Mineralogy and geochemistry of bottom sediments from water reservoirs in the vicinity of Cَrdoba, Argentina: Environmental and health constraints

The lake sediments display a typical upper crustal composition and include a less fractionated component related to the closely exposed Cambrian continental arc. No basic source component could be detected. The sediments are strongly chemically weathered (K/Cs < 2000; CIA 70–80) and depleted in most of the major and trace elements. The depositional environment is characterised by oxidising conditions regarding geochemical constraints and facies conditions. Only U (5–15 ppm), W (9–21 ppm) and As (5–22 ppm) are strongly enriched trace elements related to the post-Archaean average Australian shale or upper crust. This enrichment is explained as related to mining activities and mineralisation. W and U mines are common in closest vicinities. The enrichment in U does not reflect the concentrations in the mined bodies, thus, the loss of U during transport and sedimentation was most probably buffered by sediments deposited under anoxic conditions and/or plants. Those trace metal element traps may contain much higher element abundances as the sediments here discussed. reliminary study conducted with simple, quick but effective methodology shows alarming concentrations of trace metals in sediments, although the selected sediments are not the most likely to concentrate elements like U. This implies that suitable sediments and sedimentation areas have to be determined carefully by comprehensive fieldwork and guided by the understanding of the local drainage systems. If this is ignored, a reliable study, which excludes contamination, cannot be conducted. Based on our preliminary studies, the water, sediments and flora should not be used for human purposes until contamination sources and flux is entirely understood, which is not the case for this highly contaminated zone so far.