An alternative method for Ra determinations in water

Area of Science:

• Environmental Science
• Hydrogeology
• Radiochemistry

Background:

• The Hickory Aquifer in Texas's Llano Uplift Region is a vital water source.
• Radium isotopes (226Ra, 224Ra, 228Ra) are naturally occurring and can impact water quality.
• Existing EPA-approved methods for total radium measurement may be inaccurate in certain aquifer conditions.

Purpose of the Study:

• To quantify 226Ra and 224Ra concentrations in the Hickory Aquifer.
• To develop and validate an alternative methodology for measuring radium isotopes.
• To assess the accuracy of current EPA-approved methods for radium determination in this aquifer.

Main Methods:

• Collected water samples from 13 wells across McCulloch and Mason counties.
• Utilized alpha-particle activity measurements at specific time intervals post-isolation (12-300 h and >800 h).
• Developed a new methodology to differentiate and quantify 226Ra, 224Ra, and 228Ra concentrations.

Main Results:

• All sampled wells showed measurable alpha-particle activity.
• Seven wells exceeded the 185 Bq m-3 (5 pCi L-1) threshold for 226Ra.
• The proposed method provided self-consistent results for 226Ra and 224Ra, with negligible 228Ra contribution at shorter intervals.
• 228Ra concentrations were calculable at longer post-isolation times (>800 h).
• Significant disagreement was found between the new method's 228Ra results and previous Texas Department of Health data for one well.

Conclusions:

• The standard EPA method for total radium is unreliable in aquifers with significant 224Ra.
• The alternative methodology offers a more accurate approach for quantifying 226Ra, 224Ra, and 228Ra in the Hickory Aquifer.
• Further investigation into radium isotope concentrations and their sources in this aquifer is warranted.