Tomographic-DOAS: from sensing to visualisation of urban street canyon pollutants

摘要

With over 75% of Europeans living and working in urbanised areas the quality of air in this environment is of extreme importance, influencing directly the health and well being of a significant proportion of the continent's population as well as impacting on the greater ecosystem. A microenvironment of particular interest is the street canyon where the spatial and temporal characteristics of pollutants are known to be complex, resulting from airflow patterns that transport and disperse the pollutants. Measurement of pollutants exhibiting such spatial and temporal variability will require new sensing approaches with high data quality standards. We discuss the use of Tomographic-DOAS (Differential Optical Absorption Spectroscopy) for the visualisation of the spatial distribution of air contaminants in street canyons. We provide reviews of the DOAS remote sensing technique, explaining how DOAS works and why it has significant advantages over traditional point-sampling methods. We discuss the novel combination of DOAS and computed tomography (CT) to produce Tomographic-DOAS, demonstrating how it can be utilised to produce near realtime maps of concentration levels of multiple air contaminants in a street canyon. We demonstrate this with simulated reconstructions using model based pollutant data for a street canyon. Finally, we discuss the future direction and feasibility of this approach, highlighting current limitations and where further research and development are required.