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14 May 2011

Friday 13th May 2011; Climatic and Environmental Impacts

Week 5 of 12

Module 4: Deterioration Mechanisms; Methods of Survey & Analysis

Today Peter Brimblecombe, Professor of Atmospheric Chemistry at the University of East Anglia, discussed the topics ‘Environmental Factors of Deterioration’ and ‘Air Pollution and the Interaction of Water and Porous Building Materials’ with the group. Interestingly the issue of air pollution has been discussed for many centuries, originally referred to as ‘smoke’ in early documentation as that would be how it manifested itself. Now, however, in the majority of locations air pollution is no longer a visible thing, and in relation to stone structures it has a profound effect although this can be extremely difficult to visualise or to capture. Peter has told us that modern atmospheric deposits contain less sulphur and more nitrate than historic atmospheric deposits due to the transition from the use of coal to petrol as a fuel.

Sulphur is phytotoxic, it kills organisms, whereas nitrate is a nutrient and encourages biological growth. The modern deposits no longer appear to present the issues of ‘black crusts’ in the same form but it is likely we will start to see increasing amounts of lichens and other biological growth on our stone buildings in future in areas of high air pollution.

We had a discussion about the human perception of building soiling. Peter’s research shows that the general public does not mind how dark the soiling is, so long as it is relatively uniform- often not the case where the natural rain washing of buildings occurs.

In terms of change in climate, data shows that both average rainfall and the number of rainfall events per year are decreasing, but that when rainfall occurs, it is in increased volumes. This causes a difficult heritage issue, because buildings and structures now need to deal with larger amounts of water, more quickly, and require a drainage system that allows for this. Certainly in Scotland the ‘rainwater goods’ are often prominent features of our historic buildings and to adapt these raises a serious heritage issue in terms of architectural form and alteration of original materials. However, if they are not adapted we will face significant problems in terms of the functionality of the building- what is the solution? 

During the day we were split up into groups and were given case study sites to discuss in relation to the effect that the environment would have on the built heritage in the future.

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