Environmental factors affecting rates of nitrogen cycling

Thesis/Dissertation · Sun Jan 01 04:00:00 EST 1984

OSTI ID:5268109

Lipschultz, F

The nitrogen cycle in the eutrophic Delaware river was studied in late summer, 1983 using /sup 15/N tracer additions of NHG/sub 4//sup +/, NO/sub 2//sup -/, and NO/sub 3//sup -/. Rates for nine different transformations were calculated simultaneously with a least-squares minimization analysis. Light was found to stimulate ammonium uptake and to inhibit ammonium oxidation. Rates for nitrification, ammonium uptake by phytoplankton, and photosynthesis were integrated over 24 hours and river depth. High turbidity lifted the effect of light inhibition on nitrification and restricted phytoplankton uptake. Uptake of ammonium contributed over 95% of the inorganic nitrogen ration for phytoplankton, with dark uptake accounting for more than 50%. A mass-conservation, box model of river was used to calculate rate constants required to reproduce observed nutrient concentration changes. The calculated constants correlated well with the measured /sup 15/N and oxygen integrated rates. Water-column nitrification was the major loss term for NH/sub 4//sup +/, while water column regeneration was the primary source. Loss of oxidized nitrogen was insignificant. Oxygen consumption and air-water exchange far exceeded net photosynthetic oxygen production. Nitrification contributed less than 1% to the oxygen demand near Philadelphia but up to 25% further downstream. Production of NO and N/sub 2/O was measured under varying oxygen concentrations in batch cultures of the nitrifying bacteria Nitrosomonas europaea and Nitrosococcus oceanus. Production of both gases increased relative to nitrite production as oxygen levels decreased.

• Research Organization: Harvard Univ., Boston, MA (USA)
• OSTI ID: 5268109
• Country of Publication: United States
• Language: English

Related Subjects

520101* -- Environment
Aquatic-- Basic Studies-- Radiometric Techniques-- (-1989)
54 ENVIRONMENTAL SCIENCES
AIR-WATER INTERACTIONS
AMMONIUM COMPOUNDS
AQUATIC ORGANISMS
BACTERIA
CHALCOGENIDES
CHEMICAL REACTIONS
DELAWARE RIVER
ELECTROMAGNETIC RADIATION
ISOTOPES
LEAST SQUARE FIT
LIGHT NUCLEI
MAXIMUM-LIKELIHOOD FIT
MICROORGANISMS
NITRIC OXIDE
NITRIFICATION
NITROGEN 15
NITROGEN COMPOUNDS
NITROGEN CYCLE
NITROGEN DIOXIDE
NITROGEN ISOTOPES
NITROGEN OXIDES
NITROUS OXIDE
NUCLEI
NUMERICAL SOLUTION
ODD-EVEN NUCLEI
OXIDES
OXYGEN COMPOUNDS
PHOTOCHEMICAL REACTIONS
PHOTOSYNTHESIS
PHYTOPLANKTON
PLANKTON
RADIATIONS
RIVERS
STABLE ISOTOPES
STREAMS
STRUCTURAL MODELS
SURFACE WATERS
SYNTHESIS
UPTAKE
VISIBLE RADIATION