Department of Civil and Environmental Engineering, The Pennsylvania State University, 212 Sackett Building, University Park, Pennsylvania 16802, USA.
Environ Sci Process Impacts. 2019 Feb 21;21(2):224-241. doi: 10.1039/c8em00359a.
Accurate and precise analyses of oil and gas (O&G) wastewaters and solids (e.g., sediments and sludge) are important for the regulatory monitoring of O&G development and tracing potential O&G contamination in the environment. In this study, 15 laboratories participated in an inter-laboratory comparison on the chemical characterization of three O&G wastewaters from the Appalachian Basin and four solids impacted by O&G development, with the goal of evaluating the quality of data and the accuracy of measurements for various analytes of concern. Using a variety of different methods, analytes in the wastewaters with high concentrations (i.e., >5 mg L-1) were easily detectable with relatively high accuracy, often within ±10% of the most probable value (MPV). In contrast, often less than 7 of the 15 labs were able to report detectable trace metal(loid) concentrations (i.e., Cr, Ni, Cu, Zn, As, and Pb) with accuracies of approximately ±40%. Despite most labs using inductively coupled plasma mass spectrometry (ICP-MS) with low instrument detection capabilities for trace metal analyses, large dilution factors during sample preparation and low trace metal concentrations in the wastewaters limited the number of quantifiable determinations and likely influenced analytical accuracy. In contrast, all the labs measuring Ra in the wastewaters were able to report detectable concentrations using a variety of methods including gamma spectroscopy and wet chemical approaches following Environmental Protection Agency (EPA) standard methods. However, the reported radium activities were often greater than ±30% different to the MPV possibly due to calibration inconsistencies among labs, radon leakage, or failing to correct for self-attenuation. Reported radium activities in solid materials had less variability (±20% from MPV) but accuracy could likely be improved by using certified radium standards and accounting for self-attenuation that results from matrix interferences or a density difference between the calibration standard and the unknown sample. This inter-laboratory comparison illustrates that numerous methods can be used to measure major cation, minor cation, and anion concentrations in O&G wastewaters with relatively high accuracy while trace metal(loid) and radioactivity analyses in liquids may often be over ±20% different from the MPV.
准确和精确地分析油和天然气（O&G）废水和固体（例如沉积物和污泥）对于监管 O&G 开发以及追踪环境中潜在的 O&G 污染非常重要。在这项研究中，15 个实验室参与了一项关于阿巴拉契亚盆地三种 O&G 废水和受 O&G 开发影响的四种固体化学特征的实验室间比较，目的是评估各种关注分析物的数据质量和测量精度。使用各种不同的方法，高浓度（即 >5mg L-1）废水中的分析物很容易被检测到，并且通常具有相对较高的准确性，通常在最可能值（MPV）的 ±10%范围内。相比之下，通常只有不到 15 个实验室能够报告可检测痕量金属（loid）浓度（即 Cr、Ni、Cu、Zn、As 和 Pb），其准确度约为 ±40%。尽管大多数实验室使用电感耦合等离子体质谱（ICP-MS）进行痕量金属分析，但其仪器检测能力较低，但在样品制备过程中使用大量稀释因子和废水中痕量金属浓度较低，限制了可定量测定的数量，并可能影响分析准确性。相比之下，所有测量废水中 Ra 的实验室都能够使用各种方法报告可检测浓度，包括伽马光谱法和湿化学方法，遵循美国环保署（EPA）标准方法。然而，报告的镭活度通常与 MPV 相差大于 ±30%，可能是由于实验室之间的校准不一致、氡泄漏或未能校正自衰减造成的。固体材料中报告的镭活度变化较小（MPV 的 ±20%），但通过使用经过认证的镭标准和考虑基质干扰或校准标准和未知样品之间的密度差异导致的自衰减，准确性可能会得到提高。这项实验室间比较表明，许多方法可用于测量 O&G 废水中的主要阳离子、次要阳离子和阴离子浓度，具有相对较高的准确性，而液体中的痕量金属（loid）和放射性分析通常与 MPV 相差大于 ±20%。
