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Prepared in cooperation with the North Dakota Department of Health

Mercury and Methylmercury in Water and Bottom Sediments of Wetlands at Lostwood National Wildlife Refuge, North Dakota, 2003–04

By Steven K. Sando, D.P. Krabbenhoft, Kevin M. Johnson, Robert F. Lundgren, and Douglas G. Emerson

Scientific Investigations Report 2007-5219 PDF (6.7 MB) Abstract Certain ecosystem types, particularly wetlands, have environmental characteristics that can make them particularly sensitive to mercury inputs and that can result in large mercury concentrations in fish or other aquatic biota. To provide information needed to make effective management decisions to decrease human and wildlife exposure to methylmercury in northern prairie pothole wetlands, the U.S. Geological Survey, in cooperation with the North Dakota Department of Health, conducted a study to assess mercury and methylmercury concentrations in wetlands at the Lostwood National Wildlife Refuge (the Refuge) in northwest North Dakota. In April 2003 and 2004, water and bottom-sediment samples were collected from 44 individual wetlands that were classified as one of four wetland types. Many factors that may affect methylmercury production were considered in the study. The prairie pothole wetlands at the Refuge had large ranges in major environmental characteristics. Hydrologic differences, most notably semiannual wetting and drying cycles, that are intrinsic to prairie pothole wetlands affected methylmercury concentrations. This likely resulted from the stimulation of anaerobic microbial activity following reflooding of soils, particularly soils containing substantial organic carbon. Among the four wetland types considered for this study, seasonal and semipermanent wetlands generally had the largest methylmercury concentrations. Regardless of wetland type, however, methylmercury concentrations at the Refuge are large in relation to reported concentrations for natural aquatic systems.

Version 1.0 Posted November 2007 Report PDF (6.7 MB)

Sando, S.K., Krabbenhoft, D.P., Johnson, K.M., Lundgren, R.F., and Emerson, D.G., 2007, Mercury and methylmercury in water and bottom sediments of wetlands at Lostwood National Wildlife Refuge, North Dakota, 2003–04: U.S. Geological Survey Scientific Investigations Report 2007–5219, 66 p.

Contents

Abstract

Introduction

Description of Study Area

Methods

Wetland Sampling Site Selection

Collection, Processing, and Analysis of Water and Bottom-Sediment Samples

Collection, Processing, and Analysis of Quality-Assurance/Quality-Control Samples

Climatic Conditions Prior to Sample Collection

Mercury and Methylmercury in Water and Bottom Sediments

Wetland Water and Bottom-Sediment Sampling

Patterns in Occurrence of Mercury, Methylmercury, and Other Water-Quality Properties and Constituents

Mercury Constituents in Water and Bottom-Sediment Samples and Properties of Bottom-Sediment Samples

Water-Quality Properties and Constituents Measured at Time of Sample Collection

Major-Ion and Selected Trace-Element Constituents in Water Samples

Organic-Carbon Constituents in Water Samples

Relations Between Mercury Constituents and Other Properties and Constituents in Water

Summary and Conclusions

References

Supplement 1. Quality Assurance/Quality Control

Quality-Assurance/Quality-Control Data Collection

Quality-Assurance/Quality-Control Results

Supplement 2. Water-Quality Property and Constituent Values

Supplement 3. Major-Ion, Suspended-Solids, and Nonmercury Trace-Element Data for Water Samples

Supplement 4. Mercury and Organic-Carbon Data for Water and Bottom-Sediment Samples

Supplement 5. Analytical Results for Quality-Assurance/Quality-Control Field-Equipment Blank Samples

Supplement 6. Analytical Results and Relative Standard Deviations for Quality-Assurance/Quality-Control Replicate Samples for Sites 1, 19, 26, and 32.