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Mangrove‐dominated coastlines have high carbon sequestration capacity, but it remains unclear whether tidally outwelled carbon is transformed within the coastal ocean or exported offshore. Here, we used radium isotopes (224Ra and 223Ra) to investigate carbon outwelling in two mangrove seascapes in Brazil across multiple spatial scales. We sampled porewaters to define the source composition, mangrove creek waters to resolve tidal cycles, and cross‐shelf transects to trace outwelling in coastal seascapes. Radium isotopes were positively correlated with dissolved inorganic (DIC), organic (DOC) and particulate organic (POC) carbon across the seascapes. DIC was the primary form of carbon (mean ± SD), representing 85% of the total carbon pool as bicarbonate (75 ± 11%), carbonate (6 ± 5%), and CO2 (4 ± 9%). DOC and POC accounted for 10 ± 6% and 5 ± 6% of total carbon, respectively. Although mangrove waters emitted CO2 to the atmosphere (38–143 mmol m−2 d−1), both bays and continental shelves were a CO2 sink (−2.5 to −0.5 mmol m−2 d−1) associated to chlorophyll‐a enrichments (r2 = 0.86). Total carbon outwelled from mangroves were 3–4 times higher than soil carbon burial at both mangrove sites. Bicarbonate export (27–72 mmol m−2 d−1) to the continental shelf was the major fate of carbon outwelling, more than doubling the perceived capacity of mangrove soil to sequester carbon. Hence, disregarding outwelling as a blue carbon sink mechanism would lead to underestimated assessments of how mangroves capture CO2 and help to mitigate climate change. Plain Language Summary: Mangrove forests effectively store large amounts of carbon within their muddy soils due to their complex root systems, high sedimentation rates, and high productivity. Mangroves also play a crucial role in exporting carbon to the ocean through tidal flushing and climate change mitigation. Here, we measured overlooked lateral carbon fluxes using geochemical tracers. Our findings demonstrated that mangroves could sequester 3–4 times more CO2 if total carbon exports to ocean are accounted in addition to soil carbon burial. Most of the carbon is exported as bicarbonate, with the potential to remain in seawater for millennia. We argue that a fraction of mangrove carbon is not lost during transport offshore, but rather stored in the ocean, the largest global carbon reservoir. Key Points: Porewater exchange is a pivotal component of the carbon budget within mangrove seascapesMangrove carbon outwelling oscillates between tidal cycles and reaches the continental shelf within 1–3 weeksCarbon sequestration via outwelling to the ocean was 3–4 times greater than soil burial [ABSTRACT FROM AUTHOR]

Extreme mass ratio inspirals (EMRIs) are one of the primary targets for the recently adopted millihertz gravitational-wave observatory LISA. Some previous studies have argued that a fraction of all EMRIs form in matter-rich environments, and can potentially explain the dozens of soft X-ray band (⁠|$\sim 10^{-1}\,\rm keV$|⁠), low-frequency (⁠|$\sim 0.1$| mHz) periodic phenomena known as quasi-periodic eruptions (QPEs) and quasi-periodic oscillations (QPOs). Here, using a representative EMRI population retrofitted with cutoffs on LISA-band SNRs and luminosity distances to account for the sensitivity of current instruments, we estimate the mean frequency band in which QPEs and QPOs originating from detectable LISA EMRIs may be emitting an X-ray signal 'today' (i.e. in 2024) to be |$0.46 \pm 0.22$| mHz. We also model the well-known QPO source, RE J1034+396, which falls in this frequency band, as an EMRI assuming its primary black hole mass to be |$10^6{-}10^7 \,{\rm M}_\odot$|⁠. Through a prior-predictive analysis, we estimate the orbiting compact object's mass to be |$46^{+ 10}_{-40} \,{\rm M}_\odot$| and the source's LISA-band SNR as |$\approx 14$|⁠ , highlighting it as a candidate multimessenger EMRI target. We also highlight the role of current and near-future X-ray and UV observatories in enabling multimessenger observations of EMRIs in conjunction with LISA, and conclude with a discussion of caveats of the current analysis, such as the exclusion of eccentricity and inclination from the model, and the measurability of subsolar mass compact object EMRIs. [ABSTRACT FROM AUTHOR]

This research aimed to determine the activity concentration of 226Ra in the natural radioactivity of the surface water of the Maritsa River, Türkiye. The gamma spectrometric analysis was conducted by using 3′′ × 3′′ NaI(Tl) and (HPGe) detector. Since the direct measurement method could not acquire reliable results, the mean activity concentration of 226Ra was calculated as 0.62 Bq L−1 with the "standard addition method". The mean values of the gross alpha/beta activities and the total radium alpha activity concentration were measured. The results are 0.013 Bq L−1, 0.304 Bq L−1, and 0.014 Bq L−1 respectively. [ABSTRACT FROM AUTHOR]

Some types of fertilizers may contain various amounts of natural radionuclides like 238U, 232Th, 226Ra, 40K (Kuzmanoviæ et al. in J Radioanal Nucl Chem 331(12):5825–5834, 2022. 10.1007/s10967-022-08646-x; H Hamamo et al. in J Radioanal Nucl Chem 194(2): 331–336, 1995. 10.1007/BF02038431; M García-León et al. in J Radioanal Nucl Chem 197(1): 173–184, 1995. 10.1007/BF02040229). In this study 16 samples of commercially available fertilizers produced in Poland were selected for preliminary radiological evaluation. The samples were measured by means of low background gamma spectrometry. The results showed high concentrations of 40K in potassium and multinutrient fertilizers (2.3–13.8 kBq kg−1), and relatively high concentrations of uranium and radium isotopes in phosphate fertilizers. The obtained results allowed to calculate radium equivalent activity, absorbed dose rate increase and increase in annual effective dose equivalent. [ABSTRACT FROM AUTHOR]

As a significant source of nutrients and other components into the coastal ocean, submarine groundwater discharge (SGD) is a combination of multiple spatial‐temporal scale processes, including fresh terrestrial groundwater (FSGD), recirculating seawater (RSGD), and porewater exchange (PEX). Quantifying the different types of SGD is extremely important for understanding the coastal biogeochemical cycles of various materials. The green tide bloom in the southern Yellow Sea (China) has attracted increasing attention during the past decade. Haizhou Bay is thought to be an important green tide proliferating area, but the source of an apparent high supply of nutrients has not been identified yet. We report here on our investigations of the distribution patterns of Ra and Rn isotopes in groundwater and seawater in Haizhou Bay. By solving a combined mass balance for 224Ra, 223Ra, 226Ra, and 222Rn, we estimated that the bay's water residence time is 28.8 days, FSGD is highest at 3.6 cm d−1, RSGD is 2.7 cm d−1, and PEX is lowest at 0.6 cm d−1. The total SGD into Haizhou Bay is estimated at 9.40 × 107 m3 d−1 (6.9 cm d−1), about 12 times that of the local river discharge into the bay. SGD‐derived nutrients are shown to play an important role when considered among all known nutrient sources. Our results suggest that dissolved inorganic nitrogen (DIN) and silicate (DSi) are transported by SGD mainly via FSGD. We also note that the phosphorus (DIP) budget is heavily influenced by RSGD. Plain Language Summary: Submarine groundwater discharge (SGD) has been drawing attention as an important benthic boundary exchange pathway in the global marginal seas. As any water flow entering the sea, SGD may happen on small scales (centimeters, minutes to hours) as porewater exchange (PEX), and/or large scales (>meters, days to seasons) as fresh groundwater discharge (FSGD) and seawater recirculation (RSGD) in the subterranean estuary. To better understand its significance, it is necessary to interpret multi‐scale SGD processes and quantify associated nutrients fluxes accordingly. In this study, different types of SGD and associated nutrient fluxes were quantified based on multiple radium and radon isotopes in Haizhou Bay, China, which is one of the world's largest green tide proliferating areas. The FSGD and RSGD were found to be the main processes, accounting for more than 90% of the total SGD fluxes. SGD was recognized as a key nutrient source in Haizhou Bay, which is more than one order of magnitude higher than that of the local river discharge. This study highlights the crucial role of benthic boundary exchange for the health of marine ecosystem and sustainability of the future ocean. Key Points: Multi‐scale submarine groundwater discharge processes were differentiated and quantified via a multi‐isotope mass balance approachThe flux of fresh groundwater was about 30% higher than recirculated saline groundwater, and about 6 times higher than porewater exchangeFresh groundwater is a main nutrient source to Haizhou Bay, but recirculated saline groundwater makes a larger contribution to DIP inputs [ABSTRACT FROM AUTHOR]

The presented paper discusses the production of radioactive ion beams of francium, radium, and actinium from thick uranium carbide (UC x ) targets at ISOLDE, CERN. This study focuses on the release curves and extractable yields of francium, radium and actinium isotopes. The ion source temperature was varied in order to study the relative contributions of surface and laser ionization to the production of the actinium ion beams. The experimental results are presented in the form of release parameters. Representative extractable yields per μ C are presented for 222 - 231 Ac, several Ra and Fr isotopes in the mass ranges 214 ≤ A ≤ 233 and 205 ≤ A ≤ 231 respectively. The release efficiency for several isotopes of each of the studied elements was calculated by comparing their yields to the estimated in-target production rates modeled by CERN-FLUKA. The maximal extraction efficiency of actinium was calculated to be 2.1(6)% for a combination of surface ionization using a Ta ion source and resonant laser ionization using the two-step 438.58 nm, and 424.69 nm scheme. [ABSTRACT FROM AUTHOR]

(Ra,Ba)SO4 solid solutions are commonly encountered as problematic scales in subsurface energy-related applications, e.g., geothermal systems, hydraulic fracturing, conventional oil and gas, etc. Despite its relevance, its crystallization kinetics were never determined because of radium (226), high radioactivity (3.7 × 1010 Bq g−1), and utilization in contemporary research, therefore constrained to trace amounts (< 10−8 M) with the composition of BaxRa1-xSO4 commonly restricted to x > 0.99. What if lab-on-a-chip technology could create new opportunities, enabling the study of highly radioactive radium beyond traces to access new information? In this work, we developed a lab-on-a-chip experiment paired with computer vision to evaluate the crystal growth rate of (Ba,Ra)SO4 solid solutions. The computer vision algorithm enhances experimental throughput, yielding robust statistical insights and further advancing the efficiency of such experiments. The 3D analysis results of the precipitated crystals using confocal Raman spectroscopy suggested that {210} faces grew twice as fast as {001} faces, mirroring a common observation reported for pure barite. The crystal growth rate of (Ba0.5Ra0.5)SO4 follows a second-order reaction with a kinetic constant equal to (1.23 ± 0.09) × 10−10 mol m−2 s−1. [ABSTRACT FROM AUTHOR]

(Ra,Ba)SO4 solid solutions are commonly encountered as problematic scales in subsurface energy-related applications, e.g., geothermal systems, hydraulic fracturing, conventional oil and gas, etc. Despite its relevance, its crystallization kinetics were never determined because of radium (226), high radioactivity (3.7 × 1010 Bq g−1), and utilization in contemporary research, therefore constrained to trace amounts (< 10−8 M) with the composition of BaxRa1-xSO4 commonly restricted to x > 0.99. What if lab-on-a-chip technology could create new opportunities, enabling the study of highly radioactive radium beyond traces to access new information? In this work, we developed a lab-on-a-chip experiment paired with computer vision to evaluate the crystal growth rate of (Ba,Ra)SO4 solid solutions. The computer vision algorithm enhances experimental throughput, yielding robust statistical insights and further advancing the efficiency of such experiments. The 3D analysis results of the precipitated crystals using confocal Raman spectroscopy suggested that {210} faces grew twice as fast as {001} faces, mirroring a common observation reported for pure barite. The crystal growth rate of (Ba0.5Ra0.5)SO4 follows a second-order reaction with a kinetic constant equal to (1.23 ± 0.09) × 10−10 mol m−2 s−1. [ABSTRACT FROM AUTHOR]

Solid process fine waste or tailings of a uranium mill is a potential source of release of radiologically significant gaseous radon (222Rn). A number of variables such as radium (226Ra) content, porosity, moisture content, and tailings density can affect the extent of emanation from the tailings. Further, if a cover material is used for remediation purposes, additional challenges due to changes in the matrix characteristics in predicting the radon flux can be anticipated. The uranium mill tailings impoundment systems at Jaduguda have been in use for the long-term storage of fine process waste (tailings). A pilot-scale remediation exercise of one of the tailings ponds has been undertaken with 30 cm soil as a cover material. For the prediction of the radon flux, a numerical model has been developed to account for the radon exhalation process at the remediated site. The model can effectively be used to accommodate both the continuous and discrete variable inputs. Depth profiling and physicochemical characterization for the remediated site have been done for the required input variables of the proposed numerical model. The predicted flux worked out is well below the reference level of 0.74 Bq m−2 s−1 IAEA (2004). [ABSTRACT FROM AUTHOR]

In this study, we focus on the biogeochemical processes that produce both dissolved inorganic carbon (DIC) and total alkalinity (TA) along a subarctic subterranean estuary (STE) located in the Gulf of St. Lawrence (Magdalen Island, Qc, Canada) in order to evaluate the DIC and TA fluxes as well as the buffering capacity of the exported groundwater to coastal waters. DIC and TA do not behave conservatively during mixing along the groundwater flow path and this implies the occurrence of internal redox reactions that control both their production and consumption. In addition, we show that the origin and composition of the organic carbon within the system alter the carbonate parameters by generating low pH conditions (5.9 - 7.2) and contributing to non-carbonate alkalinity (NCA) that accounts for more than 30% of TA. Whereas iron cycling plays a key role in the production of DIC in the fresh and low-salinity groundwaters, the precipitation of sulfide minerals neutralize the acidity produced by the metabolically produced CO2, in the saline groundwater where sulfate is available. The STE pCO2, computed from the DIC-pHNBS pair ranged from a few ppm to 16000 ppm that results in a CO2 evasion rate of up to 310 mol m-2d-1 to the atmosphere. Based on Darcy flow and the mean concentrations of DIC and carbonate alkalinity (Ac = TA - NCA) in the discharge zone, fluxes derived from submarine groundwater discharge were estimated at 1.43 and 0.70 mol m-2d-1 for DIC and Ac, respectively. Despite a major part of the metabolic CO2 being lost along the groundwater flow path, the SGD-derived DIC flux was still greater than the Ac flux, implying that groundwater discharge reduces the buffering capacity of the receiving coastal waters. This site-specific scale study demonstrates the importance of diagenetic reactions and organic matter remineralization processes on carbonate system parameters in STE. Our results highlight that subarctic STEs could be hot spots of CO2 evasion and a source of acidification to coastal waters that should be considered in carbon budgets. [ABSTRACT FROM AUTHOR]

To improve the processing performance of vitrified bonded diamond fixed-abrasive lapping plates for processing sapphire substrates, a free-abrasive was added to the lapping slurry to enhance the self-dressing ability of the lapping plate to achieve efficient and high-quality processing of sapphire substrates. The processing effectiveness and mechanism of a free-abrasive assisted fixed-abrasive lapping plates (FAAFALP) lapping process for sapphire substrates were analysed and revealed via a single-factor experiment. To optimise the lapping process of the FAAFALP of sapphire substrates with good overall performance (high material removal rate (MRR), minor surface roughness (Ra) and big lapping plate wear ratio (η)), the effects and the optimal parameters combination of the lapping pressure, lapping speed and free-abrasive concentration on MRR, Ra and η of lapping-processed sapphire substrates were investigated using orthogonal experiments. Furthermore, the experimental results were combined with process parameters to establish a regression model. The multi-evaluation index optimisation problem was transformed into a single-index optimisation problem via the grey relational analysis (GRA) to evaluate each parameter's performance comprehensively. The results revealed that an MRR increased by 22.2 % to 2.48 μm/min, the smallest surface roughness Ra of 0.141 μm, and the lapping plate wear ratio η relatively increased to 14.88 was obtained when a free-abrasive of SiO 2 with a particle size of 14 μm was added into lapping slurry. Compared with no free-abrasive lapping process, free-abrasive can significantly improve the lapping plate's self-dressing ability and enhance the sapphire substrates' processing effect. The lapping speed, lapping pressure and free-abrasive concentration had different influence degrees on MRR, Ra and η. The established regression equations predicted the response values of MRR, Ra and η to be 99.87 %, 99.06 % and 98.59 %, respectively, and the relative errors between the predicted and actual measured values were <12 %. With increased lapping speed, MRR initially decreased but subsequently increased, and Ra and η gradually decreased. MRR and η continuously increased with increased lapping pressure, whereas Ra decreased. With increased free-abrasive concentration, MRR, Ra and η initially increased but subsequently decreased. Comparing the optimised results obtained by intuitive analysis, the parameters optimised via the GRA were used to obtain sapphire substrates lapping with an MRR of 3.81 μm/min, Ra of 0.133 μm and η of 20.4, and the overall lapping performance was better 42.92 %, 102.90 % and 43.60 % than that of intuitive analysis for MRR, Ra and η. Therefore, combining orthogonal experiments and GRA can provide new ideas for optimising the FAAFALP lapping process for sapphire substrates. • The processing effectiveness and mechanism for sapphire substrates were analysed and revealed. • Effects of process parameters for sapphire in lapping on MRR, Ra and lapping plate wear ratio were studied. • A regression model combined with experimental results and process parameters was established. • Grey relational analysis was used to obtain parameters with good lapping performance. [ABSTRACT FROM AUTHOR]

The half‐life of 228Ra (5.7 years) aligns well with near‐surface and near‐bottom ocean mixing timescales. Because 228Ra is sourced from sediments, regions of enhanced activity represent water that has recently interacted with sediments on the continental margin or seabed. The GP15 meridional transect from Alaska to Tahiti along152°W encountered several regions in the upper ocean where 228Ra was enriched. These enrichments follow surface and subsurface ocean current patterns and pair with earlier measurements of 228Ra and transient radionuclides to reveal the origins of these enriched regions. An enriched region at Alaska margin stations 1–3 was sourced locally but did not extend to the Alaskan trench at station 4. A large shallow region between 47° and 32°N. was sourced from the west by the North Pacific Current; another shallow enriched region between 11° and 5° N was also sourced from the west by the North Equatorial Countercurrent. Subsurface enrichments (100–400 m) between 18 and 47°N were associated with Central Mode Water and North Pacific Intermediate Water. The 228Ra activities in the upper Pacific were six times lower than activities in the Atlantic. In deep waters the primary enrichment was 27°–47°N. Two stations (32° and 37°N) were especially enriched, having near‐bottom inventories several times greater than other stations. With these two exceptions the remaining Pacific stations exhibited averaged inventories lower than those in the Atlantic. There was one region of enriched 223Ra (half‐life = 11 days) above the Puna Ridge near Hawaii. Plain Language Summary: The international GEOTRACES program aims to identify processes and quantify fluxes that control the distribution of trace elements and isotopes (TEIs) in the ocean. Some TEIs are important micronutrients, which may control biological productivity. Others may become concentrated as they pass up the food web and reach potentially harmful levels in some seafood. But measurements of these TEIs are not adequate to determine controlling processes or quantify their fluxes in the marine environment. Radionuclide tracers provide a means to link TEI measurements with fluxes and processes. Here we employ measurements of 228Radium (half‐life = 5.75 years) to trace water movements and current speeds in the upper Pacific and to determine regions near the seabed where sediment‐water interactions are most intense. The upper ocean measurements confirmed a broad circulation pattern that brought water from the Asian margin to the northeast Pacific at speeds of 2–8 cm/sec, in agreement with other estimates of these current speeds. Near the seabed we discovered a region of enhanced 228Ra activity indicating intense sediment‐water interactions. Such regions may control the release of TEIs from the seabed to the water column. We anticipate others will utilize these data to elucidate aspects of other TEI distributions. Key Points: Several open‐ocean regions of enriched 228Ra were documented in the North and Equatorial Pacific at 152°WThe upper ocean 228Ra‐enriched regions correspond to major surface and subsurface currents transporting water from the Asian marginOne seabed region near 32°N was especially enriched in 228Ra [ABSTRACT FROM AUTHOR]

Cobalt oxyhydroxide (CoOOH) is a promising catalytic material for oxygen evolution reaction (OER). In the traditional CoOOH structure, Co3+ exhibits a low-spin state configuration ( t 2 g 6 e g 0 ), with electron transfer occurring in face-to-face t 2 g * orbitals. In this work, we report the successful synthesis of high-spin state Co3+ CoOOH structure, by introducing coordinatively unsaturated Co atoms. As compared to the low-spin state CoOOH, electron transfer in the high-spin state CoOOH occurs in apex-to-apex e g * orbitals, which exhibits faster electron transfer ability. As a result, the high-spin state CoOOH performs superior OER activity with an overpotential of 226 mV at 10 mA cm−2, which is 148 mV lower than that of the low-spin state CoOOH. This work emphasizes the effect of the spin state of Co3+ on OER activity of CoOOH based electrocatalysts for water splitting, and thus provides a new strategy for designing highly efficient electrocatalysts. Regulating spin state of metal cations in catalysts is recognized as a strategy to improve water oxidation. Herein, the authors constructed high-spin cobalt ions in cobalt oxyhydroxides, experimentally demonstrating accelerated electron transfer ability and thereby superior water oxidation performance. [ABSTRACT FROM AUTHOR]

The features of the concentration distribution of 238U, 232Th, and 226Ra in the surface layer in the bottom sediments of the shelf and continental slope of Svalbard are considered. The content of 226Ra, 232Th, and 238U varied in the range 22–134.3, 22.4–50.9, and 10.9–37.7 Bq/kg, respectively. The amount of 226Ra nonequilibrium with 238U (226Raex) ranged from 23 to 73% of the total 226Ra content in sediments. The maximum concentrations of 226Ra, 238U, 232Th, and 226Raex (134.3, 37.7, 50.9, and 98.2 Bq/kg, respectively) were obtained in the area of increased bioproductivity (Eagle Trough). In this zone, the relationship between the concentrations of 226Ra and 226Raex with the content of organic matter in sediment is well expressed, the correlation coefficients are R = 0.94 and 0.92, respectively, which indicates a significant contribution of the biological community to the accumulation of 226Ra in bottom sediments. The 226Ra concentration and the 226Ra excess value are negatively related to the redox potential of the sediment (R = –0.88). This pattern is also true in other areas of the Svalbard waters. In general, for the entire array of observations, the concentrations of 238U and 232Th increase with increasing content of organic carbon in the sediment (R = 0.72 and 0.7, respectively). The concentrations of 238U and 232Th decrease with increasing Ccarb content in the sediment (R = –0.79 and –0.81, respectively). The data obtained indicate the need to take into account the 226Ra excess when assessing the total natural radioactivity of marine sediments, the value of which may exceed the radioactivity of 238U and 232Th. [ABSTRACT FROM AUTHOR]

Revealing the temporal evolution of individual heavy elements synthesized in the merger ejecta from binary neutron star mergers not only improves our understanding of the origin of heavy elements beyond iron but also clarifies the energy sources of kilonovae. In this work, we present a comprehensive analysis of the temporal evolution of the energy fraction of each nuclide based on r -process nucleosynthesis simulations. The heavy elements dominating the kilonova emission within ∼100 days are identified, including 127Sb, 128Sb, 129Sb, 130Sb, 129Te, 132I, 222Rn, 223Ra, 224Ra, and 225Ac. It is found that the late-time kilonova light curve (t ≳ 20 days) is highly sensitive to the presence of the heavy element 225Ac (with a half-life of 10.0 days). Our analysis shows that the James Webb Space Telescope (JWST), with its high sensitivity in the near-infrared band, is a powerful instrument for the identification of these specific heavy elements. [ABSTRACT FROM AUTHOR]

The cluster radioactivity of 2 2 2 , 2 2 4 , 2 2 6 Ra, 2 2 3 , 2 2 5 Ac, 2 3 2 , 2 3 4 , 2 3 5 , 2 3 6 U, 2 3 6 , 2 3 8 Pu, 2 3 4 , 2 3 6 U, 2 3 2 , 2 3 3 , 2 3 4 , 2 3 5 , 2 3 6 U and 2 3 0 , 2 3 2 Th isotopes which emitted 1 4 C, 2 4 Ne, 2 8 Mg, 2 6 Ne, 2 8 Mg, 2 4 Ne, respectively, has been analyzed with the help of fractional calculus for investigating the connection between order of the fractional derivative and nuclear structure. When the neutron number of daughter nuclei is equal to magic number, order of the fractional derivative shows a maximum. It is shown that there is a relationship between the order of fractional derivative and shell effect. This order has a similar role to the preformation factor in cluster radioactivity. [ABSTRACT FROM AUTHOR]

Targeted alpha-particle therapy using radionuclides with alpha emission is a rapidly developing area in modern cancer treatment. To selectively deliver alpha-emitting isotopes to tumors, targeting vectors, including monoclonal antibodies, peptides, small molecule inhibitors, or other biomolecules, are attached to them, which ensures specific binding to tumor-related antigens and cell surface receptors. Although earlier studies have already demonstrated the anti-tumor potential of alpha-emitting radium (Ra) isotopes—Radium-223 and Radium-224 (223/224Ra)—in the treatment of skeletal metastases, their inability to complex with target-specific moieties hindered application beyond bone targeting. To exploit the therapeutic gains of Ra across a wider spectrum of cancers, nanoparticles have recently been embraced as carriers to ensure the linkage of 223/224Ra to target-affine vectors. Exemplified by prior findings, Ra was successfully bound to several nano/microparticles, including lanthanum phosphate, nanozeolites, barium sulfate, hydroxyapatite, calcium carbonate, gypsum, celestine, or liposomes. Despite the lengthened tumor retention and the related improvement in the radiotherapeutic effect of 223/224Ra coupled to nanoparticles, the in vivo assessment of the radiolabeled nanoprobes is a prerequisite prior to clinical usage. For this purpose, experimental xenotransplant models of different cancers provide a well-suited scenario. Herein, we summarize the latest achievements with 223/224Ra-doped nanoparticles and related advances in targeted alpha radiotherapy. [ABSTRACT FROM AUTHOR]

The concentration of natural radionuclides in the soil around the world has become an environmental concern for international and national authorities because of the harmful effect of radiation exposure on human health. The samples of soil used for this study were collected from Foron and Heipang districts of Barkin Ladi Local Government Area of Plateau State. The samples were analyzed using Canberra Model 727/727R Lead Shield Gamma-ray Spectrometer with NaI(Ti) detector. The result shows that 40K ranges from 301.91 ± 0.24 Bq/kg to 124.97 ± 0.31 Bq/kg from the mining spot to 400 m away from the mining spots. 226Ra ranges from 105.43 ± 1.76 Bq/Kg to 43.10 ± 0.62 Bq/Kg from mining spots to 400 m away from the mining spots, and 232Th also ranges from 92.79 ± 0.26 Bq/kg to 26.97 ± 0.39 Bq/kg respectively. The absorbed dose rate in the air (Dr) has a mean value of 82.88 nGh-1. The annual effective dose rate (AEDR) mean value was 0.1mSvy-1, and the radium equivalent (Ra eq) mean value was 180.23 Bq/kg, Hex and Hin have mean values of 0.49 and 0.69 respectively. The calculated excess lifetime cancer risk (ELCR) ranges from 0.0003 to 0.00039 with a mean value of 0.00035 in the soil samples. Therefore, this result suggested that the area under study could be termed radiologically unsafe for people living around or close to the area. [ABSTRACT FROM AUTHOR]

The Congo River supplies vast quantities of trace metals (TMs) to the South Atlantic Ocean, but TM budgets for the Congo plume derived using radium isotopes for GEOTRACES cruise GA08 suggest additional input other than the river outflow. Considering the tight correlations between most dissolved TMs and salinity in the plume and the high rainfall during the wet season over the Congo shelf, we hypothesized that wet atmospheric deposition is a TM source to the Congo plume. Observed TM concentrations in rainwaters across the Congo shelf were mostly comparable to values from previous work in the North Atlantic and Mediterranean Sea. Wet deposition contributed the equivalent of 43% dCd, 21% dCu, 20% dPb and 68% dZn of the Congo River fluxes. Our findings show an important role of wet deposition in supplying TMs to the South Atlantic overlapping with the region that receives substantial TM fluxes from the Congo River. Plain Language Summary: The Congo River has the second largest freshwater discharge volume globally and creates an extensive near‐equatorial plume into the Atlantic Ocean. The Congo plume constitutes an important source of trace metals (TMs) to the ocean, which impacts biogeochemical cycles in the tropical and subtropical ocean. However, existing work suggests a discrepancy within the TM budgets in the Congo plume and points to unknown source other than the Congo River or shelf sediments. Most TM concentrations across the Congo plume remain tightly correlated with salinity, suggesting that any additional sources are likely also freshwater‐derived or enter the ocean at the river mouth coincidently with direct riverine TM inputs. Here, TM concentrations in ocean, river and rainwater collected during the GEOTRACES GA08 cruise are combined to suggest that wet deposition augmented some Congo TM fluxes to the ocean. Fluxes of anthropogenic Cd, Cu, Pb and Zn to the Congo shelf from wet deposition are of the same order of magnitude as the Congo River. Concentrations of these elements in rainwater are similar to prior observations reported for the North Atlantic and Mediterranean Sea, suggesting that a large fraction of the global range of rainwater concentrations over the ocean has been captured in our observations. Key Points: The Congo River is an important source of trace metals (TMs) to the South Atlantic Ocean revealed by data from GEOTRACES cruise GA08Wet deposition (rainfall) is identified as an additional TM source to the Congo plume by concurrently considering river and rain dataRainfall supplies anthropogenic dTMs (Cd, Cu, Pb and Zn) with fluxes equivalent to 20%–68% of those from the Congo River on the Congo shelf [ABSTRACT FROM AUTHOR]

Evaluated data are presented for 11 known A = 222 nuclides (Bi, Po, At, Rn, Fr, Ra, Ac, Th, Pa, U, and Np), and relevant J π and T 1/2 data for A = 226 nuclei decaying by α -decay to A = 222 nuclei. For 222Bi, only the isotopic identification is established with no measurement of its half-life. For 222Po, 222At, 222Fr, 222U, and 222Np, data are available only for the ground states, with static magnetic dipole and electric quadrupole moments, and charge radius measurements for the 222Fr ground state. For 222Ac and 222Pa, two low-lying levels are known from 226Pa α decay, and 226Np decay, respectively, but with no information about J π assignments and γ decays of these levels. For 222Pa, a long-lived isomeric state is known, decaying dominantly by α decay. 222Rn, 222Ra, and 222Th have been investigated in detail, the low-spin states by α decay and the high-spin studies of ground-state and octupole bands by in-beam γ -ray studies for all the three nuclei, as well as by Coulomb excitation for 222Rn and 222Ra. Low-spin levels in 222Ra have been investigated also through the β − decay of 222Fr. Half-lives of the excited states are known for 7 levels in 222Rn, 12 levels in 222Ra, and 3 levels in 222Th. Octupole deformations, with the presence of alternating-parity bands up to (16+) and (21 −) in 222Rn, (20+) and (19 −) in 222Ra, and (26+) and (25 −) in 222Th, and with interband E1 transitions, have been established in these three nuclei. The present evaluation supersedes the previous A = 222 ENSDF evaluations: (2011Si24), (1996El01), (1987El06) and (1977To14). [ABSTRACT FROM AUTHOR]

Background: The combination of platinum-containing cytostatic drugs with different radiation qualities has been studied for years. Despite their massive side effects, these drugs still belong to the therapeutic portfolio in cancer treatment. To overcome the disadvantages of cisplatin, our study investigated the cytotoxic effects of combining radionuclides with cisplatin. Methods: FaDu cells were treated with cisplatin (concentration ≈ 2 µM) and additionally irradiated after two hours with the alpha-emitter 223Ra, the beta-emitter 188Re as well as external X-rays using dose ranges of 2–6 Gy. Cell survival was followed by colony formation assays and plotted against cisplatin concentration and radiation dose. The results were interpreted by isobolograms. Results: Isobolographic analyses revealed a supra-additive cytotoxic effect for the combination of cisplatin and 223Ra. A sub-additive effect was observed for the combination of cisplatin and 188Re, whereas a protective effect was found for the combination with X-rays. Conclusions: The combination of cisplatin and 223Ra may have the potential to create a successfully working therapy scheme for various therapy approaches, whereas the combination with 188Re as well as single-dose X-ray treatment did not lead to a detectable radiosensitizing effect. Thus, the combination with alpha-emitters might be advantageous and, therefore, should be followed in future studies when combined with cytostatic drugs. [ABSTRACT FROM AUTHOR]

We study the cluster emission properties of 224 Ra and 238 Pu employing the Barcelona-Catania-Paris-Madrid (BCPM) energy density functional (EDF). Starting from two-dimensional potential energy surfaces, coexisting fission paths are identified. A fission valley located at large octupole deformations, corresponding to a highly-asymmetric mass distribution, is found in both nuclei. As the corresponding fragments are dominated by the presence of 208 Pb, we can relate this fission path to the emergence of cluster emission. Using the octupole moment as collective degree of freedom, we compute the cluster decay half-lives and study the impact of collective inertias, pairing strength and collective zero-point energy. The agreement with experimental data resembles the results obtained for spontaneous fission half-lives, indicating the capability of BCPM to consistently describe a large variety of fission phenomena, including cluster emission. [ABSTRACT FROM AUTHOR]

Radium isotopes, which are sourced from sediments, are useful tools for studying potential climate‐driven changes in the transfer of shelf‐derived elements to the open Arctic Ocean. Here we present observations of radium‐228 and radium‐226 from the Siberian Arctic, focusing on the shelf‐basin boundary north of the Laptev and East Siberian Seas. Water isotopes and nutrients are used to deconvolve the contributions from different water masses in the study region, and modeled currents and water parcel back‐trajectories provide insights on water pathways and residence times. High radium levels and fractions of meteoric water, along with modeled water parcel back‐trajectories, indicate that shelf‐ and river‐influenced water left the East Siberian Shelf around 170°E in 2021; this is likely where the Transpolar Drift was entering the central Arctic. A transect extending from the East Siberian Slope into the basin is used to estimate a radium‐228 flux of 2.67 × 107 atoms m−2 d−1 (possible range of 1.23 × 107–1.04 × 108 atoms m−2 d−1) from slope sediments, which is comparable to slope fluxes in other regions of the world. A box model is used to determine that the flux of radium‐228 from the Laptev and East Siberian Shelves is 9.03 × 107 atoms m−2 d−1 (possible range of 3.87 × 107–1.56 × 108 atoms m−2 d−1), similar to previously estimated fluxes from the Chukchi Shelf. These three shelves contribute a disproportionately high amount of radium to the Arctic, highlighting their importance in regulating the chemistry of Arctic surface waters. Plain Language Summary: Half of the Arctic Ocean is composed of shallow seas that extend over the continental shelf, so understanding what controls the chemical composition of the seawater in these regions is imperative to predicting how the Arctic Ocean as a whole may respond to climate change. Radium isotopes are naturally occurring radioactive elements that are produced in seafloor sediments, and they can be used to study the transfer of elements from the continental shelf into the overlying water. Here we combine measurements of radium isotopes with other chemical tracers and physical oceanographic models to study the transport and chemical signature of the Laptev and East Siberian Seas into the open Arctic Ocean. We find that the transport of elements from shelf sediments into the ocean is particularly strong in these seas and in the neighboring Chukchi Sea. Our data indicates that this region has an impact on the chemistry of the broader Arctic Ocean and emphasizes the need to continue to monitor this area for potential climate‐driven changes. Key Points: In 2021, shelf‐ and river‐influenced waters crossed the shelf‐basin boundary near 170°E, indicating the likely position of the Transpolar Drift originModels suggest a residence time of ∼13 months in the Laptev and East Siberian Seas before surface water enters the central Arctic OceanThe Laptev, East Siberian, and Chukchi Shelves contribute a disproportionately high amount of radium to Arctic surface waters [ABSTRACT FROM AUTHOR]

Natural radioactivity was measured in samples of pumice used in construction and some other human uses in the Kingdom of Saudi Arabia. The natural radioactivity produced by the elements 238U, 226Ra, 232Th and 40K in the selected samples of pumice was determined by high-resolution gamma-ray spectroscopy using the HpGe detector. The results obtained from this study show that the average values of radioactivity concentrations of the elements 238U, 226Ra, 232Th, and 40K for the pumice are 97.45, 79.03, 73.13 and 521.91 Bq/kg. In this study, we verified the existence of correlations between these radionuclides and the lack of a secular balance of the examined pumice samples. The mean absorbed dose rate regions was calculated to be 103.69 nGy/h, From the results, the average effective internal and external dose and its average value is of 0.13 and 0.51 mSv/y. The equivalent activity of the pumice radium samples, The result of the measurements is that the result of the external and internal risk indicators and the equivalent activity value of all the measured pumice stone samples are within the permissible limits of all the samples measured are within the permissible limits. also the concentrations of the radioactive elements of 238U, 226Ra, 232Th and 40Kwhich were evaluated for the all samples under study. The results obtained from this study were studied with the recommended results internationally. In this study, we used some mathematical equation models to estimate the concentration of 222Rn activity in the air with 226Ra activities. The 226Ra activity range was found from 28.4 to 122.6 and mean 79.03 Bq/kg. That is why it is not recommended to use pumice in building walls and to be exposed to it for long periods. Standard deviation was used for all measurement. [ABSTRACT FROM AUTHOR]

The major sources of macronutrients (nitrate, ammonium, phosphate, and silicic acid) in Jakolof Bay, Alaska are submarine groundwater discharge (SGD), rivers, and offshore water. We estimated SGD using natural geochemical tracers (radon and radium), a salt mass balance, and a two-component salinity mixing equation based on the change in groundwater salinity on falling lower low tide. Previous studies have hypothesized that the major macronutrient input into Jakolof Bay is offshore water. This study challenges that assumption by determining the relative contribution of macronutrients from SGD relative to offshore water and rivers. Here, SGD is tidally driven and, as the Northern Gulf of Alaska experiences some of the largest tidal ranges in the world, the SGD fluxes from this region are high relative to the global average regardless of local sediment type. The fluxes ranged from 596 ± 85 cm day−1 at low tide to 97 ± 83 cm day−1 at high tide and are predominantly composed of recirculated seawater (89%) rather than freshwater (11%). The major macronutrients in seawater had different input mechanisms into the semi-enclosed bay. SGD and offshore waters contend as the primary sources of nitrate, which is shown to be the limiting nutrient in this coastal area, while SGD dominates the input of silicic acid. Conversely, the aquifer is found to be a sink for phosphate, indicating that the nutrient is primarily sourced from offshore water. [ABSTRACT FROM AUTHOR]

Co40Fe40B10Dy10 thin films, with thicknesses varying between 10 nm and 50 nm, were grown on a Si(100) substrate. Subsequently, they underwent a 1 h annealing process in an Ar atmosphere at temperatures of 100 °C, 200 °C, and 300 °C. The oxide characteristic peaks of Dy2O3(440), Co2O3(422), and Co2O3(511) were revealed by X-ray diffraction (XRD). The low-frequency alternating current magnetic susceptibility (χac) decreases with frequency. Due to thickness and the anisotropy of the magnetic crystal, the maximum χac and saturation magnetization values rise with thicknesses and annealing temperatures. As the thickness and heat treatment temperature rise, the values for resistivity and sheet resistance tend to fall. The results of atomic force microscopy (AFM) and magnetic force microscopy (MFM) show that average roughness (Ra) lowers as the annealing temperature increases, and the distribution of strip-like magnetic domain becomes more visible. As thickness and annealing temperature increase, there is a corresponding rise in surface energy. Nano-indentation testing shows that hardness initially decreases from 10 nm to 40 nm, followed by an increase at 50 nm. Notably, annealing at 300 °C leads to a significant hardening effect, marking the highest level of hardness observed. Young's modulus increased as thicknesses and annealing temperatures increased. The magnetic, electric, and adhesive characteristics of CoFeBDy films are highly dependent on surface roughness at various annealing temperatures. [ABSTRACT FROM AUTHOR]

Present study concerns the radiological character of Malaysian honey. A total of 18 samples (representative of the various most common types) were obtained from various honey bee farms throughout the country. Using a high-purity germanium γ-ray spectroscopic system, the samples were analysed for the naturally occurring radionuclides 226Ra, 228Ra and 40K. The respective range of activities (in Bq/kg) was: 3.49 ± 0.35 to 4.51 ± 0.39, 0.99 ± 0.37 to 1.74 ± 0.39 and 41.37 ± 3.26 to 105.02 ± 6.91. The estimated associated committed effective doses were derived from prevailing data on national consumption of honey, the annual dose being found low compared with the UNSCEAR reference dose limit of 290 μSv y−1. The estimated threshold consumption rate for honey indicates a maximum intake of 339 g/d, which poses an insignificant radiological risk to public health; however, the total dietary exposure may not, the guidance level of 290 μSv y−1 being applicable to dietary intake of all foodstuffs. The study is in support of the cultivation of a healthy lifestyle, acknowledging prevailing radioactivity within the environment. [ABSTRACT FROM AUTHOR]

Study region: Hulun Lake Basin, Northern China Study focus: Understanding lacustrine groundwater discharge (LGD) is important for elucidating the hydrological cycle and sustainable use of water resources. Hulun Lake is the largest fresh water lake and has prominent ecological function in North China. However, the effect of groundwater discharge on the water balance and spatial distribution of LGD under different aquifers have not yet been evaluated in detail. Herein, radium (223Ra, 224Ra, and 228Ra) and stable isotopes (δD, δ18O) were used to identify the LGD locations and quantify the spatial LGD flux into the lake. New hydrological insights for the region: The Ra isotope activities in groundwater from the fissured bedrock in the western part of the Lake are depleted relative to those from the east, underlain by the Quaternary unconsolidated sediments aquifer overlying granitic rocks. The spatial distribution of LGD under heterogeneous aquifers was revealed and groundwater discharge from fractured bedrock aquifer is the predominant source of the lake. The LGD flux is estimated to range from (1.07 ± 1.36)× 107 to (6.54 ± 1.89)× 107 m3/d, which exceeds that in the Quaternary aquifer by one order of magnitude due to the high permeability enlarged via tectonic faults and fractures. These findings promote scientific understanding of water balance in Hulun Lake and are instructional for LGD studies of freshwater lakes with complex water systems in cold and arid regions.

Mineral springs in Massif Central, France can be characterized by higher levels of natural radioactivity in comparison to the background. The biota in these waters is constantly under radiation exposure mainly from the α-emitters of the natural decay chains, with 226Ra in sediments ranging from 21 Bq/g to 43 Bq/g and 222Rn activity concentrations in water up to 4600 Bq/L. This study couples for the first time micro- and nanodosimetric approaches to radioecology by combining GATE and Geant4-DNA to assess the dose rates and DNA damages to microorganisms living in these naturally radioactive ecosystems. It focuses on unicellular eukaryotic microalgae (diatoms) which display an exceptional abundance of teratological forms in the most radioactive mineral springs in Auvergne. Using spherical geometries for the microorganisms and based on γ-spectrometric analyses, we evaluate the impact of the external exposure to 1000 Bq/L 222Rn dissolved in the water and 30 Bq/g 226Ra in the sediments. Our results show that the external dose rates for diatoms are significant (9.7 μGy/h) and comparable to the threshold (10 μGy/h) for the protection of the ecosystems suggested by the literature. In a first attempt of simulating the radiation induced DNA damage on this species, the rate of DNA Double Strand Breaks per day is estimated to 1.11E-04. Our study confirms the significant mutational pressure from natural radioactivity to which microbial biodiversity has been exposed since Earth origin in hydrothermal springs. [ABSTRACT FROM AUTHOR]

The improved scission-point statistical model based on the dinuclear system approach is employed to describe spontaneous fission, electromagnetic-, neutron-, charged-particle- and heavy-ion-induced fission of even–even pre-actinides, actinides and superheavy nuclei and to analyze the correlations between various observables. The key element of the model is the calculation of potential energy surfaces. The evolution of fission observables with increasing excitation energy is shown to be related with the widening and migration of the minima in the potential energy surface. Conservation of asymmetric shapes of mass and charge distributions of the fission fragments at high enough excitation energies of fissioning nuclei Hg, Pb, Rn, Ra, Th, U, Cf, Fm and No is predicted. At some critical excitation energy, the saturation of the symmetric component of charge and mass yields is demonstrated. For fissioning 1 8 0 , 1 8 2 , 1 9 0 , 1 9 8 Hg, 2 5 0 – 2 5 8 Fm and 2 5 0 – 2 5 8 No, transitions from two-peaked to single-peaked mass distributions are predicted. The origin of the transition between asymmetric and symmetric fission modes with variations of neutron number and excitation energy is explored. For 1 8 2 Hg(i.f.), 1 9 8 Hg(i.f.), 2 5 4 Fm(i.f.), 2 5 7 Fm( n th , f) and 2 6 0 Fm(s.f.), the unexpected difference (symmetric or asymmetric) between the shapes of charge and mass distributions is predicted for the first time. The dependence of the neutron excess ratio of fission fragments on the fragment charge number is studied. A method is suggested for experimental verification of the multi-chance fission assumption. A possible explanation of the anomaly in charge yield of Mo/Sn fragments in the fission reaction 2 3 8 U(n , f) at low excitation energies found by γ – γ coincidence spectroscopy is presented. [ABSTRACT FROM AUTHOR]

The anomaly of the residual proton–neutron interaction δ V pn for Ra isotopes around N = 1 3 5 deviating from the general trend, the so-called Ra puzzle, is investigated within the framework of covariant density functional theory in three-dimensional lattice space. The potential energy surfaces in (β 2 0 , β 3 0) plane for Ra isotopes are given by the constrained calculations. The average values of proton–neutron interaction δ V pn extracted from the binding energies of Ra and Rn isotopes with axial, triaxial and reflection asymmetric calculations are compared with the data from AME2020 atomic mass evaluation. It is found that the octupole deformation provides a reasonable interpretation of the Ra puzzle. [ABSTRACT FROM AUTHOR]

The main aim of this work was to develop a suitable sorbent for the separation and determination of 226Ra through 133Ba (radio tracer) in water samples using fly ash sorbent. After the modification with KMnO4 the effects of pH, competing ions, the possibility of elution, and the effect of water volume were tested. As a suitable eluent 6 mol/L HCl was chosen, while the sorbent worked best at pH 6–8. The developed method is advantageous for minimizing the time required for separation, the volume of chemicals used, and the waste generated after separation. [ABSTRACT FROM AUTHOR]

Twenty surface sediment samples were gathered from Chasma Lake, deciding the radionuclides 137Cs, 226Ra, 228Ra, 232Th, and 40K and their associated hazard indices. The deliberate radionuclide activities of present research have been contrasted with earlier research, and acquired outcomes in the present study are found below the results in the world. The radiation hazard indices following the presence of natural radionuclides in sediment samples were estimated, and the results assigned the values of all the determined radiological indices found inside the worldwide suggested limits. It was concluded from the current review that the sediment of Chashma Lake is safe for construction and agriculture and does not make radiation dangerous to the nearby local area of the lake. [ABSTRACT FROM AUTHOR]

Consumption of fish containing elevated levels of radionuclides can lead to undesirable health effects for consumers. People in the Singida Municipality harvest fish from lakes and ponds of granite rocks which are linked with hazardous radioisotopes that may be bio-concentrated by fishes they consume. Currently, no study has ascertained the levels of radioisotopes in fish from these environments. This study was carried out to analyse the radioactivity levels of 226Ra, 228Ra and 40K isotopes in order to assess the radiological risk associated with Tilapia fish consumption and its environment in Singida Municipality. Some 51 samples, which included water (20), sediment (20), Nile tilapia (8) and Manyara tilapia (3), were randomly sampled and composited; then, they were analysed using a high-purity germanium (HPGe) detector, between May and June 2022. The results revealed that (i) the activity levels of 228Ra were below the detection limit for fish and water samples, while in sediment, the combined activity of 228Ra was within the acceptable international levels; (ii) the mean activity concentrations of 226Ra and 40K in all other samples were within the recommended levels; (iii) the activities of radionuclides in the samples analysed were high in sediments, followed by fish, and lastly water; (iv) the bioaccumulation results show that only 40K was bio-accumulated (with 1.26 in Nile tilapia), while other radionuclides (226Ra, 228Ra) were not bio-accumulated; (vi) the radionuclide transfer from water to fish was higher compared to the radionuclide transfer from sediment to fish; (vii) the human effective doses due to consumption of Nile tilapia and Manyara tilapia were 0.00973 and 0.005 mSv/y, respectively, which is below the 1 mSv/y international limit. These findings therefore show that the current levels of radioactivity in fish in the study area do not pose a significant radiological risk to fish consumers. However, more studies on other types of fish are recommended. [ABSTRACT FROM AUTHOR]

A simple collective model for description of the effect of the alpha-cluster degree of freedom in the structure of heavy and superheavy nuclei is suggested. The alpha-chains of nuclei based on some of the Pb isotopes are considered. It is shown based on the experimental data on nuclear binding energies that the effect of the strong coupling of the alpha-mode and the octupole correlations in Rn, Ra, Th and U isotopes is manifested. The excited states associated with the alpha-cluster degree of freedom are considered and their excitation energies are estimated as being larger than 1.7 MeV. This corresponds to α -decay probability from the ground state to these states 4–7 orders of magnitude less than α -decay between the ground states. Although, their structure is determined by the same dynamical variable as the structure of the ground states. [ABSTRACT FROM AUTHOR]

Radium-226 detection in sediment samples is generally executed by means of gamma-ray spectrometry. Data evaluation relies (besides the 186.2 keV 226Ra gamma peak) on the combined analysis of major gamma peaks that are produced by the short-lived radon (222Rn) daughters 214Pb and 214Bi. Precondition for this detection approach is equilibrium decay of all members of the decay chain between 226Ra and 214Bi. In closed systems, this equilibrium is reached after about five half-lives of 222Rn (19 days). However, a closed system can only be guaranteed if the capsule which contains the sample prevents diffusive escape of radon. Such radon-tightness cannot be guaranteed for a wide range of plastic materials. Due to its polymer structure, plastic material generally tends to allow radon diffusion and hence radon loss from the sample resulting in a disturbance of the required decay equilibrium. The paper introduces an approach that allows quantifying radon loss from sample capsules by direct radon measurements using mobile radon detection equipment. The experimental findings are supported by theoretical considerations. An examined alternative approach based on the offset of the 186.2 keV data point from an efficiency function that is calculated exclusively from short-lived radon progeny peaks in the gamma-ray spectrum did not prove to be applicable due to a lack of supporting peaks in the low-energy section of the spectrum. [ABSTRACT FROM AUTHOR]

In the open ocean, radium isotopes are useful tracers of residence time and water-mass mixing. However, limited by the measurement resolution of commonly used gamma counters, the low activity of radium in the open ocean makes it necessary to enrich radium from large volumes of seawater and pretreat radium-enriched carriers prior to measurements. The commonly applied method of radium enrichment and pretreatment, however, has limitations of uneven coating of MnO2 on cartridges, relatively expensive cartridges, time-consuming issues during cartridge-ashing, ash loss during transfer, and changes of gamma counters efficiency caused by different ash weights. To address these issues, in this study we optimized the enrichment and pretreatment of low-activity radium prior to measurements. Firstly, we replaced commonly used acrylic cartridges with cheaper polypropylene cartridges, which took 6 h to be ashed, 42 h shorter than for acrylic cartridges. Secondly, MnO2-coated cartridges were prepared with a circulating hot acidic KMnO4 solution to ensure homogeneous coating. The radium extraction efficiency of this MnO2-coated cartridge was 20%–61% higher than that prepared by directly immersing cartridges in the solution. The radium delayed coincidence counter efficiency for MnO2-coated cartridge was stable with a moisture content of 0.05–1. Lastly, after ashing cartridges, instead of directly transferring the ash to a measurement vial, a mixture of hydroxylamine hydrochloride and hydrochloric acid was used to completely leach the ash for long-lived radium, followed by coprecipitation by BaSO4, to avoid potential loss of ash during transfer and variations in measurement geometry due to different ash weights. And the recovery of long-lived radium pretreatment was 94%–102%, which improved by 11% compared with the common method. In addition, the radium extraction efficiency of the MnO2-coated cartridge varied from 3% to 4% within the in situ pump working flow rate of 4–7 L/min, which fell within the measurement errors. [ABSTRACT FROM AUTHOR]

As an important land-ocean interaction process, submarine groundwater discharge (SGD) is composed of multiple dynamical processes at different scales and plays an important role in the study of coastal ocean geochemical budgets. However, most of the existing studies focus on the quantification of the total groundwater discharge, few studies are about the differentiation and quantification of groundwater discharge processes at different scales (i.e., short-scale SGD and long-scale SGD). As a world-class river, the Huanghe River is highly turbid and heavily regulated by humans. These natural and anthropogenic factors have a significant impact on groundwater discharge processes in the Huanghe River Estuary (HRE). In this study, the distribution patterns of the natural geochemical tracer radium isotopes (224Ra and 223Ra) and other hydrological parameters in the HRE were investigated during four cruises. By solving the mass balance of 224Ra and 223Ra in the HRE, the long-scale SGD flux was quantified as 0.01–0.19 m/d, and the short-scale SGD flux was 0.03–0.04 m/d. The rate of short-scale SGD remained essentially constant among seasons, while the rate of long-scale SGD varied considerably at different periods and showed a synchronous trend with the variation of river discharge. The results of this study are significant for understanding the SGD dynamics in the HRE and the contribution of SGD to the ocean geochemical budgets. [ABSTRACT FROM AUTHOR]

Submarine groundwater discharge (SGD), which can be traced using naturally occurring radium isotopes, has been recognized as a significant nutrient source and land-ocean interaction passage for the coastal waters of the Daya Bay, China. However, uncertainties in assessing SGD fluxes must still be discussed in detail. In this study, we attempted to utilize the Monte Carlo method to evaluate the uncertainties of radium-derived SGD flux in the northeast and entirety of the Daya Bay. The results show that the uncertainties of the SGD estimate in the northeast bay are very sensitive to variations in excess radium inventories as well as radium inputs from bottom sediments, while the uncertainties of the SGD estimate for the entire bay are strongly affected by fluctuations in radium inputs from bottom sediments and radium end-members of SGD. This study will help to distinguish the key factors controlling the accuracy of SGD estimates in similar coastal waters. [ABSTRACT FROM AUTHOR]

A concise, efficient continuous-wave eye-safe Nd:GdVO4/KGW Raman laser at 1525 nm is here demonstrated. A Nd:GdVO4 crystal was used to produce the fundamental field at 1341 nm and a KGW crystal generated the intracavity Stokes field at 1525 nm via wavelength conversion of stimulated Raman scattering. The output power of the Stokes field at 1525 nm could achieve 2.1 W under the pump power of 30 W. Furthermore, two different lithium triborate (LBO) crystals with critical phase matching were exploited to obtain deep-red emission at 714 nm via the intracavity sum frequency generation of 1341 and 1525 nm waves. One cutting angle was in the XY plane and the other was in the XZ plane. The empirical thermo-optical coefficients for the LBO crystal were exploited to systematically analyze the critical phase matching conditions. Numerical results revealed that the type-I phase matching angle in the XY plane was near θ = 90° and ϕ = 3.3° at room temperature, whereas the type-I phase matching angle in the XZ plane was near θ = 86.3° and ϕ = 0° at a temperature around 47 °C. The numerical values for the optimal temperatures for the two different cutting angles were found to be in good agreement with experimental results. At the pump power of 30 W, the output power at 714 nm was approximately 2.9 W by using the LBO crystal with the cutting angle in the XY plane. On the other hand, the maximum output power at 714 nm could be up to 3.2 W under the pump power of 30 W by using the cutting angle in the XZ plane. Furthermore, the linewidth of the SFG emission was confirmed to be nearly the same for the two different cutting angles. The overall linewidth could be narrower than 0.2 nm. The developed laser at 714 nm can be useful in the exploration of ionic and atomic radium isotopes with laser spectroscopy. [ABSTRACT FROM AUTHOR]

The availability of metallic radioelements, with only short-lived isotopes, at trace quantities, does not allow simple, straightforward evaluation of their chemical properties, although they represent societal issues of primary importance (environmental contamination, uses in nuclear medicine, etc.). A strategy is presented to establish a cost-effective computational methodology that is radiometal-specific and accurate to supplement the limited experimental data with a focus on complexation properties. With radium as application, the most suitable DFT methods have been selected by comparison with structures and interaction energies determined by state-of-the-art calculations. Scarce Ra2+ complexation constants are available, but combined through isodesmic-like reactions (e.g. transmetallation), they allow for error cancellation mechanisms. Then, a radiometal-specific cavity is fitted in an implicit solvent model to reproduce solvation effects. The equilibrium constants can finally be calculated accurately, i.e. with a precision of 1 logarithmic unit, provided that the relativistic spin–orbit interaction is taken into account. The relevance of this methodology is illustrated with macropa, an 18-membered macrocyclic ligand recently considered for developing 223Ra radiotherapeutics, highlighting that the design of an innovative chelator by assuming transferability of neighboring element chemistry can only be suboptimal. [ABSTRACT FROM AUTHOR]

This article describes several extraction chromatographic materials aiming to offer improved potential for isolating trace elements with high charge/ionic radius ratio from accompanying matrix elements in natural samples. Starting with commercially available, field-proven, TRU- and RE-Spec materials (Eichrom Technologies), three resins containing less TBP in the CMPO-TBP mixtures, or even neat CMPO only, have been prepared and characterized through measurement of the distribution ratios of some fifty elements in HNO3 and HCl media of variable strength. These resins were further evaluated for analytical applications on geochemical samples. The results highlight a strong enhancement of weight distribution ratios of many elements of interest in geochemistry, cosmochemistry, and environmental sciences (Lanthanides, naturally occurring Actinides, High Field Strength Elements). Combined with good chromatographic characteristics, these high Dw's make it possible to achieve excellent group separations by using very small columns operated at relatively high, gravity-driven flow rate. Moreover, in an attempt to further improve the selectivity against Fe(III) and Ti(IV), preliminary investigations were made on an additional pair of resin prototypes impregnated with a CMPO-substituted calixarene. Although promising distribution ratio data were obtained, these prototypes did not permit to prepare columns with satisfactory chromatographic characteristics, and this approach still waits for a better impregnation methodof the porous inert support. [ABSTRACT FROM AUTHOR]

Dissolved (<0.2 μm) trace metals (dTMs) including iron (Fe), manganese (Mn), and cobalt (Co) are micronutrients that (co-) limit phytoplankton growth in many ocean regions. Here, we present the spatial and seasonal distributions of dFe, dMn, and dCo on the Northeast Atlantic continental margin (Celtic Sea), along a transect across the shelf and two off-shelf transects along a canyon and a spur. Waters on the continental shelf showed much higher dTM concentrations (dFe 0.07–6.50 nmol L−1, average 1.41 ± 0.96 nmol L−1, n = 138; dMn 0.868–14.8 nmol L−1, 2.75 ± 2.37 nmol L−1, n = 148; dCo 54.8–217 pmol L−1, 109 ± 32 pmol L−1, n = 144) than on the slope (dFe 0.03–1.90 nmol L−1, 0.65 ± 0.43 nmol L−1, n = 454; dMn 0.223–1.14 nmol L−1, 0.58 ± 0.20 nmol L−1, n = 458; dCo 27.3–122 pmol L−1, 71.7 ± 11.7 pmol L−1, n = 441), attributed to strong dTM contributions from a low-salinity endmember, i.e., riverine discharge. Benthic sedimentary input via reductive dissolution (especially for dFe and dMn), delineated by short-lived radium (Ra) isotopic activities (223Ra xs and 224Ra xs), was only prominent at a station (Site A) characterized by fine sediments. On the continental slope, dMn levels at depth were mainly determined by the formation of insoluble Mn oxides and the intrusion of Mediterranean Outflow Waters. In contrast, dFe and dCo concentrations at depth were balanced by the regeneration from remineralization of sinking organic particles and scavenging removal. In addition, bottom and intermediate nepheloid layers along the slope illustrated both elevated dTM concentrations and Ra isotopic activities. The presence of nepheloid layers is especially significant along the canyon transect relative to the spur transect, demonstrating the importance of slope topography on the off-shelf transport of dTMs into the Northeast Atlantic Ocean. As a seasonal stratified shelf sea, dTMs and nutrients showed synchronized seasonal variations on the shelf, indicating the influence of biological processes in addition to source effects. Surface dFe and dCo were depleted in summer due to enhanced biological uptake, while sub-surface dFe and dCo were elevated in summer and autumn ascribed to the remineralization of sinking organic particles. In contrast, surface dMn levels were predominantly controlled by the seasonal variations in photoreduction, while sub-surface dMn concentrations were relatively constant throughout the year. The combined effects of fluvial and benthic sources, topographical controls, and biological processes shape the seasonal variations of dTM distributions. Such seasonal variations in dTMs and biological activities can affect the biological carbon pump on the Northeast Atlantic continental margin, and may further influence the carbon cycle in the Atlantic Ocean via the dynamic dTM exchange between continental margins and the open ocean. [ABSTRACT FROM AUTHOR]

Τhe determination of uranium in calcareous samples has been investigated by means of alpha-spectroscopy after dissolution of the samples by nitrilotriacetic solution (NTA) and uranium separation by cation-exchange. Method recovery, uranium analysis and isotopic ratio composition of the samples was performed using a standard tracer solution (U-232). Comparison of the data with corresponding data obtained from experiments after EDTA-dissolution indicated lower selectivity for uranium, but higher recovery yields for phosphate rock samples. Moreover, using NTA results in the co-extraction of radium and thorium isotopes which are present in the samples, assuming broader applicability of the present method. [ABSTRACT FROM AUTHOR]

The interaction of surface water and groundwater is important in the ecology of coastal basins, affecting hydrological conditions, oxygen regime, carbon, and nutrient exchange. This study demonstrates a dynamic connection between the salt-wedge region and its underlying aquifer in the eutrophic estuary. In winter, this estuary is covered with ice, and the river flow is at its lowest; that is why the specific response to groundwater discharge is best marked in this season. Groundwater admixture was detected in the salt-wedge region by highly active radium isotopes: 223Ra—4.80 ± 0.42 dpm 100 L−1, 224Ra—55.37 ± 1.1 dpm 100 L−1, and 228Ra—189.71 ± 4.66 dpm 100 L−1. The temperature of groundwater and river water was about +4 °C and 0 °C, respectively; that of seawater was −1.6 °C, and temperature increased up to +2.3 °C in the surface water–groundwater interaction region. Groundwater admixture is accompanied by a lower level of oxygen concentration of 52 μmol/kg; at that time, the maximum oxygen concentration in the salt-wedge region was 567 μmol/kg. In waters with a high activity of radium isotopes, there was a maximum partial pressure of CO2—4454 μatm at the range 100–150 μatm in the salt-wedge region and also observed extremum of NH 4 + , NO 2 − , and dissolved phosphorus. The surface water–groundwater interaction through anoxic sediment can form localized anaerobic areas despite the general oxygen supersaturation of eutrophic estuary waters and also cause local recycling of nutrients from bottom sediments. [ABSTRACT FROM AUTHOR]

The correlation between concentrations of dissolved barium (dBa) and silicon (dSi) in the modern ocean supports the use of Ba as a paleoceanographic proxy. However, the mechanisms behind their linkage and the exact processes controlling oceanic Ba cycling remain enigmatic. To discern the extent to which this association arises from biogeochemical processes versus physical mixing, we examine the behavior of Ba and Si at the Congo River‐dominated Southeast Atlantic margin where active biological processes and large boundary inputs override the large‐scale ocean circulation. Here we present the first combined measurements of dissolved stable Ba (δ138Ba) and Si (δ30Si) isotopes as well as Ba and Si fluxes estimated based on 228Ra from the Congo River mouth to the northern Angola Basin. In the surface waters, river‐borne particle desorption or dissolution and shelf inputs lead to non‐conservative additions of both dBa and dSi to the Congo‐shelf‐zone, with the Ba flux increasing more strongly than that of Si across the shelf. In the epipelagic and mesopelagic layers, Ba and Si are decoupled likely due to different depths of in situ barite precipitation and biogenic silica production. In the deep waters of the northern Angola Basin, we observe large enrichment of dBa, likely originating from high benthic inputs from the Congo deep‐sea fan sediments. Our results reveal different mechanisms controlling the biogeochemical cycling of Ba and Si and highlight a strong margin influence on marine Ba cycling. Their close association across the global ocean must therefore mainly be a consequence of the large‐scale ocean circulation. Plain Language Summary: Across the oceans from surface waters to the deep, dissolved barium (Ba) and silicon (Si) concentrations are strongly correlated. However, we still do not fully understand the mechanisms behind this pattern. Rivers and continental shelves are the major sources of both Ba and Si to seawater and here we study the release and cycling of Ba and Si at the Congo River‐dominated central west African margin. By measuring the stable isotopes of both Ba and Si in the same seawater samples, and estimating the elemental fluxes of Ba and Si along the Congo River plume based on radioactive radium isotopes, we find differing behavior of Ba and Si in the surface Congo plume and the subsurface and deep waters of the adjacent northern Angola Basin. These different behaviors result from contrasting carriers of Ba and Si to the coastal ocean, as well as fundamentally different biological and chemical processes controlling the cycling of Ba and Si in the coastal water and sediments. The close association of dissolved Si and Ba across the global ocean must therefore mainly result from the large‐scale ocean circulation. Key Points: Stronger enrichment of dissolved barium (dBa) than silicon (dSi) observed in the shelf‐zone of the Congo plumeDiatom silica production has negligible effect on dissolved Ba isotopic compositions in large river plumesStrong dBa enrichment (up to 24 nM) in the deep water of the northern Angola Basin likely originates from high benthic inputs [ABSTRACT FROM AUTHOR]