Skip Links

USGS - science for a changing world

Scientific Investigations Report 2008–5205

In Cooperation With the Miami Conservancy District

Relation Between Solid-Phase and Dissolved Arsenic in the Ground-Water System Underlying Northern Preble County, Ohio

By Mary Ann Thomas, Sharon F. Diehl, Bruce A. Pletsch, Thomas L. Schumann, Richard R. Pavey, and E. Mac Swinford


Thumbnail of and link to report PDF (4.2 MB)

The U.S. Geological Survey (USGS), in cooperation with the Miami Conservancy District, collected and analyzed samples of the aquifer materials and ground water from multiple depths at two sites in northern Preble County, Ohio. The aquifer materials included glacial deposits and Silurian carbonate bedrock. In the study area, elevated arsenic concentrations have been detected in ground water from both types of aquifers.

The aquifer materials were described in terms of the stratigraphy and the bulk elemental composition of 70 samples. In addition, six water-producing horizons were selected for more detailed study; ground-water quality was analyzed, microanalytical techniques were used to examine thin sections of the aquifer materials, and simplified geochemical modeling was done to identify plausible reactions between the ground water and aquifer materials.

At both study sites, the highest solid-phase arsenic concentrations were from a roughly similar stratigraphic position—a transition zone that extends from just above the Wisconsinan/Illinoian contact to just below the Pleistocene/Silurian contact.

For carbonate bedrock, the solid-phase arsenic concentrations were generally low (<1 to 4 mg/kg (milligrams per kilogram)). The one notable exception was a thin horizon about 10 feet below the top of bedrock, which had an arsenic concentration of 42 mg/kg. This horizon showed some textural and compositional evidence of alteration by geothermal fluids.Additional study might be warranted to investigate whether arsenic concentrations in ground water from carbonate bedrock could be decreased by excluding discrete horizons from the open intervals of wells.

For glacial deposits, solid-phase arsenic concentrations were slightly higher in fine-grained deposits (2 to 20 mg/kg) than in coarse-grained deposits (2 to 9 mg/kg). In ground water, arsenic concentrations ranged from <1 to 51 μg/L (micrograms per liter); samples from two horizons had concentrations greater than the U.S. Environmental Protection Agency Maximum Contaminant Level (MCL) of 10 μg/L. Dissolved arsenic concentrations appear to be more closely related to redox conditions of the ground water than to the arsenic content of the aquifer materials. Geochemical modeling and thin-section analysis were generally consistent with the idea that arsenic was released to water from iron oxides under iron-reducing conditions. In addition, there was some evidence in support of the idea that arsenic can be removed from ground water by precipitation of sulfide minerals, which occurs under sulfate-reducing conditions. At one site, the dissolved arsenic concentrations in two water-bearing horizons increased from <1 to 51 μg/L over a depth of 15 feet. The large increase might be due to a shift from sulfate-reducing to methanogenic conditions; in the absence of sulfate reduction, arsenic is not sequestered in sulfide minerals and may accumulate in the ground water.

First posted February 25, 2009

  • Appendixes 1 and 2 PDF (281 kB)
    This is a screen-reader-acessible version of Appendixes 1 and 2 (descriptions of core logs), which appear as images in the main report.

For additional information contact:
Director, Ohio Water Science Center
U.S. Geological Survey
6480 Doubletree Avenue
Columbus, OH 43229-1111

Part or all of this report is presented in Portable Document Format (PDF); the latest version of Adobe Reader or similar software is required to view it. Download the latest version of Adobe Reader, free of charge.

Suggested citation:

Thomas, M.A., Diehl, S.F., Pletsch, B.A., Schumann, T.L., Pavey, R.R., and Swinford, E.M., 2008, Relation between solid-phase and dissolved arsenic in the ground-water system underlying northern Preble County, Ohio: U.S. Geological Survey Scientific Investigations Report 2008-5205, 56 p.




Purpose and Scope

Description of Study Area



Solid-Phase Characteristics


Site 1

Site 2

Bulk Elemental Composition

Site 1

Site 2

Residence of Arsenic in Sulfide Minerals

Ground-Water Quality

Site 1

Site 2

Relation Between Arsenic in Ground Water and the Solid Phase

Glacial Deposits

Carbonate Bedrock

Summary and Conclusions

References Cited

Appendix 1. Core log description for site 1, glacial deposits and bedrock

Appendix 2. Core log description for site 2

Appendix 3. Bulk elemental composition of solid phase samples, sites 1 and 2

Appendix 4. Mineralogical description of seven solid-phase samples

Appendix 5. Results of inverse mass-balance modeling

Accessibility FOIA Privacy Policies and Notices

Take Pride in America logo logo U.S. Department of the Interior | U.S. Geological Survey
Page Contact Information: Contact USGS
Page Last Modified: Thursday, 10-Jan-2013 19:04:25 EST