By Mark F. Becker, Kathy D. Peter, and Jason Masoner
Water-Resources Investigations Report 02–4257
Prepared in cooperation with the
Oklahoma Department of Agriculture, Food, and Forestry
The report is available in PDF format.
Samples collected and analyzed by the Oklahoma Department of Agriculture, Food, and Forestry from 1999 to 2001 determined that nitrate exceeded the U.S. Environmental Protection Agency maximum contaminant level for public drinking-water supplies of 10 milligrams per liter as nitrogen in 79 monitoring wells at 35 swine licensed-managed feeding operations (LMFO) in Oklahoma.
The LMFOs are located in rural agricultural settings where long-term agriculture has potentially affected the ground-water quality in some areas. Land use prior to the construction of the LMFOs was assessed to evaluate the types of agricultural land use within a 500-meter radius of the sampled wells.
Chemical and microbiological techniques were used to determine the possible sources of nitrate in water sampled from 10 wastewater lagoons and 79 wells. Samples were analyzed for dissolved major ions, dissolved trace elements, dissolved nutrients, nitrogen isotope ratios of nitrate and ammonia, wastewater organic compounds, and fecal coliform bacteria. Bacteria ribotyping analysis was done on selected samples to identify possible specific animal sources.
A decision process was developed to identify the possible sources of nitrate. First, nitrogen isotope ratios were used to define sources as animal, mixed animal and fertilizer, or fertilizer. Second, wastewater organic compound detections, nitrogen-isotope ratios, fecal coliform bacteria detections, and ribotyping were used to refine the identification of possible sources as LFMO waste, fertilizer, or unidentified animal or mixtures of these sources. Additional evidence provided by ribotyping and wastewater organic compound data can, in some cases, specifically indicate the animal source. Detections of three or more wastewater organic compounds that are indicators of animal sources and detections of fecal coliform bacteria pro-vided additional evidence of an animal source.
LMFO waste was designated as a possible source of nitrate in water from 10 wells. The source of waste in water from five of those wells was determined through ribotyping, and the source of waste in water from the remaining five wells was determined by detections of three or more animal-waste compounds in the well samples. LMFO waste in the water from wells with unidentified animal source of nitrate does not indicate that LMFO waste was not the source, but indicated that multiple animal sources, including LMFO waste, may be the source of the nitrate.
Abstract
Introduction
Purpose and Scope
Acknowledgments
Hydrogeology
Methods of Study
Site Selection and Sampling Methods
Analytical Methods
Quality Assurance and Quality Control
Identification of Possible Sources of Nitrate
Land Use
Water Quality and Chemical and Microbiological Techniques
Water Properties
Major Ions and Trace Elements
Nutrients
Nitrogen Isotopes
Wastewater Organic Compounds
Bacteria and Ribotyping
Possible Sources of Nitrate in Ground Water
Summary
Selected References
Appendix
For additional information write to:
District Chief
U.S. Geological survey
202 NW 66 St., Bldg. 7
Oklahoma City, OK 73116
Copies of this report can be purchased from:
U.S. Geological Survey
Branch of Information Services
Box 25286
Denver, CO 80225-0286
Download the PDF version of the report for high-resolution, printable pages (6MB).
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