AEROSOL COMPOSITION AS A FUNCTION OF HAZE AND HUMIDITY LEVELS IN THE SOUTHWESTERN US

The observed composition of visibility-reducing aerosols in the Grand Canyon region is summarized in climatological terms. Observations are from SCENES, a measurement program extending from 1984 to 1989. Result s are presented as average mass balances stratified by various factors . Aerosols were found to exhibit substantial seasonal variation, but l ittle systematic diurnal variation. Crustal material was a dynamic com ponent, and peaked during springtime. Aerosol composition, but not tot al concentration, depended strongly on ambient relative humidity, with crustal material augmented at low humidities and sulfates augmented a t high humidities. Total fine-particle concentrations correlated stron gly with light scattering, as expected; however, little association be tween chemical composition and light scattering was observed.