Radiochemical Sampling and Analysis of Shallow Ground Water and Sediment at the BOMARC Missile Facility, East-Central New Jersey, 1999-2000

Abstract

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.

TABLE OF CONTENTS

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

dc_nj@usgs.gov

(609) 771-3900

 

or visit our Web site at: http://nj.usgs.gov