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

The 7Be wet deposition has been intensively investigated in a semiarid region at San Luis Province, Argentina. From November 2006 to May 2008, the 7Be content in rainwater was determined in 58 individual rain events, randomly comprising more than 50% of all individual precipitations at the sampling period. 7Be activity concentration in rainwater ranged from 0.7±0.3Bql−1 to 3.2±0.7Bql−1, with a mean value of 1.7Bql−1 (sd=0.53Bql−1). No relationship was found between 7Be content in rainwater and (a) rainfall amount, (b) precipitation intensity and (c) elapsed time between events. 7Be 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 120Bqm−2, with a mean value of 32.7Bqm−2 (sd=29.9Bqm−2). The annual depositional flux was estimated at 1140±120Bqm−2y−1. Assuming the same monthly deposition pattern and that the 7Be 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 7Be input in the explored semiarid ecosystem and its potential use as tracer of environmental processes.