Multitracer study of anthropogenic contamination records in the Camargue, Southern France

Contaminants are supplied to the coastal zone by the atmosphere, rivers and point sources like wastewaters or industrial area. Wetlands retain many of these contaminants and can be used to reconstruct sources and magnitudes of contaminant inputs. Radionuclides (137Cs, 210Pb, 239Pu and 240Pu) and stable lead isotope (206Pb, 207Pb) profiles were investigated in two cores collected in wetlands of the Rhône River delta, south of France (Camargue), to estimate the recent sediment accumulation rates and reconstruct the deposition of pollutants during the last century. One site was affected by storm or flood deposition from the Rhone river and showed the influence of Marcoule reprocessing plant releases on the plutonium isotopic ratios. The other site appears suitable for the reconstruction, even if mixing is evidenced at the surface by the radionuclides profiles. Plutonium isotopic ratios are characteristic of global fallout and the 210Pb inventory of 4240 Bq m-2 is approximately 30% higher than atmospheric deposit estimation. The pollutant lead inventory is 139 µg cm-2, slightly higher than previous estimation from direct fallout. This difference can be partly due to an over-collection at this site (due to canopy cover) but also to variations with time in the deposition.