Influence of thermal and marine water and time of interaction processes on the Cu, Zn, Mn, Pb, Cd and Ni adsorption and mobility of silty-clay peloid

In order to improve the technical properties of raw clays for cosmetic and medical treatments, maturation processes are used for peloid preparation. As for metals, only their total concentrations are usually controlled. However, the dosage of the mobile fractions that could be absorbed by the skin is overlooked. By means of data monitoring, we assessed the risks that adsorbed and mobilized metals pose to humans through natural clay maturation. To do so, the total concentrations and mobile fractions of Pb, Zn, Mn, Ni and Cd were determined using a BCR procedure. Except in the case of Cd, metal concentrations in peloids that had been matured with thermal (TW) and marine water (MW) for 12 months were higher than those present in raw clay. The metal mobility indexes equaled zero were very low in raw clay, but they increased systematically with maturation (except in the case of Ni). The increases in metal concentration and mobility were higher in the case of marine than in the case of thermal water. We concluded that the matured mud can be toxic. Thus, the assessment of mobile metal fractions is highly recommended so as to protect human health.