The Determination of Radon Activities in Ground Water from Wisconsin Tills in Southwestern Ohio and Southeastern Indiana

Author Institution: ATEC Associates ; Geology Department, Miami UniversityTwo hypotheses have been suggested by previous workers to explain the relatively elevated radon activities of ground water in certain areas of southwestern Ohio and southeastern Indiana. First, radon may be produced close to or at the Ordovician-Silurian unconformity by the concentration of uranium and radium on iron and manganese oxides and hydroxides and on clay minerals at this zone of weathering. Second, radon may be formed from the radioactive decay of radium which is concentrated on iron-oxides in zones of higher hydraulic conductivity in the lower carbonate section of the Silurian System. In both cases, it has been proposed that the elevated radon activities result from either the application of radium-bearing phosphate fertilizers or from the inclusion of radium-bearing fragments of Devonian black shale in the till

Survey of 87Sr/86Sr Ratios and Total Strontium Concentrations in Ohio Stream and Ground Waters

Author Institution: Department of Geology, Miami University, Oxford, Ohio 45056 ; Department of Geology, Wright State University, Dayton, Ohio 45431 ; and Department of Geology, Miami University, Oxford, Ohio 45056A total of 23 Ohio stream and ground waters has been sampled and analyzed for total Sr and 87Sr/86Sr isotopic ratios in an attempt to evaluate the potential usefulness of the 87Sr/86Sr ratio as a tracer of water provenance. Sampling stations were selected in order to provide a wide geographic distribution and a variety of contacted lithologies. The measured 87Sr/86Sr ratios range from 0.7078 to 0.7130, with the higher ratios occurring in eastern and southern Ohio and the lower ratios to the north and west. This trend is apparently due in part to the change in the dominant lithology of the Paleozoic sediments across Ohio. In the east, clastic sediments predominate, whereas in the west, limesstone becames the major important component of the sedimentary sequence. Most limestones of Paleozoic age are known to have 87Sr/86Sr ratios of approximately 0.708, whereas shales have a range of higher values. The observed trend in 87Sr/86Sr ratios of the water samples also appears to be related to the position of the glacial boundary. The widspread occurrence of easily soluble carbonate material in the glacial till north of the boundary has apparently had a strong effect on the strontium isotopic compositions of the local waters

The Correlation Between Bedrock Uranium and Dissolved Radon in Ground Water of a Fractured Carbonate Aquifer in Southwestern Ohio

Two hypotheses have previously been proposed for the source of elevated radon in ground water of southwestern Ohio: (1) penecontemporaneous uranium at the Silurian-Ordovician unconformity, and/or (2) parent radionuclides transported from fragments of uranium-rich Ohio Shale within the glacial drift above the aquifer. To further test the first hypothesis, vertical profiles of dissolved radon in ground water and uranium in rock cores were obtained at two locations immediately underlain by the Silurian/Ordovician unconformity. Radon concentrations exceeding 1000 pCi/l occurred in zones where the bedrock had uranium concentrations greater than 1.5 ppm. Radon concentrations of less than 500 pCi/l occurred in zones where the rock had uranium concentrations below 0.25 ppm. A log-linear regression model between uranium and radon had a correlation coefficient of 0.82. Three aspects of the results support the hypothesis that the source is transported, although not necessarily from fragments of Ohio Shale. First, the high uranium-radon zones did not occur consistently or exclusively at the Silurian/Ordovician unconformity. Second, the high uranium-radon zones are correlated to fracture zones having a higher hydraulic conductivity and thus appear to be related to the zones of greater flow and transport. Third, the amount of uranium-radon disequilibrium increases exponentially with increasing hydraulic conductivity. The hypothesis of a penecontemporaneous source, not supported by our study, arose when previous investigators conducted regional surveys of domestic wells and springs and found a correspondence between elevated radon and the location of the Silurian-Ordovician unconformity. The observations of the previous investigators can be explained by the fact that the basal Silurian is in some places a horizon of higher hydraulic conductivity that facilitates transport. The two most probable external sources of uranium would be uranium-containing detritus in the glacial drift or uranium-containing phosphate fertilizers spread on the surface. Given that the uranium was transported into the aquifer during the Holocene, it could not have generated enough radium in the time elapsed since entering the aquifer to produce the radon levels that were measured. This observation indicates that radium was cotransported with uranium into the zones of high radon

The Correlation Between Bedrock Uranium and Dissolved Radon in Ground Water of a Fractured Carbonate Aquifer in Southwestern Ohio

Two hypotheses have previously been proposed for the source of elevated radon in ground water of southwestern Ohio: (1) penecontemporaneous uranium at the Silurian-Ordovician unconformity, and/or (2) parent radionuclides transported from fragments of uranium-rich Ohio Shale within the glacial drift above the aquifer. To further test the first hypothesis, vertical profiles of dissolved radon in ground water and uranium in rock cores were obtained at two locations immediately underlain by the Silurian/Ordovician unconformity. Radon concentrations exceeding 1000 pCi/l occurred in zones where the bedrock had uranium concentrations greater than 1.5 ppm. Radon concentrations of less than 500 pCi/l occurred in zones where the rock had uranium concentrations below 0.25 ppm. A log-linear regression model between uranium and radon had a correlation coefficient of 0.82. Three aspects of the results support the hypothesis that the source is transported, although not necessarily from fragments of Ohio Shale. First, the high uranium-radon zones did not occur consistently or exclusively at the Silurian/Ordovician unconformity. Second, the high uranium-radon zones are correlated to fracture zones having a higher hydraulic conductivity and thus appear to be related to the zones of greater flow and transport. Third, the amount of uranium-radon disequilibrium increases exponentially with increasing hydraulic conductivity. The hypothesis of a penecontemporaneous source, not supported by our study, arose when previous investigators conducted regional surveys of domestic wells and springs and found a correspondence between elevated radon and the location of the Silurian-Ordovician unconformity. The observations of the previous investigators can be explained by the fact that the basal Silurian is in some places a horizon of higher hydraulic conductivity that facilitates transport. The two most probable external sources of uranium would be uranium-containing detritus in the glacial drift or uranium-containing phosphate fertilizers spread on the surface. Given that the uranium was transported into the aquifer during the Holocene, it could not have generated enough radium in the time elapsed since entering the aquifer to produce the radon levels that were measured. This observation indicates that radium was cotransported with uranium into the zones of high radon