Impact assessment of metals on soils from Machu Picchu archaeological site.

Machu Picchu is an archaeological Inca sanctuary from the 15th century, located 2430 m above the sea level in the Cusco Region, Peru. In 1983, it was declared World Heritage Site by UNESCO. The surroundings and soils from the entire archaeological site are carefully preserved together with its grass parks. Due to the importance of the archaeological city and its surroundings, the Decentralized Culture Directorate of Cusco-PAN Machu Picchu decided to carry out a careful monitoring study in order to determine the ecological status of the soils. In this work, elemental and molecular characterization of 17 soils collected along the entire park was performed by means of X-ray Diffraction (XRD) and Inductively Coupled Plasma Mass Spectrometry (ICP-MS) after acidic digestion assisted by microwave energy. Thanks to the combination of these analytical techniques, it was possible to obtain the mineral composition and metal concentrations of all soils from these 17 sampling points. Finally, different statistical treatments were carried out in order to confirm the ecological status of the different sampling points from Machu Picchu archaeological site concluding that soils are not impacted.

Characterization of restoration lime mortars and decay by-products in the Meditation area of Machu Picchu archaeological site.

Machu Picchu citadel is the main archaeological Inca sanctuary widely known around the world, and a World Heritage Site of high cultural and natural value. For its construction a whitish granitic rock, extracted from the "Vilcapampa or Vilcabamba" batholith formation was used. During time, some of the granitic rocks from the natural stonewalls of the Meditation area of the Archaeological Park were restored. For the restoration works done in the 50s' a specific lime mortar called Clarobesa was used. After the inclusion of this joining mortar, many efflorescences are nowadays visible in the mortar itself and on the surface of the edges of the annexed rocks. To evaluate the possible impact of these salts crystallizations in the conservation state of these natural stonewalls, a multi-analytical methodology was designed and applied. With a combination of non-invasive and destructive techniques such as X-ray Diffraction, Raman microscopy, Scanning Electron Microscope coupled to an Energy Dispersive X-ray Spectrometer and ion chromatography, the mineralogical composition and the nature/concentration of the soluble salts present in the Clarobesa mortar was determined. The experimental results suggest that Clarobesa mortar is a hydraulic lime mortar. The study of salts crystallizations by Raman microscopy allowed identifying the presence of calcium sulfates with different hydration waters and also nitrates. In some samples, the concentration of sulfates was high, reaching values up to 10% w/w. Although the concentration of nitrates is not extremely high, a clear contribution of ammonium nitrates coming from the decomposition of the nearby vegetation was assessed. Since the Clarobesa mortar can be considered an important input of ions that can migrate to the joined granitic rocks, in the future, it will be recommendable to monitor possible changes in the conservation state of the joined rocks.

Evaluation of the role of biocolonizations in the conservation state of Machu Picchu (Peru): The Sacred Rock.

Machu Picchu Inca sanctuary (Cusco Region, Peru) was constructed on a granitic plateau, better known as Vilcabamba batholith. One of the most important carved granitic rocks from this archaeological site is the Sacred Rock, used by Inca citizens for religious rituals. Due to the location and climatic conditions, different rocks from this archaeological site are affected by biocolonizations. Concretely, the Sacred Rock shows flaking and delamination problems. In this work, a non-destructive multi analytical methodology has been applied to determine the possible role of the biodeteriogens, forming the biological patina on the Sacred Rock, in the previously mentioned conservation problems. Before characterizing the biological patina, a mineralogical characterization of the granitic substrate was conducted using X-ray Diffraction, Raman microscopy (RM) and micro energy dispersive X-ray fluorescence spectrometry. For the identification of the main biodeteriogens in the biofilm, Phase Contrast Microscopy was used. RM also allowed to determine the distribution (imaging) and the penetration (depth profiling) of the biogenic pigments present in the biopatina. Thanks to this study, it was possible to asses that some colonizers are growing on inner areas of the rock, reinforcing their possible assistance in the delamination. Moreover, the in-depth distribution of a wide variety of carotenoids in the patinas allowed to approach the penetration ability of the main biodeteriogens and the diffusion of these biogenic pigments to the inner areas of the rocky substrate.