Short-term seasonal variability in 7Be wet deposition in a semiarid ecosystem of central Argentina

Abstract

The 7Be wet deposition has been intensively investigated in a semiarid region at San Luis Province, Argentina. From November 2006 to May 2008, the 7 Be content in rainwater was determined in 58 individual rain events, randomly comprising more than 50% of all individual precipitations at the sampling period. 7 Be activity concentration in rainwater ranged from 0.7 0.3 Bq/l to 3.2 0.7 Bq/l, with a mean value of 1.7 Bq/l (sd= 0.53 Bq/l ). No relationship was found between 7Be content in rainwater and (a) rainfall amount, (b) precipitation intensity and (c) elapsed time between events. 7 Be ground deposition was found to be well correlated with rainfall amount (R= 0.92). For the precipitation events considered, the 7Be depositional fluxes ranged from 1.1 to 120 Bq/m2 , with a mean value of 32.7 Bq/m2 (sd= 29.9 Bq/m2 ). The annual depositional flux was estimated at 1140 120 Bq/m2/y . Assuming the same monthly deposition pattern and that the 7 Be content in soil decreases only through radioactive decay, the seasonal variation of 7Be areal activity density in soil was estimated. Results of this investigation may contribute to a valuable characterization of 7 Be input in the explored semiarid ecosystem and its potential use as tracer of environmental processes.