Effects of Climatic Change to the Radionuclide Levels in Tanzania

The activity concentrations data of radionuclides 7Be and 212Pb from CTBTO radionuclides monitoring station located in Dar es Salaam were for the first time measured and analyzed. In Tanzania, the data were used together with the meteorological one to investigate the mechanism that governs radionuclides concentration level in the atmosphere. The two radionuclides of different origin showed different periodic pattern of atmospheric concentration for the past 11 years (2008 – 2018). No correlation was found between 7Be and 212Pb activity concentration. This suggests that the surface air concentration between 212Pb (was a terrestrial radionuclide) and 7Be (was cosmogenic radionuclide), was affected differently by local conditions of atmospheric processes. The mean values of both 7Be and 212Pb were higher in dry seasons and lower in rain seasons due to vertical mixing and greater deposition of radionuclides. It was also observed that, both 7Be and 212Pb decrease with the increase in rainfall and humidity. The mean activity concentrations of 7Be and 212Pb were found to be within the range of 1.29 – 5.71 mBq/m3 and 10.85 – 50.06 mBq/m3, respectively. The annual mean activity concentrations of 7Be and 212Pb were 4.72 ± 1.18 mBq/m3 and 29.76 ± 13.63 mBq/m3, respectively. Distinct annual trends were depicted on 7Be and 212Pb, suggesting that the two radionuclides were affected differently with atmospheric conditions. Monthly atmospheric concentrations of 7Be showed a strong seasonal variation trend with the highest in January and February and lowest in April. 212Pb depicted the highest concentration during June and July and lowest in January and December. The regression analysis for 7Be and 212Pb activity concentrations together with number of meteorological parameters revealed that the relative humidity, rainfall, air temperature, absolute humidity and wind speed are the most significant parameters affecting radionuclides activity concentrations in the atmosphere. The sunspot numbers show 66.7% of its variability with 7Be activity concentration which further suggesting that other parameters may influence its variation. 212Pb, on the other hand, shows only 27.3% of its variability which clearly indicates that the existence of cosmic rays does not affect its activity concentration in the atmosphere. Based on the findings of this study it is evident that effect meteorological parameters on radionuclides concentrations vary from one location to another. This is due to different climatic conditions, altitude and latitude position and even the source location.