RESUMO
The cosmogenic radionuclide 7Be is one of the best tracers for aerosol transport since its half-life of 53 days is in the time scale of many atmospheric circulation phenomena. In this work, we analyze a 12-years-long daily time-series for the airborne 7Be concentration for nine air filtering stations in the Southern Hemisphere or close to it. The observed latitudinal distribution of 7Be concentration, with its maximum at the southern subtropical high-pressure belt, is similar to the one in the Northern Hemisphere. A good time correlation was found between the 7°-shift of the 7Be concentration latitudinal distribution and the seasonal displacement of the extent of the Hadley cell. This is consistent with tropopause folding events, mostly occurring in spring, being the main contribution for the injection of stratospheric 7Be into the descending branch of the Hadley cell.
Assuntos
Poluentes Radioativos do Ar , Monitoramento de Radiação , Aerossóis , Poluentes Radioativos do Ar/análise , Radioisótopos/análise , Estações do AnoRESUMO
Concentrations of (210)Pb and (137)Cs in sediment samples collected from two cores at a drainage channel to the La Plata river estuary in Buenos Aires, Argentina, were measured using ultralow-background detection systems. The (210)Pb data were used to determine the rate of sediment accumulation of the sites. These results were correlated with some heavy metal (chromium and lead) concentrations of the samples in an attempt to characterize the historical input of contaminants due to the industrial development, which has taken place in this area over the last century. The (137)Cs measurements demonstrate that cesium dating is not adequate in regions of the southern hemisphere.
Assuntos
Sedimentos Geológicos/análise , Radioisótopos de Chumbo/análise , Radioisótopos de Chumbo/química , Monitoramento de Radiação/métodos , Rios/química , Poluentes Radioativos do Solo/análise , Argentina , Sedimentos Geológicos/química , Meia-Vida , Doses de Radiação , Poluentes Radioativos do Solo/químicaRESUMO
(129)I and (127)I concentrations in animal thyroids coming from several regions of Argentina were determined by accelerator mass spectrometry (AMS) and gas chromatography (GC), respectively. The measured (129)I/(127)I ratios, ranging from 3 × 10(-12) to 4 × 10(-10), are significantly lower than those typical for areas in the northern hemisphere (10(-10)-10(-7)). The (129)I concentrations show a clear dependence with latitude and season, which can be understood considering tropospheric circulation patterns, possible (129)I sources and regional precipitation rates.