Composition and origin of summertime air pollutants at Deep Creek Lake, Maryland

Abstract

Abstrset-A 1 month intensive summe~me field study conducted in rural western Maryland resulted in a ~mprehensive set of fine particle, gaseous and met~rolo~~l data. Sulfur in the assumed form of Arnold sulfate accounted for 67% of the average tine particle mass and had a very high correlation with fine particIe mass (r=O.99). Other measured species, including carbon and nitrate, made only minor contributions to the fine mass. Peak sulfate concentrations, averaged over 6-h intervals, exceeded 50 pg mm3. Nitric acid concentrations showed strong daytime maxima and on a 24 h basis were about four times those of fine particle nitrate. Sulfur in the gas phase (SO,) constituted more than half of the total sulfur, indicating that the sampling site was being influenced by local sources. Fine particle selenium was well corretated with fine partide sulfur (r=O.70}. The ratio of fine particle suifur to selenium was 2800, characteristic of a rural site downwind of coal-burning areas. Mixed-layer back trajectories were used to id~t~y possible source regions for the measured parameters. Wind f~quency-noes con~nt~tio~ of parameters associated with coal-burning (S, Se, SO, and mass) were highest for back trajectories arriving at Reep Creek Lake from the west-northwest. Use of Rahn and Lowenthal regional signatures showed an overwhelming dominance by the Lower Midwest region, and a surprisingly weak impact by the Upper Midwest region, at the site.

Transmission of Atmospherically Derived Trace Elements Through an Undeveloped, Forested Maryland Watershed

“…The overall consistency in the wet deposition gradient for most elements (Figure 2) is in accord with diverse lines of observational evidence indicating that trace element and acid deposition in the mid-Atlantic region results primarily from mid-western U.S. emission sources (e.g., Kowalczyk et al, 1982;Helz et al, 1985;Vossler et al, 1989;Han, 1992;Scudlark et al, 1993;Wu et al, 1994;Lucey et al, 2001). The observed wet deposition gradient ( Figure 2) appears to reflect attenuation of these emissions by dispersion and wet and dry scavenging processes during their transport by prevailing westerly winds, and/or the increasing influence of comparatively "clean" marine air masses from the Atlantic Ocean.…”

“…Factor analysis of fine particulate data obtained at Deep Creek Lake, ∼220 km. miles west of Bear Branch, indicated important contributions of As from sources besides coal combustion, including motor vehicles and metal refining, which may exhibit less seasonal signals (Vossler et al, 1989).…”

Sulfate Content Correlates With Iron Concentrations in Ambient Air Pollution Particles

“…Sulfur in air pollution particles can be present as sulfates, including ammonium sulfates, rather than sulfites (Stevens & Dzubay 1978), and can make up 40 to 67% of the mass of fine particle fraction (Stevens & Dzubay, 1978;Vossler et al, 1989).…”

“…Iron is that metal in highest concentration in ambient air pollution particles (Demuynck et al, 1976;Dodd et al, 1991;Mamane, 1990;Stevens & Dzubay, 1978;Vossler et al, 1989). This metal can approach concentrations as high as 1 mM in the fogwater of urban settings and aerosol particles (Jacob et al, 1989;Munger et al, 1983;Waldman et al, 1982).…”

The sources of aerosol elemental carbon at Allegheny Mountain

“…rural Pennsylvania in 1983 (Pierson et al, 1987(Pierson et al, , 1989Vossler et al, 1989). This paper details our investigation of the source apportionment of the aerosol EC measured in that study.…”