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

During a one-year period, from November 1998 upto October 1999, the atmosph eric activity concentrations of the short-lived (Rn-222)-progeny (Po-218, P b-214, Po-214) were measured every 4 h in the open air, using a-spectrometr y. The concentration data of short-lived radon progeny together with meteor ological variables (relative humidity, air temperature, and wind speed) wer e used for a comprehensive regression analysis of daily time variation of r adioactivity in the air. The seasonal concentration pattern of all short-li ved radon progeny shows the same trend for diurnal variation with higher va lues at night and early morning hours compared with lower values at noon an d in afternoon. The activity concentrations were observed to be higher duri ng the winter months (November-January) than in other seasons. The mean act ivity concentrations of Po-218, Pb-214 and Po-214 within the whole year wer e 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 d etermine the concentrations of the long-lived radon decay product Pb-210 an d the cosmogenic radionuclide Be-7 using a single-filter technique. The cou rse of Pb-210 air concentration is characterized by higher values in autumn /winter season and lower values in spring/summer season. The seasonal conce ntration pattern of 7Be reaches regular maximum values in the spring to ear ly summer months. The annual average concentration values of Pb-210 and Be- 7 have been found to be 0.37 +/-0.06 and 20 +/-0.09 mBq m(-3), respectively . A mean aerosol mass concentration of 36.6 +/-6.2 mu gm(-3) was also deter mined during the measurements of the long-lived radionuclides. The majority of attached Pb-210 and Be-7 were observed at lower aerosol mass concentrat ions while small fractions of attached activities were found to be associat ed with the higher mass concentrations. (C) 2001 Elsevier Science Ltd. All rights reserved.