The use of Be-7 to identify event and seasonal sedimentation near the Po River delta, Adriatic Sea

In October 2000, a major flood event of the Po River occurred. the resulting seabed deposit was initially sampled in December 2000, and most sites were reoccupied on subsequent cruises over a 3-year period. using the maximum penetration depth of the short-lived radioisotope Be-7 (half-life 53.3 d), the flood deposit was found to be up to 15 cm thick. Individual depocenters of thick strata were located immediately adjacent to the distributaries at the river mouth in relatively shallow water (less than 30 m). These flood deposit thicknesses are minimum estimates because the depth of Th-234 (half-life 24.1 d) exceeds that of Be-7 in physically stratified flood sediment, indicating that the first sediment deposited furing the flood event likely originated from the river channel. Thirty to fifty-five percent of the estimated sediment load delivered to the shelf during the flood event can be accounted for using Be-7 penetration depths. Seasonal deposition also can be quantified using Be-7, after removing the effects of biological mixing. Seasonal deposition rates are a maximum of 6 cm per yr-1 (yr to the minus 1) near the Pila distributary, decreasing to 2 cm per yr-1 (yr to the minus 1)in the southern portions of the dispersal system.