A methodology for the assessment of air quality in London and Bangkok

Abstract

Road transport has a major effect on the air quality in London and Bangkok. As an aid to decision making to control and manage air pollution, air quality models are useful tools and are now applied worldwide. This research aims to modify and adapt a selected screening line source air quality model used in the UK for application in Bangkok as general tools for air quality assessment. The emphasis is on models as an aid to assess various scenarios involving traffic and emissions management. The research also aims to assess air quality in the future years and to propose scenarios to improve air quality in Bangkok. A screening air quality model, suited to this task, was selected from amongst available alternatives: the CAR, DMIRB, LEZ, and GRAM models. The DMRB and GRAM models fitted the requirements of the current research. The GRAM model gave better performance than the DMRB model on the predictions of NO2 and CO, except for PMIO in Bangkok. As the DMRB model requires urban background to be specified whereas GRAM calculates the total concentration including urban background levels, it was decided to select the GRAM model and to adapt it from its current UK orientated formulation to make it applicable to Bangkok. Various parameters were examined to identify the differences between London and Bangkok conditions. Following this a new model for predicting NO2 and PMIO was developed, called the Bangkok GRAM model, whose performance in Bangkok was shown to be better than the UK GRAM model. Future projections were also studied and indicated that the NO2 and PMIO levels in London will decrease in future, but that exceedences will still occur. The introduction of more stringent emissions controls and the early introduction of proposed vehicle emissions standards are the additional measures expected to reduce UK urban emissions by up to 30%. Under the current policy on emission reduction in Bangkok the model predicted little decline in NO2 and PMIO concentrations at very busy roadside sites for up to 2010, and continual increase in the future. Scenarios of additional measures are proposed. The emission reduction approach gives significant reductions in NO2 and PM1o concentrations in Bangkok. The model development has clarified where the main uncertainties lie in urban modelling and emphasises the need to describe re-suspended dust accurately, especially in Bangkok.