Ra-226 is an ultra-trace element with important environmental implications for many industries (including water treatment and oil and mineral extraction). Its extremely low concentrations in natural environments do not allow for direct observation and measurement of the Ra-226-bearing minerals governing Ra-226 mobility. To better understand the retention processes for Ra-226 in rocks and soil, a synthesized assemblage of Ra-226-doped minerals was made, combining montmorillonite, ferrihydrite and barite. A new methodology was developed using alpha activity maps acquired using alpha autoradiography, and elemental maps by using SEM/EDS. These maps were processed using a global approach, considering the entirety of the signal. The comparison of the alpha activity map and the elemental map enabled a correlation to be established between the Ra-226 activity and the chemical composition and identification of the main Ra-226-bearing mineral of the assemblage, from which we were able to estimate the contribution of each mineral to the total activity of the assemblage, and to quantify the Ra-226-activity for each mineral. This methodology makes it possible to link mineralogy and occurrence of Ra-226 at the scale of the mineral (tens of mu m). It can be applied to natural samples, including fine-grained samples with a complex mineralogy.
Plan de classement
Sciences fondamentales / Techniques d'analyse et de recherche [020]
;
Sciences du milieu [021]
;
Géologie et formations superficielles [064]
