Nitrate reduction in a groundwater microcosm determined by sup 15 N gas chromatography-mass spectrometry

Journal Article · Wed Nov 01 00:00:00 EST 1989 · Applied and Environmental Microbiology; (USA)

OSTI ID:5714649

Bengtsson, G; Annadotter, H ^[1]

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1. Univ. of Lund (Sweden)

Aerobic and anaerobic groundwater continuous-flow microcosms were designed to study nitrate reduction by the indigenous bacteria in intact saturated soil cores from a sandy aquifer with a concentration of 3.8 mg of NO{sub 3}{sup {minus}}-N liter{sup {minus}1}. Traces of {sup 15}NO{sub 3}{sup {minus}} were added to filter-sterilized groundwater by using a Darcy flux of 4 cm day{sup {minus}1}. Both assimilatory and dissimilatory reduction rates were estimated from analyses of {sup 15}N{sub 2}, {sup 15}N{sub 2}O, {sup 15}NH{sub 4}{sup +}, and {sup 15}N-labeled protein amino acids by capillary gas chromatography-mass spectrometry. N{sub 2} and N{sub 2}O were separated on a megabore fused-silica column and quantified by electron impact-selected ion monitoring. NO{sub 3}{sup {minus}} and NH{sub 4}{sup +} were analyzed as pentafluorobenzoyl amides by multiple-ion monitoring and protein amino acids as their N-heptafluorobutyryl isobutyl ester derivatives by negative ion-chemical ionization. The numbers of bacteria and their (methyl-{sup 3}H)thymidine incorporation rates were simultaneously measured. Nitrate was completely reduced in the microcosms at a rate of about 250 ng g{sup {minus}1} day{sup {minus}1}. Of this nitrate, 80 to 90% was converted by aerobic denitrification to N{sub 2}, whereas only 35% was denitrified in the anaerobic microcosm, where more than 50% of NO{sub 3}{sup {minus}} was reduced to NH{sub 4}{sup +}. Assimilatory reduction was recorded only in the aerobic microcosm, where N appeared in alanine in the cells. The nitrate reduction rates estimated for the aquifer material were low in comparison with rates in eutrophic lakes and coastal sediments but sufficiently high to remove nitrate from an uncontaminated aquifer of the kind examined in less than 1 month.

• OSTI ID: 5714649
• Journal Information: Applied and Environmental Microbiology; (USA), Vol. 55:11; ISSN 0099-2240
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
BACTERIA
METABOLISM
NITRATES
BIODEGRADATION
DENITRIFICATION
GAS CHROMATOGRAPHY
GROUND WATER
MASS SPECTROSCOPY
MICROCOSMS
NITROGEN 15
THYMIDINE
TRACER TECHNIQUES
TRITIUM COMPOUNDS
WATER POLLUTION
AZINES
CHEMICAL REACTIONS
CHROMATOGRAPHY
DECOMPOSITION
HETEROCYCLIC COMPOUNDS
HYDROGEN COMPOUNDS
ISOTOPE APPLICATIONS
ISOTOPES
LIGHT NUCLEI
MICROORGANISMS
NITROGEN COMPOUNDS
NITROGEN ISOTOPES
NUCLEI
NUCLEOSIDES
NUCLEOTIDES
ODD-EVEN NUCLEI
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
OXYGEN COMPOUNDS
POLLUTION
PYRIMIDINES
RIBOSIDES
SEPARATION PROCESSES
SPECTROSCOPY
STABLE ISOTOPES
WATER
540311* - Environment
Aquatic- Basic Studies- Radiometric Techniques- (1990-)