Explore the vast range of titles available.

The number of studies concerning Submarine Groundwater Discharge (SGD) grew quickly as we entered the 21st century. Many hydrological and oceanographic processes that drive and influence SGD were identified and characterized during this period. These processes included tidal effects on SGD, water and solute fluxes, biogeochemical transformations through the subterranean estuary, and material transport via SGD from land to sea. Here we compile and summarize the significant progress in SGD assessment methodologies, considering both the terrestrial and marine driving forces, and local as well as global evaluations of groundwater discharge with an emphasis on investigations published over the past decade. Our treatment presents the state-of-the-art progress of SGD studies from geophysical, geochemical, bio-ecological, economic, and cultural perspectives. We identify and summarize remaining research questions, make recommendations for future research directions, and discuss potential future challenges, including impacts of climate change on SGD and improved estimates of the global magnitude of SGD.

This study reports analyses of Ra isotopes in a Mediterranean stream, the Vidourle river, whose upper course drains the granitic and metamorphic basement of the SE part of the French Massif Central (Cévennes) and then flows through the karstified carbonates of Jurassic and Cretaceous ages. In these low-Ra waters (226Ra activities range from 1.5 to 4.9 mBq/L), all four Ra isotopes were successfully analyzed through gamma spectrometry during a single analysis. 226Ra activities and (228Ra/226Ra) ratios are distinctly higher in waters draining the Variscan basement than in waters affected by dissolution of Mesozoic carbonates, in agreement with U contents and Th/U ratios of both rock types. This results in a general N-S decrease, which parallels the evolution of the 87Sr/86Sr ratios. (228Ra/226Ra) ratios reported vs 1/(226Ra) display linear relationships suggesting mixing of several water components related to the lithology. Ra might thus have a more conservative behavior than usually assumed, possibly because of the high water/rock ratio and flow rate in karst environment. Short-lived Ra isotopes (224Ra and 223Ra) are often in excess compared to their equilibrium values, due to their supply through alpha-recoil processes. 223Ra activities in a Vidourle tributary can be explained by mixing of two water components, with a negligible radioactive decay of 223Ra during underground water flow. The calculated minimum flow rates (40–60 m/h) are in agreement with those deduced from artificial tracer experiments.

In order to characterize the features of radium isotopes in estuaries of Tianjin, a continuous survey and sampling of typical estuaries were conducted from 2013 to 2017 in this study. The activities of natural radioactive radium isotopes ( 223 Ra, 224 Ra, and 228 Ra) in groundwater and surface water were measured by the radium-delayed coincidence counting (RaDeCC) system. The non-conservative behavior of the radium isotopes was investigated under hydrogeochemical conditions and urbanization. The results indicated that in terms of horizontal distribution, the activities of radium in groundwater (Hangu, Tanggu, and Dagang) showed an upward trend from north to south and demonstrated a higher figure than surface water (Haihe River and Duliujian River). Concerning the vertical distribution, the activitives of radium at a 15 m burial depth was higher than that at a 30 m burial depth in all measurements. The activities of radium isotopes in the study area increased with the increase of total dissolved solids, and their desorption behavior on Fe-Mn oxides was constrained by the redox intensity. Different hydrogeological conditions resulted in variations in the vertical profile of radium activities. The activity of radium was regulated by seasonal variation and precipitation in groundwater and surface water. In addition, the rapid urbanization has caused a significant impact on the features of radium isotopes in typical estuaries of Tianjin. Meanwhile, radium isotopes can be applied to reflect the impact of urbanization on surface water-groundwater systems. Clarifying and cleverly utilizing the relationship between behavior of radium isotopes and urbanization will promote the development of the Tianjin Binhai New Area in a healthy way.

This is the first attempt in the world to depict the vertical distribution of radionuclides in the soil samples along several heights (900 feet, 1550 feet, and 1650 feet) of Marayon Tong hill in the Chittagong Hill Tracts, Bandarban by HPGe gamma-ray spectrometry. The average activity concentrations of 232 Th, 226 Ra, and 40 K were found to be 37.15 ± 3.76 Bqkg −1 , 19.69 ± 2.15 Bqkg −1 , and 347.82 ± 24.50 Bqkg −1 , respectively, where in most cases, 232 Th exceeded the world average value of 30 Bqkg −1 . According to soil characterization, soils ranged from slightly acidic to moderately acidic, with low soluble salts. The radium equivalent activity, outdoor and indoor absorbed dose rate, external and internal hazard indices, external and internal effective dose rates, gamma level index, and excess lifetime cancer risk were evaluated and found to be below the recommended or world average values; but a measurable activity of 137 Cs was found at soils collected from ground level and at an altitude of 1550 feet, which possibly arises from the nuclear fallout. The evaluation of cumulative radiation doses to the inhabitants via periodic measurement is recommended due to the elevated levels of 232 Th.This pioneering work in mapping the vertical distribution of naturally occurring radioactive materials (NORMs) can be an essential factual baseline data for the scientific community that may be used to evaluate the variation in NORMs in the future, especially after the commissioning of the Rooppur Nuclear Power Plant in Bangladesh in 2024.

Humans are constantly exposed to radiation from their natural environment including soil and gamma radiation has harmful effects on them, so determination of radioactivity concentration in soil are very important. The present study aims to measure the activity concentrations of naturally occurring radionuclides 226 Ra, 232 Th, and 40 K in urban soil samples collected from thirty different areas of Dhaka city. The analyzed was performed using a High-Purity Germanium (HPGe) gamma-ray spectrometer. The results showed that the mean activity concentrations of 226 Ra, 232 Th, and 40 K were found 24.2 ± 1.0 Bqkg -1 , 52.0 ± 2.0 Bqkg -1 , and 352 ± 11 Bqkg -1 , respectively. The average concentrations of 226 Ra and 40 K fall below the internationally recommended safety limits of 35 Bqkg -1 and 400 Bqkg -1 , respectively, while 232 Th value exceeded the recommended limit of 30 Bqkg -1 by approximately 1.7 times. The mean value of radium equivalent activity (Ra eq ) was calculated as 125.7 Bqkg -1 , which was far below the global safety threshold of 370 Bqkg -1 . The estimated outdoor effective dose rates were 0.070 mSvy -1 and below the worldwide recommended limit of 1 mSvy -1 . Additionally, excess life time cancer risk (ELCR) was below than the internationally accepted limit of 0.29 × 10 −3 . All things considered, the study is the first comprehensive dataset of urban soil in the area and revealed that there are no immediate health dangers due to the low radioactive hazard indices.

The concentrations of primordial radionuclides (226Ra, 232Th and 40K) in commonly used building materials (brick, cement and sand), the raw materials of cement and the by-products of coal-fired power plants (fly ash) collected from various manufacturers and suppliers in Bangladesh were determined via gamma-ray spectrometry using an HPGe detector. The results showed that the mean concentrations of 226Ra, 232Th and 40K in all studied samples slightly exceeded the typical world average values of 50 Bq kg(-1), 50 Bq kg(-1) and 500 Bq kg(-1), respectively. The activity concentrations (especially 226Ra) of fly-ash-containing cement in this study were found to be higher than those of fly-ash-free cement. To evaluate the potential radiological risk to individuals associated with these building materials, various radiological hazard indicators were calculated. The radium equivalent activity values for all samples were found to be lower than the recommended limit for building materials of 370 Bq kg(-1), with the exception of the fly ash. For most samples, the values of the alpha index and the radiological hazard (external and internal) indices were found to be within the safe limit of 1. The mean indoor absorbed dose rate was observed to be higher than the population-weighted world average of 84 nGy h(-1), and the corresponding annual effective dose for most samples fell below the recommended upper dose limit of 1 mSv y(-1). For all investigated materials, the values of the gamma index were found to be greater than 0.5 but less than 1, indicating that the gamma dose contribution from the studied building materials exceeds the exemption dose criterion of 0.3 mSv y(-1) but complies with the upper dose principle of 1 mSv y(-1).

Human populations are being exposed to a wide spectrum of radiation from soils as a result of the availability of radiation sources. Assessing the ecological and health effects of radionuclides in soils is crucial to support the optimal soil management practices but large-scale studies are limited. This study compiled data on radionuclides (226Ra, 232Th, 40K, 238U, and 137Cs) in soils located across the world (44 countries and 159 places) between 2008 and 2022 and applied radiological hazards indices and several multivariate statistical approaches. The average activity concentration (Bq/kg) of 226Ra, 232Th, 40K, 238U, and 137Cs were 408.56, 144.80, 508.78, 532.78, and 83.12, respectively, whereas 226Ra, 232Th, 40K, and 238U exceeded the standard limits. The principal component analysis explained more than 91% of variation in soils. Based on the geoaccumulation index, 40K posed moderately to heavy contamination whereas 238U and 226Ra posed moderate contamination in soils. Moreover, the mean values of radiological hazards evaluation such as radium equivalent activity (487.17 Bq/kg), external radiation hazard indices (1.32), internal hazard indices (2.15), absorbed dose rate (247.86 nGyh−1), annual effective dose rate (1.82 mSvy−1), activity utilization index (4.54) and excess lifetime cancer risk (63.84 × 10–4) were higher than recommended limit suggesting significant radiological risks in study region soils. The findings indicated that the study area soils were contaminated by radionuclides and unsafe for hazards in terms of the health risks linked with studied radioactive contents. The study is valuable for mapping radioactivity across the globe to determine the level of radioactivity hazards.

Impact assessment of building materials is a focused topic in the field of radioecology. A radiological survey has conducted to monitor radioactivity of most common building materials in Semnan Province, Iran, and assess the radiation risk. Activity concentrations of 226 Ra, 232 Th, and 40 K were measured in 29 samples including nine commonly used building materials that were collected from local suppliers and manufacturers, using a high purity germanium gamma-ray detector. The activity concentrations of 226 Ra, 232 Th, and 40 K varied from 6.7±1 to 43.6±9, 5.9±1 to 60±11, and 28.5±3 to 1085±113 Bq kg −1 with averages of 26.8±5, 22.7±4, and 322.4±4 Bq kg −1 , respectively. By applying multivariate statistical approach (Pearson correlation, cluster, and principal component analyses (PCA)), the radiological health hazard parameters were analyzed to obtain similarities and correlations between the various samples. The Pearson correlation showed that the 226 Ra distribution in the samples is controlled by changing the 232 Th concentration. The variance of 95.58% obtained from PCA resulted that the main radiological health hazard parameters exist due to the concentration of 226 Ra and 232 Th. The resulting dendrogram of cluster analysis also shows a well coincidence with the correlation analysis.

The utilization of phosphorite deposits as an industrial resource is of paramount importance, and its sustainability largely depends on ensuring safe and responsible practices. This study aims to evaluate the suitability of phosphorite deposits for industrial applications such as the production of phosphoric acid and phosphatic fertilizers. To achieve this goal, the study meticulously examines the geochemical characteristics of the deposits, investigates the distribution of natural Radioactivity within them, and assesses the potential radiological risk associated with their use. The phosphorites are massive and collected from different beds within the Duwi Formation at the Hamadat mining area. They are grain-supported and composed of phosphatic pellets, bioclasts (bones), non-phosphatic minerals, and cement. Geochemically, phosphorites contain high concentrations of P 2 O 5 (23.59–28.36 wt.%) and CaO (40.85–44.35 wt.%), with low amounts of Al 2 O 3 (0.23–0.51 wt.%), TiO 2 (0.01–0.03 wt.%), Fe 2 O 3 (1.14–2.28 wt.%), Na 2 O (0.37–1.19 wt.%), K 2 O (0.03–0.12 wt.%), and MnO (0.08–0.18 wt.%), suggesting the low contribution of the detrital material during their deposition. Moreover, they belong to contain enhanced U concentration (55–128 ppm). They are also enriched with Sr, Ba, Cr, V, and Zn and depleted in Th, Zr, and Rb, which strongly supports the low detrital input during the formation of the Hamadat phosphorites. The high Radioactivity of the studied phosphorites is probably due to the widespread occurrence of phosphatic components (e.g., apatite) that accommodate U in high concentrations. Gamma spectrometry based on NaI (Tl) crystal 3×3 has been used to measure occurring radionuclides in the phosphorite samples. The results indicate that the radioactive concentrations’ average values of 226 Ra, 232 Th, and 40 K are 184.18±9.19, 125.82±6.29, and 63.82±3.19 Bq Kg -1 , respectively. Additionally, evaluations have been made of the radiological hazards. The calculated risk indicators exceeded the recommended national and world averages. The data obtained will serve as a reference for follow-up studies to evaluate the effectiveness of the Radioactivity of phosphatic materials collected from the Hamdat mine area.

The sediment mixed layer (SML) in the deep ocean is an important interface with a rich diversity of benthic organisms. With increasing ocean mineral exploration, and eventual mining, the effect of sediment mixing on deep ocean ecosystems has raised considerable concern. We evaluate the distribution patterns and driving factors of SML depth in deep ocean nodule fields using naturally occurring 210Pb–226Ra isotopes. Results show that average SML depth has increased in Mn‐nodule fields since the end of the last century. SML processes are associated with significant desorption of 226Ra from sediments, resulting in a departure from radioactive equilibrium. By estimating possible driving factors, we conclude that anthropogenic exploration activities, rather than natural physical and/or biological drivers, are the most likely mechanism for intensified sediment mixing. 210Pb–226Ra disequilibria may be a potential tracer for quantifying the impact of human exploration on deep‐ocean sediment mixing and associated biological and geochemical effects. Plain Language Summary The surface sediment mixed layer (SML) in the deep ocean is essential to benthic community structure and the biogeochemical cycling of many elements. The typical depth of mixed layers in the global deep ocean is <15 cm, which is mainly driven by natural biological and/or physical forces. By mapping sediment excess 210Pb profiles throughout the ocean, we found the depth of the SML in manganese nodule fields has increased significantly since the end of the twentieth century (reaching to >40 cm). The determine that the deepened mixed sediment layer is related to human exploration activities rather than other previously recognized natural drivers like bioturbation, internal solitary waves, and submarine storms. Keen attentions should be paid to the deepening and associated effects of sediment mixing in the deep ocean as human demand for critical materials continues to increase in the Anthropocene. Exploration approaches that involve low or negligible disturbance to deep‐ocean sediment should be encouraged. Key Points Human exploration is the main reason for deepening of the sediment mixed layer in the manganese nodule area Sediment mixed processes are associated with significant desorption of 226Ra from sediments 210Pb–226Ra disequilibria is a potential tracer for quantifying the impact of human drivers on deep‐ocean sediment mixing