Reassessing radon as a reliable groundwater tracer
A widely used technique for tracing natural radioactive atoms within
flowing groundwater may not be as accurate as previously thought.

Date:
February 2, 2022
Source:
Springer
Summary:
As radioactive atoms are transported through groundwater aquifers
in the form of gaseous radon, they are eventually transferred to
the atmosphere.

Measurements of the rate of this transfer can, in theory, be used
to trace the infiltration of water into the surrounding soil. Yet
a new study shows that this technique could have a significant flaw.



FULL STORY ==========================================================================
All radioactive materials which naturally occur in water will produce at
least one isotope of radon as a decay product. As radioactive atoms are transported through groundwater aquifers in the form of gaseous radon,
they are eventually transferred to the atmosphere. Measurements of the
rate of this transfer can, in theory, be used to trace the infiltration
of water into the surrounding soil. Yet in a new study detailed in EPJ
Plus, researchers in Egypt and Saudi Arabia, led by Elsayed Elmaghraby
at the Egyptian Atomic Energy Authority, show that this technique could
have a significant flaw.


========================================================================== Currently, researchers use the transfer of radon from groundwater to
assess factors ranging from the environmental impacts of ore extraction
to earthquake precursors. The overall rate at which radon is transferred
to the atmosphere is governed by several processes: including its
formation through radioactive decay; transport to the water's surface; adsorption onto other surrounding atoms; and diffusion under concentration gradients. In measuring this rate, researchers typically assume that
radon's concentration is in equilibrium with its own radioactive decay products.

To test this assumption, Elmaghraby's team prepared a water-based
solution containing thorium and uranium, and then left it in isolation
for two years.

Afterwards, they exposed the solution to the atmosphere, and measured
how the resulting radon transfer rate evolved over time. Subsequently,
they simulated the experiment with a mathematical model, accounting for
all relevant processes.

These simulations revealed that during the liquid's isolation, its decay products had partially re-dissolved in the water to varying degrees,
depending partially on the geometry of the medium. This can vary widely
in the presence of grains like sand or soil, which come in a diverse
array of shapes and sizes.

In addition, re-dissolving was affected by the presence of bubbles,
containing gases such as water vapour and helium -- another natural
decay product.

Ultimately, this meant that radon and its decay products cannot be in equilibrium, throwing doubt on previous measurements of the overall
radon transfer rate.

========================================================================== Story Source: Materials provided by Springer. Note: Content may be edited
for style and length.


========================================================================== Journal Reference:
1. Elsayed K. Elmaghraby, Nahla Nagy Ataalla, Mohamed B. Afifi,
Eman Salem.

Radon exhalation and transfer processes in aqueous media. The
European Physical Journal Plus, 2021; 136 (12) DOI:
10.1140/epjp/s13360-021-02231- z ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2022/02/220202111816.htm

--- up 8 weeks, 4 days, 7 hours, 13 minutes
* Origin: -=> Castle Rock BBS <=- Now Husky HPT Powered! (1:317/3)