1,4-Dioxane is a contaminant of emerging concern, and there is significant uncertainty about how its environmental occurrence in groundwater is being assessed given the various analytical methods available. This study compiled public sampling records from 2000 to 2019 that included >106,000 analyses of 1,4-dioxane from 822 different U.S. sites. The 1,4-dioxane detection frequency in the entire dataset (including all methods) was 45%, and the median detected concentration was 10 μg/L, highlighting the dilute nature of 1,4-dioxane in environmental media and the importance of selecting methods with adequate sensitivity. The annual distribution of samples analyzed by each method type confirmed a shift towards methods designed for semi-volatile compounds (Method 8270 and Method 8270 SIM) that exhibited consistently lower reporting limits (median reporting limit for each year typically ≤1 μg/L). In contrast, the method designed for volatile compounds (Method 8260) exhibited less sensitivity for 1,4-dioxane (median reporting limit per year between 40 and 100 μg/L) and its use declined significantly over time with increasing use of the moderately sensitive Method 8260 SIM in later years. This shift contributed to an increase in the 1,4-dioxane detection frequency over time, with a strong correlation between the annual detection frequency and the median reporting limit. Sites where 1,4-dioxane was analyzed but not detected overwhelmingly used less-sensitive methods that may not have been adequate for the expected concentration levels. Given the sub-μg/L groundwater criteria issued for 1,4-dioxane by some regulatory agencies, more sensitive and accurate methods will be increasingly needed to assess compliance.

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1,4-二恶烷分析的趋势：对受污染地下水位点的识别和表征的意义

1,4-二恶烷是一种新出现的污染物，鉴于可​​用的各种分析方法，如何评估其在地下水中的环境存在存在很大的不确定性。本研究汇编了 2000 年至 2019 年的公共采样记录，其中包括对来自美国 822 个不同地点的 1,4-二恶烷的 >106,000 次分析。整个数据集（包括所有方法）中 1,4-二氧六环的检测频率为 45%，检测浓度中位数为 10 μg/L，突出了 1,4-二氧六环在环境介质中的稀释性质和选择的重要性具有足够灵敏度的方法。每种方法类型分析的样品的年度分布证实了向半挥发性化合物设计的方法（方法 8270 和方法 8270 SIM）的转变，这些方法表现出一贯较低的报告限值（每年的中值报告限值通常≤1 μg/L）。相比之下，为挥发性化合物设计的方法（方法 8260）对 1,4-二恶烷表现出较低的灵敏度（每年的中位报告限值在 40 到 100 μg/L 之间），并且随着时间的推移，随着中度灵敏度的增加，其使用量显着下降。方法 8260 SIM 晚年。这种转变导致 1,4-二恶烷检测频率随着时间的推移而增加，年检测频率与中值报告限值之间存在很强的相关性。1、对 4-二恶烷进行了分析但未检测到，绝大多数使用灵敏度较低的方法，这些方法可能不足以达到预期的浓度水平。鉴于一些监管机构针对 1,4-二恶烷发布了亚微克/升地下水标准，将越来越需要更灵敏、更准确的方法来评估合规性。