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.