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Aguas Dulces sand is frequently used as a component for preparing building materials, leading us to study it and characterize it as a Naturally Occurring Radioactive Material (NORM). Particle size distribution was determined by dry sieving and mineralogical composition was evaluated by X-ray powder diffraction and scanning electron microscopy. Natural radionuclides composition was evaluated by gamma-spectrometry. The higher the grain size of the sand, the lower the heavy mineral concentration. Ilmenite, rutile, zircon, and quartz, were identified in the 50–100 µm grain size fractions, ilmenite, quartz, albite and orthoclase were identified in the 100–200 µm grain size fractions, and quartz, albite, sanidine and anorthite were identified in the 200–315 µm sized grain fractions. Thorium and Uranium series activity concentrations reached a maximum for the 50–100 µm sized fractions, which exceed by one order of magnitude the activity concentration in the whole sample and in any other fraction. This result is in agreement with the heavy mineral composition. Finally an activity concentration index (I) of 1.27 ± 0.10, corresponding to the integral sand, was determined. This value exceeds the one recommended when using the sand as building material, and makes it necessary to study I when it is used as a component of different building materials (bricks, cinder blocks, cement, etc.). [ABSTRACT FROM AUTHOR]

The Uruguayan east coast has several mineral resources, which include black sand ores in the Barra de Valizas–Aguas Dulces area. Cancer in Uruguay shows non-homogeneous geographical distribution, with the highest standardized mortality ratio (SMR) in the northeast and east region, which includes the aforementioned area and the town of Barra de Valizas. The activity concentration of natural radionuclides (226Ra, 232Th and 40 K) in Barra de Valizas´soil was determined by gamma spectrometry in order to evaluate the radiological hazard for inhabitants and tourists. The outdoor annual effective dose (AEDE), excess lifetime cancer risk (ELCR), and annual gonadal dose equivalent (AGDE) were evaluated for inhabitants with a life expectancy of 77.7 years, a 0.2 and 0.5 occupancy factor, and using the conversion coefficients recommended by United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR). The annual effective dose was also evaluated for both summer and fortnight tourists. The radiological hazard indices for Barra de Valizas inhabitants are higher than the worldwide mean and recommended values. This may contribute to Rocha's higher SRM value, although a direct correlation cannot be assured with the epidemiological information currently available. Social, medical and anthropological studies will be carried out in future to provide data and verify this correlation. [ABSTRACT FROM AUTHOR]

The 238U, 226Ra, 210Pb, 232Th, 40K, and 137Cs activity concentrations in sand, soil, sediments, and Baccharis trimera were determined by gamma spectrometry. Gross alpha—beta activity and 226Ra, 228Ra, and 210Pb activity concentrations in water were also evaluated. The radionuclide mobility between compartments was assessed, and the transfer factor between soil and vegetation was calculated. In general, 238U series were not in secular equilibrium with 226Ra loss and 210Pb enrichment. The 226Ra, 228Ra, and 210Pb activity concentrations in water were below the detection limit in all analyzed samples. The 210Pb, 40K, and 137Cs activity concentrations in Baccharis trimera and the transfer factor from soil were quantified in different seasons. The 210Pb transfer factor ranged from 0.41 to 2.33, as affected by precipitation. Finally, 137Cs could only be identified in samples collected in winter. This work provides a radiological condition baseline of the region of Barra de Valizas—Aguas Dulces, and it will be useful for assessing future effects due to human impact. [ABSTRACT FROM AUTHOR]

Concentrations of polycyclic aromatic hydrocarbons were assessed in a sediment core retrieved from Nutrias Lagoon, located within the Rocha Lagoon Protected Area along the SE Uruguayan coast. Using a210Pb chronology, we reconstructed the historical accumulation of polycyclic aromatic hydrocarbons over the past 123 years (1895–2018). This study, the first of its kind in Uruguay, fills a research gap in understanding historical PAH accumulation and source changes. Our examination of dating, geochemical, and sedimentological data unveiled four main events, with minor instances in 1956 ± 5 and 1964 ± 4, and more significant occurrences in 1914 ± 9 and 1997 ± 2. Additionally, two prominent trend shifts were identified, one predating 1900 and the other in 1986 ± 2. Before 1900, a dry spell was apparent, supported by all proxies, alongside a notable surge in heavy polycyclic aromatic hydrocarbons, likely attributed to fires during this arid period. Post-1986 ± 2, a rise in sedimentation rates in the lagoon was observed, possibly due to increased rainfall. Also, the eutrophication of the lagoon over the years can be observed. Furthermore, a recent increase in polycyclic aromatic hydrocarbons influx at the core's surface was linked to the construction of a nearby lagoon bridge and associated roadwork. Our findings suggest that atmospheric deposition constitutes the primary source of polycyclic aromatic hydrocarbons in the lagoon, offering insights into its recent environmental history and basin dynamics. This study establishes a critical baseline for future research in the region and facilitates the development of effective and sustainable environmental management strategies. [Display omitted] • Age was determined and cross-validated using independent dating and stratigraphy. • The mass accumulation rate aligns with hydroclimatic variations supported by proxies. • Four mass accumulation peaks align with extreme events, supported by other proxy evidence. • Long-term eutrophication trends within the lagoon are evident. • PAH fluctuations suggest fires in the catchment and possible nearby construction activities. [ABSTRACT FROM AUTHOR]

This paper presents the levels and distribution of 210Po in different compartments of a coastal lagoon on the east coast of Uruguay (South America). Activity concentrations of 210Po have been obtained in different matrices, such as water, superficial sediments, clams (Diplodon sp.), freshwaters snails (Pomacea sp.), zooplankton, and fishes (Jenynsia sp.), collected at different points of the lagoon and during several sampling campaigns. In addition, the organic matter content of the sediment was determined to study the variation of 210Po along the lagoon. The activity concentrations of 210Po in the water samples are in the range between 1.1 ± 0.2–3.5 ± 0.4 mBq/L while in the sediment samples vary between 17.1 ± 1.4 and 540 ± 12 Bq/kg, DW. In the case of biota, the ranges obtained were 182 ± 5–265 ± 6 Bq/kg, DW in clams and 134 ± 4–1245 ± 16 Bq/kg, DW in snail samples. A good correlation of 210Po with the organic fractions of the sediment was observed (r = 0.8798, p-value < 0.001), being obtained high values for the distribution coefficient Kd (104 -105). In the biota samples, a clear difference was observed in the 210Po concentration values in both species, mainly due to the different feeding habits of both aquatic organisms, as it is reflected in the associated concentration ratios (CR). In this paper, a good set of results of 210Po, Kd, and CR have been obtained in different matrices, enhancing the limited archives available for modelers concerning these parameters for 210Po and freshwater systems. • Levels and distribution of 210Po in different compartments of a freshwater lagoon. • High tendency of 210Po to be associated to sediments with high organic content. • Different 210Po values in clams and snails, depending on the feeding habits. • High values in the distribution coefficient Kd (104-105). [ABSTRACT FROM AUTHOR]