Leo Lehmicke - Co2 and Water
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"UnNatural" Attenuation of 1,4-Dioxane (Southern California)

Two sites have TCA plumes; low levels of 1,4-dioxane are present in down gradient wells in one plume. In the other, dioxane was not initially observed in down gradient wells but only detected later at high concentrations during a detailed source area investigation. Little or no dioxane in distal plumes did not agree with the current belief that dioxane does not usually biodegrade under the anaerobic conditions observed in the field. Calculations generated from field data using other compounds as conservative tracers gave half-life estimates for dioxane of 0.5 to 1.5 years.

I am overseeing a lab study looking at dioxane degradation. Custom synthesized 14C-labeled dioxane was obtained for the study being done by Dr. David Freedman and a grad student (Francisco Barajas) at Clemson. Up to 29% 14C-labeled soluble products were observed at 137 days under an anaerobic condition (Barajas et al. 2011, 2012). CSIA is being attempted to confirm biodegradation.
UPDATE: Although the site was clearly anaerobic, a culture that degraded dioxane under anaerobic conditions could not be isolated. I have a complex theory why degradation is occurring at this site but it is not worth pursuing given the current site status and that if correct, it is not relevant to most other dioxane sites.