Hi Azzura

Iam not sure if there is the a relation that you can use it to calculate the quantity of 222Rn in water coming from the 226Ra in sediments.

you know that there are many factors that control the 226 radium in the aquifer like the adsorption phenomenon on the mineral surface ( for exemple Radium has a high tendency to absorb on surfaces rich in oxides or oxyhydroxides of iron and manganese by ion exchange) , so maybe we can say not all the 226Ra will become 222Rn in porewater, and there is other factors as you say like the salinity . . . . .

I suggest for you this paper maybe it will be useful :

Article On 226Ra and 222Rn concentrations in the brackish waters of ...

Youcef Zemour Many thanks for the answer

Dear Mrs. Lettini

I would like to refer to my comments given in a similar thread launched by your question.

You have to deal with the U disequilibrium in the U-238 decay chain which is physically impacted in that the gaseous radon escapes along faults and porous media from its source which can be each mineral from high-grade uraninite ore to white mica or decomposed phosphate which contain U of up to 200 ppm U. Moreover there are variable chemical solubilities of each daughter product, e.g., radium which may be precipitated in sulfate-enriched environments, because of its extremely low solubility (Ra barite). There are different solubilities of the daughter products.Th-234 and Ra-226 are less soluble than the parent radionuclide U-238. It may cause a separation of these elements owing to differential leaching. There are also certain energy effects. Energy of decay process results in oxidation, e.g. U-234 from U-238 in uraninite may cause U 6+ which more soluble than tetravalent U. Based upon that any general advice in this case would be misleading. You must show the various environments under study which are interconnected with each other by aquifers or surface waters and last-but-not-least consider the migration of radon gas in the water and in the open pore space. The best way is to conduct a sampling along a transect or on a grid using alpha-cups or –pumps to get an idea of pathway of migration. I worked for 6 years in the U branch and we used Rn for exploration. There are some textbooks displaying case histories on the migration and trapping of Rn.

With kind regards

H.G.Dill

based on my experience, 30 yeas of research on groundwater contamination with radionuclide, I have worked as a technical advisor for several projects of groundwater contamination with radionuclide in Saudi Arabia and Egypt, one of my conclusion for my study of radionuclide in groundwater in sandstone (or sedimentary aquifers), is that there is little or no correlation between Ra and Rn levels. but in shallow fracture granitic rock aquifer in shield area, there is a good correlation between U and Rn in groundwater wells penetrated the granitic aquifer.