Chemical analysis of soils

In order to characterise and identify the remains of built structures, several tools and methods need to be applied. various tools and methods. This is relatively simple for enclosures built in dry stone, but much more difficult for those made of perishable materials. perishable materials. However, the latter type of development was used in the high and medium mountains, but is currently inaccessible. mountainous areas, but are currently inaccessible to the archaeologist with "classical" methods. classical" methods.

How much do the enclosures made of branches and wood represent? What shape are they? How far apart are the huts? What Do they have the same functions or are they reserved for specific activities?

And more broadly, what can be said about the ancillary or pastoral-related activities that are Can we locate them? The Identify them? Define their spatial extent?

This can be done by chemical analysis of the soil.

a. X-Ray Fluorescence (XRF) to delineate parking areas. parking areas (Magali PHILIPPE -- GEODE (UMR 5602).

XRF is a device that allows the identification of most of the chemical elements that make up the element under study. chemical elements that make up the element under study, whether they are objects or floor. The test sample is exposed to X-rays. The effect of this beam is that the atoms of the sample leave their fundamental state and become unstable. their fundamental state and become unstable. The atoms then try to return to their ground state. During this process, the atoms release energy in the form of X- photons. Each atom releases photons of energy and length of its own waveform. of its own waveform. It is the analysis of this emission that is used to determine the nature of the chemical elements that make up a material or soil (Thirion). material or a soil (Thirion-Merle V. ,2014) XRF allows the analysis of all chemical elements, from Beryllium (Be) to Uranium (U). from Beryllium (Be) to Uranium (U) (Fig. 1).

Figure 11 - Periodic table of the elements (2012rc CC BY 3.0](https://creativecommons.org/licenses/by/3.0), from Wikimedia Commons

There are two main types of XRF :

  • Wavelength dispersive spectrometers (WD-XRF, Wavelength dispersive X-ray fluorescence spectrometry)

  • Energy dispersive spectrometers (ED-XRF, Energy Dispersive X-ray fluorescence spectrometry).

The GEODE laboratory has a portable XRF : the Nitron XL3t 980.

What we will try to characterise with this equipment is in particular the presence of elevated levels of phosphorus, magnesium, calcium, potassium, nitrogen and sodium, which will allow us to identify an anthropic action and above all a cattle parking area. (Elliott, Bendrey, Whitlam, Rauf Aziz, & Evans, 2014; Holliday & Gartner, 2006)