Correction of the effects of carbon dioxide and hydrogen sulfide on electrostatic cell monitors measurements of radon in water
Description
The present study shows that the presence of hydrogen sulfide and carbon dioxide in water have a negative effect
on the accuracy of radon measurements in samples when an electrostatic ion collector device (RAD7) is used.CO2
concentrations between 0.65 g/l and 5.19 g/l were generated in water samples containing 222Rn activities
ranging from 23.4 ± 0.9 Bq/l to 6.7 ± 0.9 Bq/l, after which the samples were measured by a RAD7 device, and
the results compared to the radon activity values of the gas-free samples. The same procedure was followed for
H2S concentrations from 0.125 mg/l to 3 mg/l. In both cases, a major impact was observed, the radon apparent
specific activities decreasing exponentially with gas concentration. For a CO2 concentration of 1.29 g/l, the
apparent specific activity underestimated the true value by 24.5%, while for a concentration of 5.19 g/l CO2 the
decrease was of 57%. For H2S, the radon measured values decreased by 42.5% for concentrations as low as 0.5
mg/l, culminating in a reduction of 86.9% for 3 mg/l H2S. We are attributing these effects to 218Po neutralization
processes, which reduces the electrostatic efficiency of the silicon detector system. To eliminate the interferences
of these gases on RAD7 measurements, a sample preparation method was developed and tested, involving the
precipitation and deposition of CO2 using Ca(OH)2, and H2S using Pb(NO3)2..The findings of the present study
clearly indicate that in order to perform valid radon measurements in gas-rich waters with RAD7, the effect of the
interfering gases must be considered.
Notes
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Manuscript_JECE.pdf
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