USGS Precipitation Quantity and Chemical Quality Monitoring Program-Program Information

Program Description

The U.S. Geological Survey (USGS) measured precipitation quantity and chemical quality at three locations: Catoctin Mountain near Thurmont, Maryland, Massanutten Mountain near Front Royal, Virginia, and Old Rag Mountain near Etlan, Virginia.

Data from Catoctin Mountain were from January 1982 to December 1996. These data were collected as part of the National Acid Precipitation Assessment Program (NAPAP), in cooperation with the Maryland Department of Natural Resources and the Maryland Department of the Environment. The Catoctin Mountain monitoring site (base elevation 1,700 ft) is located in Cunningham Falls State Park in Frederick County, 3 miles west of the Town of Thurmont, at latitude 39º37'36" north and longitude 77º28'51" west. The precipitation collection station is situated on a raised wooden platform (6.5 ft) constructed on top of a 25-ft high water storage tank in the middle of a clearing.

Data from Massanutten Mountain were collected from January 1983 to October 1996. These data were collected weekly to monthly, depending on access to this remote monitoring location. This sample location was not a part of the NAPAP, however the samples and data were treated in the same manner at Catoctin Mountain. The Massanutten Mountain monitoring site (approximate base elevation 1250 ft.) is located in George Washington National Forest in Rockingham County, about one and a half miles northeast of Seven Fountains at latitude 38^o52’30" north and longitude 78^o22’30" west.

Data from Old Rag Mountain were collected from August 1982 to September 1992 on an approximately weekly basis. This sample was also not part of the NAPAP, however, samples were collected in a manner consistent with Catoctin Mountain and data were analyzed and QA’ed in the same manner. The Old Rag monitoring site (approximate base elevation of 1600) is located in Weakley Hollow within the Shenandoah National Park, Madison County, approximately 2.5 miles west of Nethers at latitude 38^o34’00" north and 78^o19’02" west.

Sample collection activities at the monitoring include:

• Weekly collection of wet deposition samples, and
• Continuous rainfall volume monitoring.

Only wet deposition samples are collected.

The results of chemical analysis of each sample (for the 1982-1997 period) are provided on this web page (Precipitation Chemistry Data). Annual precipitation-weighted mean concentrations of chemical constituents in the samples (for the 1982-1991 period) and other statistical treatments of the data are found in the USGS report cited in the "Additional Program Information" section below.

Precipitation Sampling

In terms of equipment, the wet precipitation sample collector historically used is an Aerochem Metrics Model 301 collector. Precipitation samples deposited over the sampling period have been measured with a Belfort recording rain gage (Cat. No. 5-780).

Samples were collected from the monitoring site on a weekly basis, usually on Tuesday at 9:00 a.m., in conformance with NADP guidelines. If the quantity of precipitation collected in the bucket was too small (i.e., less than 0.2 in) for any measurements to be made, the sample was discarded.

Concentrations of dissolved calcium, magnesium, potassium, sodium, ammonium, nitrate, nitrite, chloride, sulfate, inorganic biphosphate, and non-purgeable organic carbon were measured in the laboratory. The specific conductance and pH of the sample were measured in the field, if up to 2 fl. oz of precipitation sample were available. The hydrogen ion concentration were based on the field pH value. For some weeks, there was only a sufficient volume of sample to perform field measurements.

Sample Analysis QA/QC

All chemical analyses of precipitation samples were performed in the Geochemical Cycling of Trace Elements and Nutrients Laboratory of the Eastern Region Branch of Regional Research of the USGS in Reston, Va. Quality assurance (QA) and quality control (QC) of the laboratory analyses were continuously carried out through a series of approved methods, which included the analysis of standards, blanks, and field blanks. During chemical analysis, known standard solutions were routinely analyzed after every fifth sample. Beginning in 1985, National Institute of Standards and Technology (NIST) standard solutions were analyzed at the beginning and end of each analysis session. Interlaboratory comparisons of analytical results were initiated in 1987.

Related Reports and Publications

The following document, which describes the monitoring program in greater detail, is available from the USGS. For further information, contact Dr. Owen Bricker at 703-648-5824.

• Data on the Quantity and Chemical Quality of Precipitation, Catoctin Mountain, North-Central Maryland, 1982-91, Prepared by the USGS in cooperation with the Maryland Department of the Environment and the Maryland Department of Natural Resources, 1993, Open-File Report No. 93-169.
• Open File Reports have not been prepared for Old Rag or Massanutten Mountains. Please contact Dr. Bricker for additional information about these sample locations.

Go to the USGS Catoctin Mountain Monitoring Program-Precipitation Chemistry Data Page

For more information, e-mail Dr. John Sherwell at the PPRP, or call him at 410-260-8660