Test in Southern California Forest Reveals Burning Brush Lofts Pollutants
LOS ANGELES (AP) _ Scientists who set a 300-acre brush fire last year to test the theory of ″nuclear winter″ say the controlled burn released huge amounts of automotive exhaust pollutants into the atmosphere.
Smoke from the fire contained up to 300 times the amount of some nitrogen and sulfur compounds detected in forest fires elsewhere in the nation, said Lawrence Radke, a professor of atmospheric science at the University of Washington. The pollutants had been left on the brush by auto exhaust.
Initial findings from the Dec. 13 fire in Angeles National Forest were reported Tuesday in a meeting of two dozen scientists, representing NASA, the U.S. Forest Service and the Environmental Protection Agency.
Philip Riggan, the Forest Service scientist who ran the experimental burn in Lodi Canyon, 20 miles east of Los Angeles, said forest fires have long been believed to be a significant source of pollutants that contribute to the smog problem in Los Angeles.
He said ″spectacularly high″ levels of nitrates previously have been measured in rainwater runoff of chaparral-covered slopes, but that such high levels in smoke were unanticipated.
Chaparral, the dense brush of the Southwest, is rich in nitrogen, so the previous findings suggested that the source of nitrogen compounds may have been the chapparal itself.
Radke, however, said that burning chapparal alone cannot be responsible for the levels of nitrogen oxides found in the smoke.
He said the only forest fire in the Pacific Northwest to create nitrogen oxide levels like those of the Lodi blaze occurred 15 miles downwind from a coal-burning power plant.
Lead that probably also came from automobile exhaust was among other pollutants also found in samples from small burns on one-acre sections around Lodi canyon before the big blaze, said U.S. Forest Service atmospheric scientist Darold Ward.
The concentrations of lead were four times the concentrations produced by blazes distant from urban areas, Ward said.
The Lodi project is to study how forest fires add to air pollution and to investigate the theory of nuclear winter, which holds that fires caused by a nuclear war would create enough smoke to block sunlight and cause Earth to grow cold.