Analysis of Radium-226 in High Salinity Wastewater from Unconventional Gas Extraction by Inductively Coupled Plasma-Mass Spectrometry

Abstract

Elevated concentration of naturally occurring radioactive material (NORM) in wastewater generated from Marcellus Shale gas extraction is of great concern due to potential environmental and public health impacts. Development of a rapid and robust method for analysis of Ra-226, which is the major NORM component in this water, is critical for the selection of appropriate management approaches to properly address regulatory and public concerns. Traditional methods for Ra-226 determination require long sample holding time or long detection time. A novel method combining Inductively Coupled Mass Spectrometry (ICP-MS) with solid-phase extraction (SPE) to separate and purify radium isotopes from the matrix elements in high salinity solutions is developed in this study. This method reduces analysis time while maintaining requisite precision and detection limit. Radium separation is accomplished using a combination of a strong-acid cation exchange resin to separate barium and radium from other ions in the solution and a strontium-specific resin to isolate radium from barium and obtain a sample suitable for analysis by ICP-MS. Method optimization achieved high radium recovery (101 ± 6% for standard mode and 97 ± 7% for collision mode) for synthetic Marcellus Shale wastewater (MSW) samples with total dissolved solids as high as 171,000 mg/L. Ra-226 concentration in actual MSW samples with TDS as high as 415,000 mg/L measured using ICP-MS matched very well with the results from gamma spectrometry. The Ra-226 analysis method developed in this study requires several hours for sample preparation and several minutes for analysis with the detection limit of 100 pCi/L with RSD of 45% (standard mode) and 67% (collision mode). The RSD decreased to below 15% when Ra-226 concentration increased over 500 pCi/L.

The behaviour of 226Ra in high-volume environmental water samples on TK100 resin

“…This is an important consideration for ICP-MS applications, where polyatomic 138 Ba 88 Sr can overlap with 226 Ra [23]. Results from Triskem suggest that Sr is retained in 8–10 M HNO 3 , and that Ba is retained in 1 M HNO 3 if the elution volumes are carefully controlled.…”

“…226 Ra decays by alpha emission, with a maximum decay energy of 4.79 MeV (94.0%) [1], and gamma emission with a maximum decay energy of 186.2 (13) keV (32.8%). 226 Ra is measurable by alpha spectrometry [6–8], liquid scintillation counting [9–11], gamma spectrometry [12–14] and inductively coupled plasma mass spectrometry (ICP-MS) [15–23]. Measurement of 226 Ra is important with regards to drinking water quality as well as environmental monitoring around nuclear and industrial sites, including mining and processing sites for coal, phosphogypsum and uranium.…”

Plasma source mass spectrometry for radioactive waste characterisation in support of nuclear decommissioning: a review

“…The following radionuclides, of direct interest to the nuclear decommissioning, waste characterisation and repository safety cases, have been considered as part of this review: 36 Cl, 41 Ca, 59 Ni and 63 Ni, 79 Se, 90 Sr, 93 Zr, 99 Tc, 107 Pd, 129 I, 135 Cs and 137 Cs, 151 Sm, 210 Pb, 226 Ra and 228 Ra, 231 Pa, Th and U isotopes, 237 Np, Pu isotopes, 241 Am, and isotopes of Cm and Cf. The generalised origin of these radionuclides is indicated in Fig.…”

Fouling in direct contact membrane distillation of produced water from unconventional gas extraction

“…For Ra226 analysis, 10 ml of each sample was filtered through 0.22 µm membrane and heated at 105°C to evaporate the liquid. Residual solids were crushed and spread evenly across a 46-mm Petri dish that was then sealed with vinyl tape and analyzed using gamma spectrometer at 186 keV with 24-hr counting period [42,43].…”