Studies on radioactivity in aerosols as a function of meteorological variables in Salamanca (Spain)

Ambient concentrations of aerosol radioactivity in ground-level air were measured weekly in a low-industrialized city (Salamanca, Spain). Means of about 6.9×10−5 and 4.83×10−4 Bq m−3 were found for gross α and β activities, respectively, averaged over three years. The measured activities, which include contributions from several radionuclides in the ground atmosphere, were evaluated to determine the relationship between the meteorology and the aerosol activities in air. We have studied the influence of diverse meteorological parameters such as temperature, pressure and wind direction, as well as the effect of the less often considered terrestrial electrostatic field. Concentrations of gross α and β activities were greatly affected by the meteorological conditions, showing pronounced differences between seasons. The study reveals that much of the variability (approximately 50%) in the activities is explained by the electrostatic field, its influence being higher in winter. About 40% of the α and β variability is explained by both the temperature and the humidity. The influence of the wind direction is only statistically significant for α radioactivity. A simple mathematical model based on these variables is developed to describe globally the dynamics in air of radioactive particles enabling us to estimate the air radioactive background level.