Protecting Visibility in National Parks and Wilderness Areas (1993) / Chapter Skim
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1 Introduction
1 Introduction
Pages 19-28
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From page 19... ...
Even small increases in particle concentrations can substantially degrade visibility. Fine particles in the atmosphere absorb and scatter light, thus limiting visual range, shifting colors, and obscuring the details of distant objects.
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From page 20... ...
establish a national goal of preventing and remedying visibility impairment due to anthropogenic pollution in mandatory Class ~ areas, which include most large national parks and wilderness areas in the United States.2 This goal will be difficult to achieve because many types of pollutant sources degrade visibility. Many different types of sources produce the same types of chemicals, including those that are most important in visibility degradation.
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From page 21... ...
The WHITEX report asserted that the Navajo Generating Station (NGS) , a large coal-fired power plant in Page, Arizona, is a principal contributor to visibility impairment in Grand Canyon National Park (GCNP)
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From page 22... ...
Light extinction is directly related to perceptual cues of overall human judgements of visual air quality. The 1977 Clean Air Act Amendments and EPA's implementation of these amendments extend the term visibility to cover freedom from discoloration, reduced contrast, and other visible departures from the natural atmosphere.
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From page 23... ...
Understanding these multiple connections could elucidate the potential environmental benefits of air quality improvement strategies. DllilCULTIES IN DEVELOPING EFFECTIVE PROGRAMS Scientific Difficulties Formulating and implementing effective programs to protect and enhance visibility can be impeded by several political, institutional, and scientific barriers.
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From page 24... ...
NPS analyzed data from WHITEX and issued a final report concluding that NGS was responsible for approximately 70% of the anthropogenic particulate sulfate and approximately 40% of the anthropogenic aerosolrelated light extinction during selected wintertime periods of haze at the sampling station. This committee evaluated the NPS WHITEX report and concluded that, at some times during the study period, NGS contributed significantly to haze in GCNP.
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A fundamental difficulty linked to those described above has been Me general approach taken thus far to visibility impairment. EPA's current regulations require retrofitting of controls only on those sources whose contributions to visibility impairment in mandatory Class ~ areas can be shown through "visual observation or other techniques the State deems appropriate." A source's contribution to regional haze, however, usually cannot be detected through visual observation.
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From page 26... ...
SCOPE OF THE REPORT Recently proposed strategies suggest that visibility regulation should be based on controlling a large number of sources across a broad geographic area, and the Clean Air Act Amendments of 1990 take steps in this direction. In addition to examining methods aimed at assessing the contribution of individual sources to visibility impairment, the committee considered techniques that apportion contributions to regional haze among categories of sources or among geographic regions.
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From page 27... ...
That chapter also sets forth broad regulatory paradigms that were noted by the committee as possible frameworks within which future technical analyses might have to be conducted. Chapter 4 describes scientific understanding of haze formation and visibility impairment, including the meteorological and chemical processes responsible for the transport and transformation of gases and particles in the atmosphere.
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