210Pb Activity Research Articles

222Rn, 210Pb and 210Po in coastal zone groundwater: Activities, geochemical behaviors, consideration of seawater intrusion effect, and the potential radiation human-health risk

Groundwater quality in human-influenced coastal landscapes is receiving novel attention. Radionuclides have been recognized as another important monitoring indicator in many developed countries due to the discovery of extremely high level of natural 210Po (up to 10,000 Bq/m3) and radium and radon isotopes. This study aims to evaluate the groundwater quality in the Beibu Bulf-Guangxi coast from radiological point of view. 210Po, 210Pb and 222Rn activities in 20 wells ranged from 0.24 ± 0.05 to 6.96 ± 1.62 Bq/m3, 2.17 ± 0.12 to 13.08 ± 0.74 Bq/m3 and 1500 ± 200 to 31,800 ± 900 Bq/m3, respectively. Compared with research data of other countries, groundwaters in this area have 210Po, 210Pb and 222Rn activity within low levels. The large deficiencies of 210Po and 210Pb relative to 222Rn in groundwaters implied that 210Po and 210Pb are strong particle-reactive radionuclides and they might be controlled by similar scavenging processes in groundwaters due to a good positive correlation between 210Pb and 210Po (R2 = 0.67, p < 0.01). The concentrations of 210Po and 210Pb decreased with increasing pH values and salinity, which indicated that geochemical behaviors of 210Po and 210Pb in groundwater were influenced by seawater intrusion and pH changing. Groundwater 222Rn activity concentrations decreased with increasing salinity in coastal zone, which may be caused by dilution due to seawater intrusion or intensified 222Rn escaping from well-developed pores in coastal zone. The estimated annual ingestion doses for infants, children and adults were well below the recommended reference dose level (RDL) of 0.2–0.8 mSv/a, suggesting that consumption of analyzed groundwaters is safe from radiological point of view.

Distribution of radiocarbon in sediments of the cooling pond of RBMK type Ignalina Nuclear Power Plant in Lithuania.

The vertical distribution of radiocarbon (14C) was examined in the bottom sediment core, taken from Lake Drūkšiai, which has served as a cooling pond since 1983 for the 26 years of the Ignalina Nuclear Power Plant (INPP) operation using two RBMK-1500 reactors (Russian acronym for”Channelized Large Power Reactor”). 14C specific activity was measured in alkali-soluble and -insoluble fractions of the sediment layers. Complementary measurements of the 210Pb and 137Cs activity of the samples provided the possibility to evaluate the date of every layer formation, covering the 1947–2013 period. In addition, 14C distribution was examined in the scales of pelagic fish caught between 1980 and 2012. Our measurements reveal that, during the period 1947–1999, the radiocarbon specific activity in both fractions exhibits a parallel course with a difference of 5 ± 1 pMC (percent of modern carbon) being higher in alkali-soluble fraction, although 14C specific activity in both fractions increased by 11.4–13.6 pMC during the first 15 years of plant operation. However, during the 2000–2009 period, other than previously seen, a dissolved inorganic carbon (DIC) → aquatic primary producers → sediments 14C incorporation pattern occurred, as the radiocarbon specific activity difference between alkali-soluble and -insoluble fractions reached 94, 25, and 20 pMC in 2000, 2006, and 2008, respectively. Measurements in different sediment fractions allowed us to identify the unexpected organic nature of 14C contained in liquid effluences from the INPP in 2000–2009. The discrepancy between 14C specific activity in fish scales samples and DIC after 2000 also confirmed the possibility of organic 14C contamination. Possible reasons for this phenomenon might be industrial processes introduced at the INPP, such as the start of operation of the cementation facility for spent ion exchange resins, decontamination procedures, and various maintenance activities of reactor aging systems and equipment.

Distribution of Pu isotopes and 210Pb in the Bohai Sea and Yellow Sea: Implications for provenance and transportation

Particle-reactive radionuclides are useful for tracing sediment dynamics in marginal seas. We collected a suite of surface sediment samples in May 2014 from the Bohai Sea (BS) and Northern Yellow Sea (NYS) to observe the spatial distribution of Plutonium (Pu) isotopes and 210Pb activities. 239+240Pu activities ranged from 0.001 to 0.288 and 0.040–0.269 Bq kg−1 in BS and NYS surface sediments, respectively. 210Pbex shows a significant correlation with 239+240Pu (r = 0.84, p < 0.01) that suggested these two nuclides were scavenged to the same grade. 240Pu/239Pu atom ratios in BS (0.173–0.256) and NYS (0.196–0.275) were slightly higher than the global fallout value of 0.18 and lower than the Pacific Proving Ground (PPG) value of 0.36, indicating that some fraction of Pu originating from the PPG was capable of being transported to the BS and NYS. Mass balance results showed that 41% of 239+240Pu (8.9 × 109 Bq yr−1) and 18% of 210Pb (2.4 × 1012 Bq yr−1) in the NYS originated in the oceanic input. In the BS, 63% of 210Pb originated from atmospheric deposition and 84% of 239+240Pu originated from riverine input. Using Pu and 210Pb as tracers, we estimate that (1.8–2.6) × 108 t yr−1 and (3.6–3.8) × 108 t yr−1 of sedimentary particles could be transported from the BS to the NYS and from the NYS to the Southern Yellow Sea, respectively. Furthermore, the 226Ra/238U activity ratio distribution suggested that sedimentary particles derived from the Yellow River could be transported to the middle of the BS and coastal areas of the NYS.

Reconstruction of the palaeo-ecological quality status in an impacted estuary using benthic foraminifera: The Santos Estuary (São Paulo state, SE Brazil)

The Santos Estuary (SE Brazil) is a coastal ecosystem with a high ecological importance and has been strongly impacted by human activities over the last century. A multiproxy analysis of sediment core dated by 137Cs, 210Pb and 226Ra activities and based on sediment geochemistry and benthic foraminifera is here used to reconstruct the environmental changes and the variations of the Palaeo-Ecological Quality Status (Palaeo-EcoQS) during the last ~120 years. The Palaeo-EcoQS was reconstructed by applying the diversity index Exp(H'bc) based on the benthic foraminiferal fauna. Specifically, the Ecological Quality Ratio (EQR) allowed to assess the Palaeo-EcoQS during the last ~120 years using local reference conditions. Based on our data, the pre-industrial period (~1883–1902) represents the reference conditions with “Good” Palaeo-EcoQS. The ~1902–1972 period coincides with the beginning of industrial operations and intensification of coastal urbanization leading to a deterioration of the environmental quality and Palaeo-EcoQS shifting to “Moderate” conditions. Dredging operations in 1972 led to increase the influences of adjacent sea that ultimately resulted in a “Good” Palaeo-EcoQS persisting up to the 1990s. Despite the preservation actions and recovery programs, the 1993–2012 period was characterized by an overall deterioration of the environmental conditions. Indeed, the reconstructed “Poor” to “Bad” Palaeo-EcoQS suggest the ineffectiveness of the remediation actions. This work confirmed that benthic foraminifera are reliable to evaluate EcoQS and Palaeo-EcoQS in estuarine ecosystems. Based on the present findings and previous studies showing the potential of fossil foraminifera to define in situ reference conditions, we recommend the inclusion of foraminifera in the list of biological quality elements within legislations concerning transitional and marine habitats.

Evaluating the effects of regional climate trends along the West Antarctic Peninsula shelf based on the seabed distribution of naturally occurring radioisotopic tracers

Measurements of 230Th, 14C, 210Pb and 234Th activities were made on sediment cores collected along a N-S transect exhibiting a gradient in annual sea-ice duration off the West Antarctic Peninsula. The resultant data were used to evaluate the effects of regional warming on particle flux reaching the seabed on timescales from millennial to seasonal. Shelf samples were collected at five stations, over three cruises, between February 2008 and March 2009, as part of the FOODBANCS2 Project. Sea-ice conditions (the number of days ice-free prior to core collection) were evaluated at the five stations to understand the relationship between ice abundance and particle/radionuclide flux. Based on the millennial tracer 14C, rates of sediment accumulation along the peninsula decrease southward, consistent with the observed sea-ice gradient. 230Th data provide additional evidence on millennial timescales that sediment focusing (i.e., lateral transport) occurs to a greater extent in the northern reaches of the study area compared to the southernmost stations. The distribution of steady-state, 210Pb flux to the seabed (representing centurial trends) displays a similar trend to 14C, showing higher radionuclide/particle flux in the northern study area (where sea-ice duration is diminished) and lower flux southward as sea-ice duration increases. Additionally, 210Pb data suggest that lateral transport plays an important role in the sediment distributions of this radiotracer on hundred-year timescales, which is explainable by the relatively short circulation times of peninsular waters relative to 210Pb's half-life. On seasonal and annual time scales, the distribution of steady-state 234Th flux to the seabed shows an increase in radionuclide flux at the southernmost stations. This increase in radionuclide flux on seasonal and annual time scales is consistent with the warming trend along the peninsula and the reduction in sea-ice duration over the past decade. A significant statistical relationship, however, could not be established between annual sea-ice free days and 234Th-derived particle flux to the seabed. The fluxes/distributions of long-lived particle-reactive tracers (14C, 230Th, and 210Pb) on the West Antarctic Peninsula shelf appear to be controlled primarily by the long-term pattern of increasing annual sea-ice duration in the southward direction, whereas the fluxes of the short-lived tracer (234Th) are consistent with the more recent decreases in sea-ice duration (associated with climate change) that have occurred over the past decade, primarily in the southern West Antarctic Peninsula stations.

Sedimentation rate determination and heavy metal pollution assessment in Zariwar Lake, Iran

Metal contents and enrichment factors of ten major trace metals, along with total organic matter, were studied using a 50-cm-long sediment core from Zariwar Lake in Iran. The source of elements (Fe, V, Co, Cd, Al, Cu, Zn, Ni, Cr and Mn) was investigated by chemical partitioning technique as well as cluster analysis. Results of partitioning revealed the anthropogenic portion of metals (%) to be: Zn > Cu > V > Ni > Mn > Cd > Co > Cr. Cluster analysis classified all elements into clusters A and B. The presence of Fe and Al as earth indices in both clusters indicated that all investigated elements likely originate from the lithogenic sources to some extent. Results obtained from the geochemical accumulation index, pollution index, enrichment factor and Hakanson index showed that the sediments were not contaminated and did not exhibit ecological risk. Negligible levels of pollution were seen in terms of Ni and Mn contents. Average sedimentation rate was about 5.6 mm/year according to 210Pb activity through the depth of the core, which is about 5.5 times greater than the ones reported in other freshwater lakes. Considering the lake being small, this increasing trend in sedimentation rate may create short phases of lake sedimentation and degrade the aesthetic quality of this aquatic environment.

Impact of a massive dust storm on the gross alpha, gross beta, 40K, 137Cs, 210Pb, 7Be activities measured in atmospheric aerosols collected in Tenerife, Canary Islands

Abstract From February 22 to 24, 2020, an intense dust storm affected the Spanish archipelago of the Canary Islands. Here we assess the radiological impact on the Canary Islands population of several natural and artificial radionuclides (40K, 137Cs, 210Pb, 7Be), and other radiological parameters (gross alpha and gross beta activity concentrations) measured in atmospheric aerosols before, during and after the dust storm. Total Suspended Matter highly correlated with PM10 (Pearson's correlation coefficient, ro = 0.98), showed increments ranging from 849% to 1778% against the background average levels, reaching levels of >3000 μg m−3. 40K and 137Cs radionuclides showed activity values over the minimum detection activity from January to March 2020, coupled with dust intrusion episodes during the study. This finding supports the use of these radionuclides as radiotracers for African low altitude dust intrusions occurring particularly during winter months over the Canary Islands. A high correlation between gross beta and 210Pb activities suggests that the latter is the main source for gross beta emitters in aerosol samples collected in the study region. 210Pb and 7Be showed a moderate positive correlation and did not show any significant change during the storm, suggesting a similar dynamics of alpha and beta emitters in the low atmosphere. A Principal Component Analysis of these observations showed two components representing a Saharan component (based on 40K, 137Cs, gross alpha, and PM10) and a heterogeneous component representing North Atlantic and Europe air masses (based on 7Be, 210Pb, and gross beta). In addition, a K-means cluster analysis helped to disentangle the origin of air masses arriving at the archipelago. Three different clusters were identified: a continental cluster (based on gross beta, 210Pb, and 7Be activity concentrations); an oceanic cluster (with low values of PM10 air concentrations, gross beta, gross alpha, and 210Pb, and 7Be and 40K activity concentrations), reflecting the Atlantic air contributions with lower radionuclide activity and microparticulate matter; and a dust intrusion cluster (with high PM10 values and 137Cs, 40K and gross alpha activity concentrations) representing dust intrusion episodes observed in Tenerife Island. These studies allow the detection and monitoring of radioactive elements, estimating the potential radiological risk to the population associated with mineral dust intrusions.

Accumulation rates of natural radionuclides (40K, 210Pb, 226Ra, 238U, and 232Th) in topsoils due to long-term cultivations of water spinach (Ipomoea Aquatica Forssk.) and rice (Oryza Sativa L.) based on model assessments: A case study in Dong Nai province, Vietnam

In topsoils, the activity concentrations of natural radionuclides (hereafter NRs) increase due to the addition of NRs from fertilizers, irrigation water, and air dust pollution. On the other hand, various physical-chemical and environmental processes such as radioactive decay, volatilization, leaching, erosion, and plant uptake were responsible for the decrease of the activity concentrations of NRs in the topsoils. In this study, behaviours of 40K, 210Pb, 226Ra, 238U, and 232Th in topsoils were modelled by the CEMC soil model and the HYDRUS-1D model. An exponential equation was proposed for estimating the accumulation rates of these radionuclides in the topsoils. Long-term accumulation of radionuclides was assessed for water spinach (Ipomoea Aquatica Forssk.) soil (hereafter VES) and rice (Oryza sativa L.) soil (hereafter RIS). We found that the current agricultural practices caused the increase of 40K activity concentration in the water spinach soil, and 40K, 210Pb, 226Ra, and 232Th activity concentrations in the rice soil. The accumulation rates of radionuclides were in the order 238U < 232Th < 226Ra <210Pb < 40K. 25 years of cultivation with water spinach can increase/decrease + (165 ± 6) Bq of 40K, – (8.2 ± 0.7) Bq of 210Pb, – (4.3 ± 0.2) Bq of 226Ra, – (7 0.3 ± 0.3) Bq of 238U, and – (1.8 ± 0.1) Bq of 232Th in 1 kg soil. For rice cultivation, these values are + (1004 ± 39), + (3.3 ± 0.2), + (3.0 ± 0.2), – (5.1 ± 0.3), (2.2 ± 0.1) Bq kg−1 for 40K, 210Pb, 226Ra, 238U, and 232Th, respectively.

Time marker of 137Cs fallout maximum in lake sediments of Northwest China

Caesium-137 (137Cs) has no natural source and is commonly employed in establishing the chronology of recent lake sediments in the Anthropocene epoch. Because of their location in the northern mid-latitude Westerlies circulation region, downwind of the Chernobyl accident and their proximity to the Lop Nur Chinese Nuclear Testing (CNT) site, lake sediments in NW China record a137Cs fallout maximum of global atmospheric thermonuclear weapon tests (GTWT) in 1963–1964 Common Era (CE), with probably local fallout subpeaks due to the Chernobyl accident in 1986 CE and CNT in 1976 CE. This complexity means that the use of 137Cs fallout maximum in lake sediments as a time marker in NW China is thus far not well constrained, impeding assessment of recent and future changes in paleoclimate and human activities. To identify the 137Cs time marker and provide a reliable chronology of surface lake sediments for investigating paleoclimatic changes and for defining the Anthropocene epoch in NW China during the last 50–100 years, here we describe chronologies of 6 near-surface sediment cores from NW China based on 137Cs and 210Pb activities, and review the chronology of 23 lake sediments and 10 ice cores from NW China and central Asia based on 137Cs, 210Pb, 239+240Pu, 3H, 241Am, and beta-activity dating methods, and annual layer counting, as well as 240Pu/239Pu isotopic ratios. Based on the potential influence of radioactivity transport from the Chernobyl accident and CNT, and the comparison with deposition records of 26 European lake sediments and 5 Alpine ice cores, we propose that the 137Cs fallout maximum of lake sediments in NW China and central Asia is primarily attributable to GTWT and that there is no unambiguous evidence to confirm the Chernobyl- and CNT-derived 137Cs local-fallout subpeaks. Taking into account the approximately one-year delay between injection of 137Cs into the atmosphere and its incorporation in lake sediment records, we conclude that the 137Cs fallout maximum in lake sediments of NW China provides a reliable GTWT time marker for 1964 CE.

The activities of 210Po and 210Pb in cigarette smoked in Tunisia.

In this study, the activity concentration of polonium 210 in cigarette for Tunisian consumers was investigated by alpha spectrometry. After chemical digestion of tobacco, 210Po was extracted, auto-deposited on disc and measured. The activity of 210Pb was assessed after radioactive equilibrium was achieved. The activity levels of 210Po ranged between 7.8 ± 0.3 and 17 ± 0.5mBq per cigarette with an average of 12.9 ± 0.4mBq per cigarette. Effective doses per year due to cigarette smoking were calculated assuming that 22% of the 210Pb and 210Po in tobacco were retained in the lungs of the smokers. It is concluded that for a smoker in Tunisia, the average effective dose is about 90.6 ± 3.3μSv per year for a cigarette consumption of one pack of cigarettes per day. This value is somewhat lower than 106.4 ± 5.3μSv per year estimated as the mean global effective dose from smoking.

The assessment of radiological risks associated with the ingestion of 210Po, 210Pb, and 137Cs in marine organisms collected from the local fish market of Kenitra, Morocco

210Po, 210Pb, and 137Cs activities were measured using gamma and alpha spectrometry in commonly consumed seafood collected from the local fish market of Kenitra, Morocco. 210Po activity ranged from 0.76 to 182.5 Bq kg−1 w.w, while 210Pb and 137Cs activities were 1 and 4 Bq kg−1 w.w, respectively. The potential health risks associated with the consumption of seafood were assessed through the calculation of the committed effective dose, the daily intake, and the lifetime cancer risk. The obtained results of the committed effective dose were below the limit (1 mSv year−1), while the lifetime cancer risk exceeded the range of acceptable values.

Lead sorption by extraction chromatographic resins on the base Di-(tert-butylcyclohexano)-18-crown-6 and its application for analysis of marine samples

The paper contains the results of determining the physical and chemical characteristics of lead sorption by impregnated sorbents based on Di-(tert-butylcyclohexano)-18-crown-6 and different diluents (1,1,7-trihydrododecafluoroheptanol, ionic liquid). The results of studying the influence of sorption time (kinetics) and lead concentration in the initial solution (isotherm) on the degree of lead extraction by the obtained sorbents, as well as the selectivity of lead sorption against other metals, were presented for the first time. These characteristics are important to justify the ratio of the solution to the sorbent for concentration and separation from related impurities, the rate of transmission of the solution through the sorbent, estimates of the amount of stable tracer to be inserted. The specific activity of 210Pb in the Black Sea was determined for the first time using the obtained sorbents. Samples for determining the specific activity of 210Pb in sea water were taken on cruise 101 of the R/V “Professor Vodyanitsky” (December 14–28, 2017).

Losses of Soil Organic Carbon with Deforestation in Mangroves of Madagascar

Global mangrove deforestation has resulted in substantial CO2 emissions to the atmosphere, but the extent of emissions from soil organic carbon (C) loss remains difficult to assess. Here, we sampled five intact and five deforested mangrove plots from Tsimipaika Bay, Madagascar, to examine the loss of soil C in the 10 years since deforestation. We estimated tree biomass and analyzed grain size, 210Pb activities, organic C and total nitrogen (N) and their stable isotopes in soils as well as dissolved organic C in surface waters. Deforested soils revealed evidence of disturbance in the upper 14 g cm−2 (~40 cm) when compared to reference intact soils, indicated by lower porosity, higher dry bulk density, an order of magnitude higher soil mixing and loss of C and N despite no significant soil erosion. Although C loss from biomass was unequivocal and was estimated at 130 Mg C ha−1, the C loss from soils was more difficult to assess given the large heterogeneity of intact forest soils. We estimated that the loss of C due to mangrove clearing and soil exposure over 10 years was equivalent to about 20% of the upper meter soil C stock, and about 45% of the C stock accumulated during the last century. Soil C loss rate was 4.5 times higher than the C sequestration rate in reference intact soils. These results emphasize the importance of mangrove conservation for CO2 emissions mitigation, as they suggest that deforestation-C losses will take substantially longer to offset with mangrove restoration.

Atmospheric fallout impact on 210Po and 210Pb content in wild growing mushrooms

The atmospheric fallout impact on 210Po and 210Pb content in fruitbodies of wild growing mushrooms collected from different environments were investigated. The samples of morphologically different mushroom species, namely bay bolete (Imleria badia (Fr.) Vizzini), slippery jack (Suillus luteus (L.) Roussel), fairy ring mushroom (Marasmius oreades (Bolton) Fr.) and common earthball (Scleroderma citrinum Pers.) with their mycelium and soil substrate were collected. Their fruitbodies were separated into cap skin, cap flesh and stem. Also mycelium and soil substrate were collected. The results showed the highest 210Po and 210Pb activity concentrations were found in Marasmius oreades cap skin: 3.20 ± 0.12 and 21.1 ± 0.5 Bq kg−1 ww, respectively, which constituted 31.2 and 78.7% of their content in the total fruitbody mass. In the case of open space wild growing mushrooms, their whole caps contain a significantly higher amount of 210Po and 210Pb when compared to the stem, and their content in the whole cap was determined mainly by concentrations in the cap skin.

Microplastic accumulation in deep-sea sediments from the Rockall Trough

Microplastics are widely dispersed through the marine environment. Few studies have assessed the long-term or historic prevalence of microplastics, yet acquiring such data can inform their distribution, transport and the environmental risks posed. To quantify the distribution and polymer types temporally, sediment cores were collected from >2000 m water depth in the Rockall Trough, North Atlantic Ocean. As hypothesized, a significant negative trend was observed in the frequency of microplastics with increasing sediment age, however there was an increase in polymer diversity. Microplastics were pervasive throughout the sediment analysed (10 cm depth), yet lead-210 (210Pb) activities were confined to the upper 4 cm, indicating this layer to be ~150 years old and thus the presence of microplastics far exceed the production of modern plastic. A number of mechanisms, including sediment reworking, could redistribute microplastics vertically. Additionally, microplastics abundance was significantly correlated with sediment porosity, suggesting interstitial transport via pore waters.

Distribution of uranium and thorium chains radionuclides in different fractions of phosphogypsum grains

This work presents results obtained using gamma spectrometry measurements of phosphogypsum samples on a non-fractionated (native) and fractionated phosphogypsum byproduct. The phosphogypsum was divided into particles size fractions within the range of < 0.063, 0.063–0.090, 0.090–0.125, 0.125–0.250, and over 0.250 mm and analyzed after reaching radioactive equilibrium using high-resolution gamma spectrometry technique. It was found that there is no significant differentiation between 226Ra distribution among particular grain size fractions of this material; however, tendency for preferential retention of radionuclides in particular grain size fractions is observed. The detailed analysis of results revealed that radium is preferentially retained in smaller grain size fractions, whereas lead and thorium in coarse fractions. The results indicate that overall 226Ra activity concentrations between particular fractions of phosphogypsum vary globally between − 34 and + 47% regarding non-fractionated material, and for 210Pb activity concentration, fluctuations are found between − 26 up and + 38%. Presumably, the mechanism of radium incorporation into gypsum phase is based on a sequence of radium bearing sulfate phases formation followed by a surface adsorption of these phases on the calcium sulfate crystals, whereas for lead and thorium ions, rather incorporation into crystal lattice should be expected as more likelihood process.

Measuring bismuth‐210, its parent, and daughter in aquatic systems

Abstract210Bi (t1/2: 5.01 d)—the daughter of 210Pb and parent of 210Po—has rarely been measured in aquatic systems, and its behavior in the water column is poorly understood. In this article, I present a method for quickly measuring 210Pb, 210Bi, and 210Po in aquatic samples, where (1) 210Bi and 210Po are scavenged onto an anion solid‐phase extraction disk within 15 min of pretreating the sample; (2) beta decay of 210Bi is counted on the disk immediately thereafter; (3) 210Po is subsequently removed from the disk and redeposited on a copper plate for α‐spectroscopy; and (4) 210Pb is determined via the ingrowth of 210Bi. I present decay‐corrected calculations for total, dissolved, and particle‐bound fractions of each nuclide and conclude with an analysis of 210Pb, 210Bi, and 210Po activities in rain, dreissenid (quagga) mussels, and water samples from the Milwaukee Inner Harbor in Lake Michigan. Results show that the loss of lead on the anion solid‐phase extraction disks was negligible (0.2% ± 2.1%; ± 1 SD, n = 4), and the sorption of bismuth was complete (99% ± 2%; ± 1 SD, n = 16). Relative mean absolute deviations of duplicate sample analyses of lake water were 2.4% ± 1.9% for 210Pb (geometric mean of total sample activity: 3.0 disintegrations per minute [dpm], n = 6), 7.7% ± 5.8% for 210Bi (geometric mean of total sample activity: 2.6 dpm, n = 8), and 2.7% ± 1.7% for 210Po (geometric mean of total sample activity: 1.4 dpm, n = 8).

Variability in 210Pb and 210Po partition coefficients (Kd) along the US GEOTRACES Arctic transect

The naturally occurring 210Po (t1/2 = 138.3d) and 210Pb (t1/2 = 22.3 y) radionuclide pair has been extensively used to study particle scavenging, cycling and transport in the ocean. However, the role of particle composition in the scavenging, sorption and fractionation of 210Po210Pb needs to be better understood to successfully utilize these radionuclides as oceanographic tracers. Here, we measure dissolved and particulate 210Pb and 210Po activities for both small (1-51 μm) and large particles (> 51 μm) with abundance of major phases of suspended particulate matter (SPM) from the US GEOTRACES Arctic transect to examine the role of the concentration and composition of SPM in scavenging and fractionation of these radionuclides along the coastal, Canada Basin and interior stations. 210Po210Pb disequilibria were observed throughout the water column for all stations. The Pacific end member had the highest activity of 210Po and 210Pb in dissolved samples. The calculated partition coefficients (Kd) of 210Po and 210Pb varied between 3.2 × 105 to 9.9 × 108 L kg−1 and 7.9 × 105 to 6.9 × 108 L kg−1 respectively and followed a log-linear trend with SPM for particle size fractions. Principal Component Analysis (PCA) and correlation analysis for six major particle phases indicated a significant positive correlation between 210Pb and the lithogenic phase. Both 210Po and 210Pb had significant negative correlations with opal. Our results suggest that particle composition alone cannot explain the observed variability in Kd across the different oceanic regime along the transect. Estimated Kd values from an end member mixing model were found to be within the range of observed Kd values and suggest that higher particulate Mn concentration in the Arctic may be partly responsible for the higher Kd observed in the basin compared to Atlantic and Pacific.

210Po and 210Pb activity concentrations in Greenlandic seabirds and dose assessment

Naturally occurring radionuclides, in particular, polonium-210 (210Po), have a greater contribution than anthropogenic radionuclides to the annual effective dose received by the general public due to consumption of seafood. Knowledge of potential trophic sources and transfer of 210Po to seabird species and subsequently to the Greenlandic people is, however, still poor. Here, we assess the transfer of 210Po and 210Pb to seabirds sampled during autumn and winter 2017 and 2018 in Greenland and provide a dose assessment. The activity concentrations of 210Po in muscle and liver, respectively, ranged from 0.2 ± 0.1 Bq kg−1 w.w. in glaucous gull (Larus hyperboreus) to 21.2 ± 22.6 Bq kg−1 w.w. in thick-billed murre (Uria lomvia) and from 32.0 ± 9.4 Bq kg−1 w.w. in common eider (Somateria mollissima) to 40.5 ± 49.0 Bq kg−1 w.w. in thick-billed murre. 210Po was non-uniformly distributed in the body of thick-billed murre. Kidneys and feathers showed higher 210Po activity concentrations than heart and bone. The 210Po/210Pb activity concentration ratios are higher than unity, indicating that 210Po is preferentially taken up by seabirds compared to its progenitor 210Pb. The derived annual absorbed dose from 210Po to the whole body of thick-billed murre was 6.4 × 102 ± 3.0 × 102 μGy. The annual effective dose to the average adult and representative person in Greenland due to ingestion of 210Po in seabirds was estimated to 13.0 μSv and 57.0 μSv, respectively. This derived dose is low and poses a slight risk, and risk communication is therefore deemed unnecessary.

Modeling of 210Pb and 210Po radionuclide emissions from local power plants in central Poland.

Due to the more volatile nature of 210Po in relation to 210Pb, an imbalance of activity concentrations in high temperature combustion processes can be observed, especially in fine particulates (diameter < 0.1, 0.2 and 0.5 μm). In the atmosphere and in the soil around coal-fired power plants, 210Pb and 210Po concentrations are a combination of activities from natural and anthropogenic sources. In this study only portions of 210Po and 210Pb radionuclides resulting from energy production activities were analyzed. Due to the high mobility of fine particles, a surface area of 172 km × 140 km in central Poland was chosen for simulation. For validation of the modeling approach, three grid versions were applied: 1 km, 2 km and 4 km. Simulated results confirmed experimental-computational values of an excess of both radionuclides in the atmosphere in 2017 in the city of Lodz. Different aerosol fractions, seasons and various grids in the selected area were subjected to 36 individual simulations. The 210Po activity concentrations measured in winter and summer 2017 were 42.5 and 8.99 μBq m-3, respectively. Simulated and measured values of artificial 210Po and 210Pb activities are well correlated.