Allegheny Mountain

There were many examples of early interconnected electric transmission systems extending across state territories and beyond state boundaries. Statements from a speech by Samuel Insull at Purdue University in 1924 indicated that Minneapolis, St. Paul, St. Louis, Louisville, and Cincinnati soon would be interconnected and that extension of these systems to Pittsburgh and across the Allegheny Mountains to the Atlantic Seaboard could be easily conceivable in a few years. This was but one example across the United States. To quote Insull, It makes electric service available in new places for new pui poses, so that aggregate demand for service is spread over more hours of day and night, and thus opens the way to utmost economy in production and distribution. ... 

One of the most important projects in progress in the field of hybrid receptor modeling is the Allegheny Mountain study by Pierson et al. of Ford Motor Co. (This Volume). Concentrations of many ions, major, minor and trace elements in airborne particles, rain, dew and fog and other parameters were measured at Allegheny Mt., PA and Laurel Hill, 35 km to the northwest, from 5 to 28 Aug 1983, approximately simultaneously with the Deep Creek Lake studies discussed above. These two huge data sets are now nearly complete and ready for detailed interpretations by the participants and other researchers in the field. In particular, Keeler is working with the Ford group to apply the Samson method to the data. 

Acid Deposition and Atmospheric Chemistry at Allegheny Mountain... 

The experiment was conducted August 5-28, 1983 on abandoned radio towers atop Allegheny Mountain (elevation 838 meters) and Laurel Hill (elevation 850 meters, 35 km NW of Allegheny Mountain) in southwestern Pennsylvania (Fig. 1). Both sites are heavily forested and experience little local vehicle traffic. 

The Laurel Hill rains were about 10% more concentrated in all species than those collected at Allegheny Mountain (in agreement with atmospheric aerosol and trace gas concentrations at the sites). 

The S0 ==/N03 concentration ratio in the rain was about 3.7 equivalents per equivalent vs. a ratio of about 2.5 in the dew. This is not surprising since significant amounts of sulfate are introduced into rain by nucleation scavenging (18) while aerosol sulfate deposition to dew is minimal (1). (In fact, at Allegheny Mountain (1) SO2 was responsible for about 80% of the dew... 

Comparison of the deposition efficiencies of rain, dew and fog at Allegheny Mountain shows that during the 21-day experiment, rain was responsible for the deposition of 60 times more acidity (together with related species) than was deposited during dew periods or with settled fogwater. 

Precipitation in the vicinity of Allegheny Mountain is about 107 cm per year (19), or close to the rate recorded in Table 2. If the ratio between deposition by rain and deposition to dew during the sampling period is also representative of the year, then it follows that the annual total acid deposited in rain is very roughly 60 times as great as that deposited to dew or in settled fogwater. 

These results are similar to daily-averaged values reported by Barrie (18) for sites in eastern Canada (1978-1981). His mass scavenging ratios, multiplied by 890 (the ratio between the density of water and that of air at the 838-m altitude of Allegheny Mountain in order to match units), give the following averages for 4 remote locations ... 

Estimation of Wet and Dry Acid. NO3. and S0/,= Deposition Budgets at Allegheny Mountain. To gauge the relative importance... 

Air pollutants, transport, 4 Air sampling—See Interstitial air sampling Aldehydes, determination in atmospheric samples, 299 Allegheny Mountain acid deposition and atmospheric chemistry, 28-36 deposition budgets for sulfate and nitrate, 33... 

The pilot of an IFR-equipped Cessna 172, which has adequate instrumentation to fly in the clouds, is planning a flight from eastern New York into Pennsylvania. The plane has no deicing equipment. The flight will require a minimum enroute altitude of 2500 m to maintain required terrain clearance over the Allegheny Mountains. Surface temperature at the departure airfield 200 m above sea level is 12°C, and RH is 60%. If the air along the route is characterized by an adiabatic lapse rate ... 

As with most air quality data, the concentrations of acid aerosols depend on time of day, season, and on sampling and averaging times. However, since acid aerosol concentrations display the relatively slow moving patterns typical of secondary pollutants, the temporal patterns are less "spiky" than, for example, SO2, and typically consist of periods of low levels or zeroes punctuated by "episodic" periods of a few days duration at most, as shown in Figure 5 for Allegheny Mountain, PA (data from Pierson et al., 1989) and in Figure 6 for Whiteface Mountain, NY, for example (there are also periods of missing data in the Whiteface Mountain data set). 

Pierson, W.R et al. (1989), Atmospheric Acidity Measurements on Allegheny Mountain and the Origins of Ambient Acidity in the Northeastern United States, Atm. Env. 23 431-459. 

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