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superintendent Bill Wade today issued information on how Shenandoah National Park collects visibility and air pollution data over the park. Sup. Wade said, “Recent media reports relating to air pollution in Virginia and visibility in Shenandoah National Park may have been misleading.”
Shenandoah National Park and the National Park Service use the National Add Preripitation Assessment Program (NAPAP) report, published in 1990, to determine historic regional visibility trends. The NAPAP report used 137 sites in the United States to determine visibility trends form 1948 to 1983. These trends are regional; localized visibility trends may be slightly differedt.
; Park air quality monitoring specialist Rolf Gubler monitors visibility and associated pollution by human observation, by direct measurement of particles in the air, and by using an instrument called a transmissometer. A transmissometer measures the amount of light lost as it passes through the polluted atomsphere. These measurements can be converted to “visual range”-an estimate of how far people can see.
Sulfate particles in the air cause 75 percent of the visibility impairment at Shenandoah. Direct mea! surement of sulfate particples at Big
85.8%