Would air pollution affect historical structures? In case it does how to rennovate these monuments?

"Damage to materials in polluted atmospheres can be attributed to dry or wet deposition of pollutants, or dissolution in rainfall "

some types of materials are more sensitive to pollutants and we can do nothing to renovate it such as exposed wood ......... just replace the eroded parts that have lost their details with new parts, the new parts should be from the same type of wood as the original parts

stone buildings are less sensitive to pollutants , I think compressed water is the only available way to clean them from souk and smoke without wiping out any important layers of the stone.  however ,special mix of mortar can be used to bind loose parts again and to compensate for the lose of material and to do any rehabilitation works  ,the mix of the mortar has to be similar as close as possible to the original one and should be made up from local stones and materials (stones from the same site or same type with the same color). care must be taken not to wipe out important architectural , historical or archeological details or marks.

In Syria fro example Archaeological Frescoes (2nd century AD) and wall decorations were preserved under ruins, the colors of the painted decorations are still visible till now and The good state of preservation of these remarkable findings was because the city was abandoned and covered by sand and due to the location of the city in the middle of the deserts.

Air pollutants, together with meteorological parameters, are of major importance for the deterioration of many materials used in cultural monuments. They are emitted by industrial activities and by the transport sector. These pollutants create problems on the local scale, but they are also transported in the air over long distances.

Most structures and buildings are affected by acid deposition to some degree because few materials are safe from these effects. In addition to atmospheric attack structures that are submerged in acidified waters such as foundations and pipes can also be corroded.

The pollutants that form acid rain are principally sulphur dioxide and nitrogen oxides; both of these are released from the combustion of fossil fuels like coal and oil. Since the Industrial Revolution emissions of both have increased. UK Sulphur dioxide (SO2) emissions peaked in the 1960s but have since declined by over 80%.

The effects of acid deposition on modern buildings are considerably less damaging than the effects on ancient monuments. Limestone and calcareous stones which are used in most heritage buildings are the most vulnerable to corrosion and need continued renovation.

The costs for deterioration and soiling of different materials due to air pollution are huge and the damage to culture targets seriously endangers the cultural heritage. Effective policy-making requires environmental impact assessment, cost benefit analysis and risk management. All these techniques need a serious scientific basis to support the assessment and the calculation of the effects of pollution.

For concrete structures beside sea and for high temprature, concrete absorbs salt which will affect rust of reinforcemenet  and to avoid that, epoxy coated reinforcement and low water cement ratio concrete with high cement content.

The method of repair of deteriorated rust of reinforcement is too complicated and it is beter to avoid that be using epoxy coated reinforcement and low water cement ratio concrete with high cement content.