Influence on air pollution monitoring station by vehicular emissions determined using Geographic Information System (GIS)

摘要

The present work proposes a methodology to study the influence on air pollution monitoring stations by vehicular emissions using a Geographic Information System (GIS). As a preliminary study, only one air pollution monitoring station has been chosen as an example. We studied four elements, Zn, Ba, Cu and Pb. The Gaussian plume model was adopted to determine the contribution from vehicles to elemental concentrations measured at the monitoring station. When modeling the dispersion, the line pollution sources representing emissions from vehicles traversing the streets were treated as if they were on top of the canyons. This was made possible since the time periods taken for the pollutants to reach the top of the canyons were very short, in the order of tens of seconds. A method has been devised to determine the emission factors f_c(k) (mg per km per vehicle) of different chemical elements k from a particular clipped road length from gasoline cars, diesel cars and heavy duty diesel vehicles. Together with the traffic data provided by Hong Kong Transport Department, the emission rates Q_(i,j)(k) (g hr~(-1)) can be obtained which are required in the Gaussian plume model. In conclusion, Ba concentration measurements are affected by vehicular emissions, Zn measurements can be affected but the extent depends on the wind direction, while other elemental measurements are only minimally affected. The methodology will be extended to a territory-wide study in the near future.