Modelling Spatial Variations of Black Carbon Particles in an Urban Highway-Building Environment

This study investigated pollutant transport in a highway building environment by combining field measurement and numerical simulations. The Comprehensive Turbulent Aerosol Dynamics and Gas Chemistry (CTAG) model was used in simulating the spatial variations of black carbon (BC) concentration near highway I-87 and an urban school in the South Bronx, New York. The results of CTAG simulations were evaluated against and agree adequately with the measurements of wind speed, wind directions, and BC concentration. Based on analysis, the BC concentration at the measurement point of the urban school could decrease by 43-54% if roadside buildings were absent. Two generalised conditions in a highway-building environment were characterised, i.e., highway-building canyon and highway via duct-building. The former refers to the canyon between solid highway embankment and roadside buildings, where the spatial profiles of BC depend on the equivalent canyon aspect ratio and flow recirculation. The latter refers to the area between a highway via duct (i.e., elevated highway with open space underneath) and roadside buildings, where strong flow recirculation is absent and the spatial profiles of BC are determined by the relative heights of the highway and buildings. The two configurations may occur at different locations or in the same location with different wind directions when highway geometry is complex. In conclusion, the study demonstrates the importance of incorporating highway-building interaction into the assessment of human exposure to near-road pollution and calls for active roles of building and highway designs in mitigating near-road exposure of urban population.

Authors: Tong, Zheming; Wang, Yan Jason; Patel, Molini; Kinney, Patrick; Chrillrud, Steven; Zhang, K. Max ;Full Source: Environmental Science & Technology [online computer file] 2012, 46(1), 312-319 (Eng) ;