Regional and urban scale modelling of particulate matter : can PM10 be managed at a local level?
In March 1997, the British government launched the United Kingdom National Air Quality Strategy. The Strategy sought to reduce levels of PM10 in the UK so that the objective of 50µg/m3 , measured as a daily maximum of running 24-hour means, was exceeded on no more than four days per year. Within three years this objective had been relaxed to allow for thirty five exceedences per year, albeit of a slightly lower level (because of changes in measurement technique), due to concerns that longrange transport of secondary particles would prevent local authorities from achieving this objective through local air quality management techniques. The study presented in this thesis seeks to contribute to the current body of work examining this issue. Two models, one at a regional/European scale, the other at an urban scale, have been used to estimate contributions to atmospheric PM10 levels from various sources. The results of the models, both independently and combined, have been used alongside relevant monitoring data to assess effect that local management techniques might have upon levels of PM10 in both urban and rural locations. The results suggest that, in many locations where the original air quality objective may not have been achieved, local emissions of primary combustion related sources may not have contributed more than 10-15% of total observed PM10 levels. This raises questions regarding exactly what the nature of the remaining portion of PM10 is comprised of, as current modelling techniques are unable to estimate this accurately: either due to an inability to represent the physics and chemistry, or due to lack of information about the sources. However, in the absence of a full understanding of either the composition or health effects of PM10, what factors should be considered in deciding whether or not local management strategies should be applied to the pollutant?