Dear Mr. Zemour,

Radium (Ra-226) is a radioactive isotope of the parent radionuclide U-238. It is far less soluble than U-238 and less soluble than Th-234. Radium is chemical akin in the periodical chart of elements to barium (Ba) which forms the almost insoluble mineral BaSO4 (barite). Based upon its position in the 2nd group below Ba, Ra forms a short-lived equivalent sulfate under oxidizing conditions in the presence of sulfur called “radio-barite” (Ba,Ra)SO4. It is the least soluble mineral at all and also accountable for the disequilibria in the U-238 decay chain. Due to the short half-life it only comes up in Quaternary host environments, e.g., swamps or hydrothermalites/ thermal waters. This may contribute to variation of Ra in aquatic systems.

H.G.Dill

Youcef, I assume that you are referring to activities of Ra-226 and Ra-228. If so, then you have to consider the parent nuclides from which the two species of radium are derived. Ra-226 is a daughter of the Uranium (U-238) decay series, and Ra-226 is a daughter of the Thorium (Th-232) series. The radium isotopes also have very different half-lives (Ra-226 = 1600 yrs; Ra-228 = 5.75 yrs). So, variations can be attributed to the relative abundances of the parent nuclides, the half-lives of the daughters, along with other factors such as solubilities (see Harald Dill's answer above) and the tendency of radium to be adsorbed to mineral surfaces or to become sequestered by precipitation or absorption.

Thank you for your answers Harald G. Dill and Bruce K. Darling.

Mr Harald G. Dill your answer gave me an idea that's why I found high activity in thermal waters

So it is necessary to see the correlation between Ba and Ra if the correlation is postive what can we say? I guess we can say that there is a coprecipitation between these two elements, ! !

Good luck with you research, Youcef. Please keep us apprised of your findings.

Thank you Mr Bruce K. Darling , yes i will keep you posted, also if i need a help i will contact you

There are Ra accumulations in N Czechia.

Ulrych, J. et al. (2007): Cenozoic radiobarite occurrences in the Ohře (Eger) Rift, Bohemian Massif: Mineralogical and geochemical revision.

Chemie der Erde - Geochemistry, 67, 301-312.

Kind regards

H.G.Dill