Radionuclide deposition in the Rhone River Prodelta (NW Mediterranean sea) in response to the December 2003 extreme flood

The extreme Rhone River flood that peaked in early December 2003 with water discharges as high as 11,500 m(3) s(-1), induced major damage in southern France and transferred large amounts of radionuclides that were associated with suspended particulate matter such as Be-7, Cs-137 and Pb-210. Specific marine locations in the close vicinity of the Rhone River Mouth were sampled three times in December 2003, February 2004 and April 2004 in order to quantify the consequences of flood events in the Rhone River Prodelta and to investigate the sedimentary depositional patterns through time. The Pb-210(xs) profile analyses in sediment revealed the existence of two particulate matter inputs, one that was related to the December extreme flood and the other to a peak flood of 4000 m(3) s(-1) of water discharge that occurred in January 2004. The December event net deposition was assessed at 75 +/- 19 GBq of Pb-210(xs) and 27 +/- 2 GBq Of Cs-137. The net deposition in response to the January 2004 flood event, although less damaging, is of the same order of magnitude to the December 2003 deposition, i.e. 71 +/- 21 GBq of Pb-210(xs) and 16 +/- 5 GBq of Cs-137. The sedimentary records of the December flood exhibited from the cores collected in December 2003, February 2004 and April 2004 are similar arguing for good environmental signal preservation through time but, the standard deviation of flood deposition estimate increases with time after the December flood event indicating a loss of accuracy with time. (c) 2006 Elsevier B.V. All rights reserved.