Regarding minerological analysis

[hariprasath]

why we need to find the minerals in the sediments while estimating the amount of radionuclides. although there exist a cation exchange capacity in the minerals, do they actually concentrate the primordial radionuclides in them.
further on granulometric analysis, do the clay particles retain the radionuclides and how?

 

[DrDu]

Maybe you could provide some more background. Which primordial radionuclides do you mean? Basically, there is only uranium and thorium. Thorium is almost insoluble, but the solubility of uranium depends on it's oxidation state (namely IV, which is insoluble and VI, which is soluble). The oxidation state depends on the pH of the solution, the amount of carbonate and the presence of reducing agents in the soil/ mineral with which the solution is in contact, like organic mater or inorganic carbon which may reduce the U VI to U IV.

 

[hariprasath]

Uranium can exist in five oxidation states: +2, +3, +4, +5 and +6. However, only the +4 and +6 states are stable enough to be of practical importance. Tetravalent uranium is reasonably stable and forms hydroxides, hydrated fluorides and phosphates of low solubility. Hexavalent uranium is the most stable state and the most
commonly occurring form is U3O8. this is what i had read it one of the page in internet. i request you to help me to find the exact answer for this.

 

[DrDu]

So what precisely is your question?

 

[hariprasath]

which oxide is responsible for the increase of uranium -238 in the sediments of rivers. is it U(IV) oxide is soluble or U(VI) is soluble in water?

 

[DrDu]

I would expect mainly pitchblende UO2, which is a Uranium-IV oxide.

 

[DrDu]

which oxide is responsible for the increase of uranium -238 in the sediments of rivers. is it U(IV) oxide is soluble or U(VI) is soluble in water?

Uranium-VI is very soluble in water.

 

[hariprasath]

thank you for the clarification.