Monitored Natural Attenuation (MNA) is a preferred remedy for sites contaminated with 1,4-dioxane due to its low cost and limited environmental impacts compared to active remediation. Having a robust estimate of the rate at which biodegradation occurs is an essential component of assessing MNA. In this study, an assay was developed using ¹⁴C-labeled 1,4-dioxane to measure rate constants for biodegradation based on accumulation of ¹⁴C products. Purification of the ¹⁴C-1,4-dioxane stock solution lowered the level of ¹⁴C impurities to below 1% of the total ¹⁴C activity. This enabled determination of rate constants in groundwater as low as 0.0021 yr⁻¹, equating to a half-life greater than 300 years. Of the 54 groundwater samples collected from 10 sites in the US, statistically significant rate constants were determined with the ¹⁴C assay for 24. The median rate constant was 0.0138 yr⁻¹ (half-life = 50 yr); the maximum rate constant was 0.367 yr⁻¹ (half-life = 1.9 yr). The results confirmed that biodegradation of 1,4-dioxane is occurring at 9 of the 10 sites sampled, albeit with considerable variability in the level of activity. The specificity of the assay was confirmed using acetylene and the absence of oxygen to inhibit monooxygenases.

与主动修复相比，受监测的自然衰减 (MNA) 是受 1,4-二恶烷污染场地的首选补救措施，因为其成本低且对环境的影响有限。对生物降解发生的速率进行可靠估计是评估 MNA 的重要组成部分。在这项研究中，使用¹⁴ C 标记的 1,4-二恶烷开发了一种测定法，以测量基于¹⁴ C 产物积累的生物降解速率常数。¹⁴ C-1,4-二恶烷储备溶液的纯化将¹⁴ C杂质的水平降低到低于总¹⁴ C活性的1%。这可以确定地下水中的速率常数低至 0.0021 yr ^-1，相当于半衰期大于 300 年。在从美国 10 个地点采集的 54 个地下水样本中，用¹⁴ C 测定法确定了 24 个具有统计学意义的速率常数。中位速率常数为 0.0138 yr ^-1（半衰期 = 50 年）；最大速率常数为 0.367 年^-1（半衰期 = 1.9 年）。结果证实，1,4-二恶烷的生物降解发生在 10 个采样点中的 9 个，尽管活性水平存在很大差异。使用乙炔和不存在氧气来抑制单加氧酶证实了该测定的特异性。