VISIBILITY-REDUCING ORGANIC AEROSOLS IN THE VICINITY OF GRAND-CANYON NATIONAL-PARK - PROPERTIES OBSERVED BY HIGH-RESOLUTION GAS-CHROMATOGRAPHY

Fine particle and total airborne particle samples were collected durin g August 1989 within the Grand Canyon (Indian Gardens (IG)) and on its south rim (Hopi Point (HP)) to define summertime organic aerosol conc entration and composition as a function of elevation at Grand Canyon N ational Park. Inorganic chemical constituents were analyzed also to he lp place the relative importance of organics in perspective. Fine part icle organic aerosols were approximately equal in concentration to sul fate aerosols at both sites. Monthly average mass concentrations for f ine aerosol organics ranged from 1.1 mu g m(-3) (IG) to 1.3 mu g m(-3) (HP), while the organic aerosol concentration within total suspended particulate matter samples ranged from 1.9 mu g m(-3) (IG) to 2.1 mu g m(-3) (HP). Aerosol organics that could be evaluated by gas chromatog raphy with flame ionization detection (GC-FID) (elutable organics) con stituted 27% to 53% of the total organics mass collected as fine or to tal aerosol. At each site, roughly half of the elutable organics fine aerosol fraction was composed of highly polar organic compounds. Distr ibutions of the elutable organics were compared to Los Angeles fine ae rosol samples and to distributions of authentic sources of aerosol org anics. It was found that the Grand Canyon organic aerosol during Augus t 1989 did not resemble diluted aged Los Angeles organic aerosol, indi cating that most of the organic particulate matter at the Grand Canyon at the time studied originated from other sources.