Analysis of gross alpha, gross beta activities and beryllium- 7 concentrations in surface air: their variation and statistical prediction model

Radioactivity in the atmosphere originates from natural radioactive decay, cosmogenic production, nuclear weapons testing and nuclear accidents. Results of the measurements have shown that cosmogenic 7Be is the only gamma emitting nuclide found in the atmosphere of Iran (1). 7Be (t1/2 = 53d) is one of the radioactive products of the bombardment of the atmosphere by cosmic rays. About 75% of 7Be is produced in the stratosphere, and 25% in upper troposphere (2). Once 7Be is formed in the troposphere, it rapidly associates primarily with sub-micron-sized aerosol particles. 7Be in these aerosols may subsequently enter the marine and terrestrial environment via wet or dry deposition (3). In this paper we report four years of continuous measurements of gross |α| and gross |β| activities, and concentrations of 7Be in surface air. The present research was undertaken with the following principal goals: a) To perceive the variations of gross α, gross β and 7Be concentration in Tehran as compared to Zahedan; b) To identify the main meteorological parameters which are responsible for the variation of those concentrations and c) To model the data obtained from our sampling sites as a function of meteorological parameters such as temperature, precipitation, wind speed relative humidity, etc. With the regression model, the ground level concentration associated with the changes in meteorological conditions could be estimated.