Center of Hydrogeology and Geothermics (CHYN), University of Neuchâtel, rue Emile Argand 11, 2000 Neuchâtel, Switzerland.
Environ Sci Technol. 2012 Jun 5;46(11):6096-101. doi: 10.1021/es204585d. Epub 2012 May 23.
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 δ(13)C 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 (13)C compared to industrial chloroform (-43.2 to -63.6‰). The δ(13)C values of chloroform at the water table (-22.0‰) corresponded well to the δ(13)C 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 δ(13)C 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 (<1 μg/L).
氯仿长期以来仅被认为是一种人为污染物。森林土壤和地下水中存在氯仿已被广泛证明。在没有其他污染物的情况下，地下水中经常检测到氯仿，这表明氯仿可能是自然产生的。对土壤气和地下水样本进行了氯仿的化合物特异性同位素分析，以阐明其来源是自然的还是人为的。在森林地区采集的土壤气中存在的氯仿的 δ(13)C 值（-22.8 至-26.2‰）与土壤有机质的 δ(13)C 值（-22.6 至-28.2‰）相同，但与工业氯仿（-43.2 至-63.6‰）相比，氯仿在（13）C 中更为富集。地下水位处氯仿的 δ(13)C 值（-22.0‰）与土壤气氯仿的 δ(13)C 值非常吻合，这表明氯仿的同位素特征在通过非饱和带传输过程中得以保持。通常，氯仿的同位素特征在含水层中的长距离传输过程中也得以保持。这些 δ(13)C 数据支持氯仿在某些森林土壤中自然形成的假设。这些结果对于当局对氯仿的监管可能特别重要，在丹麦，对地下水（<1μg/L）的监管非常严格。
