Excess of 210polonium activity in the surface urban atmosphere. Part (1) fluctuation of the 210Po excess in the air
The concentrations of 210Pb, 210Bi, and 210Po in the urban atmosphere of Lodz city were measured from February 2010 to May 2010 and from May 2011 to April 2012. The seasonal changes in the activity ratios for 210Po/210Pb and 210Bi/210Pb indicated that the observed fluctuations were independent of the concentration of tropospheric 210Pb and its decay products, particularly 210Po. A simple calculation method was proposed for the estimation of the excess of 210Po in urban aerosols in relation to the fraction of its activity formed from 210Pb. On the basis of the results obtained, it was concluded that a substantial part of the 210Po in urban air did not come from the decay of atmospheric 222Rn, but rather it was from artificial sources. The highest levels of measured total 210Po activity were observed during the winter period. This observation suggests that the main source of 210Po in the investigated region could be related to anthropogenic emissions from domestic heating systems and local coal power plants, rather than from other sources, such as soil resuspension or stratospheric air intrusion as usually suggested in the literature.