Geochemistry of two peats suitable for medical uses and their behaviour during leaching

The compositional characteristics of two peats, from Austria and Italy, have been studied. The Massaciuccoli peat shows a high quantity of trace elements (Br, Cd, Mo, Se, U, As and Sb) with respect to the average shale, whereas the Neydharting peat contains more Br, Se and U. Since the therapeutic properties of peats are broad and interesting, the mobility of trace elements (As, Cd, Hg, Pb, Sb, Se, Te and Tl) used for pelotherapy, during water leaching and after Na exchange, have been checked. The data concerning the leaching procedure indicate that the analysed peats are rather stable materials under laboratory conditions. Although the concentration of some toxic elements (As, Se, Cd and Hg) in bulk peats are of the same order of magnitude as in muds used in pelotherapy, the release after similar leaching is lesser. The higher release from muds could be explained by the high exchange capacity of smectite minerals. These minerals are characterised by low cation selectivity because the chemical interactions between smectite and sorbed species is mainly ionic. On the other hand, the cation–organic matter interactions can establish a higher degree of covalent bonds, that are more stable during the interactions developed with leaching. An additional possibility can be considered taking into account the genetic conditions of peat formation. In the upper part, the acidic and oxidising conditions cause the depletion of mobile elements. This process can be seen as a natural cleaning, which occurs under relatively strong conditions compared to the use during medical treatments.