Contaminants Found During Stream Survey in Potomac River Basin

U.S. Department of the Interior
U.S. Geological Survey

Jump to archives >>

Updated: May 12, 1993

A wide variety of insecticides, semivolatile organic compounds, and trace-metal contaminants were found in streambed sediments, clams and fish in the Potomac River basin during a contaminant survey, according to scientists from the U.S. Geological Survey (USGS), Department of the Interior.

Although potentially toxic, none of the contaminants were found at concentrations that exceed any established drinking-water standards.

The survey, undertaken to document the occurrence of nearly 140 contaminants in the basin, targeted streams known or suspected to contain contaminants. It was the first major sampling activity conducted by the Potomac River basin study unit of the USGS's National Water-Quality Assessment (NAWQA) program.

"Nearly 75 percent of the contaminants that we tested for in the survey were found to be present somewhere in the basin," said James Gerhart, USGS hydrologist, Towson, Md., chief of the Potomac River basin NAWQA study unit. "Of the 139 contaminants that the samples were analyzed for, 102 were found at detectable levels, including 24 of 40 insecticides, 59 of 80 semivolatile organic compounds, and all 18 trace-metal contaminants. Possible sources of the contaminants include industrial and municipal wastewater, urban and agricultural runoff, mining activities, atmospheric deposition and the natural weathering of rocks."

"Although contaminant studies of the Potomac River basin have been conducted by federal and state agencies in the past, this is the first basinwide contaminant survey to include such a broad array of contaminants at such a wide variety of stream sites," said Gerhart. "The results will help guide us in deciding what areas and issues might be particularly critical to the assessment of water quality in the Potomac River basin."

Samples of fine-grained streambed sediment were collected in August and September 1992 from 22 sites in the Potomac River and some of its major tributaries in Washington, D.C., Virginia, Maryland, West Virginia, and Pennsylvania. In addition, samples of the Asiatic clam, Corbicula fluminea, were collected at 14 of the 22 sites, and samples of bullhead catfish were collected at 8 of the 22 sites.

Although many contaminants were found in the samples, their concentrations were generally low, and for those contaminants with established criteria, well below any criteria for human health concerns. Two streambed-sediment samples from the South Fork Shenandoah River contained mercury concentrations that exceeded Virginia's sediment criterion, however, and one sample from the South Fork Shenandoah River contained PCB's at a concentration that exceeded the U.S. Environmental Protection Agency's threshold contamination criterion. These high concentrations were not unexpected, as high concentrations of mercury and PCB's have been documented in the past at these sites by the Virginia Water Control Board. No Asiatic clam or bullhead catfish samples had concentrations of any contaminants that exceeded human health criteria. "One interesting aspect of the findings," Gerhart said, "was that although the use of the insecticides chlordane, DDT, and dieldrin has been banned in the United States for the past two decades, their detection in this survey indicates their persistence in the environment."

The bed-sediment samples were analyzed for concentrations of 40 organochlorine insecticides, 80 semivolatile organic compounds, 18 trace-metal contaminants, and PCB's. The clam and catfish tissue samples were analyzed for concentrations of 28 insecticides, 18 trace-metal contaminants, and PCB's.

Organochlorine insecticides are typically used in a wide variety of urban, suburban, forested and agricultural settings to control insect pests. Included in the insecticides that were found at one or more of the survey sites were chlordane, DDT, dieldrin, endrin, heptachlor, chlorneb, and nonachlor.

Semivolatile organic compounds and PCB's are typically associated with industrial processes and urban settings. Semivolatile organic compounds found in the survey included naphthalene, anthracene, pyrene, chrysene, phenol, cresol, acridine and phenanthridine.

Trace-metal contaminants typically result from industrial processes, mining and urban runoff, but also may originate from the weathering of natural geologic materials. Mercury, lead, arsenic, cadmium, chromium, nickel and copper were some of the trace-metal contaminants that were found in the samples.

"On the basis of the 22 sites we sampled, we can make some general statements about contaminant distribution in the Potomac River basin," said Gerhart. "For instance, sites in the Washington, D.C., metropolitan area had the highest number of insecticide detections, followed by sites in the Shenandoah Valley and the middle Potomac River area. Sites in the North Branch Potomac River area had the highest number of detections of semivolatile organic compounds and trace- metal contaminants, followed by sites in the Washington, D.C., and Shenandoah Valley areas."

The number of insecticides found at a site ranged from one at the Potomac River at Shepherdstown, W. Va., to 13 at the Anacostia River at Bladensburg, Md. The lowest number of semivolatile organic compounds (8) was found in Goose Creek near Leesburg, Va., and the highest number (33) was found at the Potomac River near Cumberland, Md., and at Bull Run near Manassas, Va. The number of trace- metal contaminants found at a site ranged from 13 to 17. PCB's were found at 20 of the 22 sites.

The sites from which samples were collected were:

• North Branch Potomac River at Steyer, Maryland
• Savage River near Barton, Maryland
• North Branch Potomac River near Pinto, Maryland
• North Branch Potomac River near Cumberland, Maryland
• South Fork South Branch Potomac River near Moorefield, West Virginia
• Cacapon River near Great Cacapon, West Virginia
• Conococheague Creek at Fairview, Maryland
• Opequon Creek near Martinsburg, West Virginia
• Marsh Run at Grimes, Maryland
• Potomac River at Shepherdstown, West Virginia
• Middle River near Grottoes, Virginia
• South River at Harriston, Virginia
• South Fork Shenandoah River at Front Royal, Virginia
• North Fork Shenandoah River near Strasburg, Virginia
• Shenandoah River at Millville, West Virginia
• Monocacy River at Bridgeport, Maryland
• Goose Creek near Leesburg, Virginia
• Anacostia River at Bladensburg, Maryland
• Potomac River near Alexandria, Virginia
• Accotink Creek near Annandale, Virginia
• Bull Run near Manassas, Virginia
• St. Clement Creek near Clements, Maryland

The contaminant survey was conducted to investigate the presence of a wide variety of contaminants throughout the basin and to provide information that would be useful in designing selected future aspects of the study. Streams to be sampled were selected to best represent the diversity of physiographic, geologic, hydrologic, ecologic, and land-use settings present in the basin. Within these various settings, specific sampling sites were selected downstream from known contamination sources and in stream reaches where contaminants were most likely to be found.

Further information on the survey and on the specific data for each sampling site can be obtained from James Gerhart, Joel Blomquist, or Humbert Zappia (USGS, Towson, Md.) at (410) 238-4200.

** * USGS * * *

In-depth information about USGS programs may be found on the USGS home page at http://www.usgs.gov and http://chesapeake.usgs.gov/ for Chesapeake Bay activities.

Archived News Releases 2000-Present

2006

• 01-06-2006 Water Resources Plentiful at End of December 2005; Chesapeake Bay Flow Normal in 2005

2005

• 07-06-2005 Water Levels Fall as Summer Arrives
• 04-06-2005 March 2005 Water Levels Near Normal
• 03-04-2005 Flow Below Normal in Potomac River and Chesapeake Bay
• 02-07-2005 January 2005 Water Levels Normal to Above Normal
• 01-07-2005 2004 Ends with Normal to Above Normal Water Levels

2004

• 12-04-2004 Water Levels Remain Generally Above Normal
• 11-04-2004 Dry October Causes Water Levels to Drop
• 10-06-2004 Highest September Flow to the Chesapeake Bay Since 1937
• 09-03-2004 August Hurricanes Raise Water Levels in Southern Maryland
• 08-06-2004 Localized Flooding in Northeastern Maryland and Delaware in July
• 07-07-2004 Water Levels Normal to Above Normal in June
• 06-04-2004 Streams Return to Normal Levels in Maryland and Delaware during May 2004
• 05-06-2004 Streams Rise to Above Normal Levels in Maryland
• 04-07-2004 Streamflow and Groundwater Levels Fell in March 2004
• 03-04-2004 Streamflow and Groundwater Levels Normal to Above Normal in February 2004
• 02-04-2004 Cold, Dry January Leads to Drop in Water Levels
• 01-06-2004 Wettest Year Leads to Record-High Water Levels Including Third Highest Flow to Chesapeake Bay in December and 2003

2003

• 12-04-2003 More Record-High Water Levels in November 2003
• 11-04-2003 Record High Groundwater Levels in October 2003
• 10-03-2003 Flow to Chesapeake Bay in Water Year 2003 Second Highest Since 1937
• 09-05-2003 Third Consecutive Month of High Flow into the Chesapeake Bay
• 08-06-2003 Flow into Chesapeake Bay near Record High Levels
• 07-07-2003 Record Breaking High Water Levels in Maryland and Delaware
• 06-06-2003 Streamflow and Groundwater Levels High in May
• 05-07-2003 April Water Levels Normal
• 04-05-2003 Water Levels High in March - Water Restrictions Lifted
• 03-05-2003 Exceptionally Wet February Leads to High Water Levels
• 02-06-2003 Maryland and Delaware Streamflow and Groundwater Levels Remain Normal in January 2003
• 01-07-2003 2002: A Record-Setting Year for Low Groundwater Levels - Water Levels Recover to Normal in December 2002

2002

• 12-01-2002 Hydrologic Drought Wanes as Water Levels Rise
• 11-01-2002 Water Levels Rise Across Maryland and Delaware, But Drought Persists in Some Areas
• 10-03-2002 Water Levels Remain at Record-Setting Lows
• 09-05-2002 Groundwater in Parts of Maryland Reaches Lowest Levels Since 1962, Despite Late August Rains
• 08-06-2002 Drought Conditions Lead to 10 Record Low Monthly Groundwater Levels in July
• 07-03-2002 Record Low Water Levels Show the Effects of Long-Term Hydrologic Drought
• 06-04-2002 Groundwater Levels Reflect Long-Term Effects of Drought
• 05-02-2002 April Showers Not Enough to Raise Groundwater Levels
• 04-05-2002 The Drought in Full Bloom: Low Water Levels Result in Water Restrictions

2001

• 12-03-2001 Record Low Water Levels Set in November
• 11-02-2001 Dry October Leads to Low Water Levels
• 10-05-2001 Water Levels Low in Northern Maryland
• 09-07-2001 Water Levels Stable in August
• 08-06-2001 High and Low Water Levels in July
• 07-06-2001 Water Levels Continued to Improve in June
• 06-06-2001 Needed Rain Helps Avert a Drought in May
• 05-08-2001 Water Levels Still Normal in April, but More Rain is Needed
• 04-05-2001 Spring Rains Help Water Levels
• 03-06-2001 Water Levels Improve, But Are Still Below Normal
• 02-06-2001 Streamflow Still Low in Maryland in January
• 01-05-2001 Streamflow to Chesapeake Bay in 2000 Reflects Dry Autumn

2000

• 12-05-2000 Streamflow in Maryland Beginning to Show the Effects of Lack of Rain
• 11-07-2000 Despite Lack of Rain October Water Conditions near Normal
• 10-06-2000 September Water Conditions Above Normal in Maryland, Delaware, and D.C.
• 09-08-2000 August Water Conditions Above Normal in Maryland, Delaware, and D.C.
• 08-07-2000 July Water Conditions Continue Normal in Maryland, Delaware, and D.C.
• 07-07-2000 June Water Conditions Normal in Maryland, Delaware, and D.C.
• 06-06-2000 Water conditions begin to decline in Maryland, Delaware, and D.C.
• 05-05-2000 Water Conditions Continue to Improve in Maryland, Delaware, and D.C.
• 04-07-2000 Water Conditions Continue to Improve in Maryland, Delaware, and D.C.
• 03-07-2000 Water Conditions Improving in Maryland, Delaware, and D.C.
• 02-08-2000 January Streamflow and Ground Water Levels Still Low
• 01-06-2000 1999 Flow Into Chesapeake Bay Lowest Since 1960s Drought