Unperturbed, high spatial resolution measurement of Radon-222 in soil-gas depth profile. (January 2019)

• Record Type: Journal Article
• Authors: Mitev, K.; Dutsov, Ch.; Georgiev, S.; Boshkova, T.; Pressyanov, D.
• Is Part Of: Journal of environmental radioactivity. Volume 196(2019)
• Page Start: 253
• Page End: 258
• Publication Date: 2019-01
• Subjects: 222Rn in soil-gas -- Activity distribution profile -- Polycarbonates -- Liquid scintillation counting; Radioactivity -- Periodicals; Radiation, Background -- Periodicals; Radioecology -- Periodicals; Radioactive pollution -- Periodicals; Environmental Pollutants -- Periodicals; Radioactive Pollutants -- Periodicals; Radioactivity -- Periodicals; Radioécologie -- Périodiques; Pollution radioactive -- Périodiques; Fond de rayonnement -- Périodiques; 539.752
• DOI: 10.1016/j.jenvrad.2018.01.019
• Languages: English
• ISSNs: 0265-931X

Abstract

Abstract: This work presents a method for measuring the depth distribution of 222 Rn activity in soil gas. The method is based on the capacity of polycarbonates to absorb 222 Rn and on the possibility of performing sensitive measurements of 222 Rn absorbed by the polycarbonates via liquid scintillation counting (LSC). The method is the following: cylindrical holes are drilled along a metal rod and Makrofol ® N polycarbonate foils enclosed in polyethylene envelopes are placed in each hole. The rod is driven into the soil and kept for a certain time. As long as the rod is in the soil, the polycarbonate foils are exposed to the 222 Rn concentration at their depth. At the end of the exposure the rod is pulled out and the foils are transferred to liquid scintillation (LS) vials filled with liquid scintillator. The 222 Rn absorbed in the foils is then measured with a LS analyzer. The rod with the polycarbonate foils acts as a passive probe which senses the 222 Rn concentration at different depths beneath the ground surface. The achievable minimum detectable 222 Rn activity concentration with the equipment and conditions used in this study is around 12.5 kBq/m 3 . It can easily be lowered below 1 kBq/m 3 if larger foils and low-background LS analyzers are used. Since the method does not require air sampling the depth distribution of 222 Rn in the soil is unperturbed by the sampling. The spatial distribution and the maximum measurement depth are set by the distance between the holes and the depth to which the rod can be fixed into the ground. Results from in situ applications of the method in terrains with high 222 Rn in soil-gas are reported, which demonstrate the feasibility and the usefulness of the proposed approach. Highlights: A method for measuring the depth distribution of 222 Rn in soil-gas is proposed. The in-depth 222 Rn profile is measured with high spatial resolution. Liquid scintillation counting of 222 Rn absorbed in polycarbonate foils is used. Results from pilot experiments on NORM contaminated areas are presented.