Isotopes in Environmental and Health Studies最新文献

Argentina is a Latin American country which encounters soil degradation problems. The most productive regions have implemented conservative land practices (no-till). However, agricultural frontier has been displaced to marginal lands with arid and semiarid climates, with the consequent disappearance in many areas of native forest and land degradation. In this work, the fallout of gamma-emitting radionuclides, ¹³⁷Cs and ⁷Be, was jointly used to assess changes in soil erosion in a recently converted semiarid ecosystem into agricultural land. ¹³⁷Cs was utilized to estimate the erosion over the past 60 years, whereas ⁷Be was employed to estimate the erosion after the conversion of the area to cultivated land and soil tillage. For ¹³⁷Cs the Proportional Model (PM), the Mass Balance Model II (MBMII) and the MODERN model were used, for ⁷Be the Profile Distribution Model (PDM) and the MODERN model were used. ¹³⁷Cs indicates mean erosional rates of 8.2, 10.5 and 6.5 Mg ha^-1 a^-1, using MBMII, PM and MODERN, respectively, and that a soil layer between 0.5 and 0.8 mm was annually lost by erosion. By applying a ⁷Be tracer, we measured erosion rates of 2.4 and 3.3 Mg ha^-1 (with PDM and Modern, respectively), indicating the loss of the upper 0.2 mm of soil. This erosion can be attributed to a few heavy rainfalls that occurred within the past 90 days. The results suggest that current land management practices have led to an increase in soil erosion. This could be attributed to the fact that the soil remains bare after crop harvest, which may compromise its conservation and future productivity.

We characterized the elemental and C and N stable isotope compositions of Tillandsia fasciculata Sw., Tillandsia balbisiana Schult. & Schult.f. and Tillandsia recurvata (L.) L. samples collected in Cienfuegos (Cuba). Results showed high enrichment factors for S, Hg, Cd, Pb, P, Zn, Cu, Mo, Sb and Ca in all Tillandsia species, indicating inputs from local anthropogenic activities (road traffic, industries and cement production). Carbon concentrations and δ¹³C varied from 38.3-47.7 % and -20.4 to -13.4 ‰ within the three species, respectively. δ¹³C showed seasonal dependence with the dry and wet periods and more ¹³C-depleted values in urban/industrial areas, coherent with the input of anthropogenic emissions. Nitrogen concentrations (0.4-1.3 %) and δ¹⁵N values (-9.9-4.4 ‰) exhibit larger variations and are positively correlated in the three species. The most positive δ¹⁵N in T. recurvata (-0.2-4.4 ‰) are attributed to contributions from industrial activities and road traffic. In fact, both δ¹⁵N and total nitrogen (TN) values increase in sites with higher road traffic and show significant correlations with typical road traffic and industrial tracers. Finally, we calculate an average total nitrogen deposition rate of 4.4 ± 2.3 kg ha^-1 a^-1 from N content in T. recurvata, similar to the existing values determined in the region by field measurements, but higher than the global terrestrial average.

The biogeochemical consequences of dihydrogen (H₂) underground storage in porous aquifers are poorly understood. Here, the effects of nutrient limitations on anaerobic H₂ oxidation of an aquifer microbial community in sediment microcosms were determined in order to evaluate possible responses to high H₂ partial pressures. Hydrogen isotope analyses of H₂ yielded isotope depletion in all biotic setups indicating microbial H₂ consumption. Carbon isotope analyses of carbon dioxide (CO₂) showed isotope enrichment in all H₂-supplemented biotic setups indicating H₂-dependent consumption of CO₂ by methanogens or homoacetogens. Homoacetogenesis was indicated by the detection of acetate and formate. Consumption of CO₂ and H₂ varied along the differently nutrient-amended setups, as did the onset of methane production. Plotting carbon against hydrogen isotope signatures of CH₄ indicated that CH₄ was produced hydrogenotrophically and fermentatively. The putative hydrogenotrophic Methanobacterium sp. was the dominant methanogen. Most abundant phylotypes belonged to typical ferric iron reducers, indicating that besides CO₂, Fe(III) was an important electron acceptor. In summary, our study provides evidence for the adaptability of subsurface microbial communities under different nutrient-deficient conditions to elevated H₂ partial pressures.

The extraction of lipids by the Folch method from the muscles of all the fish studied led to statistically significant differences in the values of δ¹⁵N. At the same time, lipid extraction led to a statistically significant increase in δ¹³C in pike and roach, and to a statistically insignificant decrease in δ¹³C in perch and bream. Thus, lipid extraction cannot serve as a universal method of sample preparation for the analysis of the isotopic composition of carbon (¹³C/¹²C) and nitrogen (¹⁵N/¹⁴N) in fish muscles. The differences between the δ¹³C values in the samples before and after lipid extraction were statistically investigated by different models. It is shown that mathematical correction method models can be used, but the results are depending on the fish types.

In Taiwanese volcanic watersheds, we investigated stable water isotopes in meteoric water, plants, and thermal water. Meteoric water exhibited a seasonal cycle, with heavier isotopes in winter and lighter ones in summer, especially in the southern region. The northern monsoon signal lagged the south by two weeks. In the Tatun mountains, young water fractions indicated prevalent old water sources. In the northern watershed, streamwater mainly came from the winter monsoon, while the southern one was influenced by alternating monsoons. Both indices indicated that winter plants depended on summer rainfall. Streamwater and plants had distinct sources in winter, supporting ecohydrological separation. Thermal spring water's d-excess helped identify water-rock interactions, with low d value signaling such interactions. The topographic wetness index showed a higher summer monsoon contribution to southern streamwater but a lower one to plants. The mean linear channel direction significantly affected the monsoon contribution fraction, with northeast-oriented channels vulnerable to northeastward winter monsoons. Finally, we developed a model illustrating hydrological processes on short and long timescales. Our findings enhance our understanding of hydrological disturbances' impact on water resources and ecosystems.

ABSTRACTEnvironmental and health risks posed by radionuclides in quarry pit soils are of great concern in environmental health monitoring. The current investigation was aimed at determining the natural radionuclide activity concentration (in Bq kg^-1) of the understudied quarry pit granules used as construction materials. The collection and preparation of pit soil samples from Abeokuta quarry sites were done using standard methods, analysis of radiological parameters was carried out using hyperpure germanium (HPGe) spectrometer. Specific activity concentrations of ²²⁶Ra, ²³²Th, and ⁴⁰K were measured. The values obtained were greater than the world weighted average of 35, 30, and 400 Bq kg^-1 for ²²⁶Ra, ²³²Th, and ⁴⁰K, respectively. The absorbed dose, the annual effective dose, and the radium equivalent were calculated and demonstrated significant values. The radionuclide content of the samples is relatively high and the use of pit soils as a building material, therefore, raises radiological concerns for dwellers in this area and requires periodic monitoring and undergoing a radiation protection program.

Advanced computational fluid dynamics (CFD) simulations are essential for predicting airflow in ventilated spaces and assessing indoor air quality. In this study, a focus was set on techniques for the reduction of indoor radon-222 activity concentration [Rn], and it is demonstrated how true-to-scale 3D CFD models can predict the evolution of complex ventilation experiments. A series of ventilation experiments in an unoccupied flat on the ground floor of a residential block in Bad Schlema (Saxony, Germany) were performed. Specifically, the 'Cross-ventilation 100 %' experiment resulted in room-specific [Rn] reductions from ∼3000 to ∼300 Bq m^-3. We quantitatively interpreted the results of the ventilation experiment using a CFD model with a k-ϵ turbulent stationary flow model characterised by the used decentralised ventilation system. The model was coupled with a transient transport model simulating indoor [Rn]. In a first approach, the model overestimated the decrease in the starting of the experiment and the steady state. Adjusting the model parameters inflowing radon and inlet velocity the model results are in a good agreement with the experimental values. In conclusion, this paper demonstrates the potential of CFD modelling as a suitable tool in evaluating and optimising ventilation systems for an effective reduction of elevated [Rn].

In order to study the trophic level of small tuna species and their contribution to the carbon flow in pelagic food webs, an analysis of carbon and nitrogen stable isotopes was carried out. The investigation was focused on four small tuna species (Auxis rochei, Auxis thazard, Euthynnus alletteratus and Sarda sarda) commonly harvested in the northeast Atlantic Ocean. The isotope analysis showed how the results for S. sarda are different from the rest of the species analysed, with a higher trophic level, similar to other major tuna species. The greatest niche overlap in δ¹³C and δ¹⁵N occurs among A. rochei, A. thazard and E. alletteratus. Auxis rochei and E. alletteratus showed a size-dependent variability in δ¹⁵N, and in δ¹³C for S. sarda. The small tuna S. sarda exhibits the highest migration rates among various geographical areas in comparison to other small pelagic tunas, and the seasonal variability of isotope values in the area studied can be attributed to the incorporation of larger individuals with a higher lipid content. The results of this work provide new information on the ecological role played by small tuna in food webs, which is more complex and varied than currently thought. This knowledge is essential for a more effective management of fisheries.

ABSTRACTThe objective of this study was to assess the impact of water deficit stress during fruit cultivation on the δ¹³C values of citric acid and malic acid in Japanese apricots at different ripeness stages and their resulting liqueurs. Our experiments show that water deficit stress increases the δ¹³C values of citric acid and malic acid in tree-ripened fruits, counteracting the typical decrease during ripening. However, water deficit treatment has a minimal effect on the δ¹³C values of organic acids in green fruits. Regardless of fruit ripeness or water status, the δ¹³C values of organic acids in fruits are directly reflected in the resulting liqueurs. Overall, water deficit stress during fruit cultivation has the potential to promote similarity in the δ¹³C values of organic acids across fruits at different ripeness levels, reducing variations among liqueurs derived from fruits of varying ripeness levels.