Naturally occurring highly chlorinated organic compounds in soils with elevated OCDD concentration

Area of Science:

• Environmental Chemistry
• Organic Geochemistry

Background:

• Elevated octachlorodibenzo-p-dioxin (OCDD) levels are frequently observed globally.
• The precise origin of OCDD remains unclear, with multiple hypotheses lacking universal acceptance.

Purpose of the Study:

• To investigate the presence and identity of other polyhalogenated organic compounds in highly OCDD-contaminated soils.
• To explore potential natural formation pathways for OCDD.

Main Methods:

• Utilized a non-target High-Performance Liquid Chromatography-High-Resolution Accurate Mass Spectrometry/Mass Spectrometry (HPLC-HRAM MS/MS) approach.
• Analyzed Vietnamese soil samples with high OCDD contamination.

Main Results:

• Detected and identified over 100 highly chlorinated compounds across seven distinct structural classes.
• Identified compounds with molecular formulas similar to natural antibiotics and novel structures.
• Observed that some compounds were ubiquitous, while others were specific to OCDD hotspots.

Conclusions:

• The structural diversity and limited isomerism of detected compounds, coupled with the absence of clear anthropogenic precursors, point towards natural formation processes.
• Findings support the hypothesis of biogenic or other natural origins for OCDD.