Department of Civil & Environmental Engineering and ‡Department of Geology & Planetary Science, University of Pittsburgh , Pittsburgh, Pennsylvania 15261, United States.
Environ Sci Technol. 2015 Mar 3;49(5):2969-76. doi: 10.1021/es504656q. Epub 2015 Feb 12.
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.
由于对环境和公共健康的潜在影响，从马塞勒斯页岩气开采中产生的废水中天然存在的放射性物质（NORM）浓度升高引起了极大的关注。开发一种快速而强大的方法来分析 Ra-226（这种水中的主要 NORM 成分）对于选择适当的管理方法来正确解决监管和公众关注的问题至关重要。传统的 Ra-226 测定方法需要长时间的样品保持时间或长时间的检测时间。本研究开发了一种将电感耦合质谱法（ICP-MS）与固相萃取（SPE）相结合的新方法，用于从高盐度溶液中的基质元素中分离和纯化镭同位素。该方法减少了分析时间，同时保持了必要的精度和检测限。通过使用强酸阳离子交换树脂从溶液中的其他离子中分离钡和镭，以及使用锶特异性树脂从钡中分离镭并获得适合 ICP-MS 分析的样品，实现了镭的分离。方法优化实现了高镭回收率（标准模式下为 101±6%，碰撞模式下为 97±7%），用于总溶解固体（TDS）高达 171,000mg/L 的合成马塞勒斯页岩废水（MSW）样品。使用 ICP-MS 测量的 TDS 高达 415,000mg/L 的实际 MSW 样品中的 Ra-226 浓度与伽马谱法的结果非常吻合。本研究中开发的 Ra-226 分析方法需要数小时进行样品制备，数分钟进行分析，检测限为 100pCi/L，标准模式下的相对标准偏差（RSD）为 45%，碰撞模式下为 67%。当 Ra-226 浓度超过 500pCi/L 时，RSD 降低至 15%以下。
