21.	Air pollution and aspects of degradation "Umayyad Liwãn-Amman citadel as a case study"
Many natural stone monuments have suffered from serious damages that due to natural weathering, pollution and other factors of deterioration and using insufficient maintenance of susceptible materials or inappropriate conservation. Considerable attention has been paid in recent years to the decay of carbonate building stones [Limestone and Marble] especially in aggressive polluted environments, moreover, color changes, patina, blacking of rock's ... إقراء المزيد