Surface charge of environmental and radioactive airborne particles

Abstract. Self-charging of radioactive uranium oxide particles was measured by comparing the electrostatic surface-charge characteristics of the uranium particles to various airborne dust particulates. Though radioactive aerosols can gain charge through various decay mechanisms, researchers have traditionally assumed that the radioactive aerosols do not carry any additional charge relative to other atmospheric dust particles as a consequence of charge neutralization over time. In this work, we evaluate this assumption by directly examining the surface charge and charge density on airborne uranium oxide particles and then comparing those characteristics with charging of other natural and engineered airborne dust particles. Based on electric field–assisted particle levitation in air, the surface charge, charge distribution as a function of particle size, and surface charge density were determined for uranium oxide aerosols (< 1 µm) and other nonradioactive dusts, including urban dust, Arizona desert dust, hydrophilic and hydrophobic silica nanoparticles, and graphene oxide powders. Of these dusts, uranium oxide aerosols exhibited the highest surface change density. Additionally, a self-charging model was employed to predict average charge gained from radioactive decay as a function of time. The experimental and theoretical results suggest that radioactive self-charging likely occurs on airborne particles containing radionuclides and may potentially affect the transport of radioactive particles in the atmosphere.