Air Force Center for Engineering and the Environment, Technical Support Division, 2261 Hughes, Site 155, Lackland AFB, Texas 78236, USA.
Integr Environ Assess Manag. 2012 Oct;8(4):731-7. doi: 10.1002/ieam.1306. Epub 2012 May 17.
Increasing regulatory attention to 1,4-dioxane has prompted the United States Air Force (USAF) to evaluate potential environmental liabilities, primarily associated with legacy contamination, at an enterprise scale. Although accurately quantifying environmental liability is operationally difficult given limited historic environmental monitoring data, 1,4-dioxane is a known constituent (i.e., stabilizer) of chlorinated solvents, in particular 1,1,1-trichloroethane (TCA). Evidence regarding the co-occurrence of 1,4-dioxane and trichloroethylene (TCE), however, has been heavily debated. In fact, the prevailing opinion is that 1,4-dioxane was not a constituent of past TCE formulations and, therefore, these 2 contaminants would not likely co-occur in the same groundwater plume. Because historic handling, storage, and disposal practices of chlorinated solvents have resulted in widespread groundwater contamination at USAF installations, significant potential exists for unidentified 1,4-dioxane contamination. Therefore, the objective of this investigation is to determine the extent to which 1,4-dioxane co-occurs with TCE compared to TCA, and if these chemicals are co-contaminants, whether or not there is significant correlation using available monitoring data. To accomplish these objectives, the USAF Environmental Restoration Program Information Management System (ERPIMS) was queried for all relevant records for groundwater monitoring wells (GMWs) with 1,4-dioxane, TCA, and TCE, on which both categorical and quantitative analyses were carried out. Overall, ERPIMS contained 5788 GMWs from 49 installations with records for 1,4-dioxane, TCE, and TCA analytes. 1,4-Dioxane was observed in 17.4% of the GMWs with detections for TCE and/or TCA, which accounted for 93.7% of all 1,4-dioxane detections, verifying that 1,4-dioxane is seldom found independent of chlorinated solvent contamination. Surprisingly, 64.4% of all 1,4-dioxane detections were associated with TCE independently. Given the extensive data set, these results conclusively demonstrate for the first time that 1,4-dioxane is a relatively common groundwater co-contaminant with TCE. Trend analysis demonstrated a positive log-linear relationship where median 1,4-dioxane levels increased between approximately 6% and approximately 20% of the increase in TCE levels. In conclusion, this data mining exercise suggests that 1,4-dioxane has a probability of co-occurrence of approximately 17% with either TCE and/or TCA. Given the challenges imposed by remediation of 1,4-dioxane and the pending promulgation of a federal regulatory standard, environmental project managers should use the information presented in this article for prioritization of future characterization efforts to respond to the emerging issue. Importantly, site investigations should consider 1,4-dioxane a potential co-contaminant of TCE in groundwater plumes.
日益增加的监管关注度促使美国空军（USAF）从企业层面评估潜在的环境责任，主要与遗留污染有关。尽管由于历史环境监测数据有限，准确量化环境责任在操作上具有挑战性，但 1,4-二恶烷是氯化溶剂的已知成分（即稳定剂），特别是 1,1,1-三氯乙烷（TCA）。然而，有关 1,4-二恶烷和三氯乙烯（TCE）共同出现的证据一直存在争议。事实上，主流观点认为 1,4-二恶烷过去不是 TCE 配方的成分，因此，这两种污染物不太可能出现在同一地下水羽流中。由于过去氯化溶剂的处理、储存和处置做法导致美国空军设施的地下水广泛受到污染，因此存在大量未识别的 1,4-二恶烷污染的可能性。因此，本研究的目的是确定 1,4-二恶烷与 TCA 相比与 TCE 共同出现的程度，如果这些化学物质是共污染物，是否存在显著相关性，使用可用的监测数据。为了实现这些目标，查询了美国空军环境修复计划信息管理系统（ERPIMS）中与地下水监测井（GMW）有关的所有记录，这些 GMW 中含有 1,4-二恶烷、TCA 和 TCE，对这些 GMW 进行了分类和定量分析。总体而言，ERPIMS 包含了来自 49 个设施的 5788 个 GMW 记录，这些设施都有 1,4-二恶烷、TCE 和 TCA 分析物。在有 TCE 和/或 TCA 检测的 GMW 中，有 17.4%检测到 1,4-二恶烷，这占所有 1,4-二恶烷检测的 93.7%，验证了 1,4-二恶烷很少独立于氯化溶剂污染而存在。令人惊讶的是，所有 1,4-二恶烷检测中有 64.4%都与 TCE 独立相关。考虑到广泛的数据集，这些结果首次明确表明 1,4-二恶烷是 TCE 的一种相对常见的地下水共污染物。趋势分析显示中位数 1,4-二恶烷水平与 TCE 水平的增加之间存在正对数线性关系，增加了约 6%至约 20%。总之，这项数据挖掘研究表明，1,4-二恶烷与 TCE 和/或 TCA 共同出现的概率约为 17%。鉴于 1,4-二恶烷修复带来的挑战以及即将颁布的联邦监管标准，环境项目经理应利用本文提供的信息，为未来的特征描述工作确定优先级，以应对新出现的问题。重要的是，现场调查应考虑到 1,4-二恶烷是地下水羽流中 TCE 的潜在共污染物。
