Atmospheric 210Pb, 210Po and 210Po/210Pb activity ratio in urban aerosols: temporal variability and impact of biomass burning emission

Atmospheric 210Pb, 210Po and their activity ratio (210Po/210Pb) have been studied for two years (January 2007–April 2009) from an urban site (Kanpur: 26.5°N and 80.3°E) in the Indo-Gangetic Plain. The average activities of 210Pb and 210Po centre on 1.8 mBq m 3 (range: 0.5–4.8 mBq m 3 for n=99) and 0.094 mBq m 3 (n=21, range: 0.002–0.28 mBq m 3), respectively. The temporal variability in the activity of 210Pb is significantly pronounced, with relatively high levels during October–November and December–February; a trend similar to that observed for the carbonaceous species. The high aerosol abundance coinciding with the biomass burning emissions (agricultural-waste burning) during October–November and stagnant boundary layer in the wintertime (December–February) is the dominant factor for the observed temporal trend. The preliminary data suggest that biomass burning emissions also contribute to the atmospheric 210Po activity, as evident from the large variability in the 210Po/210Pb activity ratio (range: 0.02–0.23) at this urban site. These results have implications to the model-based activity levels of 210Pb and 210Po from in-situ decay of the parent nuclide (222Rn) for given latitude.