Improved Automated Analysis of Radon (²²²Rn) and Thoron (²²⁰Rn) in Natural Waters

Abstract

Natural radon ((222)Rn) and thoron ((220)Rn) can be used as tracers of various chemical and physical processes in the environment. We present here results from an extended series of laboratory experiments intended to improve the automated analysis of (222)Rn and (220)Rn in water using a modified RAD AQUA (Durridge Inc.) system. Previous experience with similar equipment showed that it takes about 30-40 min for the system to equilibrate to radon-in-water concentration increases and even longer for the response to return to baseline after a sharp spike. While the original water/gas exchanger setup was built only for radon-in-water measurement, our goal here is to provide an automated system capable of high resolution and good sensitivity for both radon- and thoron-in-water detections. We found that faster water flow rates substantially improved the response for both isotopes while thoron is detected most efficiently at airflow rates of 3 L/min. Our results show that the optimum conditions for fastest response and sensitivity for both isotopes are at water flow rates up to 17 L/min and an airflow rate of 3 L/min through the detector. Applications for such measurements include prospecting for naturally occurring radioactive material (NORM) in pipelines and locating points of groundwater/surface water interaction.

Phytoplankton primary productivity around submarine groundwater discharge in nearshore coasts

“…1). We employed a multi-detector method (Dulaiova et al 2005) using 3 radon detectors (RAD7, Durridge) at Site A and a dual-loop method (Dimova et al 2009) at Sites B and C using one RAD7. The count uncertainties of the methods were < 30%.…”

Occurrence, distribution and prey items of juvenile marbled sole Pseudopleuronectes yokohamae around a submarine groundwater seepage on a tidal flat in southwestern Japan

“…We applied the multidetector method (Dulaiova et al, 2005) in 2013 and the dual-loop method (Dimova et al, 2009) in 2014 for continuous 222 Rn measurements at a ship velocity of about 1.0 knot during flood tide with water depths between 1.5 and 4.0 m with an interval of 2 min for each measurement, a depth of 1 m (from the surface) for water pumping, and a pumping rate of N 5 L min −1 . Average values of the 222 Rn (in 2013 and 2014) and chlorophyll-a (only 2014) concentrations for every 120 s were calculated and then processed for mapping a contour plot.…”

The influence of groundwater inputs and age on nutrient dynamics in a coral reef lagoon

“…Salinity, temperature and water level measurements were recorded using a CTD diver (Van Essen Instruments) at 15 minute intervals. 222 Rn was measured using a continuous radonin-air monitor (Rad7, Durridge Company) adapted for radon-in-water (Dimova et al, 2009) and averaged over 10 minute time frames.…”