Assessment of Po and Pb in marine biota of the Mallipattinam ecosystem of Tamil Nadu, India

To provide baseline data on background radiation levels for the future assessment of the impact of nuclear and thermal power stations, a systematic study was carried out in the Mallipattinam ecosystem of Tamil Nadu, India. Mallipattinam is located between the Kudankulam and Kalpakkam nuclear power plants and near to Tuticorin thermal power plant. Water, sediments, seaweeds, crustaceans, molluscs, and fish were collected to measure the concentrations of ²¹⁰Po and ²¹⁰Pb. The concentrations of ²¹⁰Po and ²¹⁰Pb in most samples are comparable to values reported worldwide. In fish, the concentrations of ²¹⁰Po and ²¹⁰Pb are in the range 16-190 Bq kg⁻¹ and 8-153 Bq kg⁻¹, respectively. The concentration factors of ²¹⁰Po and ²¹⁰Pb for the biotic components ranges from 10³ to 10⁶.     

Quantification of transfer of U, Ra, Th, K and Cs in mosses of a semi-natural ecosystem

There is a lack of appropriate data on transfer of some radionuclides on many terrestrial biota groups. To expand the available data concentration ratios of ²³⁸U, ²²⁶Ra, ²³²Th, ⁴⁰K and ¹³⁷Cs in mosses are presented in this paper. The relationship between concentration ratios of radionuclides and physicochemical characteristics of the underlying soil was also investigated. The data on concentration ratios obtained here will provide a useful addition to the currently used database of transfer parameters, particularly for natural radionuclides.     

Direct comparison of 210Po, 234Th and POC particle-size distributions and export fluxes at the Bermuda Atlantic Time-series Study (BATS) site

Particle-reactive, naturally occurring radionuclides are useful tracers of the sinking flux of organic matter from the surface to the deep ocean. Since the Joint Global Ocean Flux Study (JGOFS) began in 1987, the disequilibrium between ²³⁴Th and its parent ²³⁸U has become widely used as a technique to measure particle export fluxes from surface ocean waters. Another radionuclide pair, ²¹⁰Po and ²¹⁰Pb, can be used for the same purpose but has not been as widely adopted due to difficulty with accurately constraining the ²¹⁰Po/²¹⁰Pb radiochemical balance in the ocean and because of the more time-consuming radiochemical procedures. Direct comparison of particle flux estimated in different ocean regions using these short-lived radionuclides is important in evaluating their utility and accuracy as tracers of particle flux. In this paper, we present paired ²³⁴Th/²³⁸U and ²¹⁰Po/²¹⁰Pb data from oligotrophic surface waters of the subtropical Northwest Atlantic and discuss their advantages and limitations. Vertical profiles of total and particle size-fractionated ²¹⁰Po and ²³⁴Th activities, together with particulate organic carbon (POC) concentrations, were measured during three seasons at the Bermuda Atlantic Time-series Study (BATS) site. Both ²¹⁰Po and ²³⁴Th reasonably predict sinking POC flux caught in sediment traps, and each tracer provides unique information about the magnitude and efficiency of the ocean's biological pump.     

Solid partitioning and solid-liquid distribution of Po and Pb in marine anoxic sediments: roads of Cherbourg at the northwestern France

A sequential extraction protocol has been used to determine the solid-phase partition of ²¹⁰Po and ²¹⁰Pb in anoxic marine sediment from the roads of Cherbourg (France) in the central English Channel. Measurements were also obtained in pore waters, in which ²¹⁰Po activities range between 1 and 20 mBq L⁻¹ and ²¹⁰Pb activities between 2.4 and 3.8 mBq L⁻¹, with highest activities in the topmost layer. These activities are higher than in seawater, suggesting that sediment act as a source of both ²¹⁰Po and ²¹⁰Pb for overlying water. The ²¹⁰Po profile in the pore waters is apparently correlated with those obtained for Fe, Mn and SO₄²⁻, suggesting an influence of early diagenetic processes on the ²¹⁰Po solid-liquid distribution. In the sediment, ²¹⁰Po is predominantly bound to organic matter or chromium reducible sulphides, and residuals (clay minerals and refractory oxides). Our results indicate that ²¹⁰Po is not significantly bound to AVS, i.e. acid volatile sulphides: bioturbation could play a role by the early redistribution of ²¹⁰Po bound to acid volatile sulphides in the sediment. ²¹⁰Po, ²¹⁰Pb and Pb exhibit differences in terms of distribution, probably due to a different mode of penetration in the sediment. This work provides information on solid and liquid distribution of ²¹⁰Po and ²¹⁰Pb in marine sediment. These data are very scarce in the litterature.