Isotopes in Environmental and Health Studies最新文献

The concentrations of natural radioactivity in soil samples collected from chromite mines of two different towns, Khanozai and Muslim Bagh, districts of Pishin and Killa Saifullah, respectively, were measured using a high purity germanium (HPGe) detector. The average values of ²²⁶Ra, ²³²Th and ⁴⁰K in soil of Khanozai chromite mines were found to be 26.414, 37.321 and 404.561 Bq kg^-1, respectively. In Muslim Bagh chromite mines, these values were found to be 17.59, 29.677 and 380.475 Bq kg^-1, respectively. The maximum average values of radium equivalent (Ra_eq), external hazard index (H_ex) and internal hazard index (H_in) were found to be 110.851, 0.299 and 0.356 Bq kg^-1, respectively, in chromite mines of Khanozai, while the minimum average values were found to be 89.253, 0.276 and 0.275 Bq kg^-1, respectively, in Muslim Bagh chromite mines. Similarly, maximum average values of absorbed dose rate (D_R), external absorbed dose rate (D_out) and internal absorbed dose rate (D_in) were found to be 50.742, 54.651 and 77.058 nGy h^-1, respectively, in soil of Khanozai chromite mines while the minimum average values were found to be 41.311, 44.385 and 62.583 nGy h^-1, respectively, in Muslim Bagh chromite mines. Also, the maximum average values of annual effective dose risk (AEDR), gamma activity index (I_γ) and alpha activity index (I_α) were found to be 2.30 × 10^-1 mSv y^-1, 0.409 and 0.132, respectively, in soil of Khanozai chromite mines while the minimum average values were found to be 2.02 × 10^-1 mSv y^-1, 0.333 and 0.087, respectively, in Muslim Bagh chromite mines. The values were found to be below the world permissible range. Therefore, it is concluded that the chromite mines under the study have no health hazards.

Sulphur and oxygen stable isotopes of sulphate have been used to trace the sources of sulphur into aquatic systems. These isotopes have also been used to understand the transformation and fate of sulphur in the water bodies contaminated by AMD discharge from active and/or abandoned mines. Stable isotopes of oxygen in dissolved sulphate (δ¹⁸O_SO4) and water (δ¹⁸O_H2O) have helped to decipher the sulphide oxidation pathways and estimate their contributions. The present study is focused on analysing the composition of sulphur and oxygen stable isotopes of sulphate and oxygen stable isotope in AMD and Lunar-Lukha River water flowing through the coal mining area of the East Jaintia Hills District, Meghalaya, in order to decipher the sulphide oxidation pathways. The results showed that the sulphur stable isotope of sulphate (δ³⁴S_SO4) ranged between -12.5 and -8.0 ‰ (VCDT). The oxygen isotope of sulphate (δ¹⁸O_SO4) ranged between 1.4 and 2.0 ‰ (VSMOW). The oxygen isotope of water (δ¹⁸O_H2O) was distributed between -6.2 and -4.2 ‰ (VSMOW). Pyrite oxidation was found to be the dominant source of sulphate in the Lunar-Lukha Rivers. The results of the stoichiometric isotope balance model showed that 68-83 % of sulphate derived Fe³⁺ oxidation pathway, with a high portion of sulphate oxygen derived from water. The sulphite-water oxygen exchange model revealed the release of intermediate sulphoxyanions, suggesting the presence of an oxidation pathway of sulphide minerals to sulphate via sulphoxyanions. The results from this study will be helpful in defining effective remediation strategies to mitigate AMD impacts.

Invasive silver carp (Hypophthalmichthys molitrix) threaten Mississippi River basin ecosystems due to their ability to outcompete native species. Stable carbon (δ¹³C) and nitrogen (δ¹⁵N) isotope analysis has been used to study how silver carp impact native ecosystems, but lipids in fish tissues commonly bias their δ¹³C values. Chemical lipid extraction and mathematical equations that normalise δ¹³C values for lipid content can account for this bias, but have not been assessed for silver carp. We examined δ¹³C, δ¹⁵N, and C:N ratios before and after chemical lipid extraction using 2:1 chloroform:methanol in silver carp muscle and whole fish collected along the Mississippi River. We used linear and natural log models to estimate lipid-extracted δ¹³C values in silver carp muscle and whole fish samples based on their non-lipid-extracted δ¹³C values and elemental C:N ratios. Arithmetic models were evaluated for best fit, parsimony, and accuracy between mathematically normalised and chemically lipid-extracted δ¹³C values. Chemical lipid extraction increased silver carp δ¹³C values and decreased C:N ratio in muscle and whole fish, and increased δ¹⁵N values in whole fish but not fish muscle. While both linear and natural log models accurately estimated lipid extracted δ¹³C values, natural log models provided better fit and parsimony throughout a wide range of C:N ratios. These results confirmed the need to account for lipid effects on δ¹³C values in silver carp. Moreover, our study will allow researchers to conduct isotopic analysis without the added time and cost of chemical lipid extraction and facilitate the comparison of silver carp muscle and whole fish isotopic values across studies.

This study presents an investigation into the natural radioactivity levels of ²³⁸U, ²³²Th, and ⁴⁰K using a thallium-doped sodium iodide (NaI(TI)) detector and associated radiological hazards in river sediments, specifically sand, which serves as a crucial building material in the KwaZulu-Natal Province of South Africa. The assessment aims to provide insights into potential radiological risks posed by the utilization of these sediments in construction activities. The mean activity concentrations of ²³⁸U, ²³²Th, and ⁴⁰K are 145.33, 38.67, and 362.67 Bq kg^-1, 124.64, 60.60, and 353.00 Bq kg^-1, 144.00, 48.80, and 371.00 Bq kg^-1, 92.95, 52.00, and 368.75 Bq kg^-1, 133.55, 45.60, and 324.40 Bq kg^-1, and 109.50, 52.50, 381.50 Bq kg^-1 for Umngeni River, Umsunduzi River, Ashburton Sarupen, Hammersdale, Kwanjobekazi, and Cator Ridge, respectively. The obtained values of the radiological hazard indices (radium equivalent activity, external hazard index, internal hazard index, and activity utilization index) were below the world average values reported for building materials. Therefore, the studied samples are radiologically safe for use as building materials in the study area because they may not constitute any severe radiological hazards to residents.

Plant test systems are a sensitive way to detect the genetic effects of various contaminants in environmental compartments: water, soil and sediments. Biotesting of the genotoxicity of soil samples with various activity concentrations of naturally occurring (²²⁶Ra, ²³²Th, ⁴⁰K) and artificial (¹³⁷Cs) radionuclides in soil, from the territory of the Aragats Massif (Armenia) was carried out with the application of the Tradescantia micronucleus (Trad-MСN) and stamen hair mutation (Trad-SHM) bioassays of Tradescantia (clone 02) model test-object in the soil - plant system. Undisturbed soil sampling was performed in the southern slopes of the Aragats Massif, from different altitudes (from 1000 to 3200 m above sea level). The soils of the Aragats Massif exhibited a background level of naturally occurring materials (NORM) activity. The highest variability was indicated for ⁴⁰K. The activity concentration of ¹³⁷Cs in soils exhibited a naturally increased as the altitude increased. Tradescantia (clone 02) was grown on the undisturbed soils in the greenhouse. To determine the level of genotoxicity of the studied soil samples, the Tradescantia-based Trad-MCN and Trad-SHM tests were applied. The activity concentrations of NORM and artificial ¹³⁷Cs in soil and phytomass were determined using an HPGe detector-based gamma spectrometer (Canberra). Tradescantia (clone 02) accumulated mainly ⁴⁰K, accumulation of ²²⁶Ra observed in one soil sample. In the areas with elevated activity of NORM, levels of genotoxicity were significantly higher compared to the control soil sample with the low rate of spontaneous mutation frequency. The positive correlation between genetic damages of Tradescantia (MCN and SSH) and contents of ⁴⁰K and ²²⁶Ra in soils was revealed. The obtained results indicated the possibility of using Trad-MCN and Trad-SHM tests of Tradescantia (clone 02) for biotesting of background radioactivity in natural areas.

Stable H-O and radiogenic Sr isotopic compositions of bottled water in South Korea were investigated to trace water origins and to elucidate hydrogeochemical water-rock interactions within aquifers. Eighty-one bottled water samples were collected across the country. The δD and δ¹⁸O values, and ⁸⁷Sr/⁸⁶Sr ratios and Sr contents of groundwater-sourced bottled water samples were in the ranges of -68 to -40 ‰, -10 to -7 ‰, 0.7050-0.8112, and 14-400 μg L^-1, respectively. The corresponding ranges for desalinated deep-ocean water samples were -1.2 to 1.6 ‰, -0.35 to 0.10 ‰, 0.7078-0.7092, and 12-407 μg L^-1, respectively. Isotopic compositions indicate spatial variations in stable isotopic signatures with geographical location, while Sr isotopic ratios are correlated with the geological characteristics of water sources. Oxygen isotopic compositions of bottled water show a negative correlation with latitude, while Sr isotopic ratios vary with aquifer geology. The integration of stable and radiogenic isotopic compositions improves our understanding of water-rock interactions, enabling accurate authentication of water sources.

Understanding the stable hydrogen isotope (δ²H) composition and fractionation in lipid biomolecules of primary producers, such as terrestrial and aquatic plants, is crucial for deciphering past environmental conditions, as well as applying compound-specific stable isotope analysis for the study of metabolic and ecological processes. We conducted a new tracer experiment to explore the δ²H composition of algal fatty acid biomarkers, focusing on freshwater algae, which form the base of aquatic food webs. We selected a range of algal species widely found in freshwater ecosystems and cultivated them under controlled conditions. First, we added ²H₂O to ambient water as a tracer to investigate the net hydrogen isotope fractionation during algal lipid synthesis at isotopic equilibrium, which is particularly informative for paleo-geochemical studies. Then, we conducted kinetic experiments to quantify the time needed for algal fatty acids to achieve isotopic steady-state conditions in response to the change in ambient water δ²H values. Our findings revealed substantial variability in hydrogen isotope fractionation among different algal taxa and various fatty acids. Based on taxa, different fatty acids exhibited faster integration of water hydrogen than others, but they were not necessarily in the order of the biosynthetic pathway. This experiment underscores the complexity of hydrogen isotope fractionation and the requirement for controlled laboratory studies to properly apply compound-specific stable H isotope analysis techniques in ecological and paleo-environmental studies.

This study investigates the levels of natural and artificial radioactivity in rice samples collected from various local markets in Islamabad, Pakistan. The ²²⁶Ra, ²³²Th, and ⁴⁰K activity concentrations were measured through gamma-ray spectrometry with a NaI(Tl) detector. The average activity concentrations were 1.67 ± 1.19 Bq kg^-1 for ²²⁶Ra, 3.31 ± 1.83 Bq kg^-1 for ²³²Th, and 88.51 ± 11.65 Bq kg^-1 for ⁴⁰K. Calculated radium equivalent (Ra_eq) values ranged from 7.35 to 18.08 Bq kg^-1, with a mean value of 11.11 Bq kg^-1, all below the permissible maximum of 370 Bq kg^-1. The absorbed dose rates ranged from 6.85 to 16.39 nGy h^-1, with an average of 10.64 nGy h^-1, falling below the acceptable limit of 51 nGy h^-1. The outdoor and indoor radiation hazard indices (H_ex and H_in) had mean values of 0.03, both below the threshold value of one. The external and internal hazard indices (I_γ and I_α) were both 0.088, also below the critical value of one. The excess lifetime cancer risk (ELCR) ranged from 0.28 to 0.11, with a mean value of 0.18, which is less than the critical value of one. Overall, the radioactivity levels in the analyzed rice samples are within the acceptable limits set by the International Commission on Radiological Protection and are below global averages. These results offer important insights into the radiological safety of rice consumption in the study area.