Daily Variation of Metals in Streams Can Confound Scientific Studies

Graph of diurnal variation of metals in Prickly Pear Creek, Montana (Click on photo for larger version)

USGS scientists have found that concentrations of some metals dissolved in stream waters fluctuate significantly on a daily cycle, and that this phenomenon occurs consistently across the northern Rocky Mountains. This suggests that assessing the levels of trace metal contamination in streams can be more complex than previously thought.

The two important characteristics of these diurnal variations are:

1. the time of day when maximum and minimum concentrations occur, and
2. the magnitude of the difference between maximum and minimum concentrations.

Collecting water samples for metals analysis, Prickly Pear Creek, Montana (Click on photo for larger version)

Diurnal variations in metal concentrations are attributed to a number of factors: sorption of metals to bed material, dissolution of metal-bearing minerals, uptake by aquatic plants, source variations, geochemical changes in the streambed, and streamflow variations. Diurnal variations in concentration for most metals have been observed in streams that have neutral to slightly alkaline pH, which is typical of most streams in the Nation.

Diurnal variations have been observed in acidic streams for some metals, such as iron. Water-quality data collected to establish baseline environmental metal concentrations, to identify important metal sources, to characterize metal contamination, and to evaluate potential effects on aquatic ecology can be confounded unless diurnal variations are considered in the study designs, and in interpreting historical data.

References

• Jones, C.A., Nimick, D.A., and McCleskey, R.B., 2004, Relative effect of temperature and pH on diel cycling of dissolved trace-elements in Prickly Pear Creek, Montana: Water, Air, and Soil Pollution, v. 153, p. 95-113.
• Nimick, D.A., Gammons, C.H., Cleasby, T.E, Madison, J.P., Skaar, Don, and Brick, C.M., 2003, Diel cycles in dissolved metal concentrations in streams: Occurrence and possible causes: Water Resources Research, v. 39, no. 9, 1247, doi:10.1029/WR001571
• Nimick, D.A., 2003, Diurnal variation in trace-metal concentrations in streams: U.S. Geological Survey Fact Sheet FS-086-03, 4 p.

More Information

• Biofilms in Streams Help Create Daily Variations in Metal Concentrations
• Importance and Causes of Daily Variation in Metal Concentrations in Streams
• Diel Cycling of Trace Metals in Streams
• Chemical Modeling and Thermodynamic Data Evaluation of Major and Trace Elements in Acid Mine Waters and Ground Waters
• Diurnal Metal Variations in Streams Photo Gallery

Related Headlines

• How Do Contaminants Mix at the Confluence of Streams
• Mercury Concentrations in Streams Found to Go Through Daily Cycles
• Multidisciplinary Approach to Remediating Watersheds Contaminated from Abandoned Mine Lands
• Nature's Way of Cleaning Up Mining-Contaminated Streams
• Tracer-Tests Steer Cleanup of Mined Watersheds
• Cleaning up Contamination in Hard Rock Mine Lands

USGS Information on Contamination from Mining Activities

• Contamination Associated with Active and Abandoned Hard Rock Mining
• USGS Abandoned Mine Lands Initiative
• Hard Rock Mining Contamination in Rocky Mountain Terrain -- Upper Arkansas River, Colorado
• Hard Rock Mining Contamination in Arid Southwest Alluvial Basins -- Pinal Creek, Arizona
• Hydrologic Research on Metals

Back to Headlines page