Atmospheric transport studies of 7Be in Kaiga environment

Concentration of 7Be, which is a cosmic ray produced radionuclide, in ground level air and rainwater at Kaiga is determined by gamma spectrometry analysis. Dry deposition velocity, wet deposition velocity and annual deposition flux of 7Be in Kaiga environment is calculated. Activity levels in air, rainwater, annual deposition flux, dry and wet deposition velocity values are compared with those reported elsewhere. Seasonal variation of activity with a maximum in March to April and minimum in July is observed. 7Be in ground level air at Kaiga is correlated with weather elements such as air temperature and humidity. 7Be activity in air decreases with relative humidity with a correlation coefficient 0.593. Correlation of 7Be activity in ground level air with air temperature is not significant. 7Be activity in rainwater is used as a tool for the determination of wet deposition coefficient and scavenging ratio. The scavenging ratios are found to be varying from 1.641 x 104 to 2.699 x 105 (mBq/m3 rain water per mBq/m3 air). The ratio between maximum and minimum is found to be 16.45. The mean value is calculated as 1.257 x 105 (mBq/m3 rain water per mBq/m3 air). Wet deposition velocity is found to be varying from 1.84 x 10-2 m/s to 2.13 x 10-1 m/s and the mean value is observed as 7.33 x 10-2 m/s. Dry deposition velocity is found to be varying from 8.66 x 10-5 m/s to 2.27 x 10-4 m/s with a mean value of 1.59 x 10-4 m/s. Wet deposition velocity is found to be greater than dry deposition velocity by about 2 orders of magnitude. (author)