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PUBLICATIONS—Scientific Investigation Report |
By Zoltan Szabo, Otto S. Zapecza, Jeannette H. Oden, and Donald E. Rice
The report is available in PDF Format (2,181 KB)
A field sampling experiment was designed using low-flow purging with a portable pump and sample-collection equipment for the collection of water and sediment samples from observation wells screened in the Kirkwood-Cohansey aquifer system to determine radionuclide or trace-element concentrations for various size fractions. Selected chemical and physical characteristics were determined for water samples from observation wells that had not been purged for years. The sampling was designed to define any particulate, colloidal, and solution-phase associations of radionuclides or trace elements in ground water by means of filtration and ultrafiltration techniques. Turbidity was monitored and allowed to stabilize before samples were collected by means of the low-flow purging technique rather than by the traditional method of purging a fixed volume of water at high-flow rates from the observation well. A minimum of four water samples was collected from each observation well. The samples of water from each well were collected in the following sequence. (1) A raw unfiltered sample was collected within the first minutes of pumping. (2) A raw unfiltered sample was collected after at least three casing volumes of water were removed and turbidity stabilized. (3) A sample was collected after the water was filtered with a 0.45-micron filter. (4) A sample was collected after the water passed through a 0.45-micron filter and a 0.003-micron tangential-flow ultrafilter in sequence. In some cases, a fifth sample was collected after the water passed through a 0.45-micron filter and a 0.05-micron filter in sequence to test for colloids of 0.003 microns to 0.05 microns in size. The samples were analyzed for the concentration of manmade radionuclides plutonium-238 and -239 plus -240, and americium-241. The samples also were analyzed for concentrations of uranium-234, -235, and -238 to determine whether uranium-234 isotope enrichment (resulting from industrial processing) is present. A subset of samples was analyzed for concentrations of thorium-232, -230, and -228 to determine if thorium-228 isotope enrichment, also likely to result from industrial processing, is present.
Concentrations of plutonium isotopes and americium-241 in the water samples were less than 0.1 picocurie per liter, the laboratory reporting level for these manmade radionuclides, with the exception of one americium-241 concentration from a filtered sample. A sequential split sample from the same well did not contain a detectable concentration of americium-241, however. Other filtered and unfiltered samples of water from the same well did not contain quantities of americium-241 nearly as high as 0.1 pCi/L. Therefore, the presence of americium-241 in a quantifiable concentration in water samples from this well could not be confirmed. Neither plutonium nor americium was detected in samples of settled sediment collected from the bottom of the wells. Concentrations of uranium isotopes (maximum of 0.05 and 0.08 picocuries per liter of uranium-238 and uranium-234, respectively) were measurable in unfiltered samples of turbid water from one well and in the settled bottom sediment from 6 wells (maximum concentrations of 0.25 and 0.20 picocuries per gram of uranium-238 and uranium-234, respectively). The uranium-234/uranium-238 isotopic ratio was near 1:1, which indicates natural uranium. The analytical results, therefore, indicate that no manmade radionuclide contamination is present in any of the well-bottom sediments, or unfiltered or filtered water samples from any of the sampled wells. No evidence of manmade radionuclide contamination was observed in the aquifer as settled or suspended particulates, colloids, or in the dissolved phase.
Abstract
Introduction
Review of Previous Radiochemical Data
Purpose and Scope
Site Hydrogeology
Detection of Colloids, Radionuclides, and Trace Elements in Ground Water
Size Classification of Aquatic Particles
Mobility of Colloids, Radionuclides, and Trace Elements in Ground Water
Tangential-Flow Ultrafiltration as a Technique for Removal and Characterization of
Colloids in Ground Water
Methods of Radiochemical Sampling
Design of Field-Sampling Experiment
Sampling Network
Preparation for the Field-Sampling Experiment
Well Development and Settled-Sediment Sampling
Geophysical Logging and Placement of the Sampling Pump
Well Sampling Procedures
Low-Flow Purge and Monitoring of Turbidity, Other Physical Characteristics, and Water Level
Sample Type
Sample Collection with Filtration and Tangential-Flow Ultrafiltration
Safety Considerations
Techniques of Quality Assurance
Laboratory Analysis for Radionuclides
Detection Methods
Reporting of Analytical Results for Radionuclides
Analysis of Shallow Ground Water and Settled Sediment
Quality-Assurance Evaluation of Laboratory Results for Equipment Blanks
Turbidity
Concentrations of Plutonium, Americium, Uranium, and Thorium in Water
Concentrations of Plutonium, Americium, and Uranium in Settled Sediment
Summary and Conclusions
Acknowledgments
References Cited
Glossary
Appendix 1. Natural Gamma Ray Logs, Screened Interval, and Pump Setting for Wells at the BOMARC Missile Facility, Ocean County, N.J.
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For further information, contact:
Richard Kropp, Director
U.S. Geological Survey
New Jersey Water Science Center
810 Bear Tavern Road Suite 206
West Trenton, NJ 08628
(609) 771-3900
or visit our Web site at: http://nj.usgs.gov
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