A rapid method to determine ²²⁶Ra concentrations in Marcellus Shale produced waters using liquid scintillation...

Area of Science:

• Environmental Science
• Analytical Chemistry
• Radiochemistry

Background:

• Naturally occurring radioactive material (NORM) in Marcellus Shale produced water poses management challenges due to large fluid volumes.
• High total dissolved solids (TDS) complicate traditional EPA methods for measuring radium-226 (²²⁶Ra) in produced water.
• Existing alternative methods often involve complex sample preparation, hazardous chemicals, and long analysis times.

Purpose of the Study:

• To develop and validate a rapid, reliable method for quantifying ²²⁶Ra in high-TDS produced water.
• To provide a cost-effective and efficient protocol suitable for field-appraisal and screening.
• To support beneficial reuse and resource recovery initiatives by enabling accurate radium monitoring.

Main Methods:

• Developed a liquid scintillation counting (LSC) protocol involving fluid evaporation and re-suspension in acidified water.
• Utilized alpha-beta discrimination and spectrum deconvolution to separate ²²⁶Ra and its daughter isotopes.
• Validated the LSC method against concurrent gamma spectrometry analyses for nine Marcellus Shale produced water samples.

Main Results:

• The LSC method achieved radium recoveries ≥93% with a minimum detectable activity of 0.33 Bq/L for ²²⁶Ra.
• LSC results showed comparable accuracy to gamma spectrometry, with an R² of 0.92.
• The protocol demonstrated reduced sample preparation, lower cost, and rapid analysis times compared to conventional methods.

Conclusions:

• The presented LSC method offers a pragmatic and efficient solution for monitoring ²²⁶Ra in high-TDS produced waters.
• This protocol is well-suited for field screening and can be calibrated with gamma spectrometry for near-real-time monitoring during hydrofracturing.
• The method is particularly effective for samples with low levels of radium-228 (²²⁸Ra), avoiding spectral interferences.