Friday, November 12, 2010

Modelling Air Quality in an Urban Canyon

Estimation of CO concentrations for an urban street canyon in Ireland (8 page pdf, Air Quality, Atmosphere & Health, Mar. 5, 2010)

Today’s review article looks at the performance of two canyon air quality models – STREET and OSPOM – when compared with stationary monitor located near a busy roadway in Dublin. In addition an assessment is made using emission factors (HEF for hourly and CEF for Composite) to judge the models as to the emissions from the source

Key Quotes:

“The WHO has estimated that 1.4 billion urban residents in developing countries breathe air in which pollutant concentrations exceed WHO air quality guidelines (WHO 1992). Urban air pollution episodes are associated with sudden incidences of high concentrations of pollutants, which are generally governed by local meteorology, emissions and dispersion conditions (Mayer 1999). The major source groups responsible for urban air pollution are primarily motor traffic and industries”

“In most European cities, traffic is the most important source of air pollution, with the highest ambient concentrations often found on streets in urban centres. Vehicular pollution dispersion models are therefore essential computational tools for predicting the impacts of emissions from road traffic”

“two urban street canyon models, namely STREET and Operational Street Pollution Model (OSPM), were investigated at Pearse Street, an important traffic route in the centre of Dublin city

“Hourly background concentrations were obtained from an urban air quality monitoring station.. approximately 100 m from the nearest trafficked street. All this recorded parameters were used in computing the modelled CO concentrations. These were then compared with measured CO concentrations”

“An emission factor is the relationship between the amount of pollution produced and the amount of raw material processed or burned. For road traffic, it is the relationship between the amount of pollution produced and the number of vehicle kilometres travelled (grams per kilometre). By using the emission factor of a pollutant and specific data regarding quantities of materials used by a given source, it is possible to compute emissions for the source”

“This paper tries to highlight the STREET model as a suitable screening model for the prediction of CO concentrations in an urban street canyon. When compared with monitored data, concentrations calculated using STREET and OSPM both successfully predict observed variations in air quality”

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