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

Contamination of soil with Ra 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 Ra in contaminated soils collected from an oilfield using a three-step sequential extraction procedure (BCR). The total activity concentrations of Ra in contaminated soils were measured and found to be in the range from 1030 ± 90 to 7780 ± 530 Bq kg, with a mean activity concentration of 2840 ± 1840 Bq kg. The correlation between the total concentration of Ra and soil properties, mainly pH, LOI, C, clay and Ca, was investigated using the principal component analysis method (PCA). The chemical fractionation of Ra was studied using the sequential extraction method (BCR). The highest fraction of Ra (27-65%) was found to be in the acid-reducible fraction, which suggests that Ra is mainly bound to FeMn oxides. The BCR method showed that high percentages of Ra were found to be in mobile soil phases (between 45 and 99%). Consequently, groundwater contamination could occur due to the remobilization of Ra 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.