||Sonoma Technology, Inc., Santa Rosa, CA. ;Meteorology Research, Inc., Santa Rosa, CA. ;Washington Univ., St. Louis, MO. Dept. of Chemistry. ;Systems Applications, Inc., San Rafael, CA.;Environmental Sciences Research Lab., Research Triangle Park, NC.
VISTTA (Visibility Impairment due to Sulfur Transport and Transformation in the Atmosphere) is a cooperative program involving numerous government agencies, private companies, and universities and is jointly sponsored by the U.S. Environmental Protection Agency and Salt River Project. During the summer and winter of 1979, plume measurement programs were conducted near the Navajo Generating Station (NGS), at Page, Arizona. Results indicated that: (1) For the NGS plume, under most lighting and viewing conditions, NO2 dominates the blue light extinction and brown coloration due to the plume. (2) Widespread areas of elevated aerosol concentrations were documented in the Southwest due to long range transport from the Southern California area and wildfires. Other causes of regional haze are known to exist but were not documented in this study. (3) Evaluation of the chemistry, aerosol growth, and optics components of the PLUVUE plume visibility model showed predictions to be in reasonable agreement with the measurements. More uncertainty was encountered with the diffusion component. A set of nine reactions among NO, NO2, O3, SO2, OH, H2O, and O('D) was found to adequately simulate the plume chemistry for the clean dry background conditions at NGS.