USGS Study Confirms An Urban Air-Pollution Problem At Mount Rainier National Park

The study, by Dr. David Peterson of the USGS Forest and Rangeland Ecosystem Science Center, was published in the scientific journal "Atmospheric Environment," and adds to the growing body of evidence that protected areas such as national parks are vulnerable to pollution from outside sources. The ozone at Mt. Rainier, for example, is blown in from Seattle and other urban centers in western Washington.

Ozone is a natural component of the Earth's atmosphere, but its effects vary depending on where and in what concentration it occurs. High above the Earth's surface, in the stratosphere, a protective layer of ozone screens the earth from biologically harmful frequencies of ultraviolet radiation. The stratospheric ozone layer is essential to the existence of many forms of life.

However in the lower part of the atmosphere, called the troposphere, human-produced ozone can be a dangerous pollutant. The colorless gas is formed from byproducts released during the burning of fossil fuels, and can be toxic to both plants and animals, including humans, even at fairly low concentrations.

"It's well documented that both periodic episodes of high ozone exposure and chronic moderate ozone exposure can be harmful to plants," said Peterson. "We know this from other regions of North America including national parks such as Sequoia and Great Smoky Mountains."

Sources of ozone-producing compounds, including automobile exhaust and fuel-burning industries, tend to be concentrated in urban areas. But the common assumption that ozone pollution is strictly an urban problem is proving to be false, Peterson said.

Peterson and his students monitored ozone at Mount Rainier National Park from 1993 to 1997, and quantified the spatial distribution of this pollutant throughout western Washington in 1996. The park consistently had the highest average weekly levels of tropospheric ozone measured anywhere in the state. Ozone concentrations tend to increase at higher altitudes, partly because of passive dispersion from the stratosphere, but largely due to the transport of pollutants by prevailing winds inland from urban sources, such as the Seattle metropolitan area.

A common visitor destination in the park, known as Paradise, is on the southern slope of Mount Rainier at an elevation of 5,400 feet and a distance of about 60 miles from Seattle. Peterson said that Paradise had almost twice the monthly mean ozone concentration as Lake Sammamish, which is near sea level and less than ten miles east of Seattle.

Mount Rainier National Park resource manager Barbara Samora said the ozone study "is just one more indication of how difficult it is to protect our national parks. It isn't a simple matter of telling people to stay on footpaths or of sensibly locating campgrounds and parking lots. How do you manage a threat that is produced 60 miles from the park and transported here by winds?"

A number of other North American wildlands have concentrations of tropospheric ozone sufficiently high to harm vegetation. They, too, are located downwind of metropolitan areas. These areas include El Desierto de Los Leones near Mexico City, San Bernardino National Forest to the east of Los Angeles, Sequoia National Park and Sequoia National Forest to the east of several metropolitan areas in California, and Great Smoky Mountains National Park in the eastern U.S.

Peterson noted that in the rapidly urbanizing Puget Sound region, with its higher population and additional vehicles will produce more local pollution sources in the future. "It is time to consider the potential for damage to park ecosystems and even potential health hazards to park visitors," Peterson said. "We've long known that parks cannot be managed as islands, separate from their surroundings. These findings about tropospheric ozone concentrations lend additional support to that management position."

As the nation's largest water, earth and biological science and civilian mapping agency, the USGS works in cooperation with more than 2000 organizations across the country to provide reliable, impartial, scientific information to resource managers, planners, and other customers. This information is gathered in every state by USGS scientists to minimize the loss of life and property from natural disasters, contribute to the sound conservation, economic and physical development of the nation's natural resources, and enhance the quality of life by monitoring water, biological, energy, and mineral resources.