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RESULTS FROM THE MOUNTAIN ACID DEPOSITION PROGRAM
Citation:
Isil, S., T. L. Lavery, C. Rogers, AND R E. Baumgardner. RESULTS FROM THE MOUNTAIN ACID DEPOSITION PROGRAM. Presented at Second International Conference on Fog and Fog Collection, St. Johns, Newfoundland, Canada, July 15-20, 2001.
Impact/Purpose:
Our main objective is to assess the exposure of selected ecosystems to specific atmospheric stressors. More precisely, we will analyze and interpret environmental quality (primarily atmospheric) data to document observable changes in environmental stressors that may be associated with legislatively-mandated emissions reductions.
Description:
The Mountain Acid Deposition Program (MADPro) was initiated in 1993 as part of the research necessary to support the objectives of the Clean Air Status and Trends Network (CASTNet), which was created to address the. requirements of the Clean Air Act Amendments (CAAA). The main objectives of MADPro were to. develop automated cloudwater measurement systems and to update the cloudwater concentrations and deposition data collected in the Appalachian Mountains during the National Acid Precipitation Assessment Program (NAPAP) in the 1980.
Measurements were conducted from 1994 through 1999 during the warm season at three permanent mountaintop sampling stations: Whiteface Mountain, New York. Clingman's Dome, Tennessee; and Whitetop Mountain, Virginia Cloudwater concentrations (normalized with respect to liquid water content) of major ions (SO2/4, NO3, NH4, and H) showed statistically significant results for all three sites; Clingman's Dome showed an increase for a11 four ions for both normalized and non-normalized concentrations; Whitcface Mountain results showed a significant decrease forNH'4 and SO 1/4 for both normalized and non-normalized concentrations; and Whitetop Mountain normalized concentrations exhibited a significant increase for SO3/4 only. Clingmun's Dome excited the highest mean and median 6-year (I 994 to 1999) average concentrations for the four major ions, whereas Whiteface Mountain consistently had the lowest mean and median concentrations for these ions. Cloudwater deposition estimates were made, by applying the cloudwater depositioncomputer model.CLOUD, parameterized with site-specific cloudwater cbemistry and meteorological data. Monthly cloudwater depositionestimates were highly variable with deposition values typically peaking in luly or August. Seasonal depositionamounts were highest for Whiteface Mountain because of the higher wind speeds and liquid water content 0LWC) experienced at this site, No temporal tread was evident in the deposition estimates. Dry, wet, and cloud deposition estimates were calculated on a monthly basis As for June through September for 1994 through 1998 at all three sites. Between 80 and 90 percent of sulfur (S) deposition occurred via cloud exposure at all three sites as did 70 to 87 percent of the total H loading. Cloud deposition was also responsible foy 90 to 95 percentof NW+/4 deposition at the southern sites. Dry deposition was a very minor contributor to the total S and NH+/4 Ioading,but contributed between 22 and 28 percent of nitrogen (N) deposition and approximately 16 percent of H depositionat the southern sites. In comparison to nearby low-elevation CASTNet sites, total deposition values from MADPro sites were approximately 6 to 20 times greater for- S, N and NH, while H depositions were from 1.3 to 10 times greater. Dry deposition values from MADPre sites for S, N, and H fall within the range of dry deposition values for CASTNet sites, Wet deposition values for all three species were generally I to 3 times higher at the CASTNet sites. Thus, the difference in total deposition between MADPro and CASTNet sites is directly attributable to cloud deposition.