Regional analysis of factors affecting visual air quality

Abstract

The U.S. Environmental Protection Agency, National Park Service, Visibility Research Center, and University of California at Davis are currently operating a monitoring program in national parks and monuments throughout much of the western United States. Project VIEW, the Visibility Investigative Experiment in the West, includes measurement of visibility parameters using manual telephotometers, and measurement of particle concentrations averaged over 72 h. Variation of these parameters occurs in both space and time. To better understand these variations, several techniques including principal component analysis and data comparisons among sites are applied to Fall, 1979 data for much of the network. Then the Grand Canyon is chosen for additional analysis. Best and worst case visibility days are determined and compared with particle concentrations. Finally, hypothetical causes for visibility reduction are further verified by computing wind trajectories back in time for these special case days. Highlights of this preliminary investigation include evidence that fine sulfur and fine particles are responsible for visibility variation at the VIEW sites; that fine particle copper may be suitable as a tracer for copper smelter impact and that at the Grand Canyon, the majority of trajectories for days of visibility greater than 310km come from the north and west, over Utah and Nevada.