrafine particles into a residential building” DOI: 10.1039/b907140g

“Analysis of indoor air pollution trends and characterization of infiltration delay time using a cross-correlation method” DOI: 10.1039/b907144j

• Evaluate the effectiveness of a shelter-in-place area for protection against outdoor-released PM pollutants.

“Parameterization of meteorological variables in the process of infiltration of outdoor ultrafine particles into a residential building” DOI: 10.1039/b907140g

• Use wind tunnel and computational fluid dynamics (CFD) simulations to determine the predominant airflow and pollutant dispersion patterns within the neighborhood.

“The effect of a tall tower on flow and dispersion through a model urban neighborhood, Part 1. Flow characteristics” DOI: 10.1039/b907135k

“The effect of a tall tower on flow and dispersion through a model urban neighborhood, Part 2. Pollutant dispersion” DOI: 10.1039/b907137g

The series of papers presented here represents part of our ongoing efforts in investigating urban air pollution, air quality monitoring, and exposure assessment. The B-TRAPPED study is unique because it has studied these objectives using comprehensive tools combining many mechanisms and parameters representing coupled processes of PM origin, transport, dispersion, and exposure. The B-TRAPPED study is one of only a few urban field studies that aim to research urban pollution–dispersion–exposure problems by applying spatially and temporally synchronized and concurrent observations of PM concentration and meteorological variables in multiple monitoring locations within a busy metropolitan urban residential area. Urban inhalation exposure studies typically are concerned with long-term exposure (days to years) and use probabilistic methods to assess human exposure. In this study, we are concerned with real-time exposures and use both deterministic and probabilistic analysis to assess possible exposures. We are currently working on a follow-up series of papers detailing more analyses regarding human exposure in an urban area and its impact on both public health and homeland security risk analysis.

Disclaimer

The U.S. Environmental Protection Agency through its Office of Research and Development funded and managed the research described here under Contract EP-D-05-065 with Alion Science and Technology. The views expressed in this paper are those of the authors and do not necessarily reflect the views or policies of the U.S. Environmental Protection Agency. Mention of trade names or commercial products does not constitute endorsement or recommendation for use.

Footnote

† Part of a themed issue on a real-time study of airborne particulate dispersion in urban canyons.

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