Eighth Symposium on the Urban Environment


Source emissions and transport and dispersion models for Toxic Industrial Chemicals (TICs) released in cities

Steven R. Hanna, Hanna Consultants, Kennebunkport, ME; and R. Britter, J. Leung, O. R. Hansen, R. I. Sykes, P. Drivas, J. C. Weil, and D. Strimaitis

A review is given of source emissions models for Toxic Industrial Chemicals (TICs), with emphasis on chemicals stored and/or transported as pressurized liquefied gases (e.g., chlorine, anhydrous ammonia, and sulfur dioxide), for which many tons of a gas/aerosol mixture can be released into the atmosphere in one or two minutes. Some recommendations are given for specific source emissions equations, with scientific rationale provided. Field experiments on TIC source emissions are reviewed and some results of evaluations are presented. A hypothetical chlorine railcar release in Chicago is simulated with a CFD model (FLACS) and with several widely-used simpler dispersion models and the results compared. The CFD model-simulated effects of the urban buildings on the dense gas transport and dispersion are discussed, such as constraints by buildings near the source, reductions in transport speed, diversion of the dense gas down drainage slopes, increases in turbulence intensities, and hold-up in building wakes for 30 or more minutes after the main cloud has passed. In addition, results of some sensitivity runs with the SCIPUFF and SLAB models are shown where wind speed, surface roughness, stability, and dry deposition velocity are varied.

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wrf recording  Recorded presentation

Joint Session 14, Dense Gas Dispersion (Joint with the Meteorological Aspects of Air Pollution Committee)
Tuesday, 13 January 2009, 1:30 PM-3:00 PM, Room 124B

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