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Soiling and decay of N.M.E.P. limestone tablets
H A Viles1, M P Taylor, T J S Yates
1School of Geography, University of Oxford, UK. heather.viles@geog.ox.ac.uk
The Science of the Total Environment
|July 31, 2002
Summary
The British National Materials Exposure Programme studied limestone decay. Analysis revealed that while pollutants are rare, microorganisms and pollen significantly contribute to soiling and material degradation.
Area of Science:
- Building Materials Science
- Environmental Science
- Geochemistry
Background:
- The British National Materials Exposure Programme (N.M.E.P.) assessed material degradation from 1987-1995.
- Limestone tablet deterioration was previously quantified by weight change, soluble salts, and soiling.
Purpose of the Study:
- Investigate the nature and distribution of particulate material on limestone.
- Determine the role of particulate matter in soiling and decay processes.
- Correlate soiling characteristics with climate and pollution histories.
Main Methods:
- Analysis of limestone samples from exposed and sheltered sites.
- Utilized spectrophotometry, optical microscopy, and scanning electron microscopy (SEM).
- Examined samples from Wells, Bolsover, and Lough Navar.
Main Results:
- Recognizable pollutant particles were infrequently found.
- Filamentous microorganisms and pollen grains were widely distributed.
- Soiling composition and changes over time varied by site, influenced by climate and pollution.
Conclusions:
- The nature of decay, not just the degree of soiling, is crucial in understanding limestone degradation.
- Biological materials play a significant role in the soiling and decay of exposed limestone.
- Site-specific environmental factors critically influence material weathering patterns.