Impact of krypton-85 beta radiation on aerosol particle formation and transformation

Abstract

In this study the effect of the air ionization by 85 Kr beta radiation on the new particle formation and evolution of aerosol particle size distribution in the experimental chamber was investigated. During the experiments the interaction between air ionization and gas-to-particle conversion processes was distinctly observed. Results showed that the amplitude of the ionic current was dependent both on the chemical impurity concentration and the ionization source activity. Calculated values of parameters (growth and formation rates) of the particle nucleation process were larger when in the experimental chamber concentrations of SO2 and 85 Kr were higher. The growth rate values (42.1 and 45.3 nm/h) were by one order of magnitude higher than the environmental ones (1.2-9.9 nm/h at the Preila station, Lithuania). Experimental data showed that after injection of high SO2 and 85 Kr concentrations in the chamber during the 20 min interval nanometre-size particles created by nucleation were produced in large amounts. Thus, a larger amount of SO2 significantly influenced the formation of new particles. During the first 5 min the concentration of 10 nm particles increased by 3 orders of magnitude with the formation rate of 7.47 cm −3 s −1 . The formation rate of 0.06 cm −3 s −1 in the experiment with the average ambient SO2 concentration (2-3 µg/m3 ) was analogous to the environmental one (0.14 cm −3 s −1 ). The coagulation sink (CoagS 1,2,3 ) was higher in the experiment with the ambient SO2 concentration and resulted in the lower concentration of particles. The smaller values of the coagulation sink at the higher concentration of SO2 gas have shown that these nano-particles in the air could persist for a longer time, probably in a stable size due to the ion charge.