Carbon and Chlorine Isotope Fractionation Patterns Associated with
Author(s)
Rodriguez-Fernandez, Diana
Heckel, Benjamin
Meyer, Armin
Domenèch, Christina
Rosell, Monica
Soler, Albert
Elsener, Martin
Date issued
May 2017
In
Environmental Science and Technology
Vol
12
No
51
From page
6174
To page
6184
Reviewed by peer
1
Abstract
To use compound-specific isotope analysis for confidently
assessing organic contaminant attenuation in the environment,
isotope fractionation patterns associated with different transformation
mechanisms must first be explored in laboratory experiments. To
deliver this information for the common groundwater contaminant
chloroform (CF), this study investigated for the first time both carbon
and chlorine isotope fractionation for three different engineered
reactions: oxidative C−H bond cleavage using heat-activated persulfate,
transformation under alkaline conditions (pH ∼ 12) and reductive C−
Cl bond cleavage by cast zerovalent iron, Fe(0). Carbon and chlorine
isotope fractionation values were −8 ± 1‰ and −0.44 ± 0.06‰ for
oxidation, −57 ± 5‰ and −4.4 ± 0.4‰ for alkaline hydrolysis (pH
11.84 ± 0.03), and −33 ± 11‰ and −3 ± 1‰ for dechlorination,
respectively. Carbon and chlorine apparent kinetic isotope effects (AKIEs) were in general agreement with expected mechanisms
(C−H bond cleavage in oxidation by persulfate, C−Cl bond cleavage in Fe(0)-mediated reductive dechlorination and E1CB
elimination mechanism during alkaline hydrolysis) where a secondary AKIECl (1.00045 ± 0.00004) was observed for oxidation.
The different dual carbon-chlorine (Δδ13C vs Δδ37Cl) isotope patterns for oxidation by thermally activated persulfate and
alkaline hydrolysis (17 ± 2 and 13.0 ± 0.8, respectively) vs reductive
assessing organic contaminant attenuation in the environment,
isotope fractionation patterns associated with different transformation
mechanisms must first be explored in laboratory experiments. To
deliver this information for the common groundwater contaminant
chloroform (CF), this study investigated for the first time both carbon
and chlorine isotope fractionation for three different engineered
reactions: oxidative C−H bond cleavage using heat-activated persulfate,
transformation under alkaline conditions (pH ∼ 12) and reductive C−
Cl bond cleavage by cast zerovalent iron, Fe(0). Carbon and chlorine
isotope fractionation values were −8 ± 1‰ and −0.44 ± 0.06‰ for
oxidation, −57 ± 5‰ and −4.4 ± 0.4‰ for alkaline hydrolysis (pH
11.84 ± 0.03), and −33 ± 11‰ and −3 ± 1‰ for dechlorination,
respectively. Carbon and chlorine apparent kinetic isotope effects (AKIEs) were in general agreement with expected mechanisms
(C−H bond cleavage in oxidation by persulfate, C−Cl bond cleavage in Fe(0)-mediated reductive dechlorination and E1CB
elimination mechanism during alkaline hydrolysis) where a secondary AKIECl (1.00045 ± 0.00004) was observed for oxidation.
The different dual carbon-chlorine (Δδ13C vs Δδ37Cl) isotope patterns for oxidation by thermally activated persulfate and
alkaline hydrolysis (17 ± 2 and 13.0 ± 0.8, respectively) vs reductive
Publication type
journal article
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