Annual cycle of gross β activities in aerosol around Daya Bay area, China

In this paper, the monthly gross β activities in aerosol during 1995–2004 at Daya Bay area are reported. The gross β activities were observed to vary in the range of 0.22–5.14 mBq m−3 with an arithmetic average of 1.60 ± 1.00 mBq m−3 and a geometric average about 1.78 ± 0.33 mBq m−3. It is shown an obvious seasonal variation characteristic, which is ascribed to the washout mechanism and the radon-suppressing mechanism from the soil by the seasonal rainfall. The exponential attenuation with the rainfall is verified and an attenuation index is defined, which is deduced as 0.007 ± 0.002 mm−1 by regression analysis. Finally, the correlation between gross β activities and 210Pb concentrations is analyzed. It is indicated that the radionuclide 210Pb contributes about 61 ± 9% to the gross β activities in the aerosol.