Particulate pollution and stone deterioration

The soiling and damage of building surfaces may be enhanced by particulate air pollution, reducing the aesthetic value and lifetimes of historic buildings and monuments. This thesis focuses on the deposition of atmospheric particulate material to building surfaces and identifies potential sources of this material. It also identifies environmental factors influencing two deterioration effects: surface soiling and black crust growth. Two soiling models have been compared to assess their effectiveness in predicting the soiling rates of two materials - stone and wood - in five cities in Europe. An exponential decay model was found to describe the reduction of reflectance well at two of these sites, while a square root relationship is not as effective. Different measures of weekly particulate concentration were not statistically related to soiling rate, whereas S02, rainfall, and temperature were statistically related to reflectance loss over time. Wind speed and solar insolation were also indicated to influence soiling rates. Concentrations of total suspended particulate (TSP), particulate elemental carbon (PEC), total organic carbon (TOC) and thirty-nine particulate-associated hydrocarbons were measured in airborne particles at two sites in London, for one year. These hydrocarbons were also measured in black crusts from St Paul's Cathedral to relate atmospheric and deposited material, and to identify potential sources of the deposited particulate matter. Detailed scanning electron microscope-energy dispersive X-ray (SEM-EDX) analysis of black crust \ similarly indicated potential sources of these deposition layers. Analysis revealed the complex structure of these crusts, comprising gypsum "growth stems ", calcite and large numbers of particles mainly originating from oil combustion. Hydrocarbon analysis supported the fact that oil combustion - probably at Bank power station - was the dominant source of this deposited layer. Other particle morphologies were commonly found, such as those typical of coal combustion and diesel engine exhaust. Metals analyses also indicated other possible sources such as vehicles.