New Jersey Water Science Center
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This investigation is the first regionally focused study of the presence of natural radioactivity in water from the Vincentown and Wenonah-Mount Laurel aquifers, Englishtown aquifer system, and the Hornerstown and Red Bank Sands. Geologic materials composing the Vincentown and Wenonah-Mount Laurel aquifers and the Hornerstown and Red Bank Sands previously have been reported to contain radioactive (uranium-enriched) phosphatic strata, which is common in deposits from some moderate-depth coastal marine environments. The decay of uranium and thorium gives rise to natural radioactivity and numerous radioactive progeny, including isotopes of radium. Naturally occurring radioactive isotopes, especially those of radium, are of concern because radium is a known human carcinogen and ingestion (especially in water used for drinking) can present appreciable health risks.
A regional network in southwestern and south-central New Jersey of 39 wells completed in the Vincentown and Wenonah-Mount Laurel aquifers, the Englishtown aquifer system, and the Hornerstown and Red Bank Sands was sampled for determination of gross alpha-particle activity; concentrations of radium radionuclides, major ions, and selected trace elements; and physical properties. Concentrations of radium-224, radium-226, and radium-228 were determined for water from 28 of the 39 wells, whereas gross alpha-particle activity was determined for all 39. The alpha spectroscopic technique was used to determine concentrations of radium-224, which ranged from less than 0.5 to 2.7 pCi/L with a median concentration of less than 0.5pCi/L, and of radium-226, which ranged from less than 0.5 to 3.2 pCi/L with a median concentration of less than 0.5 pCi/L. The beta-counting technique was used to determine concentrations of radium-228. The concentration of radium-228 ranged from less than 0.5 to 4.3 pCi/L with a median of less than 0.5. Radium-228, when quantifiable, had the greatest concentration of the three radium radioisotopes in 9 of the 12 samples (75 percent). The concentration of radium-224 exceeded that of radium-226 in five of the six (83 percent) samples when both were quantifiable. The radium concentration distribution differed by aquifer, with the highest Ra-228 concentrations present in the Englishtown aquifer system and the highest Ra-226 concentrations present in the Wenonah-Mount Laurel aquifer. Radium-224 generally contributed a considerable amount of gross alpha-particle activity to water produced from all the sampled aquifers, but was not the dominant radionuclide as it is in water from the Kirkwood-Cohansey aquifer system, nor were concentrations greater than 1 pCi/L of radium-224 widespread.
Gross alpha-particle activity was found to exceed the U.S Environmental Protection Agency (USEPA) Maximum Contaminant Level (MCL) of 15 pCi/L in one sample (16 pCi/L) from the Vincentown aquifer. A greater part of the gross alpha-particle activity in water from the Wenonah-Mount Laurel aquifer resulted from the decay of Ra-226 than did the gross alpha-particle activity in the other sampled aquifers; this relation is consistent with the concentration distribution of the Ra-226 itself.
Concentrations of radium-224 correlate strongly with those of both radium-226 and radium-228 (Spearman correlation coefficients, r, +0.86 and +0.66, respectively). The greatest concentrations of radium-224, radium-226, and radium-228 were present in the most acidic ground water. All radium-224, radium-226, and radium-228 concentrations greater than 2.5 pCi/L were present in ground-water samples with a pH less than 5.0. The presence of combined radium-226 and radium-228 concentrations greater than 5 pCi/L in samples from the Vincentown and Wenonah-Mount Laurel aquifers and the Englishtown aquifer system was not nearly as common as in samples from the Kirkwood-Cohansey aquifer system, likely because of the slightly higher pH of water from these aquifers relative to that of Kirkwood-Cohansey aquifer system. Only about 25 percent of the sampled wells in the unconfined parts of the aquifers studied contained water with pH less than 5.0, whereas about 75 percent of the wells sampled in the Kirkwood-Cohansey aquifer system contained water with pH less than 5.0.
Abstract
Introduction
Purpose and Scope
Naturally Occurring Radionuclide Decay Series
Description of Study Area
Geologic Setting
Hydrogeologic Setting
Vincentown Aquifer
Hornerstown and Red Bank Sands
Wenonah-Mount Laurel Aquifer
Englishtown Aquifer System
Land Use
Previous Investigations of Radionuclide Occurrences in Water and Sediment in Southern and Central New Jersey
Ground Water
Sediment
Methods
Design of Sampling Network
Sampling Procedures
Quality-Assurance Program
Analytical Methods
Radium-224 and Radium-226
Radium-228
Gross Alpha-Particle and Beta-Particle Activities and Radon-222
Reporting of Results of Analysis of Radionuclides
Ancillary Inorganic and Organic Constituents
Land-Use Classification
Statistical Analysis of Radionuclide Occurrence
Occurrence of Radium-224, Radium-226, Radium-228, and Gross Alpha-Particle Activity in the Ground Water
Quality Assurance
Gross Alpha-Particle Activity
Radium-224
Radium-226 and Radium-228
Significance of Radium-224 Concentrations for Gross Alpha-Particle Activity
Ratio of Radium-224 to Gross Alpha-Particle Activity
Correlations Among Concentrations of Radium-224, Radium-226, and Radium-228, and Gross Alpha-Particle Activity
Factors That Affect Radium-224 Concentrations in the Ground Water
Geochemical Factors and Land Use
Relations Between Radium and pH
Relations Between Radium and Nitrate
Chemical Classification of Ground Waters and Possible Effects on Radium Occurrence
Unconfined Parts of the Aquifers
Confined Parts of the Aquifers
Radium Isotopes in, and Land Use Overlying, the Unconfined Parts of the Lesser Aquifers
Hydrogeological Factors
Occurrence of Radium Isotopes Among the Aquifers
Relations of Radium and pH to the Geologic Composition of Aquifer Materials
Geographic Distribution of Radium Isotopes within the Lesser Aquifers
Regional Significance of Ra-224 Concentrations and Gross Alpha-Particle Activity
Comparison of the Occurrence of Ra-224, Ra-226, Ra-228 and Gross Alpha-Particle Activity in the Lesser Aquifers with that in the Kirkwood-Cohansey Aquifer System
Comparison of the Occurrence of Ra-224, Ra-226, Ra-228 and Gross Alpha-Particle Activity in the Lesser Aquifers with that in Other Aquifers in the Mid-Atlantic Coastal Plain
Summary and Conclusions
Acknowledgments
References Cited
Glossary
Appendix 1. Construction information for wells sampled for radioactive constituents in water or natural gamma-ray activity in sediment from the Vincentown and Wenonah-Mount Laurel aquifers, Englishtown aquifer system, and the Hornerstown and Red Bank Sands, southwestern and south-central New Jersey, 1999-2001
Appendix 2. Concentrations of radionuclides, major ions, and selected trace elements in equipment blank samples for radionuclide sampling, New Jersey, 1999-2001
Appendix 3. Concentrations of radionuclides, major ions, selected trace elements in, and physical properties of, water from the Vincentown and Wenonah-Mount Laurel aquifers, Englishtown aquifer system, and the Hornerstown and Red Bank Sands, southwestern and south-central New Jersey, 1999-2001
Download: PDF of SIR2007-5064 (Version 1.1 - October 2007) [2.4 Mb]
(Errata sheet for Version 1.0 - September 2007)
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