CO and NO_x levels at the center of city roads in Jerusalem

CO and NO_x monitors in conjunction with a data acquisition system were installed inside a small van, together with an independent battery operated power supply, to study air pollution levels in the zones where Jerusalem commuters are exposed. The results revealed that along most sections of the test road, CO and NO_x concentrations exceed the short term lower Israeli national air quality standards of 30 and 0.5 ppm, respectively. In addition, there were also a large number of violations of the higher standard for NO_x (1.0 ppm). Traffic volume correlated reasonably well with pollution levels; however, the geometry of the road was found to be equally important. The highest pollution levels were recorded in the narrower segment of the test road near the market place, despite the fact that the traffic counts along these road segments were relatively low. This phenomenon is related to the trapping caused by the canyon effect resulting from the buildings bordering the road. No significant relationship with the general meteorological conditions was found, however, rain washout of NO_x was observed during one sampling trip, while CO concentrations ramained almost unaffected.