Abstract
Traffic derived air pollution, especially nitrogen dioxide (NO2), is the target of much monitoring and regulation in the UK due to its potential health risks. A large proportion of the monitoring is carried out using passive diffusion sampling equipment, with each UK local authority required to deploy at least four of these devices as part of a national survey. Data collected from this monitoring network from across the county of Surrey, comprising 148 sites, was analysed for trends and patterns, both temporal and spatial. The potential to extract useful spatial information from this data was found to be heavily affected by the uneven distribution of the sites across the area. This study examines the potential for improving the distribution of monitoring with the aim of extracting spatial information about air pollution, and for generating interpolated maps of the pollution within an area. This was undertaken using a series of techniques and tools employed within a Geographical Information System (GIS) environment. Different types of monitoring schemes were tested as to their suitability for reproducing spatially useful data. Hypothetical scenarios were examined to determine the optimum distribution of sampling for interrogating spatial patterns. The optimal sampling strategies were found to relate directly, in scale, to the extent of the pollution elements searched for. A strategy of monitoring was devised to distinguish background variations in pollution within the current monitoring framework: a correlation of R2> 0.8 was attained for rural areas, using a 4Km regular grid across the region (approximately 30 sites for a borough area) The successful monitoring of urban patterns required greater numbers of monitoring devices to be deployed than are currently being used. It was found that a 2Km regular grid (approximately 108 sites) was necessary in order to produce R2> 0.8 for all the scenarios tested. Techniques for optimising the distribution of gridded sampling across any area were developed from the study.