Diurnal and seasonal variation of short-lived radon progeny concentration and atmospheric temporal variations of 210Pb and 7Be in Egypt

Abstract

During a one-year period, from November 1998 upto October 1999, the atmospheric activity concentrations of the short-lived ( 222Rn)-progeny ( 218Po, 214Pb, 214Po) were measured every 4 h in the open air, using α-spectrometry. The concentration data of short-lived radon progeny together with meteorological variables (relative humidity, air temperature, and wind speed) were used for a comprehensive regression analysis of daily time variation of radioactivity in the air. The seasonal concentration pattern of all short-lived radon progeny shows the same trend for diurnal variation with higher values at night and early morning hours compared with lower values at noon and in afternoon. The activity concentrations were observed to be higher during the winter months (November–January) than in other seasons. The mean activity concentrations of 218Po, 214Pb and 214Po within the whole year were found to be 6.7±0.8, 4.9±0.5 and 4.4±0.3 Bq m −3, respectively. Also, within that time period, approximately 120 samples were analysed to determine the concentrations of the long-lived radon decay product 210Pb and the cosmogenic radionuclide 7Be using a single-filter technique. The course of 210Pb air concentration is characterized by higher values in autumn/winter season and lower values in spring/summer season. The seasonal concentration pattern of 7Be reaches regular maximum values in the spring to early summer months. The annual average concentration values of 210Pb and 7Be have been found to be 0.37±0.06 and 2.0±0.09 mBq m −3, respectively. A mean aerosol mass concentration of 36.6±6.2 μg m −3 was also determined during the measurements of the long-lived radionuclides. The majority of attached 210Pb and 7Be were observed at lower aerosol mass concentrations while small fractions of attached activities were found to be associated with the higher mass concentrations.