The effect on materials of an individual air pollutant is difficult to separate from the

effect of others. Many of the effect on materials have been ascribed to the multipollutant

situation in the urban atmosphere than to the action of separate pollutants.

Nitrogen oxides may contribute to damage in several ways, but their role is not yet

clarified. However, the role of nitrogen oxides is secondary compared to that of ozone

for dyes, fabrics, plastics and elastomers, to that of oxygen, sulphur dioxide and

wetting by rain, condensation, mist etc. on metals and to that of rain, carbon dioxide

and sulphur dioxide for calcareous stonework. There is also a possibility that nitrate

deposited on outdoor surfaces, can enhance the microbial activity and thus increase

bio-degradation. Increased growth of algae due to deposition of nitrogen compounds

on surface is considered as a soiling and undesirable effect. Nitrogen containing

compounds have also been recognised as a possible problem in museums (De Santis

& Allegrini, 1992).

 

 

 

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