Chemical fractionation of radium-226 in NORM contaminated soil from oilfields

Contamination of soil with ²²⁶Ra is a common problem in the oilfields, leading to costly remediation and disposal programmes. The present study focuses on the chemical fractionation and mobility of ²²⁶Ra in contaminated soils collected from an oilfield using a three-step sequential extraction procedure (BCR). The total activity concentrations of ²²⁶Ra in contaminated soils were measured and found to be in the range from 1030 ± 90 to 7780 ± 530 Bq kg^-1, with a mean activity concentration of 2840 ± 1840 Bq kg^-1. The correlation between the total concentration of ²²⁶Ra and soil properties, mainly pH, LOI, C_org, clay and Ca, was investigated using the principal component analysis method (PCA). The chemical fractionation of ²²⁶Ra was studied using the sequential extraction method (BCR). The highest fraction of ²²⁶Ra (27-65%) was found to be in the acid-reducible fraction, which suggests that ²²⁶Ra is mainly bound to FeMn oxides. The BCR method showed that high percentages of ²²⁶Ra were found to be in mobile soil phases (between 45 and 99%). Consequently, groundwater contamination could occur due to the remobilization of ²²⁶Ra from soils under normal environmental conditions. However, the obtained results could be useful to reduce the volume of NORM wastes generated from the oilfields and decision-making process for final treatment and disposal of NORM-contaminated soil.