Apportionment of sulfur oxides at Canyonlands during the winter of 1990—III. Source apportionment of SOx, and sulfate and the conversion of S02 to sulfate in the Green River Basin

During January-March of 1990 a study was conducted to determine the sources of sulfur oxide emissions present in the Canyonlands area in Utah. Samples were collected at the Island-in-the-Sky visitors center in Canyonlands National Park and at several sites circling the park to characterize the chemical composition of air masses influencing the receptor sites from various geographical regions. The results of the sampling program and the identified chemical fingerprints of the sources that can impact the Canyonlands receptor site have been given in the first two papers in a series of three papers. In this paper are presented the results of chemical mass balance source apportionment of the SOx, present at Canyonlands, Green River, Bullfrog Marina and Edge of the Cedars, Utah, using the chemical composition and source fingerprint data given in the preceding papers. The results indicate that the presence of sulfur oxides at the Canyonlands area is a regional problem not dominated by a single source. The contributions to SOx, at Canyonlands during the 21 days included in the source apportionment analyses included sources to the southwest (37%),south and southeast (20%), north and northeast (19%), and northwest (23%). At the Edge of the Cedars State Park to the southeast of Canyonlands, sources from the southeast contributed 51 % of the observed SOx. At Bullfrog Marina in the Lake Powell National Recreation Area, southwest of Canyonlands, sources to the southwest were responsible for 81 % of the SOx present. At Green River, to the north of Canyonlands, the contribution of sources to the north and northeast were reduced (10%) because the major transport path of sources from these directions was the movement of emission from northwestern Colorado down the Colorado River drainage and south of Green River. The apportionment of sulfate at Canyonlands has been estimated from a combination of the chemical mass balance SOx source apportionment results, the measured concentrations of S02 and particulate sulfate, and meteorological data. This analysis indicates that, while the main source of SOx at Canyonlands is from emissions to the southwest, the main source of sulfate is from SOx emissions originating from the southeast of Canyonlands.