Medidas de 214Po em São José dos Campos e Cachoeira Paulista: Correlação com Dados Meteorológicos

Abstract

The concentration of airborne radioactive elements is influenced by meteorological parameters such as rainfall and atmospheric stability. 214Po, a short life daughter product of 222Rn, was measured by alpha-ray spectrometry of atmospheric particles sampled on Millipore filters (0,8 µm pore) at São José dos Campos (23° 12'S, 45° 51'W) and Cachoeira Paulista (22°41′19″S, 45°00′22″W). The influence of rainfall on the atmospheric 214 Po was studied at São José dos Campos. The mean activity was 98 pCi/m³ for dry days (without rain during the preceding two days). On the contrary, a low mean activity of 35 pCi/m³ was observed for high pluviometry days 08/30 to 10/26 for which total rainfall was 365.5mm. At Cachoeira Paulista the 214Po activity was correlated with the stability of the air (measured by the Richardson number), showing an accumulation of natural radioactive aerosols during periods of higher stability of the lower atmosphere.