Progeny enhanced deposition rates primarily from increased particle diffusivity at high radon concentrations

Prior work found that high 222Rn concentrations produced an enhanced radon progeny surface deposition effect (EDE) in a 0.283-m3 electrically grounded aluminum test chamber. To study a possible charge mobility effect, we report here additional measurements with the chamber lined with nonconducting, insulated materials. Specifically, with insulated, chemically clean glass we provide results of measurements at a number of 222Rn concentrations past the threshold and transition 222Rn levels (up to 60 kBq m(-3)). For EDE it was found at most a 14% charge mobility deposition effect. Without electrical grounding in the Al chamber with +/- 2,000 DC volts applied showed a 10% increase in 218Po surface deposition. Ambient and hot (37 degrees C) wetted filter paper to simulate lung tissue was measured and showed EDE of the same factor of > or = 2 as for all other materials. It is concluded that the enhanced progeny deposition from high radon concentration is primarily from a decrease in attached fraction, thus reducing progeny mean particle size, and increasing diffusivity and surface deposition.