Characterization of NORM Contaminated Sites at the Syrian Oilfield: Depth Profiles and Leaching Processes

Abstract

Production water containing naturally occurring radioactive materials (NORM) has been collected in unlined artificial lagoons for evaporation in some Syrian oilfields. These lagoons have become highly contaminated with NORM and the situation has urged the operating oil companies in Syria to initiate a remediation program in cooperation with the Atomic Energy Commission of Syria. Part of this national remediation program is to characterize the contaminated soil as a preliminary step for disposal of this waste. Depth profiles of radioactivity have been established and found to be variable from one field to another. Factors that influence this distribution have been evaluated and are presented. Laboratory leaching experiments were performed using six 60-cm cores collected from highly contaminated areas in the oil fields. Results show that 226Ra is transferred to deep layers via erosion caused by disposal of production water and some heavy rain water that occurred in the past. This erosion process is mainly affected by the mineralogical compositions of the contaminated soil and the particle size distribution. Gypsum present in the soil has increased transfer of 226Ra from surface layers to deeper layers; water has caused some sink holes (caves) in those soils containing high amount of gypsum. In addition, 226Ra was also determined in different particle size soil samples before and after leaching experiments where small soil particles sizes were found to be moved downwards by water. Radium was only more concentrated in smaller particle sizes than larger ones in those samples containing low concentration of gypsum. In addition, halite content in the upper soil layers has increased the radium specific activity after leaching since it dissolved in water and moved to deeper layers.