Activity size distribution and residence time of Be-7 aerosols in the Arctic atmosphere

作者：Ioannidou Alexandra^*; Paatero Jussi

来源：Atmospheric Environment, 2014, 88: 99-106.

DOI：10.1016/j.atmosenv.2013.12.046

• Beryllium-7
• Radioactive aerosols
• AMAD
• Activity size distribution

The activity size distributions of the natural radionuclide tracer Be-7 in different size range fractions (< 039 mu m, 0.39-0.69 mu m, 0.69-1.3 mu m, 1.3-2.1 mu m, 2.1-4.2 mu m, 4.2-10.2 mu m and > 10.2 pm) were determined in the boreal atmosphere in the Arctic Research Centre of the Finnish Meteorological Institute (FMI) at Sodankyla, Finland (67 degrees 22' N, 26 degrees 38' E, 180 m asl. The activity median aerodynamic diameter (AMAD) ranged from 0.54 mu m to 1.05 mu m (average 0.83 mu m). A residence time of about 8 days applies to aerosols of 0.83 mu m diameter, representing the residence of aerosol particles in arctic environment. The observed positive correlation between AMAD values and RH% can be explained by the fact that condensation during high relative humidity conditions becomes more intense, resulting in increased particle sizes of atmospheric aerosols. However, greater aerosol particle sizes means higher wet scavenging rate of aerosols and as a result lower activity concentration of Be-7 in the atmosphere, explaining the anti-correlation between the AIVIAD values and activity concentrations of Be-7. But this associated with possibly higher scavenging rates of aerosols does not necessarily alone explain the anti-correlation between the AMAD and the Be-7 activities. The air mass origin associated with synoptic scale weather phenomena may contribute to that too. The Flextra model was used to assess the transport pattern and to explain the deviation in radionuclide activity concentrations and AMAD values observed in the site of investigation.

• 出版日期2014-5