Solid partitioning and solid-liquid distribution of ~(210)Po and ~(210)Po in marine anoxic sediments: roads of Cherbourg at the northwestern France

摘要

A sequential extraction protocol has been used to determine the solid-phase partition of ~(210)Po and ~(210)Pb in anoxic marine sediment from the roads of Cherbourg (France) in the central English Channel. Measurements were also obtained in pore waters, in which ~(210)Po activities range between 1 and 20 mBq L~(-1) and ~(210)Po 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 ~(210)Po and ~(210)Po for overlying water. The ~(210)Po profile in the pore waters is apparently correlated with those obtained for Fe, Mn and SO_4~(2-), suggesting an influence of early diagenetic processes on the ~(210)Po solid-liquid distribution. In the sediment, ~(210)Po is predominantly bound to organic matter or chromium reducible sulphides, and residuals (clay minerals and refractory oxides). Our results indicate that ~(210)Po is not significantly bound to AVS, i.e. acid volatile sulphides: bioturbation could play a role by the early redistribution of ~(210)Po bound to acid volatile sulphides in the sediment. ~(210)Po, ~(210)Pb 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 ~(210)Po and ~(210)Po in marine sediment. These data are very scarce in the litterature.