Workreport 2017-2



Geochemical and Physical properties and in Situ distribution Coefficients of the Deep Soil Pits OL-KK25 and OL-KK26 at Olkiluoto


Kuusisto, J.



Page count:



In this working report the geochemical and physical properties together with in situ distribution coefficients, Kd values of the deep soil pits (OL-KK25 & OL-KK26) were analyzed. The in situ Kd values are used to estimate the mobility of radionuclides in different environments. In this research the focus was in the indigenous key elements (Ag, Cl, Cs, I, Mo, Nb, Ni, Pb, Se, Sn and Sr). These elements are the most important elements in safety assessment because they are analogues to the highest doses
contributing radionuclides from the repositories.

The Kd values were calculated from the total and bioavailable element concentrations. The bioavailable concentrations were analysed with NH4Ac (pH 4,5) extraction and total concentrations with HNO3-HF (trace) extraction or LiBO2 fusion. In addition to the Kd values for the deep soil layers, grain size distribution, organic matter content (LOI), pH, organic and inorganic carbon, main anions of the pore water and mineralogy were analysed. The cation exchange capacity (CEC) and base saturation (BS) were calculated using the the results of NH4Ac (pH 4.5) extraction. Finally, all the soil parameters and Kd values were taken into correlation analysis to find out the most important parameters that have influence on the mobility of elements.

According to the earlier and this study at Olkiluoto, heterogeneity is more common than homogeneity. The soil types among other properties varies significantly between the soil pits and vertically within the pits. Due the high variability on soil properties, also the concentrations and Kd values varied widely. According to this study, significant factors that effect on Kd values are mineralogy, clay content, grain size, organic matter content and pH. The environmental factors influence on the speciation of elements which after all determines the behavior of elements at the geo-biosphere interface. The results of this study improves understanding the dependency of element mobility with soil parameters which enables to assess the radionuclide transportation from repositories to surface environment with more accurate site specific soil parameters. The soil type-classification functions also as a basis for overburden modelling, biotope classification and forecasts of future environment developments by determining the vegetation succession and available habitats for fauna.


Deep soil pits, soil profiles, geochemical properties, distribution coefficients (Kd values) and Olkiluoto.


Geochemical and Physical Properties and in Situ Distribution Coefficients of the Deep Soil Pits OL-KK25 and OL-KK26 at Olkiluoto (pdf) (4.5 MB)


Share article: