No full-text available
To read the full-text of this research,
you can request a copy directly from the author.
Abstract
A method is presented for the determination of polonium-210 at very low levels in the presence of many different ions. Essentially quantitative recoveries were obtained in 60 min by deposition on to a silver plate in a special holder from 50 ml solution at 85–90° with sodium citrate present.RésuméOn propose une méthode pour le dosage du polonium-210, en trés faibles teneurs, en présence de nombreux ions étrangers. Des rendements quantitatifs sont obtenus en 60 minutes par déposition sur une plaque d'argent avec support spécial. On utilise 50 ml de solution á 85–90° en présence de citrate de sodium.ZusammenfassungEs wird eine Methode zur Bestimmung von Polonium-210 bei sehr geringen Konzentrationen in Gegenwart zahlreicher verschiedener Ionen beschrieben. Durch die Abscheidung auf einer Silberplatte in einem Spezialhalter bei 85–90° aus 50 ml Lösung, die Natriumcitrat enthält, konnte das Polonium nahezu quantitativ zurückgewonnen werden.
... 210 Po Isolation: Electrochemical deposition was employed to isolate 210 Po onto silver discs. This method adhered to the standard protocols outlined by Flynn [22] with the modifications proposed by Iyengar [23]. 210 Pb Activity Determination: Established techniques for 210 Pb assay and subsequent determination of its activity concentration were utilised for both abiotic and biotic samples [24]. ...
... Polonium analysis requires radiochemical separation and measurements in alpha spectrometer. We used a slightly modified Po separation method earlier described by Flynn (1968), Ehinger et al. (1986), and Henricsson et al. (2011). See (Text S1 in Supporting Information S1) for more details. ...
Fjords are net carbon sinks with high organic carbon (OC) burial rates; however, the key drivers of OC burial in these systems are not well constrained. To study the role of water column redox condition and OC composition on OC preservation in fjord sediments, we determined OC accumulation rates (OCAR), OC source, and OC degradation in three Swedish fjords with variable redox conditions (long‐term oxic, seasonally hypoxic, and long‐term anoxic). Average OCARs were variable between and within the fjords studied (2–122 g OC m⁻² yr⁻¹), but highest rates were at the mouth for each fjord. Based on a δ¹³C mixing model, Swedish fjords bury predominantly marine‐derived OC (∼83% of the total OC burial) likely because of relatively gentle slopes, low riverine discharge, and high marine inflow. Using a multi‐biomarker approach (lignin, photosynthetic pigments, and total hydrolyzable amino acids) we found, terrestrially‐ and marine‐derived OC were moderately degraded under the various redox conditions sampled, suggesting water column redox and OC source are not primary drivers of OC burial in these fjords. Rather, high sediment accumulation rates, common to fjords globally, lead to low oxygen exposure times, thus promoting efficient burial of OC regardless of its chemical composition.
... The residue was dissolved in 0.5 M HCl, adding 0.5 g of ascorbic acid, and the polonium measurement targets were prepared by its autodeposition at 90˚C for 4 h on a 99.99% silver disc. The activities of 209 Po and 210 Po were measured using an alpha spectrometer Alpha Analyst equipped with a surface barrier detector with an active surface of 450 mm 2 and 18 keV resolution (Flynn, 1968;Strumińska-Parulska, 2015. The 210 Pb determination method was based on its indirect measurement via its daughter 210 Po activity measurement in the alpha spectrometer. ...
Herbal plants are considered natural pharmaceuticals but also accumulate chemical elements and compounds at high levels. ²¹⁰Po and ²¹⁰Pb are highly radiotoxic and may cause carcinogenesis due to ionizing radiation. Thirteen of the most popular wild‐growing herbaceous plant species, mostly included in the European Pharmacopoeia, were collected across Ukraine. ²¹⁰Po and ²¹⁰Pb were determined in the medicinal plants, and their radiotoxicity and cancer risk were calculated. The results of ²¹⁰Po activities measured in herbal raw material ranged from 2.28 Bq kg⁻¹ dw (where dw is dry weight) in herb of common horsetail (Equisetum arvense L.) collected near Lviv to 37.7 Bq kg⁻¹ dw in leaves of common birch (Betula pendula Roth.) from Rava Ruska. The activity concentrations of ²¹⁰Pb varied from 0.44 Bq kg⁻¹ dw in leaves of common birch from Starokostyantyniv to 28.4 Bq kg⁻¹ dw in leaves of common birch from Mizhhirya. There were statistically significant differences between ²¹⁰Po and ²¹⁰Pb content in flowers, leaves, and aerial portions. The studies indicated that the estimated annual effective radiation dose from Ukrainian herbs consumption was low, ranging 5.00–82.6 µSv from ²¹⁰Po and 0.56–35.8 µSv from ²¹⁰Pb, while the cancer morbidity and mortality risk ranged from 10⁻⁴ to 10⁻⁶. The presented data indicated no radiological risk related to using herbal plant materials.
... After these steps, 5 mL of 20% hydroxylamine hydrochloride and 2 mL of 25% sodium citrate solution were added to the acid solution. The pH was subsequently adjusted to 2.0 by adding concentrated ammonia solution (Flynn 1968). Polonium was in sequence plated onto a 2.5-cm diameter copper disc suspended in the solution and placed on a hot plate magnetic stirrer, which was heated to approximately 90 °C, and stirred for about 90 min with a Teflon stirrer. ...
Carbonate speleothems contain measurable concentration of ²¹⁰Pb, which can be used to estimate modern growth rates up to a 150-years timescale. However, data referring to such application of this geochronological method are scarce in the Southern Hemisphere, with most studies based on temperate climate locations in the Asian continent. Such a lack of data makes it difficult to approach an investigative comparison of the main physical parameters that influence the precipitation rate of calcium carbonate in caves. In this context, the present study describes the record of longitudinal growth rates of carbonate speleothems sampled in two different Brazilian regions: Pains municipality (Midwestern Minas Gerais State) and Curitiba Metropolitan Area (CMA, eastern Paraná State), whose climates are subtropical with dry winter (Cwa) and wet temperate (Cfb), respectively. Segments of variable thickness from eight stalactites samples were subjected to HCl dissolution, ²¹⁰Po deposition onto copper discs, and ²¹⁰Po analysis by alpha spectrometry for yielding the activity concentration data. ²¹⁰Po activity concentration data provided the ²¹⁰Pb values due to radioactive equilibrium condition between these radionuclides. Although all samples exhibited a quantifiable measure of the ²¹⁰Pb activity concentration in their sectional layers, the longitudinal growth rate could not be estimated by the CF:CS method for three of the eight stalactites. However, the modified CRS method allowed determine growth rates for all speleothems. The mean ²¹⁰Pb CRS growth rate obtained at Pains and CMA sites is 1.4 ± 0.1 mm/year and 1.5 ± 0.2 mm/year, respectively, indicating coincidence at both sites and suggesting that the approach is reliable for determining modern growth rates.
... Next, the solution was evaporated with 6 M hydrochloric acid HCl to dryness and then dissolved in 0.5 M HCl. Polonium isotopes were spontaneously deposited within 4 hours on silver discs (74). After deposition, the discs were washed with methanol and analyzed for 210 Po and 209 Po using a 7200-04 APEX Alpha Analyst spectrometer (Canberra, USA) equipped with PIPS A450-18AM detectors. ...
Plastics are a recent particulate material in Earth's history. Because of plastics persistence and wide-range presence , it has a great potential of being a global age marker and correlation tool between sedimentary profiles. In this research, we query whether microplastics can be considered among the array of proxies to delimit the Anthro-pocene Epoch (starting from the year 1950 and above). We present a study of microplastics deposition history inferred from sediment profiles of lakes in northeastern Europe. The sediments were dated with independent proxies from the present back to the first half of the 18th century. Regardless of the sediment layer age, microplas-tic particles were found throughout the cores in all sites. Depending on particles' aspect ratio, less elongated particles were found deeper, while more elongated particles and fibers have reduced mobility. We conclude that interpretation of microplastics distribution in the studied sediment profiles is ambiguous and does not strictly indicate the beginning of the Anthropocene Epoch.
... Estimation of 210 Po and 210 Pb 210 Po test standard procedures were used for abiotic and biotic samples (Musthafa and Krishnamoorthy, 2012). Electrochemical deposition of 210 Po onto the silver discs was performed in accordance with the standard methodology commended by Flynn (1968) and modified by Iyengar et al. (1980), established standard techniques for 210 Pb assay and 210 Pb activity concentration determination in abiotic and biotic samples, respectively (Kamath et al., 1964). To evaluate emission, a gas flow type Geiger Muller low background radiation counting system was used, and its efficiency (40%) was calibrated using 40 K standard sources. ...
Natural radioactive concentration assessment was conducted on sediment, water, and biota obtained on Vaan and Koswari islands in the Tuticorin group of islands, Tamil Nadu, India. For biotic and abiotic components, radiation profiles such as gross alpha, beta, primordial radionuclide, polonium, and lead analyses were performed. The gross α and β range from BDL to 15.18 ± 1.7 Bq/kg and 40.43 ± 4.9 Bq/kg to 105.12 ± 11.7 Bq/kg, respectively. Primordial radionuclides were analyzed using Nal(TI)-based scintillator with PC-MCA, and the concentrations ranged from 13.43 ± 3.3 Bq/kg to 30.97 ± 9.6 Bq/kg with a mean of 21.31 ± 2.7 Bq/kg for ²³⁸U; for ²³²Th, the values ranged from 11.09 ± 2.6 Bq/kg to 33.55 ± 9.5 Bq/kg with an average value of 23.89 ± 3.7 Bq/kg; and for ⁴⁰ K, the values are 93.33 ± 27.3 Bq/kg to 219.91 ± 39.6 Bq/kg with an average value of 148.27 ± 21.7 Bq/kg. The present study values are lesser than the world average values. ²¹⁰Po and ²¹⁰Pb concentrations with an average value were determined to be 33.13 Bq/L and 16.56 Bq/L, 47.55 Bq/L and 22.37 Bq/L in the water sample, and 50.437 Bq kg1 and 62.012 Bq kg1, 46.99 Bq/kg and 58.625 Bq/kg in sediments of Vaan island and Koswari island. The concentrations of ²¹⁰Po and ²¹⁰Pb of Pogonias cromis were 19.27 ± 1.5 Bq/kg and 8.27 ± 1.01 Bq/kg, Belonidae 28.54 ± 2.4 Bq/kg and 18.32 ± 2.3 Bq/kg, Lepisosteidae 18.68 ± 1.4 Bq/kg and 11.17 ± 1.8 Bq/kg. The committed effective dosage was determined to be 35.74–54.61 µSv/y for ²¹⁰Po and 25.39–56.25 µSv/y for ²¹⁰Pb, in which the ²¹⁰Pb value is lower; however, the ²¹⁰Po value is higher than the global average value. The annual committed effective dosage as well as the radiological hazard indices were assessed and found to be much below the global average and the recommended limit, respectively. This research provides an extensive analysis of natural background radiation and establishes a baseline report on the radiological profile of biotic and abiotic factors in the Tuticorin group of islands, namely Vaan and Koswari, in Tamil Nadu, India.
... The radon formed inside the bubbler was transferred to scintillation Lucas cell [8][9][10], and gross alpha was counted after a suitable delay. Polonium was auto-deposited on a brightly polished silver rotating disk in 200 ml of 0.5 N HCl solution at 97°C [11][12][13][14][15][16]. Interferences due to deposition of ferric iron were suppressed by ascorbic acid. ...
A closed container having a specified quantity of 226Ra was constructed as encapsulated 226Ra–222Rn source. The source in the form of a modified Lucas cell (LC) was used for standardization of Lucas cell alpha counting system. The performance of the prepared source was evaluated by simultaneous measurement of dissolved radon in water by Lucas cell method using alpha counting system and Alpha guard. Radon alpha counting system measures dissolved radon in water sample by gross alpha counting of aerated dissolved transferred to LC. The same samples were also measured simultaneously by Alpha guard using instant measurement of emanated radon in a closed circuit. The gross alpha counting method using the radon counting system produced result that is closely matching with the Alpha guard measurement. This validates the calibration of radon counting system by designed encapsulated source. The study provides an alternative for calibration in the absence of expensive radon source available in the market.
... The 210 Pb activities (dpm g −1 ) were estimated for the first 15 cm through its daughter radionuclide 210 Po which is in secular equilibrium (Table 1 Supplementary Material). The chemical procedure included the acid digestion of sediment samples with the addition of 209 Po as a yield tracer and the deposition of the 210 Po onto ultrapure silver discs (Flynn, 1968). Activities were quantified in a Canberra Quad Alpha Spectrometer until a 1 s error was achieved. ...
Mountain ecosystems located in the Andes cordillera of central Chile (29–35°S) have been strongly affected by the ongoing Mega Drought since 2010, impacting the snow cover, the surficial water resources (and thereby water storage), as well as the mountain biota and ecosystem services. Paleoenvironmental records in this part of the semiarid Andes are key to estimating the effects of past climate changes on local communities helping to forecast the ecological and biological responses under the aridification trend projected during the 21st century. Here we present a 2400-year multiproxy paleoenvironmental reconstruction based on pollen, diatoms, chironomids, sedimentological and geochemical data (XRF and ICP-MS data) of Laguna El Calvario (29°S; 3994 m a.s.l), a small and shallow Andean lake. Four main hydrological phases were established based on changes in the lithogenic and geochemical results associated with allochthonous runoff input and the subsequent response of the biological proxies. Between 2400 and 1400 cal yrs BP, wetter than present conditions occurred based on the intense weathering of the lake basin and the dominance of upper Andean vegetation. A decrease in moisture along with sub-centennial discrete wet pulses and lake-level changes occurred until ~800 cal yrs BP followed long-term stable climate conditions between 1850 and 1950 AD as suggested by a drop in vegetation productivity and low lake levels. From 1950 AD to the present, a decline in moisture with a severe trend to drier conditions occurring in the last decades occurred as reflected by an upward vegetation belt displacement around Laguna El Calvario along with a turnover of diatom assemblages and high productivity in the water column.
... After the microwave digestion, the samples were dried on a hot plate to evaporate to dryness. Spontaneous polonium deposition on a copper disc was performed using 0.5 M HCl in the presence of 0.4 g of ascorbic acid to reduce Fe 3+ to Fe 2+ by modifying the standard technique of Flynn (1968). This ensures the optimum conditions for ...
The effects of technologically enhanced naturally occurring radioactive material (TENORM) on coastal zones were ecologically evaluated using Posidonia oceanica. Radionuclides and trace element levels were investigated in Posidonia oceanica to evaluate if seagrasses can be assessed as a biomarker for biomonitoring surveys. The radionuclide concentrations were determined using radiometric methods. Furthermore, trace element levels were obtained using energy-dispersive X-ray fluorescence spectrometry. The mean activity concentrations of ²¹⁰Po and ⁴⁰K were found to be 375.5 and 1.6 Bq/kg, respectively. The mean levels of trace elements of Al, Fe, Mn, Ni, Zn, Pb and Cr were 1620, 183, 15.3, 7.9, 7.1, 2.8 and 67 ppm, respectively. The absorbed dose rates (D) of ²¹⁰Po and ⁴⁰K were calculated, with the average levels being 1.2 × 10− 3 and 4.4 × 10− 3 µGy/h, respectively. In marine ecology, P. oceanica can be a biomarker for detecting trace metals (⁴⁰K and ²¹⁰Po) and absorbed dose rates. The concentrations and sources of TENORM were evaluated in terms of ecological and industrial hazards to the marine environment.
... Polonium was separated from the sample using strong hydrochloric and nitric acids, and 30 wt% hydrogen peroxide was used to eliminate organic matter. Polonium was deposited onto silver disks (Flynn 1968). The activity of 210 Po and 208 Po was measured using a DUO alpha spectrometer produced by EG&G ORTEC and corrected for background measurements. ...
Changes in local hydrological and climatic conditions over the last 5500 years have been reconstructed based on geochemical and paleobiological features recorded in the sediments of two mountain lakes. The lakes are located in the Tatra Mountains, in the highest mountain range of the Carpathians (Central Europe), which during the Holocene constituted an important climatic barrier. Because both studied lakes are relatively shallow, even relatively minor fluctuations in water level are clearly recorded both in the geochemical characteristics of the sediments and in the phyto- and zooplankton communities. The multiproxy records indicate several periods of high water stands: 5.4–5.2 ka, 3.5–2.7 ka, 1.4–1.0 ka and 0.5–0 ka, and prominent dry periods 2.7–2.1 ka and 1.7–1.5 ka. Comparison of the reconstructed water levels of the Tatra lakes with records from other European regions suggests that at the boundary of the Middle and the Late Holocene, the hydrological conditions in the Tatras were similar to those in Western and Central Europe. Later, beginning approximately 3500 years ago, records from the Tatras, the northern surroundings of the Pannonian Basin, and the southern part of the Carpathians were unified. In addition to changes in local and regional hydrology, the records from the studied lakes allowed us to reconstruct changes in lake productivity. Relatively high δ¹³C values, compared to the sedimentary organic matter of other lakes in the region, point to in-lake primary production as a major source of sedimentary organic matter in both lakes. The stable C:N ratio values suggest a constant proportion of organic matter coming from in-lake primary production and transported from the lake catchment. However, the amount of organic carbon and nitrogen and, most of all, differences in the composition of stable C and N isotopes indicate changes in the lake environment. These changes were correlated with some paleotemperature proxies from the region.
... About 0.5 g of sediment from each sediment layer was used for the determination of 210 Po. After sample dissolution using the microwave digestion method, polonium was self-deposited from weak HCl solution onto silver disc [32][33][34]. As chemical yield determinate, 209 Po was used. ...
Organic carbon (OC) burial efficiency, which relates the OC burial rate to respiration in the seafloor, is a critical parameter in the reconstruction of past marine primary productivities. The current accepted theory is that sediments underlying oxygen-deficient (anoxic) bottom waters have low respiration rates and high OC burial efficiencies. By combining novel in situ measurements in anoxic basins with reaction-transport modelling, we demonstrate that sediments underlying anoxic bottom waters have much higher respiration rates than commonly assumed. A major proportion of the carbon respiration is concentrated in the top millimeter—the so-called ‘reactive surface layer’—which is likely a feature in approximately 15% of the coastal seafloor. When re-evaluating previously published data in light of our results, we conclude that the impact of bottom-water anoxia on OC burial efficiencies in marine sediments is small. Consequently, reconstructions of past marine primary productivity in a predominantly anoxic ocean based on OC burial rates might be underestimated by up to an order of magnitude.
... The IntCal20 curve was used to calibrate the resulting radiocarbon dates (Reimer et al., 2020). Measurements of 210 Pb activity (Flynn, 1968) were done to infer a chronology for the surficial KB sediments, 8 samples for LBL, 3 for CHA, and 5 from FUR. Constant rate of supply model (CRS) (Appleby and Oldfield, 1983) was used to determine the age of the surface samples. Finally, age depth modeling was done using the R package clam 2.2 (Blaauw, 2010). ...
An isolated sugar maple ( Acer saccharum Marsh.) stand is located in the boreal forest of Abitibi, about 75 km beyond its present northern range limit. When did this relatively thermophilous tree species establish after ice retreat? Were its populations more abundant than now sometimes in the past? If so, when and how did they expand then retracted? How did the species persist in boreal forest over time? What could have been the role of fire on this stand? To answer those questions, we reconstructed the postglacial fire and vegetation history from three lacustrine sediment sequences distributed along a c. 180 km latitudinal transect from southern boreal forests to the northern portion of deciduous forests. From north to south, those are lakes Labelle, Chasseur and Fur. We explored a procedure based on pollen accumulation rates in order to detect the probable presence of sugar maple within the lakes’ watershed. The procedure successfully indicates a sugar maple establishment c. 7800–5100 cal. BP at Fur, 5500–4400 cal. BP at Chasseur and c. 4000–2700 cal. BP at Labelle, in the north. At Fur, the subsequent sugar maple expansion happened 1 to 2 thousand years after establishment, during colder and moister climatic conditions favoring Pinus strobus L. replacement by Betula spp. c. 6000–5000 cal. BP. Sugar maple establishment, persistence or expansion is apparently not linked to a change in fire activity at Fur and Chasseur, but at Labelle, the species was more abundant during periods of shorter fire return intervals from 2000 to 500 years ago. Our study suggests that northern (Chasseur and Labelle) sugar maple establishment and possible expansion was probably more controlled by a complex interaction of inhibition and facilitation dynamics than by climate alone, a process reliant on the dominant vegetation’s composition and structure.
... Total 210 Pb was determined via its grand-daughter 210 Po (proxy method of Flynn, 1968) which was leached from 3 g sediment subsamples with aqua regia after addition of 50 μL 209 Po yield tracer (0.2 Bq/mL). The leachates were evaporated to dryness, re-dissolved in 1 M HCl and auto deposited on silver discs before counting for 2 days using Octete alpha spectrometry systems (Ortec, Oak Ridge, TN) in the GAU-Radioanalytical Laboratories, University of Southampton. ...
Huge amount of trace metals emitted through manmade activities are carried by the Changjiang River into the East China Sea. Most of them deposit in the Changjiang River Estuary and threaten the regional aquatic environment. In this study, major and trace elements of 34 archive surface sediments and two cores are examined. Sequential extraction procedures were also performed on surface sediments from 12 sites. We found that Tl, Tm, Er show distinct accumulation in surface sediments in the order of Tm > Tl > Er. Particularly, abnormally elevated HREE are observed mainly in those sites near the mouth of the estuary. Most elements exhibit an obvious reduction in the upper 30 cm of core B8, reflecting a decrease of sediment discharge from Changjiang River runoff. The increase of some trace elements recorded in the upper 20 cm of core C3 demonstrates a distinct local anthropogenic input in recent years.
... Se utilizaron planchetas de plata para la autodeposición de polonio durante 4 horas en HCl 1,5 M, y a una temperatura máxima de 80 °C siguiendo la técnica de Flynn (Flynn, 1968). La adición de ácido ascórbico evita el recubrimiento de hierro sobre la hoja de plata. ...
Phosphate rock, raw material used to produce fertilizers, due to its composition can be a source of metals, radionuclides and other traces. The application of phosphate fertilizers can redistribute and increase the concentrations of both metals and radionuclides in soil and water profiles, influencing their availability and subsequent transfer to the food chain. Knowing the proportion of this transfer is essential due to the implications it can have on human and animal health. This work studies the sample treatment, radiochemical separation and deposition/electrodeposition conditions for the quantification of polonium-210, uranium-238 and uranium-234 by alpha spectrometry for a Uruguayan agricultural system. Both processes require optimization for each type of matrix, to avoid the self-absorption effect as well as possible interference from other radionuclides present in the sample. The method was verified by quantifying polonium-210, uranium-238 and uranium-234 in International Atomic Energy Agency (IAEA) reference materials: IAEA-447 soil, IAEA-434 phosphogypsum, IAEA-330 spinach. These radionuclides were quantified in environmental matrices and the results were compared with those obtained by Inductively Coupled Plasma Mass Spectrometry (ICP-MS), showing comparable results and indicating that the developed radiochemical separation is suitable for the determination of uranium and polonium radionuclides by alpha spectrometry in the studied matrices.
... Hydroxylamine hydrochloride (20%, 5 mL) plus sodium citrate solution (25%, 2 mL) were added into a Teflon beaker (50 mL capacity) containing each sample. Then, ammonia was used to adjust the pH to 2 as described by Flynn (1968). Thereafter, the solution was put in a magnetic stirrer with a hot plate, and a 2.5-cm diameter copper disc was immersed in it for plating the polonium. ...
This work was conducted at the Pardo River hydrographic basin, which is a federal watershed belonging to the Paranapanema River hydrographic basin (PRHB) in Brazil (São Paulo State and Paraná State). The aim was to realize an integrated hydrochemical and radiometric (U-isotopes and ²¹⁰Po) approach, highlighting the water/soil-rock and surface water/groundwater interactions, with implications to the weathering processes occurring there. The study area has been often considered one of the best preserved/unpolluted river in São Paulo State, contributing to the water supply of several cities distributed along its banks. However, the results reported here suggest possible lead diffuse pollution caused by the use of phosphate fertilizers in agricultural activities taking place in the basin. The analyzed groundwaters and surface waters tend to be neutral to slightly alkaline (pH of 6.8–7.7), possessing low mineral concentration (total dissolved solids up to 500 mg/L). SiO2 is the major dissolved constituent in the waters, while bicarbonate is the dominant anion, and calcium is the preponderant cation. The effects of the weathering of silicates to control the dissolution of constituents in the liquid phase have been identified from some diagrams often utilized in hydrogeochemical studies. Chemical weathering rates have been estimated from hydrochemical data associated to analytical results of the natural uranium isotopes ²³⁸U and ²³⁴U concerning to samples of rainwater and Pardo River waters. The fluxes in this watershed are permitted to obtain the following rates: 11.43 t/km² year (sodium), 2.76 t/km² year (calcium), 3.17 t/km2 year (magnesium), 0.77 t/km² year (iron), and 8.64 t/km2 year (uranium). This new dataset constitutes valuable information for people engaged on the management of the Pardo River watershed, as well as to researchers interested on comparative studies considering the available data from other basins worldwide.
... Dry sediment samples of 0.2 g were later packed into PTFE containers, spiked with a 209 Po yield tracer, and digested with concentrated HNO 3 , HClO 4 , and HF at a temperature of 100 • C, using a CEM Mars 6 microwave digestion system. Next, polonium isotopes were spontaneously deposited on silver discs following the procedure introduced by Flynn (1968). The activity of total 210 Pb was determined indirectly by measuring 210 Po, using a 7200-04 APEX Alpha Analyst integrated alpha-spectroscopy system (Canberra), equipped with PIPS A450-18AM detectors. ...
Sediments from Lake Lubińskie, western Poland, were investigated to determine the limnological responses to environmental changes during the last 3,000 years. To identify the mechanisms driving the eutrophication in the lake, we distinguished six lithozones along with five major varve microfacies. An age-depth model based on varve counting and radiometric measurements was established resulting in final age of 946 +113 /-144 before the Common Era at the bottom of the composite profile. Varve microfacies as well as geochemical, pollen, and diatom data was used to determine major phases of landscape and lake ecosystem transformations. Our data shows that until the 4 th century of the Common Era, conditions in the lake were stable. Several shifts occurred before the first millennium, when changes were observed in every proxy as a response to the increased agricultural activity in the area as well as climate fluctuations. The highest frequency of shifts was observed from the 17 th century onward and mirrored further deforestation (decrease in arboreal pollen), accelerated erosion (in-crease in Ti), increased nutrient delivery (increased total nitrogen content), and better ventilation of the water body (higher Mn/Fe ratio). Simultaneously, the lake became more eutrophic as a response to changes in the lake catchment area. Our study suggests that inferred lake-level changes are primarily related to human activity in the catchment area.
... Next, the solution was evaporated with 6 M hydrochloric acid HCl to dryness, and then dissolved in 0.5 M HCl. Polonium isotopes were spontaneously deposited within 4 h on silver discs 73 . After deposition, the discs were washed with methanol and analysed for 210 Po and 209 Po using a 7200-04 APEX Alpha Analyst spectrometer (Canberra, USA) equipped with PIPS A450-18AM detectors. ...
Plastics are a particulate novel material in Earth’s history. Due to its persistence and wide-range presence, it has a great potential of being a global age marker and correlation tool between sedimentary profiles. Hence, microplastics are currently considered among the array of proxies to delimit the Anthropocene Epoch (starting from the year 1950 and above). Here we present a study of microplastics deposition history inferred from sediment profiles of three lakes in north-eastern Europe. The sediments were dated with independent proxies from nowadays back to the first half of the 18th century. Surprisingly, regardless of the sediment layer age, we found microplastic particles throughout the cores in all sites. The factor driving microplastic particles to penetrate deeper in sediment layers appears to be particles' dimensional (aspect) ratio: less elongated particles tend to be transported deeper while more elongated particles and fibres have a decreased ability to be mobile. We conclude that interpretation of microplastics distribution in sediment profiles is ambiguous and does not strictly indicate the beginning of the Anthropocene Epoch.
... Coffee beans were digested, and the residue was filtered. Polonium was autodeposited on silver discs from 0.5 M HCl solution with ascorbic acid addition (Flynn 1968;Skwarzec 1997). Nitric acid (65%), hydrochloric acid (37%), and ascorbic acid were obtained from POCH Avantor (Gliwice, Poland). ...
We determined radiotoxic ²¹⁰Po in roasted coffee beans from different regions worldwide, the beverages, and tried to create the prediction model of ²¹⁰Po content based on its growth location. Additionally, the experiments on ²¹⁰Po losses and extraction were performed to describe the actual exposure to ²¹⁰Po. ²¹⁰Po concentrations in coffee beans and brews tuned out low (maximally of 0.20 Bq∙kg⁻¹ and 2.31 Bq∙L⁻¹, respectively). We assessed the impact of the roasting process on ²¹⁰Po content and its losses at a maximum of 56.7%. During infusion experiments, we estimated the extraction of ²¹⁰Po to the coffee brew at a maximum of 40.6%. The amount of ²¹⁰Po in the coffee brew depended on the infusion style and water type. We calculated the effective radiation doses from the coffee drink ingestion. Coffee drinking does not contribute significantly to the annual effective radiation dose worldwide.
Graphical Abstract
... An amount of 200 ml of 0.5 M 37% HCl was added to all dried samples, mixed, waited for a night and then filtered into a 250 ml beaker using filter paper. An amount of 0.4 g of ascorbic acid was added to reduce Fe +3 to Fe +2 (Flynn 1968). 210 Po is provided to be deposited on one surface of the copper disc. ...
Ecological effects in marine living can be understood via the determination of antioxidant molecules in aquatic organisms against pollutants. This study aims to evaluate the radionuclides and trace element stress with response molecules. Cystoseira crinita and Halopteris scoparia have been chosen as study materials because of their susceptibility to pollution. The radionuclides 210Po, 238U, 232Th and 40K and trace elements Al, Fe, Mn, Cr, As, Zn and Pb levels were analysed as well as antioxidants and antioxidant enzymes in two brown algae, seasonally. Marine pollutants in terms of radionuclides and trace elements were correlated with antioxidant molecules in these species and may be used as biomarkers for assessing the radioactive stress. The 210Po and Mn concentrations in C. crinita seem to activate catalase (CAT) and superoxide dismutase (SOD) enzyme activities while 210Po concentrations inclined the proline amount in H. scoparia. This study demonstrated the radiation stress-induced the antioxidant defence system in macroalgae, the primary producers of the marine environment.
... The polonium measurement discs were prepared by its autodeposition on pure 99.99 % silver (Mennica-Metale Sp. z o.o.). The activities of 209 Po and 210 Po were measured using an alpha spectrometer Alpha Analyst (Canberra) equipped with a surface barrier detector with an active surface of 450 mm 2 (Flynn, 1968;Strumińska-Parulska, 2015, 2016a. After the first 210 Po deposition, all samples were evaporated, and the dry residue was heated very strongly, with 30 % H 2 O 2 added to remove potential polonium residues. ...
Algae are believed to give health benefits. However, the studies showed they contain toxic elements, including radionuclides, and may affect human health. The study presents the values of activity concentrations of 210Po and 210Pb in the algae supplements available worldwide for adults. The activity concentrations (Bq/kg dw) ranged from 0.07 to 14.5 (210Po) and from 0.06 to 8.48 (210Pb). Also, the effective radiation doses and the cancer risk from 210Po and 210Pb decay ingested with analyzed algal supplements have been assessed. The highest values of annual effective doses have been estimated for 210Po in the recommended portion of Spirulina (Arthrospira platensis) from China (59.7 μSv/year) and Diatomaceous earth from the USA (50.4 μSv/year). The cancer morbidity and mortality risk ranged from 10-4 to 10-8. The study indicated the activity concentrations of 210Po and 210Pb were low, and algae supplements for human consumption could be considered safe food.
... The fine-grained fraction (<63 microns) was used for isotope-dilution alpha spectrometry to quantify 210 Pb via the granddaughter isotope, 210 Po, which is assumed to be in secular equilibrium with 210 Pb [43][44][45][46]. Raw 210 Pb data and dry bulk density for each depth interval for all 12 creek cores, both of which are needed for geochronology modelling, are presented in the attached S1 Data. ...
Land cover and use around the margins of estuaries has shifted since 1950 at many sites in North America due to development pressures from higher population densities. Small coastal watersheds are ubiquitous along estuarine margins and most of this coastal land-cover change occurred in these tidal creek watersheds. A change in land cover could modify the contribution of sediments from tidal creek watersheds to downstream areas and affect estuarine habitats that rely on sediments to persist or are adversely impacted by sediment loading. The resilience of wetlands to accelerating relative sea-level rise depends, in part, on the supply of lithogenic sediment to support accretion and maintain elevation; however, subtidal habitats such as oyster reefs and seagrass beds are stressed under conditions of high turbidity and sedimentation. Here we compare sediment accumulation rates before and after 1950 using 210Pb in 12 tidal creeks across two distinct regions in North Carolina, one region of low relief tidal-creek watersheds where land cover change since 1959 was dominated by fluctuations in forest, silviculture, and agriculture, and another region of relatively high relief tidal-creek watersheds where land-use change was dominated by increasing suburban development. At eight of the creeks, mass accumulation rates (g cm-2 y-1) measured at the outlet of the creeks increased contemporaneously with the largest shift in land cover, within the resolution of the land-cover data set (~5-years). All but two creek sites experienced a doubling or more in sediment accumulation rates (cm yr-1) after 1950 and most sites experienced sediment accumulation rates that exceeded the rate of local relative sea-level rise, suggesting that there is an excess of sediment being delivered to these tidal creeks and that they may slowly be infilling. After 1950, land cover within one creek watershed changed little, as did mass accumulation rates at the coring location, and another creek coring site did not record an increase in mass accumulation rates at the creek outlet despite a massive increase in development in the watershed that included the construction of retention ponds. These abundant tidal-creek watersheds have little relief, area, and flow, but they are impacted by changes in land cover more, in terms of percent area, than their larger riverine counterparts, and down-stream areas are highly connected to their associated watersheds. This work expands the scientific understanding of connectivity between lower coastal plain watersheds and estuaries and provides important information for coastal zone managers seeking to balance development pressures and environmental protections.
... It is well known that Fe 3+ , NO 3 − and high concentration of acid interfere with the spontaneous deposition of Po on a silver disc [2,3,14], and high Fe 3+ content in the sample solution will significantly reduce the recovery of polonium during spontaneous deposition by competing with polonium for the deposition onto the silver disc. The polonium coprecipitate with Fe(OH) 3 was dissolved with HCl-H 2 O 2 , which was then evaporated to dryness to remove H 2 O 2 and excessive HCl. ...
A method for determining the content of 210Po in soil and sediment samples without the use of hydrofluoric acid has been developed. Soil and sediment samples were fused with sodium hydroxide and sodium peroxide to achieve a clear solution without any visible traces of the solid matrix. After extracting 210Po by spontaneous deposition from the sample, the sample was measured by alpha spectrometry. The average recovery for the method in environmental soil samples was 81.2 ± 6.0% and the detection limit of the method reaches 0.1 mBq/g.
... The 210 Pb activity was measured via its daughter nuclide 210 Po by standard radiochemical procedure (Flynn 1968). Before the analysis by alpha spectroscopy, 210 Po was separated from other alpha-emitting isotopes. ...
Sediment components, major and trace elements, and radionuclide (210Pb) of estuarine mudflat sediment cores collected from the Mandovi, Kalinadi, and Aghanashini estuaries, along the central western coast of India, were investigated to understand the source, processes, and depositional environments. The distribution and abundance of parameters studied reveal that they were controlled largely by the catchment area geology, geomorphology, and estuarine processes together with a contribution from anthropogenic activities. The variations in sediment proxies of mudflat cores reveal changing environmental conditions with time. The sedimentation rate in the study area varied in two phases, the relatively low rate in the lower part and the high rate in the upper part of the cores in Mandovi and Aghanashini estuaries. The increased deposition of finer sediments and metals in the recent past regulated by natural and enhanced anthropogenic input was responsible for higher sedimentation rates. In the Kalinadi estuary, however, sedimentation was uniform with a single phase.KeywordsEstuarine mudflatsSediment componentsElementsRadionuclide (210Pb)SourceDepositional environmentsMetal enrichment
... Sources were prepared through the radiochemical separation procedure which involves sequential extraction using UTEVA resin (Triskem) of purified uranium eluate and electrodeposition onto stainless steel discs at 1.8 A for 1 hour [42,43]. The method used for 210 Po determination was based on co-precipitated with Fe(OH)3 and autodeposition onto silver discs for 4 hours [44,45]. The activity concentration of 210 Po corresponded to the 210 Po in excess, thus, the activity concentration measured from αparticle spectrometry was corrected with the γ-ray spectrometry 210 Pb activity. ...
According to the European Council Directive 51/2013 EURATOM, the radionuclide content in human consumption waters must comply with the stated recommendations to ensure the protection of public health. The radiological characterisation assessed in Laboratorio de Radiaciones Ionizantes y Datación of Universidad de Salamanca, in more than 400 groundwater samples gathered from intakes intended for human consumption from the Castilla y León region (Spain), has provided worthwhile data for evaluating the spatial distribution of the radioactivity content in the Duero basin. For this purpose, geostatistical exploration and interpolation analysis, using the inverse distance weighting (IDW) method, was performed. The IDW prediction maps showed higher radioactivity occurrence in western and southern areas of the study region, mainly related to the mineralogical influence of the igneous and metamorphosed outcroppings in the Cenozoic sediments that formed the porous detritic aquifers of the Duero basin edges. The hydraulic characteristics promote the distribution of these radioactivity levels towards the centre of the basin as a consequence of the unconfined nature of the aquifers. Prediction maps provide a worthwhile tool that can be used for better planning and managing of groundwater monitoring programmes.
... Two depositions were made in time of around 6 months; 0.1 g of dried sample with concentrated hydrochloric and nitric acid was digested in the Anton Paar microwave system. The samples were then centrifuged and evaporated with 2 mol dm −1 HCl; polonium was spontaneously deposited on a silver disc (Flynn 1968) in the presence of hydroxylamine hydrochloride or ascorbic acid within 3 h at temperatures of 85-88 °C. An alpha spectrometer (Alpha Analyst, Canberra, USA) with a PIPS (passivated implanted planar silicon) semiconductor detector was used for polonium measurements. ...
The aim of this work was to prove the use of radionuclides deposited in sediment core taken from an overgrowing dystrophic lakes surrounded by marsh-peat vegetation to estimate sedimentary conditions. Sediment core samples were taken from the Toporowe Stawy Lakes (Niżni (TSN) and Wyżni (TSW); Tatra Mountains). The sampling was done using a Limnos corer. After the physical sample preparations, gamma measurements were performed. Radiochemical analysis was applied with the aim of determining ²¹⁰ Pb radioactivity by means of ²¹⁰ Po. The mean values for TSN lake are as follows: ¹³⁷ Cs ~ 123 Bq∙kg ⁻¹ , ⁴⁰ K ~ 389 Bq∙kg ⁻¹ , ²²⁸ Th ~ 55 Bq∙kg ⁻¹ , ²²⁶ Ra ~ 86 Bq∙kg ⁻¹ , ²⁴¹ Am ~ 5 Bq∙kg ⁻¹ , and ²¹⁰ Pb uns ~ 180 Bq∙kg ⁻¹ . For TSW lake, the radioactivity levels of ²²⁶ Ra and ²⁴¹ Am are comparable to the TSN. The mean values of ¹³⁷ Cs, ⁴⁰ K, and ²²⁸ Th are almost twice as high as in TSN. The level of ²¹⁰ Pb in uppermost layer of TSN is higher than in TSW. Sediments were dated by use of ²¹⁰ Pb method, and the rate of sedimentation of each layer was also estimated. Basic chemometric tools were used to confirm the way of deposition of radionuclide, find the correlations between variables, and compare analyzed lakes. It was concluded that the presented type of lakes are a valuable source of information and the vertical distribution of radionuclide can be used to interpret the source of material supply and factors that influence the sedimentation process in recent 150–200 years.
... The lower limits of detection for 238 U and 226 Ra derived from the background measurements at 100,000 s. were 0.5 and 3 Bq kg − 1 , respectively. 210 Po and 209 Pb were measured using the standard technique (the silver disc technique) [37]. Five grams' dry weight of plant samples were spiked with 0.2 Bq of 209 Po (Polonium chloride in 0.1 mol L 1 HCl provided by Amersham nternational UK) as a yield tracer. ...
Transfer Factors (Fv) of 238U, 226Ra, 234Th, 210Po and 210Pb from five different agricultural soils in semi-arid region (Syria) to four different barley genotypes were studied in an agricultural potted experiment. The geometric mean of the Fv values were (0.08) for 210Pb, and (0.02) for 210Po, while it ranged from 0.18 to 0.42 ,from 0.08 to 0.15 and from 0.22 to 0.4 for 238U, 234Th and 226Ra, respectevily. The Fv values of 238U and 226Ra were within the recommended global medians, while the Fv values of 234Th, 210Pb and 210Po were higher. There is no clear relationship between the soil properties and Fv of all studied radionuclides to barley genotypes. Moreover, the expression of glutathione (GSH) gene, which is belived to be involoved in heavy metal removal was generally low in all studied varieties grown in all soil types.
... g sub-samples 55 . Polonium was extracted from the samples using concentrated hydrochloric and nitric acids and deposited on silver disks 55 . For the complete removal of organic matter, 30% perhydrol was used. ...
Lake sediments not only store the long-term ecological information including pollen and microfossils but are also a source of sedimentary DNA ( sed DNA). Here, by the combination of traditional multi-proxy paleolimnological methods with the whole-metagenome shotgun-sequencing of sed DNA we were able to paint a comprehensive picture of the fluctuations in trophy and bacterial diversity and metabolism of a small temperate lake in response to hemp retting, across the past 2000 years. Hemp retting (HR), a key step in hemp fibre production, was historically carried out in freshwater reservoirs and had a negative impact on the lake ecosystems. In Lake Slone, we identified two HR events, during the late stage of the Roman and Early Medieval periods and correlated these to the increased trophy and imbalanced lake microbiome. The metagenomic analyses showed a higher abundance of Chloroflexi, Planctomycetes and Bacteroidetes and a functional shift towards anaerobic metabolism, including degradation of complex biopolymers such as pectin and cellulose, during HR episodes. The lake eutrophication during HR was linked to the allochthonous, rather than autochthonous carbon supply—hemp straws. We also showed that the identification of HR based on the palynological analysis of hemp pollen may be inconclusive and we suggest the employment of the fibre count analysis as an additional and independent proxy.
... For 210 Po analysis, 1 g of dried and homogenized Sargassum sample was spiked with a known amount of 209 Po, digested by concentrated HNO 3 , H 2 O 2 and concentrated HCl and self -deposited on a silver disc in 0.5 M HCl with ascorbic acid added to ensure spontaneous electroplating of Po following the standard published protocol (Flynn, 1968;Fleer and Bacon, 1984;Bam et al., 2020). The prepared Po sources were counted for at least two days by alpha-particle spectrometry (Ametek Ortec) with the resulting detection limits 0.12-0.36 ...
In recent years, the North Atlantic and the Caribbean Sea have experienced unusual and unprecedented pelagic Sargassum blooms, which may adversely affect coastal ecosystems and productive ocean. Sargassum has the potential to scavenge trace elements and radionuclides from seawater, and when bioaccumulated and thus concentrated, can pose a potential threat to higher trophic organisms, including humans that consume impacted seafood. In this study, trace elements and naturally-occurring U/Th-series radionuclides were measured in Sargassum that were collected in the coastal waters of the Caribbean Sea (Antigua/Barbuda, Belize, and Barbados) to better define baseline concentrations and activities, and to assess the scavenging potential for these trace elements and radionuclides. The mean concentration of trace elements observed in Sargassum collected across these three Caribbean Sea are ranked accordingly to the following descending order: Sr > As>Fe > Mn > Zn > Ni > V > C > Cd > Se > Co > Cr > Pb > Ag > Hg. 210-Po and 210Pb activities in Sargassum were observed to be more elevated than previously reported values.
... For 210 Po analysis, 1 g of dried and homogenized Sargassum sample was spiked with a known amount of 209 Po, digested by concentrated HNO 3 , H 2 O 2 and concentrated HCl and self -deposited on a silver disc in 0.5 M HCl with ascorbic acid added to ensure spontaneous electroplating of Po following the standard published protocol (Flynn, 1968;Fleer and Bacon, 1984;Bam et al., 2020). The prepared Po sources were counted for at least two days by alpha-particle spectrometry (Ametek Ortec) with the resulting detection limits 0.12-0.36 ...
In recent years, the North Atlantic and the Caribbean Sea have experienced unusual and unprecedented pelagic Sargassum blooms, which may adversely affect coastal ecosystems and productive ocean. Sargassum has the potential to scavenge trace elements and radionuclides from seawater, and when bioaccumulated and thus concentrated, can pose a potential threat to higher trophic organisms, including humans that consume impacted seafood. In this study, trace elements and naturally-occurring U/Th-series radionuclides were measured in Sargassum that were collected in the coastal waters of the Caribbean Sea (Antigua/Barbuda, Belize, and Barbados) to better define baseline concentrations and activities, and to assess the scavenging potential for these trace elements and radionuclides. The mean concentration of trace elements observed in Sargassum collected across these three Caribbean Sea are ranked accordingly to the following descending order: Sr > As>Fe > Mn > Zn > Ni > V > C > Cd > Se > Co > Cr > Pb > Ag > Hg. 210-Po and ²¹⁰Pb activities in Sargassum were observed to be more elevated than previously reported values.
... The acceptance criterion of these analyses was recovery of the standards within 10% of variability (Table 1). 210 Pb determination was carried according to Flynn (1968). Briefly, a 0.5 g sub-sample of dry sediment was subject to total acid digestion with a mixture of HNO 3 , HCL, and HF, using 209 Po (2.22 dpm g − 1 ) as an internal tracer. ...
Among the main sources of atmospheric mercury emissions are thermoelectric plants that use coal to generate electricity. This heavy metal is transported by air from its origin to neighboring coastal areas, where it is deposited in the sediment record. This research evaluated the content and temporal distribution of Hg in the coastal sediments of Central Chile, Coronel Bay, industrialized zone with two operative thermoelectric plants, and Coliumo Bay, reference zone free of industry. To this end, sediment cores from the centers of the two bays were obtained. Laboratory results show that the greatest Hg contents were found in the surface strata of the Coronel Bay core, with concentrations up to an order of magnitude greater than those obtained in the same strata in Coliumo Bay. This increase in Hg concentration coincides with the beginning of industrial activity in Coronel, with greater concentrations observed from 2012 on, the year in which the industrial operation of two coal-fired thermoelectric plants on the bay began. Based on ²¹⁰Pb activity and the relationships between Hg content and organic matter, it was established that the main pathway of Hg to sediment is atmospheric deposition, while Coliumo presented inputs that reflect local non anthropogenic sources.
Description
Reviews and evaluates field methods used to study ground-water contamination. 30 peer-reviewed papers examine:
• ground-water sampling and sampling in unsaturated soils
• well-drilling (construction and monitoring)
• geophysical exploration
• quality assurance
• soil permeability
• and nonpoint source investigations.
Some case histories are included: for hydrologic engineer, hydrogeologists, soil scientists, and geotechnical engineers.
The development of unconventional reservoir explorations at the Middle Magdalena Valley Basin (MMVB) from Colombia has allowed to determine the natural radionuclides concentration and doses and its interaction with all matrices related with the hydraulic fracturing technic, associated with the local conditions (weather, industrial processes around, and soil). The main objective of this project is to evaluate the behavior of natural radionuclides in the unconventional reservoir environment at MMVB considering all conditions around, comparing the results with other cases related, generating a start point to the radioactive characterization of the area. The study area selected for this project was Kalé, the first research project for hydraulic fracturing in Colombia, locating in Puerto Wilches-Santander at the MMVB, a region recognized for the palm crops. In this case, were selected 81 sampling points for doses (natural background) around Kalé's area using portable detectors and 44 sampling points for activity concentrations using ICP-MS and gamma spectrometry, measuring natural radionuclides such as: U-238, Th-232, Ra-226, Ra-228, K-40 and Pb-210. The results obtained were compared with other cases related around the world in unconventional reservoirs from USA, Argentina and China, and additionally in relation to palm crops. The results of effective doses obtained in the Kalé's area were in a range from 0.07 to 0.39 mSv/y, well below the limit value established by the International Commission for Radioactive Protection (ICRP) of 1 mSv/y, demonstrating a very low risk of radioactive affection. On the other hand, the activity concentrations of natural radionuclides were variables according to radioisotope; for natural decay of U-238 from 18 to 80 Bq/kg, in secular equilibrium with Ra-226; for Th-232 from 22 to 103 Bq/kg, in secular equilibrium with Ra-228, whereas that K-40 showed a range from 162 to 611 Bq/kg and Pb-210 from 37 to 140 Bq/kg. The comparison with other cases around the world demonstrated that Kalé's area is very influenced for the weather, industrial processes around and specially for palm crops, in this way, the behavior of natural radionuclides at MMVB may be closely related not only to the geological conditions, but also with external processes in the area. The results of this project representing an important data to strengthen the baseline of necessary information need to the evaluation of radiometric risks in extractive processes in oil & gas in Colombia, to avoid health and environmental affections.
A simple spontaneous deposition kit for 210Po determination using alpha spectrometry was newly designed, and polonium deposition characteristics under various physicochemical conditions were evaluated using it. The high-purity silver disc (99.99%) showed high deposition efficiencies of over 85.1% in the HCl concentration range of 0.01-6 M. Optimal physicochemical factors were determined to be a temperature of 90 °C, deposition time of 90 min, and the use of ascorbic acid as a reducing agent in an amount similar to that of the interfering element (Fe).
Studsvik, a Swedish nuclear research facility, has been releasing aquatic radioactive discharges in the Baltic Sea, through the bay Tvären, since 1959. The permissible discharge levels are regulated by the Swedish Radiation Safety Authority (SSM) but only information about 60Co, 137Cs, 152Eu, total alpha and beta activities were reported up to 2002. Since then, the reports cover most a more comprehensive set of radionuclides. In this context, the seabed can be utilized as a chronological archive to investigate historical Studsvik releases. To this end, 23 sediment cores covering the whole area of the bay were studied and 5 of them were dated using 210Pb-dating methods. Since the discharges from Studsvik contain both plutonium and caesium, neither can be used to validate the 210Pb-dating method. Instead, stable lead with maximum deposition, known to be dated to 1970, was used. Cobalt-60, 137Cs, and 152Eu depth distributions were studied from the dated sediment cores and compared with reported levels of aquatic discharges. The expected sediment 137Cs-peak from the fallout from the Chornobyl accident was however smeared out, indicating an ongoing inflow of 137Cs with the Baltic seawater. Our findings show that reported releases of aquatic discharges of 60Co and 152Eu are consistent with measured sediment activity distribution. The sediments from the deepest parts of Tvären, with intact chronology and with a high time resolution, are ideal for investigating historical nuclear discharges and can be a tool to investigate unreported radionuclide releases. Dated sediment can in this way be a tool for nuclear safeguards to evaluate past and present activities in nuclear facilities.
Based upon present ideas of physical-chemical properties of polonium and its up-to-date determination techniques, a technique of ²¹⁰ Po radiochemical determination in urine samples was developed followed by alpha-spectrometry. The technique was tested on 24-hour urine samples collected from the personnel of the branch “Institute of Radiation Safety and Ecology” RSE NNC RK. The range of ²¹⁰ Po absolute activity per a 24-hour urine sample was determined to be 1.8·10 ⁻³ ÷0.12 Bq. ²¹⁰ Po contribution to the total dose of personnel internal exposure was estimated to be equal to 0.3 mSv/year.
Over the past century, an increase in temperatures and a decrease in dissolved oxygen concentrations have been observed in the bottom waters of the Laurentian Channel (LC), throughout the Lower St. Lawrence Estuary (LSLE) and the Gulf of St. Lawrence (GSL), eastern Canada. To document the impact of these changes, we analyzed the benthic foraminiferal assemblages and geochemical signatures of four sediment cores taken in the LC. Radiometric measurements (210Pb, 226Ra, 137Cs) indicate that the studied cores encompass the last 50 years of sedimentation in the LSLE and the last ∼160 years in the GSL. The sedimentary record shows a 60 to 65% decrease in benthic foraminiferal taxonomic diversity in the LC since the 1960s. An accelerated change in the foraminiferal assemblages is observed at approximately the same time at all studied sites, around the late 1990s and the early 2000s, towards populations dominated by the hypoxia-tolerant indicator taxa Brizalina subaenariensis, Eubuliminella exilis, and Globobulimina auriculata. This evolution of assemblages reflects incursions of the hypoxic zone into the western GSL over the last decades. The results of our multivariate analyses highlight the potential of benthic foraminiferal assemblages as a proxy of bottom-water hypoxia.
A comprehensive radioactivity characterisation of Castilla y León (Spain) groundwater intakes intended for human consumption is addressed between 2017 and 2021. This study responds to the radiological requirements stated in the European Council Directive 51/2013/EURATOM concerning drinking water for public health. Given that the gross α- and gross β-activity determination is used as a screening strategy for water radioactivity monitoring, the reliability of the thin-source deposit method (ISO 10704, 2019) has been improved to achieve representative values of the total activity coming from α- and β-particle emitters in the samples. More than 400 groundwater samples have been considered for this purpose, analysing their 238,235,234U, 228,226Ra, 210Pb, and 210Po activity concentrations, which are needed for the indicative dose assessment. These results, considered reference activity values, are compared with the gross α- and gross β-activities determined by the different procedure approaches. Ultimately, the results of the liquid scintillation counting method (ISO 11704, 2018) are also used to validate the optimised method.
Plastics are a particulate novel material in Earth’s history. Due to its persistence and wide-range presence, it has a great potential of being a global age marker and correlation tool between sedimentary profiles. Hence, microplastics are currently considered among the array of proxies to delimit the Anthropocene Epoch (starting from year 1950 and above). Here we present a study of microplastics deposition history inferred from sediment profiles of three lakes in north-eastern Europe. The sediments were dated with independent proxies from nowadays back to the first half of the 18 th century. Surprisingly, regardless of the sediment layer age, we found microplastic particles throughout the cores in all sites. The factor driving microplastic particles to penetrate deeper in sediment layers appears to be particles' dimensional (aspect) ratio: less elongated particles tend to be transported deeper while more elongated particles and fibres have a decreased ability to be mobile. We conclude that interpretation of microplastics distribution in sediment profiles is ambiguous and does not strictly indicate the beginning of the Anthropocene Epoch.
p>The effects of three biotic factors (a new species, grazing, and plant-plant interactions) were considered on the spatial patterns and temporal changes observed on coastal methods and manipulative field experiments were conducted at several locations in the Solent region. The Solent has a rich resource of saltmarsh habitats, which are of high scientific value and are of national conservation importance. Palaeoecological saltmarshes. Palaeoecological investigations were carried out on three sites (Beaulieu, Hythe and Marchwood) to investigate the long term effects of the appearance of the hybrid grass Spartina anglica C.E. Hubbard (common cord grass). Historical records were researched to complement the data obtained from the analysis of sediment cores, to characterise the saltmarsh environments before the appearance of the new species. The evidence suggests that before S. anglica appeared in the region (in the second half of the nineteenth century), mudflat and pioneer marsh were much more significant features of the Solent coast than they are at present. Manipulative experiments were carried out at two locations on the Beaulieu Estuary. The effects of excluding large wild grazing animals (principally geese, rabbits and deer) on the plant communities were investigated by constructing experimental exclosures. These were monitored for three years, after which above ground biomass was harvested from randomly selected parts. Excluding grazing animals produced rapid structural changes in the plant canopy. Palatable species, which had previously been suppressed by grazing (e.g. Plantaeo maritima L.), proliferated rapidly. Some low-growing species, which had previously been conspicuous in the community (e.g. Armeria maritima (Mill.)), declined significantly, possibly due to shading by the increased growth of other species. The importance of competition and facilitation in setting the positions of two plant species within the zonation of a saltmarsh was investigated by transplanting them to different vertical zones. When the lower marsh grass S. anglica was transplanted to the upper marsh it was outcompeted by more competitive plant species. When the surrounding above ground vegetation was removed, it grew successfully. The upper marsh rush Juncus gerardii Loisel was transplanted to the lower marsh. This species could not tolerate the harsher physical conditions at a lower level, but that the presence of neighbouring plant growth increased its success.</p
The Constant Flux: Constant Sedimentation (CF:CS) and Constant Rate of Supply (CRS) of unsupported/excess 210Pb models have been applied to a 210Pb data set providing of two sediments profiles (GUA-T1 and GUA-T2) sampled at Guarapiranga reservoir, in the Metropolitan Region of São Paulo city, São Paulo State, Brazil. Sedimentation rates obtained by the CF:CS model corresponded to 9.3–12.3 and 30 mg.cm− 2yr− 1, respectively, for profiles GUA-T1 and GUA-T2, indicating a better chronological performance relatively to that of the CRS model in the study area, also allowing successful estimates of the P fluxes in the reservoir.
The U.S. Geological Survey has processed six silicate rocks to provide new reference samples to supplement G-1 and W-1. Complete conventional, rapid rock, and spectrochemical analyses by the U.S. Geological Survey are reported for a granite (replacement for G-1), a granodiorite, an andesite, a peridotite, a dunite, and a basalt. Analyses of variance for nickel, chromium, copper, and zirconium in each rock sample showed that for these elements, the rocks can be considered homogeneous. Spectrochemical estimates are given for the nickel, chromium, copper, and zirconium contents of the samples. The petrography of five of the six rocks is described and CIPW norms are presented.
A method for the analysis of polonium-210 (138.4-day half life) and lead-; 212 (10.6-hour half life) in zircons and other natural systems was developed. ; The procedure employs spontaneous electrodeposition on silver for the isolation ; of polonium-210 and controlled-potential electrogravimetric separation of lead-; 212 plus added lead carrier. A diethyidithiocarbamate extraction procedure for ; the lead was developed to be used prior to piating in the presence of ions which ; precipitate at the pH used for lead deposition. The amounts of the deposited ; nuclides are then determined by alpha counting. The effects of temperature, ; volume, and inhibiting ions on the yield and rate of deposition of polonium were ; also studied. The procedure was calibrated using minerals whose lead-210 and ; thorium-232 contents had been determined by other methods; it was tested on a ; composite uraninite-thorite mixture. Finally, it was applied in the analysis of ; four zircon samples and one uranothorite sample. (auth);
The efficient coprecipitation of polonium-210 with tellurium by stannous chloride as precipitant is applied to the determination of polonium-210 in water. The doubly precipitated tellurium-polonium-210 precipitates are alpha counted on 0.22-micron membrane filters. A short-cut single-precipitation method is also given. Methods were tested at six levels of polonium-210 activity (0.06 to 1636 pc. per liter); in this range, the weighted average recovery was 98.8% for both methods. Radiochemical specificity is very good; there are no interferences from stable substances in samples whose compositions approach drinking water standards. The methods have sufficient sensitivity to permit their use in the determination of lead-210 in water by polonium-210 ingrowth.
Radioactive Dating and Methods of Low-level Counting
- Gale