Wet depositional fluxes of 210Pb- and 7Be-bearing aerosols at two different altitude cities of North Pakistan

Abstract

Abstract The natural radionuclides 210Pb and 7Be have been widely used as tracers of aerosols for the study of pollution and atmospheric transport processes. The depositional fluxes of atmospheric 210Pb and 7Be-bearing aerosols in precipitation samples have been continuously measured from October 2006 to April 2010 at a high altitude city of Murree (33° 85′ N, 73° 41′ E, Alt.2300 m a.s.l) and low altitude city of Islamabad (33° 38′ N, 73° 09′ E, Alt. 534 m a.s.l), Pakistan, using a high resolution spectrometer. The specific activity values of 210Pb and 7Be measured in rain samples collected monthly from open lawn of Murree ranged from 2–87 mBq l−1 and 80–1680 mBq l−1 with their mean values of 30 ± 11 mBq l−1 and 573 ± 201 mBq l−1, respectively. Similarly the mean specific concentration values of 210Pb and 7Be in open lawn rain samples of Islamabad are 123 ± 12 mBq l−1 and 442 ± 321 mBq l−1 respectively. The specific concentrations of 210Pb and 7Be in throughfall samples collected at Murree site only are in the range from 5–34 mBq l−1 and 110–1177 mBq l−1 with the mean values of 17 ± 6 mBq l−1 and 442 ± 321 mBq l−1 respectively. The annual deposition fluxes of these radionuclides at Murree varied from 1 to 129 Bq m−2 y−1 and 17 to 2202 Bq m−2 y−1 in the open lawn rain samples and from 1 to 35 Bq m−2 y−1 and 9 to 975 Bq m−2 y−1 in throughfall samples respectively. Similarly the annual mean flux values of both radionuclides in open lawn rain samples of Islamabad are 1137 Bq m−2 y−1 and 3801 Bq m−2 y−1 respectively. Observed seasonal variations of deposition of 210Pb and 7Be are explained in terms of different environmental features. The role of plantation in the interception of radionuclides in throughfall samples is analyzed and discussed. The effect of the altitude on the deposition processes at the investigated site is studied using the comparison of present results with the relevant published results and analysis.