Absorbed dose rate for marine biota due to the oil spilled using ICRP reference animal and Monte Carlo simulation

Exploratory research on the multi-life stages mesh-type model of Caenorhabditis elegans in radiation ecology

To address the lack of effective dose quantification methods for the model organism Caenorhabditis elegans (C. elegans) in radiation ecology research, this study employs remeshing techniques to develop a comprehensive mesh-type model covering multi-life stages, from embryonic to larval (L1, L2, L3, L4) and adulthood. Using these models, Dose Coefficients (DC) for C. elegans in a soil environment under different exposure conditions (external and internal), material settings, and radioactive nuclides (³H, ⁶⁰Co, ⁹⁰Sr, 12⁹I, 1³1I, 1³⁴Cs, 1³⁷Cs) were calculated with the Monte Carlo toolkit Geant4. The results show that the difference in DC, when C. elegans material is set as either biological material or water, is within 5%. Under external exposure conditions, the impact of life stages on the population's average DC is minimal (with a maximum deviation not exceeding 10%). However, the distribution within the population varied significantly across life stages (under external exposure to 137Cs, the dispersion was 12.02% for adults and a considerably higher 60.30% for larvae). The earlier the life stage, the greater the variability in DC distribution within the C. elegans population. Furthermore, correlation analysis indicates a strong relationship between DC and life stages under internal exposure scenarios. The mesh-type model of C. elegans established in this study provides a valuable tool for radiation ecology research and has potential applications in broader research fields.

Internal dose rate due to intake of uranium and thorium by fish from a dam reservoir associated with a uranium mine in Brazil

Uranium mining can cause environmental impacts on non-human biota around mine sites. Because of this, the reduction in non-human biota exposure becomes an important issue. Environmental radioprotection results from the evolution of human radioprotection; it is based on dose rate to non-human biota and uses, as a biological target, and has harmful effects on populations. In the present study, a flooded impoundment created following dam construction in a uranium mine plant undergoing decommissioning was investigated. Internal dose rates due to activity concentration of natural uranium (Unat) and 232Th in omnivorous, phytophagous, and carnivorous fish species were estimated. Radionuclide activity concentrations were obtained by spectrophotometry with arsenazo III in the visible range. The dose rate contribution of 232Th was lower than that of Unat. There were no differences between the internal dose rates to studied fish species due to 232Th, but there were differences for Unat. A dose rate of 2.30·10-2 µGy∙d-1 was found due to the two studied radionuclides. Although this value falls below the benchmark for harmful effects, it is important to acknowledge that the assessment did not account for other critical radionuclides from uranium mining, which also contribute to the internal dose. Moreover, the study did not assess external doses. As a result, the possibility cannot be excluded that dose rates at the study area overcome the established benchmarks for harmful effects.