[en] The optimization of alpha/beta separation in liquid scintillation using pulse shape analysis is convenient for the simultaneous determination of alpha and beta emitters in natural water and other samples. In this work, alpha/beta separation was studied for different scintillant/vial combinations and it was observed that both the optimum pulse shape discrimination level and the total interference value (that is, the summed relative interference between alpha and beta spectra) were dependent on the sample quenching and independent of the scintillant/vial combination. These results provide a simple method for modifying the counting configuration, such as a change in the cocktail, vial or sample characteristics, without the need to perform exhaustive parameter optimizations. Also, it was observed that, for our counting conditions, the combination of Ultima Gold AB scintillation cocktail with Zinsser low diffusion vials presented the lowest total interference, namely 0.94 ± 0.28%, which is insignificant for the counting of environmental samples. (Author)

[en] The distribution, transport and accumulation mechanisms of transuranics (and other radionuclides) in the marine environment depend on the source term, biogeochemical cycles, transport with the water masses, sedimentation processes and transfer mechanisms in the trophic chain. The biogeochemical behaviour of plutonium, which has been the focus of our work, was studied using the following approaches: determination of the physico-chemical speciation of plutonium in marine waters, vertical flux in the water column, uptake by marine organisms (phytoplankton and zooplankton) and distribution in dements cores. A preliminary model of the accumulation and distribution of plutonium in the first levels of the marine food chain in the Irish Sea has also been formulated. All this information allowed us to obtain an integrated view of the behaviour of plutonium in the marine environment. (Author) 14 refs

[en] ¹³⁷Cs concentration surface water time series in 12 latitudinal boxes of the Pacific Ocean are re-investigated for the period from 1970 to 2005. The apparent half-residence times of ¹³⁷Cs ranged from 11 to 36 years, depending on the position of the box. Generally these revised estimations of the apparent half-residence times are in good agreement with previous estimations. However, in a few boxes in the South Pacific we found longer apparent half-residence times. ¹³⁷Cs inventories in the water column of the Pacific were also re-investigated for the period from 1970 to 2003. They are much smaller in the north of the subtropical gyre, however, they showed a less decrease in the south edge of the subtropical gyre. In the equatorial areas, ¹³⁷Cs inventories had increased or been maintained constant. The main processes of these differences are caused by the southward transport of water masses due to subduction, and due to the existence of mid-depth minima at 300-400 m layers which correspond to the central mode water. (author)