The number one reason for visiting Death Valley National Park is sightseeing. Since most of the land is treeless and since it encompasses a great range of elevations, the park has an abundance of striking and easily accessible views. Unfortunately, the view across the valley is often hazy, especially in the late spring and summer. On bad days, Telescope Peak is not visible from the visitor center, even though it is only 23 miles away.
One might think that the air would be pristine at Death Valley National Park due to its remote location. However, pollutants can be carried great distances on the wind. The general trend in upper air movement brings pollutants from metropolitan areas, industrial areas, and transportation corridors from the west. In summer, surface winds come from the southwest, where major population centers, industrial areas, and a dry lakebed are located. In winter, surface winds come from the northeast. Since these winds bring an air mass that originates in less developed areas, our air quality is better in the winter.
Pollutants carried in from other areas usually change form by the time they reach Death Valley. For example, sulfur dioxide and nitrogen dioxide emitted by power plants and cars react with other molecules to form sulfates and nitrates, which interfere with visibility and contribute to acid rain. Similarly, ozone is formed by nitrogen dioxide and volatile organic carbons. Pollutants such as nitrogen dioxide that are directly emitted into the air are called primary pollutants, whereas the pollutants these are converted into are called secondary pollutants. During the summer months, more sunlight and higher temperatures speed up these conversion reactions.
Nature also contributes to the haziness by blowing dust into the air. But, humans increase the amount of dust available to be blown by the wind when they drive on unpaved roads or break up the salt crust by walking on it.
The park has an air quality monitoring station near Furnace Creek that measures ozone, wet and dry acid deposition, visibility-reducing particles, and meteorological data. The monitoring station is part of a nationwide network. Collecting long-term data on air pollutants allows the National Park Service to take action if they exceed certain standards. Also, this information allows us to predict bad air pollution days and inform visitors about how to reduce negative health effects on these days. Death Valley National Park currently measures ozone levels that are unhealthy for sensitive groups a few times a year. A system for forecasting high ozone days is in the works.