The behaviour of Rn-222 decay products at the air-glass interface and its implication for retrospective radon exposure estimates

Glass sheets investigated regarding their Po-210 signal originating from indoor radon exposure will have a depth distribution down to about 100 nm. The geometrical probability of implantation into glass of glass-attached radon daughter activity in one alpha recoil event is 50%. A particulate layer on the glass sheet (dust, grease or other particles) will stop the alpha recoil nucleus partly or totally, and the alpha-recoiled Po-210 nucleus will be implanted into the glass surface at a lesser depth. Clean glass sheets were pre-exposed to different types of nonradioactive aerosol particles and then exposed to radon-laden air. After a build-up period, the surface activity of Po-210 was determined by alpha spectrometry. The implanted fraction of (210)po for these sheets of glass, with respect to mass load and type of particulate surface layer, was determined to be between 30 and 80% depending on the mass load (mu g cm(-2))