Distribution and inventories of fallout radionuclides (239+240Pu, 137Cs) and 210Pb to study the filling velocity of salt marshes in Doñana National Park (Spain)

Within an extensive multinational and multidisciplinary project carried out in Doñana National Park (Spain) to investigate its preservation and regeneration, the filling velocity of the salt marshes has been evaluated through the calculation of their average sediment accumulation rates.239+240Pu and 137Cs from weapons testing fallout and total 210Pb distribution profiles and inventories have been determined in some of the most characteristic zones of the park, namely, the ponds (or “lucios”) and the waterjets (or “caños”). Plutonium inventories range from 16 to 101 Bq m−2, 137Cs values fluctuate between 514 and 3758 Bq m−2 and unsupported 210Pb values comprise between 124 and 9398 Bq m−2. Average sedimentation rates range from 3 to 5 mm y−1 (1952–2002). These data are higher than those obtained by carbon dating for the period 6500 AD–present, estimated as 1.5–2 mm y−1, suggesting an increase in the accumulation of sediments and the alteration of the park’s hydrodynamics caused by the re-channeling of the major rivers feeding the salt marshes.