210Pb and 210Po in Geological and Related Anthropogenic Materials: Implications for Their Mineralogical Distribution in Base Metal Ores

Abstract

Abstract: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.

Combined U-Pb isotopic signatures of U mill tailings from France and Gabon: A new potential tracer to assess their fingerprint on the environment

“…For JOU-97 sample the radiogenic Pb is also encountered in association with micrometricsized U-poor phases that could potentially be either clay minerals or oxyhydroxides related to (i) the weathering of minerals from the mineralized granites or (ii) the rapid diagenesis of neutralized U mill tailing after deposition in the disposal (Somot et al, 2000;Somot et al, 2002, Cook et al, 2018Ballini et al, 2020;Chautard et al, 2020;Ram et al, 2021b).…”

Ecotoxicological effects of decommissioning offshore petroleum infrastructure: A systematic review

“…Even if organisms have the innate ability to repair induced damage from naturally occurring radiation, enhanced doses from industrial activities such as the petroleum decommissioning process could interfere with the sensitivity levels of marine fauna. 210 Pb and 210 Po are present as cations in seawater and bind to surfaces, including barite and exterior skeletons of biological organisms (Cook et al, 2018). Therefore, the isotopes are likely to be bound to sediment particles on the benthos and in particulate forms on organic matter floating in the water column (Fisher et al, 1989;Stewart & Fisher, 2003).…”

“…Though this illustrates the potential for 226 Ra and other radionuclides associated with BaSO 4 to suspend in the water column and become bioavailable for pelagic and benthic organisms (plankton, fish, crustaceans), the processes that lead to these pathways and level of measurable effects are still unknown. There has been a strong link identified across studies between the distributions of 210 Pb and 210 Po and that of parent 226 Ra, so the occurrence of 226 Ra may predict the behavior of the daughters (Cook et al, 2018). As 210 Pb and 210 Po are daughter products of 226 Ra, it is likely the daughters are strongly integrated within the scale BaSO 4 matrix and therefore also exhibit low solubility potential and minimal bioavailability.…”

A preliminary study of rapid measurements of aqueous 210Po by accelerator mass spectrometry

“…14–17 In general, the activities of 210 Po and its progenitor 210 Pb, are often monitored together in environmental samples for exposure risk assessments. 1,2,18,19…”