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Title: Application of a modified denitrifying bacteria method foranalyzing groundwater and vadose zone pore water nitrate at the HanfordSite, WA, USA.

Abstract

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.more » 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.« less

Authors:
; ;
Publication Date:
Research Org.:
Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
Sponsoring Org.:
USDOE Director. Office of Science. Office of AdvancedScientific Computing Research. Office of Biological and EnvironmentalResearch
OSTI Identifier:
900934
Report Number(s):
LBNL-54061-Ext.-Abs.
R&D Project: G41701; TRN: US200711%%655
DOE Contract Number:  
DE-AC02-05CH11231
Resource Type:
Conference
Resource Relation:
Conference: 2003 Seattle Annual Meeting, Seattle, WA, 2-5November 2003
Country of Publication:
United States
Language:
English
Subject:
54; BACTERIA; CENTRIFUGATION; CONTAMINATION; HYDROLOGY; INOCULATION; METRICS; MODIFICATIONS; NITRATES; NITROGEN; OXYGEN; PELLETS; PLUMES; RADIOISOTOPES; SEDIMENTS; STORAGE FACILITIES; TRANSPORT; WATER

Citation Formats

Woods, KatharineN, Singleton, Michael J, and Conrad, Mark. Application of a modified denitrifying bacteria method foranalyzing groundwater and vadose zone pore water nitrate at the HanfordSite, WA, USA.. United States: N. p., 2003. Web.
Woods, KatharineN, Singleton, Michael J, & Conrad, Mark. Application of a modified denitrifying bacteria method foranalyzing groundwater and vadose zone pore water nitrate at the HanfordSite, WA, USA.. United States.
Woods, KatharineN, Singleton, Michael J, and Conrad, Mark. 2003. "Application of a modified denitrifying bacteria method foranalyzing groundwater and vadose zone pore water nitrate at the HanfordSite, WA, USA.". United States. https://www.osti.gov/servlets/purl/900934.
@article{osti_900934,
title = {Application of a modified denitrifying bacteria method foranalyzing groundwater and vadose zone pore water nitrate at the HanfordSite, WA, USA.},
author = {Woods, KatharineN and Singleton, Michael J and Conrad, Mark},
abstractNote = {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.},
doi = {},
url = {https://www.osti.gov/biblio/900934}, journal = {},
number = ,
volume = ,
place = {United States},
year = {Tue Nov 18 00:00:00 EST 2003},
month = {Tue Nov 18 00:00:00 EST 2003}
}

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