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Application of a modified denitrifying bacteria method foranalyzing groundwater and vadose zone pore water nitrate at the HanfordSite, WA, USA [electronic resource].

Published
Washington, D.C. : United States. Dept. of Energy, 2003.
Oak Ridge, Tenn. : Distributed by the Office of Scientific and Technical Information, U.S. Dept. of Energy.
Additional Creators
United States. Department of Energy and United States. Department of Energy. Office of Scientific and Technical Information
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Summary
The Hanford Site in southern Washington contains a largeproportion of the 250,000 metric tons of nitrate estimated to reside atDOE sites across the USA. Nitrate concentrations>600 mg/L have beenreported for Hanford groundwaters, where nitrate commonly accompanieselevated levels of radionuclide contamination. Much of the Hanfordnitrate is stored in the vadose zone, where complicated hydrology andpoorly understood chemical and biochemical processes lead to uncertainfate and transport. Analysis of the nitrogen and oxygen isotopiccomposition of nitrate provides a promising method to identify sourcesand investigate biochemical degradation of nitrate in the subsurface atHanford. A preliminary investigation of NO3- fate and transport at theHanford Site focuses on pore water nitrate, extracted by 1:1 sediment toDI water rinses of vadose zone sediments, in a vertical profile through aradionuclide plume at the TX-TY tank farm, and compares these resultswith transects across major nitrate plumes in the Hanford unconfinedaquifer.Until recently, methods for analyzing d15N and d18O of NO3- inwaters were unwieldy for routine analyses of dilute groundwaters and porewater extracts from vadose zone sediments; however, Sigman, et al., 2001(Anal. Chem) and Casciotti, et al., 2002 (Anal. Chem), developed a methodusing denitrifying bacteria with a truncated enzymatic pathway togenerate N2O for analyzing both isotopes simultaneously from NO3- indilute samples. Our modifications to this method decrease both culturepreparation and sample processing times. Culturing time has been reducedto 2-3 days by increasing the initial inoculation volume to 2mL in 100mL.We grow cultures on a bench top and mix by inversion twice daily, insteadof growing on a constant shaking unit. These changes have not been shownto affect the cell yield nor the N2O levels in blanks. Secondly, cellpreparation for NO3- reduction has been modified to decrease sampleprocessing time. Intense centrifugation was found to be unnecessary andloose pellet formation at a lower g is more than adequate. We found nodetectable background level of N2O in the cultures, and have reduced thesample venting time. Lastly, we have found that samples can be injected,cells lysed, and N2O run in the same day with negligible affects to N2Oyield and d15N/d18O values.
Report Numbers
E 1.99:lbnl--54061-ext.-abs.
lbnl--54061-ext.-abs.
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Note
Published through SciTech Connect.
11/18/2003.
"lbnl--54061-ext.-abs."
2003 Seattle Annual Meeting, Seattle, WA, 2-5November 2003.
Conrad, Mark; Singleton, Michael J.; Woods, KatharineN.
Ernest Orlando Lawrence Berkeley NationalLaboratory, Berkeley, CA (US)
Funding Information
DE-AC02-05CH11231
G41701
View MARC record | catkey: 14133816