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Understanding anomalous uranium concentrations in groundwater


In aquifers, the primary source of dissolved inorganic constituents in groundwater are water-rock reactions. The water composition reflects dissolution, precipitation, sorption, ion-exchange, and redox reactions that depend on the prevalent physicochemical and biotic conditions. The uranium concentration in natural waters tends to be low (< 1 µg/L) and values higher than 30 µg/L (provisional guideline value for drinking water) are not frequent. If U concentrations are higher than the regulated value, the water is inappropriate for consumption. The presence of solubilized U suggests its mobilization from solid phases (minerals), which usually requires redox conditions to oxidize U(IV) to U(VI) and the formation of stable dissolved complexes, all depending on medium composition. Alternatively, mobile U can associate with stable colloidal particles. The objective of this research proposal is to understand the processes responsible for U concentrations in groundwater extracted through a well located at the University of Campinas campus (Barão Geraldo district, Campinas/SP), that systematically register more than twice the U regulated value. The area has three aquifers and to understand the source of dissolved U, which we suppose is a result of dissolution, oxidation and complexation reactions in the local aquifer(s), the study includes the chemical and isotopic analyses of groundwater and rock samples, and any subtract to be retrieved through a rotating perforation nearby the well. Besides the chemical composition of both matrices (and minerals), some isotope ratios (´2H, ´18O, ´13C, 14C, 234U/238U and ´7Li) will be measured in groundwater and the last one also in solid samples. The data will serve to do reactive transport modeling of the local hydrogeology and hydrogeochemistry. By understanding the processes that give rise to the U mobility in the local aquifer, we envisage to propose water management and remediation solutions for the area and apply the knowledge to other aquifers with anomalous U concentrations in groundwater. (AU)

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(References retrieved automatically from Web of Science and SciELO through information on FAPESP grants and their corresponding numbers as mentioned in the publications by the authors)
NAVARRO, MARGARETH S.; PAULA-SANTOS, GUSTAVO M.; MARTELETO, THAIS DE P.; ENZWEILER, JACINTA. Lithium Isotopic Ratios by Single-Collector ICP-SFMS: A Critical Evaluation Using Reference Materials. GEOSTANDARDS AND GEOANALYTICAL RESEARCH, JUL 2021. Web of Science Citations: 0.

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