Hydrological and Geochemical Controls on Episodic Acidification of Streams in Shenandoah National Park

Atmospheric Wet Deposition of Trace Elements to a
Suburban Environment near Washington, D.C., USA

Karen C. Rice,
U.S. Geological Survey, P.O. Box B, Charlottesville, VA 22903

Kathryn M. Conko
U.S. Geological Survey, MS 432 National Center, Reston, VA 20192

During 1998, wet deposition from Reston, Virginia, USA, a suburb of Washington, D.C., was collected and analyzed for anion and trace-element concentrations. Wet-deposition samples were retrieved every two weeks from an automated collector; trace-element clean sampling and analytical techniques were used. Reston, approximately 26 km west of Washington, D.C., is a developed, densely populated (1,116 people/km²) area, and samples from this site provide an indication of local anthropogenic effects on wet-deposition quality.

The annual volume-weighted concentrations of As, Cd, and Pb were similar to those previously reported for an undeveloped, more remote site on Catoctin Mountain, Maryland (70 km northwest), suggesting a regional depositional pattern for these elements. At the suburban site, concentrations and depositions of Cu and Zn nearly were double those at the undeveloped site. Both of these elements are contained in brake linings and tires; therefore, resuspension of Cu and Zn particulates from roadways likely is a local source of these elements in atmospheric deposition. Patterns of higher deposition of Cl^- during the winter months, when roads are salted, is an additional indication that resuspension of particulates from roadways is affecting wet-deposition quality in this suburban environment.

Analysis of digested total (dissolved plus particulate-associated) trace-element concentrations in a subset of samples showed that a larger portion was composed of refractory elements at the suburban site than in undeveloped areas. Whole-water analyses, therefore, may be more precise indicators of total deposition mass of trace elements than the acid-leachable fraction of samples at sites affected by local anthropogenic sources.

Rice, K.C., and Conko, K.M., 2004, Atmospheric Wet Deposition of Trace Elements to a Suburban Environment near Washington, D.C., USA [abs.], National Atmospheric Deposition Program Scientific Symposium, Sept. 21-24, 2004, Halifax, Nova Scotia.

URL va.water.usgs.gov/GLOBAL/Abst/rice_atmospheric_deposition.htm
Last update: 10/04/04 12:47