The long-term behavior of radium associated with oil-field brines is not well known. A production facility located on an interdistributary delta plain in southern Louisiana discharged brine into an estuarine marsh from 1957 until early 1983, when the facility began injecting produced water into an injection well. Produced water at this facility has elevated radium concentrations.
A study of the marsh soil adjacent to the facility in 1980 reported elevated radium concentrations. The 1980 sample sites were resampled for this study and analyzed for radium. Concentrations are now below natural background levels. The largest reductions were observed in samples that previously reported the highest values. The mineralogical host of the radium appears to be a solid barium sulfate (BaSO4) phase, in contrast to previous reports of radium being adsorbed on clay minerals.
The study area was severely impacted by Hurricane Katrina in 2005, lying directly in the path of the eye. Some of the production facilities that handle naturally occurring radioactive material (NORM) were destroyed, and spills of both oil and formation water occurred.
Study results indicate that remediation of the marsh is occurring naturally in a time frame as short as two decades. The long-term effects of discharging oil-field brines with NORM in an area with active sedimentation appears to be minimal.