The University of California, Davis, Air Quality Group recently took a break from analyzing air samples from the nation's parks, Owens Lake and Kuwait to discover what was making the local air look so "gunky," according to Director Thomas Cahill. "What you see are fine particulates floating in the atmosphere," Cahill said. "What they do is scatter light, cutting down visibility. Where they go is to the ground, trees, buildings and your lungs." Using an ion beam technique, researchers analyzed two 24-hour samples taken from test samplers on the UC Davis Physics/Geology Building on Oct. 9. The group found 11 micrograms per cubic meter of air of fine particles, which are less than 2.5 micrometers in diameter. (For comparison, a human hair is about 100 micrometers in diameter.) These small particulates scatter light and create the visible haze. According to Cahill, the fine particulates last week were from many sources: • Ammonium sulfate, 25 percent (primarily from Bay Area refineries) • Fine soils, 20 percent (primarily from agriculture, dirt roads) • Smoke, 13 percent (primarily from field burning) • Nitrates, 5 percent (primarily from automobiles, power plants) • Water, 36 percent (trapped on the sulfates and nitrates) • Plus many elements in small concentrations, 1 percent (vanadium, chromium, copper, zinc, arsenic, selenium, bromine and lead) The test sampler also collected large particles, which range in size from 2.5 to 10 micrometers, but these don't scatter light and are virtually invisible to the human eye. Cahill says the air seems to be dirtier than usual, with its poor quality perhaps exacerbated by the season's air inversions and the lack of rain. Protocols developed at UC Davis are being used to monitor air quality around the world. The UC Davis Air Quality Group is known for its recent investigation of the effects of a coal-fired power plant on winter air quality in Grand Canyon National Park and assistance in the settlement that resulted in 90 percent control of the plant's emissions.