Radon-222, a radioactive noble gas with a half-life of 3.8 days produced by radium-226, is a health hazard in caves, but also a powerful tracer of atmospheric dynamics. Here we show how airborne radon-222 can be analysed in a cave with multiple openings, the Pech Merle Cave in South-West France. This two-level cave hosts prehistoric remains and Gravettian paintings in its lower level. Radon concentration, monitored at 15 points with one-hour sampling intervals for more than one year, including two points for more than three years, showed mean values from 1274 ± 11 to 5281 ± 20 Bq m-3, with transient values above 15,000 Bq m-3. Seasonal variations were observed, with a weak normal cycle (low in winter) at two points in the upper level and a pronounced inverse seasonal cycle (low in summer) at the other points in the cave. The radon-222 source (effective radium-226 concentration, ECRa) was measured in the laboratory for floor deposits, soil and rock samples. While ECRa values obtained for rocks and speleothems are smaller than 1 Bq kg-1, most ECRa values for soils are larger than 10 Bq kg-1. Quantitative modelling confirms that the floor fillings inside the cave are responsible for the stationary lower concentrations, while the higher concentrations observed in winter are explained by percolation of outside air, which collects radon-222 as it passes through the soil layers. In addition, Stored Available Radon (SAR) is sufficient to account for transient variations. While air currents occur when visitors enter the cave or when the cave is deliberately ventilated, the climatic processes revealed by their radon-222 signatures appear to be essentially natural. These processes, enhanced by global climate change, could cause or accelerate the deterioration of prehistoric paintings. Radon-222 source analysis using ECRa-based modelling and SAR appears essential for the preservation of underground heritage.

Consumption of local and imported bottled water in Canada has greatly increased during the past three decades. While the presence of natural radioactivity is often overlooked when dealing with the water quality of these bottled products, it could contribute substantially to the uptake of radionuclides especially when sourced from regions with higher radioactivity levels compared to where it is consumed. In this study, the activity of several naturally occurring radionuclides (i.e., 210Po, 226,228Ra, 230,232Th, 234,235,238U) were measured in bottled water available in Québec, Canada after sample pretreatment and analysis by either radiometric or mass spectrometry approaches. 230,232Th and 228Ra concentrations were below minimum detectable activity levels in all samples tested. Analytical results for 234U, 235U, 238U, and 226Ra showed concentrations that ranged from 0.38 to 115 mBq/L, (2.2-313) x 10-2 mBq/L, 0.48-58.4 mBq/L, and 1.1-550 mBq/L, respectively. 210Po was detected in only 5 samples and its activity ranged from 2 to 26 mBq/L. To determine variability in activity within brands, the same brands of bottled water were purchased during two consecutive years and analyzed. The possible radiological impact of the consumption of these types of water was assessed based on different drinking habit scenarios. Some of the imported water brands showed higher activity concentrations than local sources or tap water, suggesting that individuals drinking predominantly imported bottled water would receive a higher radiation dose than those who drink mainly local water.

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.

Sorites marginalis as one of the benthic foraminifer\'s genera were collected from three coastal lagoons (Abu Shaar, Umm al-Huwaytāt, and Marsa Shūni) on the Egyptian Red Sea coast and investigated for their 226Ra, 232Th, and 40K content using HPGe gamma-ray spectrometry. S. marginalis shells show high radioactivity levels with average activity concentration values of 251.8 ± 18.3, 86.8 ± 7.7, and 791.2 ± 57.6 Bq kg-1, 327.1 ± 11.4, 97.4 ± 7.1, and 751.6 ± 54.7 Bq kg-1, 246.6 ± 17.7, 65.1 ± 4.8, and 477.6 ± 34.8 Bq kg-1 for 226Ra, 232Th, and 40K in the samples from Abu Shaar, Umm al-Huwaytāt, and Marsa Shūni, respectively. 226Ra and 40K have a high tendency to accumulate in S. marginalis compared to 232Th. High bioaccumulation of the studied radionuclides was found for samples from Umm al-Huwaytāt and Abu Shaar lagoons. Radiological parameters such as radium equivalent activity, gamma absorbed dose rate in air, and outdoor annual effective dose were calculated, and values higher than the permissible limits were obtained. Based on the obtained results, the estimation of radioactivity levels in S. marginalis shells may serve as an indicator of marine environment pollution.

Assessing the recovery of aquatic ecosystems from metal and radionuclide contamination requires knowledge of the concentration of radionuclides and metals before anthropogenic releases. Pre-operational conditions, or baseline, are often unknown for many mining operations initiated decades ago. The objectives of this study were to quantify baseline levels of metals and radionuclides and describe historical releases of an industrialised watershed in Northern Ontario where mining operations were carried out from 1955 to 1996. For this purpose, water and surface sediment samples were collected from this watershed and in an adjacent non-industrialised watershed every 2 km. Using metal and radionuclide concentrations in the non-impacted watershed, we calculated water and sediment baseline concentrations as upper 95th percentile values. Baseline pH, 226Ra and uranium in water of lakes and rivers were similar at pH of 6.8, 10 mBq·l-1, and 2.5 μg·l-1, respectively. For sediments, baseline lake sediment exhibited concentrations of radionuclides that were higher than river sediments. We calculated baseline concentrations in lake sediment at 2,115 Bq·kg-1 210Pb, 535 Bq·kg-1 210Po, 218 Bq·kg-1 226Ra, 235 Bq· kg-1 228Th, 184 Bq·kg-1 230Th, and 223 Bq·kg-1 232Th. Baseline concentrations of metal levels in lakes were at 98 mg kg-1 Ni, 119 mg kg-1 Cu, 2300 mg kg-1 Zn, 112 mg kg-1 Pb and 19 mg kg-1 U. In Lake Huron, we collected two sediment core profiles along with surface sediment to estimate baseline radionuclide activities and metal concentrations and quantify historical releases from the industrialised watershed. The sediment core profiles reflected baseline conditions prior to releases from the uranium mining operation and contamination from its onset in 1955 to its closure in 1996. Concentration of metals in pre-industrial sediment layers were lower than in surface sediment of Lake Huron, suggesting atmospheric depositions. Our study indicates that collecting surface sediment in this non-impacted watershed may yield baseline concentrations for uranium and radionuclides. For metal, collecting surface sediment may yield ambient metal concentrations because of long-range atmospheric transport from remote sources. By comparison, sedimentary profiles can provide baseline concentrations of both metals and radionuclides. In the case of the Serpent River watershed, we report that water quality has recovered downstream of Quirke Lake as of 1993 and that additional sediment cores would better assess sediment recovery.

We demonstrate cyclotron production of high-quality 225Ac using an electroplated 226Ra target.
226Ra was extracted from legacy Ra sources using a chelating resin. Subsequent ion-exchange purification gave pure 226Ra with a certain amount of carrier Ba. The radium target was prepared by electroplating. We successfully deposited about 37 MBq of 226Ra on a target box. Maximum activation was achieved using 15.6 MeV protons on the target at 20 µA for 5 h. Two functional resins with various concentrations of nitric acid purified 225Ac and recovered 226Ra. Cooling the intermediate 225Ac for 2-3 weeks decayed the major byproduct of 226Ac and increased the radionuclidic purity of 225Ac. Repeating the same separation protocol provided high-quality 225Ac.
We obtained 225Ac at a yield of about 2.4 MBq at the end of bombardment (EOB), and the subsequent initial purification gave 1.7 MBq of 225Ac with 226Ac/225Ac ratio of < 3% at 4 days from EOB. Additional cooling time coupled with the separation procedure (secondary purification) effectively increased the 225Ac (4n + 1 series) radionuclidic purity up to 99 + %. The recovered 225Ac had a similar identification to commercially available 225Ac originating from a 229Th/225Ac generator.
This procedure, which involves the 226Ra(p,2n)225Ac reaction and the appropriate purification, has the potential to be a major alternative pathway for 225Ac production because it can be performed in any facility with a compact cyclotron to address the increasing demand for 225Ac.

Carbon and nitrogen stable isotope compositions (δ13C and δ15N) of organic matter (OM) and total organic carbon to total nitrogen ratio (Corg/TN) in a sediment core collected in Sagua estuary (Cuba), were investigated to elucidate the origin of the Sedimentary OM (SOM) and changes in its main sources, over the last 100 years. Results showed almost constant values in the elemental and isotope composition of SOM from 1908 to 1970 with an abrupt change after 1970. From 1970 to 2005, δ13C increased from -21.2 up to -19.3 ‰, while δ15N declined from 1.5 to values close to 0 ‰. The output of the mass-balance model for the identification of OM sources indicated that δ13C and Corg/TN values are generally influenced by marine Particulate OM (POM) sources. Between 1900 and 1970, the main OM source in sediments was marine POM (>85 %), with freshwater POM contributing ca. 15%. Since 1970, the establishment of the Alacranes Dam determined drastic environmental changes influencing the OM sources in the area. Mixing models pointed to seagrasses (79 %) as the main contributors to SOM in the first period, while since 1973 onward, the contribution of human-derived sources such as fertilizers and urban discharges became greater. This information can provide baseline data for the environmental management of the Sagua watershed.

This article describes a novel and simple method to measure ultra-trace 226Ra in river water samples at fg L-1 (mBq L-1) levels as a means for surveying 226Ra in an unintended contamination in river water. To simplify the procedure, a single column was used for separation and purification; 10 mL of AG 50W-X8 resin was packed into a 10 mL Eppendorf pipette tip, which was used as a separation column. A 500 mL sample solution was loaded, and interfering elements were removed with 80 mL 4 M HCl in 20% ethanol. Subsequently, Ra together with Ba was eluted by 20 mL 5 M HNO3 prior to SF-ICP-MS analysis; this allows the naturally existing Ba in water samples to be employed as a yield tracer for 226Ra analysis. Using the medium mode of SF-ICP-MS, the instrumental detection limit of 380 fg L-1 (10 mBq L-1) was obtained. An extremely low method detection limit of 0.46 fg L-1 (0.02 mBq L-1) was achieved with 500-fold pre-concentration. Finally, the developed technique was applied to analyze natural water samples collected from Japanese rivers, in which the 226Ra concentrations varied in the range of 0.7-49.6 fg L-1 (0.03-1.82 mBq L-1).

Concentrations of naturally occurring radioactive material (NORM) in Marcellus Shale produced water presents a challenge for effective management and treatment, because of the vast fluid volumes generated. With an increased emphasis on beneficial reuse and resource recovery from the produced waters, a rapid, yet reliable, method for quantifying radium in these produced waters is needed. The high total dissolved solids (TDS) concentration introduces difficulties when measuring 226Ra by recommended EPA methods that were specifically developed several decades ago for drinking water. While other techniques for measuring radium in these high-TDS fluids have since been developed, these newer techniques often require extensive and complicated pre-concentration steps; and they thus require extensive analytical chemistry skills, utilize hazardous chemicals like hydrofluoric acid, demand long holding times or measurement times, and require high sample volumes. We present a rapid method for 226Ra measurements in high-TDS produced waters by liquid scintillation counting, which has been corroborated herein by concurrent gamma spectrometry analyses. Samples were prepared for analysis by evaporating the fluid and re-suspending the evaporate with acidified distilled deionized water prior to liquid scintillation counting for 1 h. This protocol yielded radium recoveries ≥93%. Per this protocol, the alpha and beta spectra of 226Ra and its daughters were computationally separated by alpha-beta discrimination and spectrum deconvolution. The minimum detectable activities of 226Ra was 0.33 Bq/L (9.0 pCi/L) when the counting time was 60 min and the sample volume was 4 mL. Nine produced waters of varying TDS and radium concentrations from the Marcellus Shale Formation were analyzed by this method and compared with gamma spectroscopy; and these yielded comparable results with an R2 of 0.92. The reduced sample preparation steps, low cost, and rapid analysis position this as a well-suited protocol for field-appraisal and screening, when compared to comprehensive radiochemical analysis. We offer that for a given produced water region, routine and local liquid scintillation analyses can be compared and calibrated with infrequent gamma spec analyses, so as to yield a near-real time protocol for monitoring 226Ra levels during hydrofracturing operations. We present this as a pragmatic and efficient protocol for monitoring 226Ra when produced water samples host low levels of 228Ra-since the progeny of 228Ra can significantly confound the LSC analyses.

Beneficial reuse and resource recovery of produced water often require treatment to remove radium before valuable products are extracted. The radium content of the treatment waste solids and beneficial products must be accurately determined when evaluating the efficacy and social validity of such treatments. While gamma spectroscopy remains the recommended method for radium measurements, these measurements can be impacted by the composition/mineralogy of the solids, which influence the attenuation of the gamma decay energy - with denser sediments incurring greater degrees of attenuation. This self-attenuation must be accounted for when accurately measuring radium, otherwise radium measurements are found to be inaccurate, sometimes by as much as 50%. To meet industry needs, measurements should be both accurate and rapid, even for small sample sizes. Consequently, we propose a rapid method for accurate radium measurements with an empirical technique to account for sample attenuation in well-detector gamma spectroscopy. This technique utilizes the sample density and sample volume in the measuring vial. These corrections are relevant to a wide range of solid samples and sediment densities that may be encountered during treatment and management of oil and gas solids, including clays, environmental sediment samples, sand grains, and precipitated salts. These corrections can also be applied for situations were low volumes of material are present, as in bench scale studies, thereby rendering this technique applicable to a wider range of scenarios.