†GSI Environmental Inc., Houston, Texas 77098, United States.
‡Air Force Civil Engineer Center, Lackland Air Force Base, San Antonio, Texas 78236 United States.
Environ Sci Technol. 2015 Jun 2;49(11):6510-8. doi: 10.1021/acs.est.5b00964. Epub 2015 May 22.
There is a critical need to develop appropriate management strategies for 1,4-dioxane (dioxane) due to its widespread occurrence and perceived recalcitrance at groundwater sites where chlorinated solvents are present. A comprehensive evaluation of California state (GeoTracker) and Air Force monitoring records was used to provide significant evidence of dioxane attenuation at field sites. Temporal changes in the site-wide maximum concentrations were used to estimate source attenuation rates at the GeoTracker sites (median length of monitoring period = 6.8 years). While attenuation could not be established at all sites, statistically significant positive attenuation rates were confirmed at 22 sites. At sites where dioxane and chlorinated solvents were present, the median value of all statistically significant dioxane source attenuation rates (equivalent half-life = 31 months; n = 34) was lower than 1,1,1-trichloroethane (TCA) but similar to 1,1-dichloroethene (1,1-DCE) and trichloroethene (TCE). Dioxane attenuation rates were positively correlated with rates for 1,1-DCE and TCE but not TCA. At this set of sites, there was little evidence that chlorinated solvent remedial efforts (e.g., chemical oxidation, enhanced bioremediation) impacted dioxane attenuation. Attenuation rates based on well-specific records from the Air Force data set confirmed significant dioxane attenuation (131 out of 441 wells) at a similar frequency and extent (median equivalent half-life = 48 months) as observed at the California sites. Linear discriminant analysis established a positive correlation between dioxane attenuation and increasing concentrations of dissolved oxygen, while the same analysis found a negative correlation with metals and CVOC concentrations. The magnitude and prevalence of dioxane attenuation documented here suggest that natural attenuation may be used to manage some but not necessarily all dioxane-impacted sites.
由于 1,4-二恶烷（二恶烷）广泛存在且在含氯溶剂存在的地下水场所具有较强的抗降解性，因此迫切需要开发适当的管理策略。综合评估加利福尼亚州（GeoTracker）和空军监测记录，为现场证明二恶烷衰减提供了重要证据。使用全场地最大浓度的时间变化来估算 GeoTracker 场地的源衰减率（监测期中位数= 6.8 年）。虽然并非所有场地都能确定衰减，但在 22 个场地确认了具有统计学意义的正衰减率。在存在二恶烷和含氯溶剂的场地中，所有具有统计学意义的二恶烷源衰减率的中位数（等效半衰期= 31 个月；n = 34）值低于 1,1,1-三氯乙烷（TCA），但与 1,1-二氯乙烯（1,1-DCE）和三氯乙烯（TCE）相似。二恶烷衰减率与 1,1-DCE 和 TCE 的衰减率呈正相关，但与 TCA 无关。在这组场地中，几乎没有证据表明含氯溶剂修复工作（例如，化学氧化，增强生物修复）会影响二恶烷的衰减。根据空军数据集的特定井记录得出的衰减率证实了二恶烷的明显衰减（加利福尼亚州场地观察到的频率和程度相似，中位数等效半衰期= 48 个月）。在加利福尼亚州，线性判别分析确定了二恶烷衰减与溶解氧浓度增加之间存在正相关，而相同的分析发现与金属和挥发性有机氯化物（CVOC）浓度之间存在负相关。此处记录的二恶烷衰减的幅度和普遍性表明，自然衰减可能用于管理一些但并非所有受二恶烷影响的场地。
