TY - JOUR
T1 - Assessing the role of trichloroacetyl-containing compounds in the natural formation of chloroform using stable carbon isotopes analysis
AU - Breider, Florian
AU - Albers, Christian Nyrop
AU - Hunkeler, Daniel
N1 - Funding Information:
We thank Simon Jeannottat and Roberto Costa for their support in the laboratory and Dr. Jorge Spangenberg for the isotope analysis of soil and humic substances. The project was funded by the Swiss National Science Foundation (F. Breider, Project Nos. 200020-117860 and 200020-132740) and the Villum Kann Rasmussen Foundation (C.N. Albers).
PY - 2013/1
Y1 - 2013/1
N2 - Chloroform (CHCl3) is an environmental contaminant widely distributed around world, as well as a natural compound formed in various aquatic and terrestrial environments. However, the chemical mechanisms leading to the natural formation of chloroform in soils are not completely understood. To assess the role of trichloroacetyl-containing compound (TCAc) in the natural formation of chloroform in forest soils, carbon stable isotope analyses of chloroform and TCAc in field samples and chlorination experiments were carried out. The isotope analysis of field samples have revealed that the δ13C value of natural chloroform (δ 13Cmean=-25.8‰) is in the same range as the natural organic matter (δ13C mean=-27.7‰), whereas trichloromethyl groups of TCAc are much more enriched in 13C (δ13Cmean=-9.8‰). A similar relationship was also observed for TCAc and chloroform produced by chlorination of natural organic matter with NaOCl. The strong depletion of 13C in chloroform relative to TCAc can be explained by carbon isotope fractionation during TCAc hydrolysis. As shown using a mathematical model, when steady state between formation of TCAc and hydrolysis is reached, the isotope ratio of chloroform is expected to correspond to isotope composition of NOM while TCAc should be enriched in 13C by about 18.3‰, which is in good agreement with field observations. Hence this study suggests that TCAc are likely precursors of chloroform and at the same time explains why natural chloroform has a similar isotope composition as NOM despite large carbon isotope fractionation during its release.
AB - Chloroform (CHCl3) is an environmental contaminant widely distributed around world, as well as a natural compound formed in various aquatic and terrestrial environments. However, the chemical mechanisms leading to the natural formation of chloroform in soils are not completely understood. To assess the role of trichloroacetyl-containing compound (TCAc) in the natural formation of chloroform in forest soils, carbon stable isotope analyses of chloroform and TCAc in field samples and chlorination experiments were carried out. The isotope analysis of field samples have revealed that the δ13C value of natural chloroform (δ 13Cmean=-25.8‰) is in the same range as the natural organic matter (δ13C mean=-27.7‰), whereas trichloromethyl groups of TCAc are much more enriched in 13C (δ13Cmean=-9.8‰). A similar relationship was also observed for TCAc and chloroform produced by chlorination of natural organic matter with NaOCl. The strong depletion of 13C in chloroform relative to TCAc can be explained by carbon isotope fractionation during TCAc hydrolysis. As shown using a mathematical model, when steady state between formation of TCAc and hydrolysis is reached, the isotope ratio of chloroform is expected to correspond to isotope composition of NOM while TCAc should be enriched in 13C by about 18.3‰, which is in good agreement with field observations. Hence this study suggests that TCAc are likely precursors of chloroform and at the same time explains why natural chloroform has a similar isotope composition as NOM despite large carbon isotope fractionation during its release.
KW - Chlorination
KW - Chloroform
KW - Hydrolysis
KW - Isotope
KW - Natural organic matter
KW - Trichloroacetyl group
UR - http://www.scopus.com/inward/record.url?scp=84869883173&partnerID=8YFLogxK
U2 - 10.1016/j.chemosphere.2012.07.058
DO - 10.1016/j.chemosphere.2012.07.058
M3 - Article
VL - 90
SP - 441
EP - 448
JO - Chemosphere
JF - Chemosphere
SN - 0045-6535
IS - 2
ER -