Degradation of 1,4-Dioxane in Groundwater – Field Study Integrating Compound-Specific Isotope Analysis

1,4-Dioxane is commonly found as a co-contaminant at chlorinated solvent sites, most notably alongside 1,1,1-trichloroethane (1,1,1-TCA). To a lesser extent, it can also occur as a primary contaminant at sites where it is used as a solvent, such as in the pharmaceutical industry. Due to its widespread occurrence and classification as a likely human carcinogen, understanding its environmental fate is of significant interest.

The biodegradation of 1,4-dioxane occurs primarily under aerobic conditions, whereas anaerobic degradation has been shown to be negligible. Aerobic degradation may proceed either metabolically or co-metabolically and is initiated by monooxidation of the dioxane ring, followed by spontaneous oxidation and ring cleavage, ultimately leading to complete mineralization.

An increasing number of laboratory studies have investigated 1,4-dioxane–degrading bacteria, which may facilitate its removal. However, relatively few studies have directly assessed the relevance of these processes under field conditions. The primary objective of this study was to examine the in situ degradation of 1,4-dioxane in groundwater at various sites using compound-specific carbon isotope analysis (δ¹³C). The δ¹³C values of 1,4-dioxane extracted from these sites will be presented and discussed.