School of Civil and Environmental Engineering, Cornell University, 220 Hollister Hall, Ithaca, NY 14853, USA.
Environ Sci Process Impacts. 2019 Feb 21;21(2):195-205. doi: 10.1039/c8em00135a.
Hydraulic fracturing (HF) operations utilize millions of gallons of water amended with chemical additives including biocides, corrosion inhibitors, and surfactants. Fluids injected into the subsurface return to the surface as wastewaters, which contain a complex mixture of additives, transformation products, and geogenic chemical constituents. Quantitative analytical methods are needed to evaluate wastewater disposal alternatives or to conduct adequate exposure assessments. However, our narrow understanding of how matrix effects change the ionization efficiency of target analytes limits the quantitative analysis of polar to semi-polar HF additives by means of liquid chromatography electrospray ionization mass spectrometry (LC-ESI-MS). To address this limitation, we explored the ways in which matrix chemistry influences the ionization of seventeen priority HF additives with a modified standard addition approach. We then used the data to quantify HF additives in HF-associated fluids. Our results demonstrate that HF additives generally exhibit suppressed ionization in HF-associated fluids, though HF additives that predominantly form sodiated adducts exhibit significantly enhanced ionization in produced water samples, which is largely the result of adduct shifting. In a preliminary screening, we identified glutaraldehyde and 2-butoxyethanol along with homologues of benzalkonium chloride (ADBAC), polyethylene glycol (PEG), and polypropylene glycol (PPG) in HF-associated fluids. We then used matrix recovery factors to provide the first quantitative measurements of individual homologues of ADBAC, PEG, and PPG in HF-associated fluids ranging from mg L-1 levels in hydraulic fracturing fluid to low μg L-1 levels in PW samples. Our approach is generalizable across sample types and shale formations and yields important data to evaluate wastewater disposal alternatives or implement exposure assessments.
水力压裂（HF）作业使用数百万加仑的水，其中添加了包括杀菌剂、缓蚀剂和表面活性剂在内的化学添加剂。注入地下的流体作为废水返回地面，其中含有添加剂、转化产物和地质化学成分的复杂混合物。需要定量分析方法来评估废水处理替代方案或进行充分的暴露评估。然而，我们对基质效应对目标分析物电离效率的影响的理解有限，限制了通过液相色谱电喷雾电离质谱（LC-ESI-MS）对极性到半极性 HF 添加剂的定量分析。为了解决这个限制，我们探索了基质化学如何影响十七种优先 HF 添加剂的电离的方法，采用改进的标准添加方法。然后，我们使用这些数据来定量 HF 相关流体中的 HF 添加剂。我们的结果表明，HF 添加剂通常在 HF 相关流体中表现出抑制电离，尽管主要形成加钠离子的加合物的 HF 添加剂在产出水中表现出显著增强的电离，这主要是由于加合物转移的结果。在初步筛选中，我们在 HF 相关流体中鉴定出戊二醛和 2-丁氧基乙醇以及苯扎氯铵（ADBAC）、聚乙二醇（PEG）和聚丙二醇（PPG）的同系物。然后，我们使用基质回收率因子提供了 HF 相关流体中 ADBAC、PEG 和 PPG 各个同系物的首次定量测量，范围从液压压裂液中的 mg/L 水平到 PW 样品中的低μg/L 水平。我们的方法适用于各种样品类型和页岩地层，并提供了评估废水处理替代方案或实施暴露评估的重要数据。
