210 Pb (210 Po) speciation of aquatic deposits: Refinement and utility (original) (raw)
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Editorial: Geochemical Cycling of 210Po and 210Pb in Marine Environments
2022
INTRODUCTION The radioactive isotope 210Po (T1/2 = 138.4 days) and its grandparent 210Pb (T1/2 = 22.3 years) have been increasingly used to trace particle dynamics and the biogeochemical cycling of chemical species in aquatic environments over recent decades (Verdeny et al., 2009). This Research Topic provides a set of new studies focusing on the biogeochemical cycling of both 210Po and 210Pb in the marine environments. A total of 11 articles were published on this Research Topic, covering the biogeochemical behaviors of 210Po and 210Pb in various oceanic settings, their ability to bind with diatomand coccolithophore-associated biopolymers, the utilization of 210Po/210Pb to quantify the sinking flux of particulate organic carbon and the residence times (or ages) of particulate matter in a variety of environmental settings, and the coupled application with other radionuclides and soot to expand their utilities as biogeochemical proxies.
Minerals
The distributions of 210 Pb and 210 Po, short half-life products of 238 U decay, in geological and related anthropogenic materials are reviewed, with emphasis on their geochemical behaviours and likely mineral hosts. Concentrations of natural 210 Pb and 210 Po in igneous and related hydrothermal environments are governed by release from crustal reservoirs. 210 Po may undergo volatilisation, inducing disequilibrium in magmatic systems. In sedimentary environments (marine, lacustrine, deltaic and fluvial), as in soils, concentrations of 210 Pb and 210 Po are commonly derived from a combination of natural and anthropogenic sources. Enhanced concentrations of both radionuclides are reported in media from a variety of industrial operations, including uranium mill tailings, waste from phosphoric acid production, oil and gas exploitation and energy production from coals, as well as in residues from the mining and smelting of uranium-bearing copper ores. Although the mineral hosts of the two radionuclides in most solid media are readily defined as those containing parent 238 U and 226 Ra, their distributions in some hydrothermal U-bearing ores and the products of processing those ores are much less well constrained. Much of the present understanding of these radionuclides is based on indirect data rather than direct observation and potential hosts are likely to be diverse, with deportments depending on the local geochemical environment. Some predictions can nevertheless be made based on the geochemical properties of 210 Pb and 210 Po and those of the intermediate products of 238 U decay, including isotopes of Ra and Rn. Alongside all U-bearing minerals, the potential hosts of 210 Pb and 210 Po may include Pb-bearing chalcogenides such as galena, as well as a range of sulphates, carbonates, and Fe-oxides. 210 Pb and 210 Po are also likely to occur as nanoparticles adsorbed onto the surface of other minerals, such as clays, Fe-(hydr)oxides and possibly also carbonates. In rocks, unsupported 210 Pb-and/or 210 Po-bearing nanoparticles may also be present within micro-fractures in minerals and at the interfaces of mineral grains. Despite forming under very limited and special conditions, the local-scale isotopic disequilibrium they infer is highly relevant for understanding their distributions in mineralized rocks and processing products.
Activities of 210Po and 210Pb in the water column at Kuala Selangor, Malaysia
Journal of environmental radioactivity, 2005
Natural radionuclides, such as (210)Po and (210)Pb were measured in the water samples collected from six stations at Kuala Selangor, Malaysia. Results for (210)Po and (210)Pb in dissolved and particulate phases have showed the difference in distribution and chemical behavior. The fluctuation activities of (210)Po and (210)Pb depend on wave action, geology and degree of fresh water input occurring at study areas and probably due to different sampling dates. The distribution coefficient, K(d), values of (210)Po and (210)Pb ranged from 2.0 x 10(3)lg(-1) to 265.15 x 10(5)lg(-1), and from 3.0 x 10(3)lg(-1) to 558.16 x 10(5)lg(-1), respectively. High K(d) values of (210)Po and (210)Pb indicated that a strong adsorption of (210)Po and (210)Pb onto suspended particles, and the sinking of both nuclides on the seabed at study locations were controlled by the characteristics of suspended particles.
Journal of Radioanalytical and Nuclear Chemistry, 2012
210 Pb activities were analyzed in surface sediments from the Coatzacoalcos River (Gulf of Mexico) to evaluate its distribution according to sediment grain size and in different geochemical compartments by using sequential extraction techniques. The geochemical fractionation experiments provided compatible results: by using the Tessier's method [1] more than 90% of the 210 Pb activity in the samples was found the residual fraction (primary and secondary minerals) and the remaining (\10%) in the iron and manganese oxides fraction of the sediments; whereas using the Huerta-Diaz and Morse method [2] the 210 Pb content was found in comparative amounts in the reactive, the silicate, and the pyrite fractions (accounting together for [80%), and the rest was found in the residual fraction. The grain size fractionation analyses showed that the 210 Pb activities were mostly retained in the clay fraction, accounting up to 60-70% of the 210 Pb total activity in the sediment sample and therefore, it is concluded that the separation of the clay fraction can be useful to improve the analysis of low 210 Pb content sediments for dating purposes.
Journal of Environmental Radioactivity, 2014
Some of the daughter products in the 222 Rn-decay series, such as 210 Po and 210 Pb, have been widely used as tracers and chronometers in aqueous systems. We measured the concentrations of 210 Pb and 210 Po in the dissolved (0.5 mm), bulk (unfiltered) and particulate phases (!1 mm) collected in the Clinton River in the Lake St. Clair watershed in Southeast Michigan in order to investigate their partitioning between particulate and dissolved phases. Activity measurements of the dissolved and particulate phases revealed that an average of 38% (range: 12e59%) and 33% (range: 12e66%) of the total 210 Pb and 210 Po, respectively, in the water column was found in the particulate phase. The activity of dissolved and total 210 Pb was higher than that of 210 Po because of the higher atmospheric depositional fluxes of 210 Pb compared to 210 Po. Although the calculated K d values of 210 Pb and 210 Po were similar, there was an inverse relationship between the K d and suspended particulate matter concentration, indicating the presence of a particle concentration effect and we attribute this observation to the presence of significant amounts of colloidal 210 Po and 210 Pb in the dissolved phase. The fractionation factors for Po and Pb were found to be less than 1 in most cases. The first-order box model calculation-based residence times with respect to scavenging varied from 2 to 25 days for 210 Pb and 19e78 days for 210 Po, indicating higher particle-reactivity of 210 Pb compared to 210 Po.
Applied Spectroscopy, 2000
An intercomparison of methodology and of dating results, from α-counting and from the more recent γ-spectrometry method, has been made for marine sediment cores from several locations. The former method involves considerable chemical manipulation, whereas the latter is more straightforward and enables direct interpretation of the results. Similar precisions (∼ 12%) were found for both methods. With the constant flux model, the methods gave calculated sedimentation rates between 4.3 and 7.8 cm a−1 for replicate cores near a ferry pier in Hong Kong Harbor. The γ-spectrometry method is thus a reliable, more rapid method for routine monitoring and investigation of the harbor dynamics and history of pollution.
Geochimica et Cosmochimica Acta, 1995
The geochemical processes controlling the behavior of stable Pb, ""Pb, and ""PO in seasonally anoxic Lake Sammamish, Washington were identified from water column distributions and box model calculations. Total (sum of dissolved and particulate) inventories of stable Pb, "?b, and *"'PO increased in the whole lake during the latter part of the oxic stage of the lake and were attributed to diffusion from sediments. Large decreases in the total inventories of these elements occurred during the transition from oxic to anoxic conditions, and the lowest inventories were observed during the sulfidic stage of stratification. The cycling of stable Pb and ""Pb during oxic periods appeared to be linked to Fe cycling while ""PO cycling was more closely linked to the cycling of Mn. The behavior of stable and radioactive Pb and, possibly, *"'PO during anoxia was influenced by sulfur cycling. Thermodynamic calculations indicated that dissolved Pb concentrations might be controlled by PbS precipitation during anoxia.
Determination of 210Pb and 210Po in soil or rock samples containing refractory matrices
Applied Radiation and Isotopes, 2007
A new method has been developed for determination of 210 Pb and 210 Po in soil or rock samples containing refractory matrices. The samples were first fused with Na 2 CO 3 and Na 2 O 2 at 600 1C for pre-treatment and then 210 Pb and 210 Po were sequentially leached out at 200-250 1C with HNO 3 +HF, HClO 4 and HCl. About 10% of the leaching solution was used for 210 Po determination, carried out by spontaneous deposition of polonium on a silver disc from a weakly acidic solution that contained hydroxylamine hydrochloride, sodium citrate and 209 Po tracer, measurement being made by a-spectrometry. The remains of the leaching solution were used for determination of 210 Pb, conducted by precipitation as sulphate, purification with Na 2 S as PbS in 6 M ammonium acetate, separation from a-emitters by an anion-exchange resin column, source preparation as PbSO 4 , and measurement with a b-counter. The procedure has been checked with two certified IAEA reference materials, showing good agreement with the recommended values. The lower limits of detection for 1 g of analysed soil or rock samples were found to be 0.75 Bq kg À1 for 210 Po and 2.2 Bq kg À1 for 210 Pb. A variety of solid sample species analysed through use of the procedure gave average yields of 90.079.8% for 210 Po and 88.477.1% for 210 Pb.
Potential factors affecting accumulation of unsupported 210Pb in soil
Radiation Physics and Chemistry, 2014
Airborne 210 Pb, daughter of 222 Rn, is frequently used as a tracer in different studies concerning atmospheric transport, sedimentation, soil erosion, dating, etc. Concentration of 210 Pb was measured in 40 soil samples collected in urban and industrial areas in order to get evidence of possible influence of some factors on accumulation of airborne 210 Pb in soil. Different soil properties such as the content of organic matter, free CaCO 3 , and available phosphorus (P 2 O 5 ) were measured to explore their possible correlation with the amount of 210 Pb. Special attention was given to the correlation between 210 Pb and stable lead accumulated in the soil. Several samples were taken near a battery manufacturer to check if extremely high concentrations of lead can affect the uptake of the airborne 210 Pb in soil. Soil samples were also taken at different depths to investigate the penetration of lead through the soil.