Spatial and temporal distribution of particulate pollution in London from high-temperature combustion sources
The urban atmospheric environment contains a complex cocktail of pollution from numerous sources. However, the contribution to this mixture from power stations and other high-temperature combustion point sources is uncertain. Spheroidal carbonaceous particles (SCPs) and inorganic ash spheres (IASs) are uniquely formed as a by-product of high-temperature combustion of fossil fuels and therefore are ideal indicators of fossil-fuel derived pollution in London. Deposition of SCPs in London from power stations and other combustion processes regulated by the Environment Agencies under Part A of the Environment Act 1990 was modelled using the atmospheric dispersion modelling system (ADMS 3) developed by the Meteorological Office and the Cambridge Environmental Research Consultancy. The results agreed well with the spatial distribution of SCP concentrations in surface sediments from twenty-seven lakes and ponds within the M25. SCP size distributions were used to identify the dominant sources of SCPs for each site. Multivariate statistical analyses showed that lake and pond processes were generally not important variables affecting the concentration of SCPs in the surface sediments. High resolution SCP and IAS time-series collected by Burkard Spore Traps on a transect linking the centre of London with the power stations in the east Thames Corridor showed the presence of several pollution events, both SCP and IAS, that occurred simultaneously at a number of sites. Potential sources were identified for each IAS and SCP event based on SCP size data and meteorological conditions. The relationship between the IAS and SCP concentrations indicated whether the event was caused by a coal- or oil-fired source. Multivariate statistical analyses of the meteorological data did not consistently extract any one variable that would explain the SCP and IAS profiles. However, a subjective analysis of the data shows that many IAS events in London are caused by emissions from the power stations in the east Thames Corridor.