Hi,

The primery source of 222Rn is the 226Ra.

Secondly source of Radon concentration in groundwater is associated with geological formation such as metasediments, magmatic intrusions and shale, also ther is some relation with Radon concentration and physicochemical characteristic of water, for exemple hight Radon concentrations are observed generally in waters that are rich in sodium-chloride ( I confirm that by my own resultat of 220Rn in thermal waters).

Dear Azzurra Lentini

Usually closed (sealed) water area can have natural radioactivity. This radio activity can be U-238, Th-232 and K-40. Due to a series of decay the daughter of this parents can be radon-222. If the examined area is good ventilated and this reason is still found it indicates that there is another reason you have to search about it and if yes it can be as we explained.

Regards

Radon originates from the natural decay of uranium and radium found in nearly all rocks and soils.

Please have a look at this useful RG link.

Article Estimation of radon concentration in soil and groundwater sa...

I think that this publication will give a good sense of how commonly Radon is found in ground water: https://pubs.usgs.gov/sir/2011/5059/

The key health hazard associated with Radon is its accumulation in a building. The US EPA has extensive information about this: https://www.epa.gov/radon

As has already been mentioned in the posts of others, once ground water reaches the surface, any dissolved Radon gas tends to disperse. Likewise, absent a building, undissolved Radon gas rising out of soil also disperses as it reaches the surface. Thus, the hazards associated with Radon are easily dealt with if one is aware of its presence in an area.

I should have mentioned that the map of Radon is found on page 30 of the USGS publication.

Probably related to very deep tectonic faults

Probably related to very deep tectonic faults

Dear Mrs. Lettini

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.

See also:

CARL, C. and DILL, H.G. (1983) Uranium disequilibria and modern redistribution phenomena in alteration zones in the Höhensteinweg uranium occurrence. - Uranium, 1: 113-125.

CARL, C. and DILL, H.G. (1985) Age of secondary uranium mineralization in the basement rocks of northeastern Bavaria, F.R.G..- Chemical Geology, 52: 295-316.

With kind regards

H.G.Dill