Demonstrating a Natural Origin of Chloroform in Groundwater Using Stable Carbon Isotopes

Chloroform has been for a long time considered only as an anthropogenic contaminant. The presence of chloroform in forest soil and groundwater has been widely demonstrated. The frequent detection of chloroform in groundwater in absence of other contaminants suggests that chloroform is likely produce...

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Bibliographic Details
Published in:Environmental science & technology 2012-06, Vol.46 (11), p.6096-6101
Main Authors: Hunkeler, Daniel, Laier, Troels, Breider, Florian, Jacobsen, Ole Stig
Format: Article
Language:English
Subjects:
Analysis methods
Applied sciences
Aquifers
Carbon Isotopes
Chemical contaminants
Chloroform - analysis
Denmark
Earth sciences
Earth, ocean, space
Engineering and environment geology. Geothermics
Exact sciences and technology
Forest soils
Geography
Groundwater
Groundwater - chemistry
Groundwaters
Industry
Isotope Labeling - methods
Isotopes
Natural water pollution
Pollution
Pollution, environment geology
Water Pollutants, Chemical - analysis
Water treatment and pollution
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Summary:Chloroform has been for a long time considered only as an anthropogenic contaminant. The presence of chloroform in forest soil and groundwater has been widely demonstrated. The frequent detection of chloroform in groundwater in absence of other contaminants suggests that chloroform is likely produced naturally. Compound-specific isotope analysis of chloroform was performed on soil-gas and groundwater samples to elucidate whether its source is natural or anthropogenic. The δ13C values of chloroform (−22.8 to −26.2‰) present in soil gas collected in a forested area are within the same range as the soil organic matter (−22.6 to −28.2‰) but are more enriched in 13C compared to industrial chloroform (−43.2 to −63.6‰). The δ13C values of chloroform at the water table (−22.0‰) corresponded well to the δ13C of soil gas chloroform, demonstrating that the isotope signature of chloroform is maintained during transport through the unsaturated zone. Generally, the isotope signature of chloroform is conserved also during longer range transport in the aquifer. These δ13C data support the hypothesis that chloroform is naturally formed in some forest soils. These results may be particularly relevant for authorities’ regulation of chloroform which in the case of Denmark was very strict for groundwater (
ISSN:0013-936X
1520-5851
DOI:10.1021/es204585d