Non-destructive analytical methods to study the conservation state of Apadana Hall of Persepolis.

Atmospheric and biological agents are the main enemies of the building material conservation. In this work an innovative methodological approach, based on Near Infrared Spectroscopy (NIR) and X-Ray Fluorescence Spectroscopy (XRF), has been employed to evaluate the conservation state of Persepolis limestone samples collected both, under a protective shelter and outside the shelter, at Apadana Audience Hall area in Persepolis. The use of NIR spectra permitted to discriminate, by using Principal Component Analysis (PCA), the differences between samples collected inside and outside the protective shelter and we have been able to identify a major degradation state of the out shelter stone samples due to a major presence of organic compounds.