7.2 Computational Scheme Accounting for Heterogeneous Surface Emissions in CTMs

摘要

Chemistry transport models (CTMs) have been widely used for urban air-quality forecast over the last 10 years but rarely for human exposure studies or health impact assessment (HIA). Exposure models require information on pollutant concentration at the neighborhood scale (sub-kilometer resolution). High resolution modelling applications may look appealing but their high computational cost makes them inappropriate for this purpose. Spatio-temporal analysis of monitor data is used in most cases in exposure studies (Georgopoulos et al., 2005). On the other hand, traditional HIA methods use area-aggregated monitor data. Not taking into account the spatial variability of pollutant concentrations has been shown to lead to significant bias in health risk estimates in HIA methods (Smith, 1997). It becomes clear that CTMs should adapt to the needs of such studies and provide information on small scale concentration variability. We applied an emission scheme to the CHIMERE CTM that allows to extract information on the variability of pollutant concentrations at sub-grid scale. The application is based on the split of grid-averaged emission into separate contributions of emitting activities co-existing over the same grid-cell area (e.g. traffic transportation, residential emissions, etc.). Different concentrations are calculated for each emission scenario allowing the evaluation of concentration variability between source-specific areas inside grid-cells. The advantage of the application is that modelled concentrations are directly associated to human-activities during the day and are therefore, easily adapted to human exposure models.