Saturated Zone Denitrification at California Dairies
Denitrification can effectively mitigate the problem of high nitrate concentrations in groundwater under dairy operations by reducing nitrate to N{sub 2} gas, at sites where biogeochemical conditions are favorable. We present results from field studies at central California dairies that document the occurrence of saturated-zone denitrification in shallow groundwater using biomolecular indicators, stable isotope compositions of nitrate, and measurements of dissolved excess N{sub 2} gas. Excess N{sub 2} concentrations provide a measure of the extent to which nitrate in groundwater has been partially or completely denitrified. Abundant excess N{sub 2} and young {sup 3}H/{sup 3}He apparent groundwater ages indicate high denitrification rates near manure lagoons where multiple lines of evidence indicate seepage of lagoon water into the groundwater system. Natural tracers of lagoon water include high chloride and dissolved organic carbon concentrations, distinctive trace organic compounds, and high groundwater {delta}{sup 18}O values (relative to other recharge sources). Proximal to the lagoons, NH{sub 4}{sup +} may be present in groundwater, but is strongly adsorbed on to sediment particles. Bubble formation in the lagoons causes the exsolution of other gases (N{sub 2}, Ar, Ne, He, etc.), which partition into the gas phase and strip the lagoon water of its dissolved gas load, providing a unique tracer of lagoon seepage in groundwater.
- Research Organization:
- Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- W-7405-ENG-48
- OSTI ID:
- 892782
- Report Number(s):
- UCRL-PROC-219421; TRN: US0605865
- Resource Relation:
- Conference: Presented at: International Conference on The Future of Agriculture: Science, Stewardship, and Sustainability, Sacramento, CA, United States, Aug 07 - Aug 09, 2006
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
09 BIOMASS FUELS
58 GEOSCIENCES
37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
54 ENVIRONMENTAL SCIENCES
60 APPLIED LIFE SCIENCES
AGRICULTURE
BUBBLES
CALIFORNIA
CARBON
CHLORIDES
DENITRIFICATION
GASES
MANURES
NITRATES
ORGANIC COMPOUNDS
SEDIMENTS
STABLE ISOTOPES
WATER
DAIRY INDUSTRY