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

The Be-7 wet deposition has been intensively investigated in a semiarid region at San Luis Province, Argentina. From November 2006 to May 2008, the Be-7 content in rainwater was determined in 58 individual rain events, randomly comprising more than 50% of all individual precipitations at the sampling period. Be-7 activity concentration in rainwater ranged from 0.7 +/- 0.3 Bq l(-1) to 3.2 +/- 0.7 Bq l(-1), with a mean value of 1.7 Bq l(-1) (sd = 0.53 Bq l(-1)). No relationship was found between Be-7 content in rainwater and (a) rainfall amount, (b) precipitation intensity and (c) elapsed time between events. Be-7 ground deposition was found to be well correlated with rainfall amount (R = 0.92). For the precipitation events considered, the Be-7 depositional fluxes ranged from 1.1 to 120 Bq m(-2) with a mean value of 32.7 Bq m(-2) (sd =29.9 Bq m(-2)). The annual depositional flux was estimated at 1140 +/- 120 Bq m(-2) y(-1). Assuming the same monthly deposition pattern and that the Be-7 content in soil decreases only through radioactive decay, the seasonal variation of Be-7 areal activity density in soil was estimated. Results of this investigation may contribute to a valuable characterization of Be-7 input in the explored semiarid ecosystem and its potential use as tracer of environmental processes. (c) 2009 Elsevier Ltd. All rights reserved.