Gross beta activities and Beryllium-7 concentrations in surface air

ABSTRACT

Measurement of gross beta activities and cosmogenic Beryllium-7 concentrations were made each week during year 2002 from samples of atmospheric aerosols filtered from the air at Tehran Nuclear Research Center. The aerosol samples were collected weekly with high-volume air sampler at the Nuclear Research Center meteorological station in Tehran [40[degree sign] 35. N]. The [7]Be contents of samples were determined with semiconductor gamma spectrometry. The long-lived beta activity, i.e. total beta activity measured four days after the end of sampling [after decay of [220]Rn progeny and short-lived [220]Rn progeny], was assessed with an automatic beta analyzer. The long-lived beta activity consists mainly of [210]Bi, the daughter nuclide of [210]Pb, as the amount of artificial radionuclides in the air is negligible. The air concentrations of both the [7]Be and the long-lived beta activity displayed a lognormal distribution during the study period 2002. The arithmetic mean of annual concentrations of [7]Be and [210] Pb was 6.30 and 0.50 mBqm[-3], respectively. Despite the different origins, the concentrations of both the [7]Be and the long.lived beta activities are partially correlated. Both have maximum concentrations during warm mid-year months