Bem H, Gasiorowski A, Szajerski P. A fast method for the simultaneous determination of soil radon (
222Rn) and thoron (
220Rn) concentrations by liquid scintillation counting.
THE SCIENCE OF THE TOTAL ENVIRONMENT 2020;
709:136127. [PMID:
31884268 DOI:
10.1016/j.scitotenv.2019.136127]
[Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/02/2019] [Revised: 12/06/2019] [Accepted: 12/13/2019] [Indexed: 05/21/2023]
Abstract
This paper presents a fast method dedicated to measurements of radon nuclides in the soil gas. The soil gas is sampled by a typical hollow tube probe by 10 min of sucking of about 3 dm3 of gas and passing it directly through a 16 cm3 of water-immiscible liquid scintillator placed in a typical 20 cm3 scintillation vials, where the radon and thoron nuclides are effectively absorbed. Most of the presently used active methods for radon isotopes determination (e.g., RAD7 or AlphaGuard) require the soil gas transfer to the measuring device. The serious limitation of such approach is the necessity to wait until the radon daughter isotopes decay, before counter is ready for the next measurement. In the proposed method, several samples can be simultaneously gathered from the examined areas in the form of the scintillation vials, which are ready for later measurements in the automatic liquid scintillation counters in the lab or directly in situ. For that purpose, the combined mathematical model for the simultaneous radon and thoron determination has been elaborated. The direct in situ measurements of the sample activity between 60 and 240 s after the end of sampling followed by a second activity measurement after 3 h allow for the determination of both 220Rn and 222Rn concentrations in the soil gas. The limit of detection for 222Rn isotope during 10 min counting is 25 Bq·m-3, whereas for a 3 min counting of 220Rn just after sampling was found to be ca. 150 Bq·m-3. The method was successfully verified and applied for the simultaneous radon and thoron concentrations measurements in the soil gas in Central Poland region.
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