Contribution of Naturally Occurring Radioisotopes to Gross Alpha-Particle Activity in Ground Water in Bedrock Aquifers of Northern New Jersey: Research Project Summary



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Trenton, N.J. : New Jersey Department of Environmental Protection, Division of Science, Research and Environmental Health


A study was conducted to determine the relative contributions of uranium and radium isotopes to overall gross alpha-particle activity in ground water from the Highlands and Piedmont Provinces of New Jersey. The general relationship between the occurrence of these two radionuclides and other water quality parameters in aquifers of these regions was also evaluated. A total of 80 ground water samples were collected from public and private drinking water wells in the Highlands and Piedmont Provinces between 2007 and 2011. Bedrock composition, including mineralogy, lithology, and mineral surface coatings, as well as geochemical conditions including pH and oxidation-reduction potential in the aquifer, directly affect the occurrence and distribution of naturally occurring radionuclides in ground water. Gross alpha-particle activity exceeding the U.S. Environmental Protection Agency and New Jersey Maximum Contaminant Level (MCL) of 15 pCi/L (picocuries per liter) was documented in ground water from widely scattered areas in the bedrock aquifers of northern New Jersey. Most of the measured alpha-particle activity in the waters was attributable to the long-lived isotopes of uranium (U) and, to a lesser extent, radium-226 (Ra-226). Uranium isotope ratios were extremely variable in some areas of the Piedmont, and uranium may account for more of the gross alpha-particle activity in these areas than is evident from a simple uranium mass measurement. Some limited guidance as to the occurrence of uranium and radium for homeowners with private wells is possible on the basis of gross alpha-particle activity, dissolved oxygen, and, to lesser extent, other parameters (pH, bicarbonate alkalinity, filtered iron and/or manganese, and rock type), but none of these “surrogates” are completely definitive. Further investigations to improve understanding of parameters that are predictive of the occurrence of radium and uranium in ground water may be useful to further refine this guidance.


Prepared by Nicholas A. Procopio, Ph.D.


New Jersey