Concentration measurements of Be-7 and Cs-137 in ground level air in the Belgrade city area

Concentrations of Be-7 and Cs-137 in ground level air in the city area (Bel grade, central Serbia) were determined in the period from 1991-1996, The av erage monthly concentrations of Be-7 in ground level air were in the range of 2-7 mBq/m(3) with pronounced one or two maxims in summer or early fall a nd a minimum in winter; The average air concentrations for Cs-137 were from 0.5-8.5 x 10-5 Bq/m(3), with a spread maximum in the spring-summer period and a pronounced maximum during the winter. A general increase in Be-7 and Cs-137 concentrations during 1993 was recorded. The maximum seasonal indice s were 1.3 for Be-7 (summers) and 2.7 (late springs and early summers) and 3,4 (winters) for Cs-137. No correlation with the amount of precipitation a nd Cs-137 concentrations in air was determined, while the washout effect of rainfalls seems to be more closely related with variations in Be-7 concent rations. (C) 1999 Elsevier Science Ltd.