Construction and validation of parametric models to predict radium sorption in soils

• Published in: The Science of the total environment Vol. 944; p. 173953
• Main Authors: Serra-Ventura, Joan, Vidal, Miquel, Rigol, Anna
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 20.09.2024
• Subjects: data collection; desorption; Distribution coefficient; ecosystems; environment; exchangeable calcium; Interaction; prediction; Prediction model; Radium; regression analysis; risk assessment; Soil; sorption; surface area; variance; water solubility; Soil; Distribution coefficient; Interaction; Prediction model; Radium
• DOI: 10.1016/j.scitotenv.2024.173953
• ISSN: 0048-9697; 1879-1026

Elucidating the factors affecting the transfer of naturally occurring radionuclides (NOR) between environmental compartments is a key part of the assessment of ecosystem's exposure to naturally occurring radionuclide materials (NORM). For that, the sorption and desorption solid-liquid distribution coefficients (Kd) of radium (Ra) were quantified in a collection of 31 soil samples with contrasting edaphic properties under controlled conditions in laboratory batch experiments. Ra sorption was demonstrated to be moderate to high, with Kd (Ra) values ranging from 102 to 103 L kg−1. Ra sorbed was mostly irreversible, as evidenced by desorption percentages lower than 2 %. An exploratory analysis with partial least squares (PLS) regression identified the soil properties that correlated with Kd (Ra) and discarded those that were not relevant for describing Kd variability. A dataset of the sorption Kd (Ra) values and associated soil properties was built from our own data and from the literature after performing an in-depth review of similar Ra sorption studies. For the first time, Kd (Ra) parametric prediction models were constructed using univariate linear regression (ULR) and multivariate linear regression (MLR). Ra sorption in soils was mostly explained by the soil properties directly or indirectly related to the available exchange sites, such as the levels of water-soluble and exchangeable Ca and Mg as well as the pH of the contact solution. The most promising models explained around 80 % of the Kd (Ra) data variance, only needing Kd (Ca + Mg) or additional soil descriptors such as pH, Mn content, and the specific surface area. The validation of the proposed models confirmed that Kd (Ra) can be predicted with only a few soil properties that can be characterised in routine analysis. Thus, the proposed models could be used to estimate the interaction of Ra in soils in risk assessment. [Display omitted] •Ra sorption in soils was strong and irreversible.•Datasets of own and literature Kd (Ra) were constructed including soil properties.•Soil properties related to exchange sites influenced Ra sorption in soils.•ULR/MLR equations explained up to 82 % Kd (Ra) variance using few soil descriptors.•Three parametric sorption models were validated to predict Kd (Ra) values in soils.