Geochemical and mineralogical characterization of Ria de Aveiro (Portugal) saltpan sediments for pelotherapy application

Abstract

The present study aims to characterize sediments textural, geochemical and mineralogical composition used in a SPA for pelotherapy applications. Six samples were collected in two areas of an open-air saline SPA, a former saltpan in Ria de Aveiro (Portugal). Sampling areas are predominantly composed by recent alluvium that had been affected by chemical industrial effluents for over 50 years. Samples < 2000, 63, and 2 µm fractions were analyzed by X-ray Diffraction (XRD) and X-ray Fluorescence (XRF), for identification of mineral phases and chemical composition. SEM analysis was used for individual particles morphological characterization and chemical semi-quantification. Texture, mineral phases and chemical composition showed the influence of SPA pond beneficiation works. The two SPA areas revealed distinct mineral phases, one with higher quartz content, and the other with higher halite content, consistent with their environmental conditions. Illite constituted the most abundant mineral phase of the clay fraction. Preliminary results suggested concentrations of potential toxic elements (e.g., As, Cd) above reference values, representing a risk to the ecosystem and humans.