In-situ detection equipment for radon-in-water: unattended operation and monthly investigations
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Abstract: Radon is recognized as a powerful tracer of certain geophysical processes in marine and aquatic environments. In the past few decades, the instruments and methods for measuring radon concentration in water have been developed to some extent but still lack underwater in-situ measurements. Here we present an in-situ detection equipment for radon-in-water (pulsed ionization chamber (PIC)-radon) to measure dissolved radon in ocean and groundwater settings. The equipment has been successfully deployed in the Jiaozhou Bay in July 2022 and has achieved 14 d of unattended underwater in-situ observation. Then it was successfully placed in a groundwater monitoring well in the Laizhou Bay in November 2022 and monitored radon activities for over 30 d. The results showed that this instrument had a good indication of submarine groundwater discharge. The PIC-radon detector takes advantage of smaller size, lower power consumption, and is barely influenced by humidity, making it particularly suitable for long-term in-situ measurement, especially in harsh environments with limited human care or deployment spaces.
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Key words:
- radon /
- pulsed ionization chamber (PIC) /
- in-situ measurement /
- membrane /
- groundwater /
- ocean
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Figure 1. Schematic diagram of the pulsed ionization chamber (PIC)-radon system for continuous measurements of radon-in-water. The system consists of an equilibration unit, a measuring unit, and a control unit. The blue arrows indicate the direction of the airflow; the black arrows indicate the power supply to each module; the yellow arrows indicate communications between each component. Esrs is the abbreviation for environment.
Figure 2. The internal structure of the pulsed ionization chamber (PIC)-radon system (a); the lower part is the measurement unit, and the upper part is the control unit. b. An overall photo of the PIC-radon. The entire capsule is made of polyoxymethylene which can withstand water pressure of 100 m depth.
Figure 4. A continuous measurement of tap water in an indoor tank via the pulsed ionization chamber (PIC)-radon system with a commercial RAD AQUA-RAD7 system.
Figure 6. Map for conducting radon concentration measurement in the Laizhou Bay (a); the instrument was placed in the brine well (length: 40 cm; width: 30 cm) (b).
Figure 7. Radon activities measured by the pulsed ionization chamber (PIC)-radon system (blue spots) and a commercial RAD7-AUQA system (orange spots). The error bars were calculated by counting statistics (1σ).
Figure 8. Relationship between radon activities and tide. These measurements overlap for the first 3 d (a) and were then extended for 2 weeks (b). a. The pulsed ionization chamber (PIC)-radon was represented by the blue lines, the RAD AQUA-RAD7 system was represented by the orange lines, the local tides were represented by the black lines; b. the PIC-radon was represented by the blue lines, while the local tides were represented by the black lines (
https://www.chaoxibiao.net/tides/11.html ). -
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