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Titel |
Variability in carbon and nitrogen isotope fractionation associated with bacterial hydrolysis of atrazine |
VerfasserIn |
A. Meyer, H. Penning, M. Elsner |
Konferenz |
EGU General Assembly 2009
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Medientyp |
Artikel
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Sprache |
Englisch
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Digitales Dokument |
PDF |
Erschienen |
In: GRA - Volume 11 (2009) |
Datensatznummer |
250029038
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Zusammenfassung |
Even after legislative prohibition in 1991 by the European Union, the pesticide atrazine and
its metabolites are still detected in surface and ground water frequently exceeding the
permitted drinking water concentration limit of 0,1 μg/L. Despite much recent
research on atrazine, its risk assessment in the environment is still a major challenge
because of the difficulty of establishing mass balances in the subsurface. To obtain
a better insight into the fate of atrazine, we developed compound-specific stable
isotope analysis (CSIA) for atrazine. CSIA has proven valuable for assessing organic
contaminants in subsurface environments, on the one hand for source identification and
on the other hand to trace (bio)chemical degradation reactions through isotope
fractionation in the compounds. Such assessment is based on the Rayleigh equation and
therein on the isotope enrichment factor É, which must be determined experimentally
beforehand.
In ongoing work, we therefore measured carbon and nitrogen isotope fractionation
associated with biotic hydrolsis of atrazine. C and N isotope enrichment factors were
determined in resting cell experiments for Pseudomonas sp. ADP, Chelatobacter heintzii and
Arthrobacter aurescens TC1, strains that hydrolyse atrazine in the initial transformation
reaction. Carbon and nitrogen isotope enrichment factors were distinctly different between
the bacterial strains. However, when plotting shifts in carbon isotope ratios versus
shifts in nitrogen isotope ratios the slopes of the different degradation experiments
coincided well. These results give evidence that all bacterial strains were carrying out
the same initial biochemical degradation reaction, but that the associated isotope
fractionation, as represented by the enrichment factors, was masked to a different extent
owing to different rate determining steps prior to the isotopically sensitive bond
cleavage (commitment to catalysis). Our study therefore illustrates the benefit of
multi-element isotope approaches to assess the environmental fate of atrazine by CSIA. |
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