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Simulation of rail yard emissions transport to the near-source environment
Citation:
Hagler, G. AND W. Tang. Simulation of rail yard emissions transport to the near-source environment. Atmospheric Pollution Research. Turkish National Committee for Air Pollution Research and Control, Izmir, Turkey, 7(3):469-476, (2016).
Impact/Purpose:
Journal article summarizing findings from computational fluid dynamics modeling of emissions dispersion in a generic rail yard environment.
Description:
Rail yards are critical nodes in the freight transportation network and locations of clustered emission sources. When people reside in close proximity to an active rail yard, the near-field effect of rail yard emissions is of concern. Field characterization of near-rail yard air quality is challenging due to spatially-variable emissions over a large area. Numerical models can provide valuable insight into factors affecting emission dispersion and resulting near-field air pollution. This study utilizes computational fluid dynamics (CFD) modeling to investigate near-field air pollution surrounding a generic, moderate-sized intermodal rail yard with emissions of a neutrally buoyant gaseous pollutant. Rail yard and surrounding neighborhood structures were added in succession to a base case to study the influence of surface roughness on the generic pollutant’s spatial concentration profile. A spatially weighted emissions scenario reveals highly variable pollutant levels in downwind neighborhoods, strongly modulated by wind direction. Rail yard topography (containers, cranes, small buildings) was found to result in a modest increase in near-field pollution levels. Densely located two-story homes surrounding the rail yard reduced downwind concentrations by 16% and 15% at 25 m and 100 m downwind of the rail yard boundary, respectively. Adding a 6 m boundary wall to the rail yard, with four open sections in the wall enabling traffic flow, leads to a reduction in downwind pollution levels by 25% and 12% at 25 m and 100 m downwind, respectively. While area-wide pollution levels are reduced with the addition of neighborhoods and a surrounding boundary wall, high spatial variability in pollution levels in the near-field area lead to some areas with increased pollution levels offset by a reduction in pollution in other near-field areas. Overall, these findings suggest that pollution levels in the near-rail yard area have a high degree of spatial variability, with topographical elements surrounding the rail yard (neighborhood structures, boundary wall) resulting in a net effect of near-field pollution reduction.
URLs/Downloads:
RAIL_CFD_PAPER_20150810_FNL.PDF (PDF, NA pp, 712 KB, about PDF)http://dx.doi.org/10.1016/j.apr.2015.11.003
