[en] The isotopic composition of Pb measured in soil samples was used to determine rates and mechanisms of anthropogenic Pb migration in the soil. Petrol-Pb found in soluble halogenated aerosols migrates into the soil and is retained in the soil by the stationary soil particles. Lead infiltration velocity is approximately 5 x 10^-1 cm/year, and its retardation factor is estimated to be on the order of 1 x 10³. The infiltration of Pb into the soil is best described by the advection-dispersion equation under the assumption that the time scale of the longitudinal dispersion is much longer than the time scale of advection. Therefore, the contribution of dispersion to the solution of the advection-dispersion equation is negligible. As a result, the soil profile of petrol-Pb resembles the time-dependent input function of petrol-Pb. The estimated petrol-Pb penetration velocity and the isotopic composition profile of Pb in off-road soil are used for the computation of the fraction of anthropogenic Pb in this soil. It is calculated that the fraction of anthropogenic Pb in the acid-leached soil samples and in the soil residue of this soil profile drops from 60 and 22% near the surface to 6 and 0% at a depth of 33 cm, respectively. The downward migration velocity of Pb in soils of the studied area, which are typically 50 to 100 cm deep, implies a residence time of Pb in the soil of 100 to 200 years

[en] A simple and fast technique of micro gel electrophoresis of single cells (DNA Comet Assay) was used to detect DNA comets in irradiated quail meat samples. Quail meat samples were exposed to radiation doses of 1.05, 2.00 and 4.00 kGy in gamma cell (Gamma cell ⁶0Co, dose rate 1.31 kGy/h) covering the permissible limits for enzymatic decay and stored at 4 degree C. The cells isolated from muscle (chest, thorax) in cold PBS were analysed using the DNA comet assay on 1, 4, 8 and 11 day post irradiation. The cells were lysed between 2, 5 and 9 min in 2.5% SDS and electrophoresis was carried out at a voltage of 2 V/cm for 2 min. and then prospidium iodide staining was employed to visualize DNA. After prospidium iodide staining, the slides were evaluated through a fluorescent microscope (Olympus BX 51 model with florescence and DIC attachments). In all irradiated samples, fragmented DNA stretched towards the anode and damaged cells appeared as a comet. The density of DNA in the tails increased with increasing radiation dose. However, in non-irradiated samples, the large molecules of DNA remained relatively intact and there was only minor or no migration of DNA; the cells were round or had very short tails only.

[en] Complete text of publication follows: Our ability to use uranium isotopes as a tool for determining rates and timescales of weathering critically depends on the processes that produce fractionation between ²³⁴U and ²³⁸U. First, during water rock interaction, ²³⁴Th can be directly recoiled into the water phase and subsequently decays to ²³⁴U. Second, mineral dissolution can lead to an enhancement of ²³⁴U in the water. We have used both a theoretical and experimental approach to better model both processes. We used continuous leaching experiments of a ground granite reported in Andersen et al. [1] combined with major element analyses to constrain the preferential leaching rates ²³⁴U relative to ²³⁸U for each mineral. To model these experiments, we have considered that ²³⁴U consist of two pools one that is easily leachage and one that has annealed at a slow rate and becomes indistinguishable from ²³⁸U. This model provides a good fit to the experiments but can also be extended to longer timescales. In order to better describe the recoil efficiency we have used surface area measurements based on the BET method and used this data to determine the fractal dimension of the surface. This fractal dimension is then used to correct the recoil efficiency for surface roughness at the length scale of recoil (∼ 30 nm). DePaolo et al. [2] had underlined that BET measurements overestimate the surface area to calculate recoil efficiency. Our methodology now provides a refined estimate of recoil efficiency that is more consistent with observations. The combination of these approaches provides a predictive framework with which one can estimate more reliably weathering rates based on U isotopes. This will be done using examples from the literature as well our study of carbonate weathering in Eastern France. Notably, an improper estimate of preferential leaching leads to an incorrect estimate of weathering rates