Oxygen and Chlorine Isotopic Fractionation during Perchlorate Biodegradation: Laboratory Results and Implications for Forensics and Natural Attenuation Studies
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- 作者：Neil C. Sturchio ; John Karl Bö ; hlke ; Abelardo D. Beloso ; Jr. ; Sheryl H. Streger ; Linnea J. Heraty ; Paul B. Hatzinger
- 刊名：Environmental Science & Technology
- 出版年：2007
- 出版时间：April 15, 2007
- 年：2007
- 卷：41
- 期：8
- 页码：2796 - 2802
- 全文大小：204K
- 年卷期：v.41,no.8(April 15, 2007)
- ISSN：1520-5851
文摘
Perchlorate is a widespread environmental contaminanthaving both anthropogenic and natural sources. Stable isotoperatios of O and Cl in a given sample of perchlorate maybe used to distinguish its source(s). Isotopic ratios may alsobe useful for identifying the extent of biodegradation ofperchlorate, which is critical for assessing natural attenuationof this contaminant in groundwater. For this approach tobe useful, however, the kinetic isotopic fractionations of Oand Cl during perchlorate biodegradation must first bedetermined as a function of environmental variables suchas temperature and bacterial species. A laboratorystudy was performed in which the O and Cl isotope ratiosof perchlorate were monitored as a function of degradationby two separate bacterial strains (Azospira suillum JPLRNDand Dechlorospirillum sp. FBR2) at both 10 
f">C and 22 f">Cwith acetate as the electron donor. Perchlorate wascompletely reduced by both strains within 280 h at 22 f">Cand 615 h at 10 f">C. Measured values of isotopic fractionationfactors were 
fchars/epsilon.gif" BORDER=0 >18O = -36.6 to -29.0” and fchars/epsilon.gif" BORDER=0 >37Cl = -14.5to -11.5”, and these showed no apparent systematicvariation with either temperature or bacterial strain. Anexperiment using 18O-enriched water (fchars/delta.gif" BORDER=0 >18O = +198”) gaveresults indistinguishable from those observed in theisotopically normal water (fchars/delta.gif" BORDER=0 >18O = -8.1”) used in theother experiments, indicating negligible isotope exchangebetween perchlorate and water during biodegradation.The fractionation factor ratio fchars/epsilon.gif" BORDER=0 >18O/fchars/epsilon.gif" BORDER=0 >37Cl was nearly invariantin all experiments at 2.50 ± 0.04. These data indicatethat isotope ratio analysis will be useful for documentingperchlorate biodegradation in soils and groundwater. Theestablishment of a microbial fractionation factor ratio (fchars/epsilon.gif" BORDER=0 >18O/fchars/epsilon.gif" BORDER=0 >37Cl) also has significant implications for forensicstudies.
f">C and 22 f">Cwith acetate as the electron donor. Perchlorate wascompletely reduced by both strains within 280 h at 22 f">Cand 615 h at 10 f">C. Measured values of isotopic fractionationfactors were fchars/epsilon.gif" BORDER=0 >18O = -36.6 to -29.0” and fchars/epsilon.gif" BORDER=0 >37Cl = -14.5to -11.5”, and these showed no apparent systematicvariation with either temperature or bacterial strain. Anexperiment using 18O-enriched water (fchars/delta.gif" BORDER=0 >18O = +198”) gaveresults indistinguishable from those observed in theisotopically normal water (fchars/delta.gif" BORDER=0 >18O = -8.1”) used in theother experiments, indicating negligible isotope exchangebetween perchlorate and water during biodegradation.The fractionation factor ratio fchars/epsilon.gif" BORDER=0 >18O/fchars/epsilon.gif" BORDER=0 >37Cl was nearly invariantin all experiments at 2.50 ± 0.04. These data indicatethat isotope ratio analysis will be useful for documentingperchlorate biodegradation in soils and groundwater. Theestablishment of a microbial fractionation factor ratio (fchars/epsilon.gif" BORDER=0 >18O/fchars/epsilon.gif" BORDER=0 >37Cl) also has significant implications for forensicstudies.