NPS: Nature & Science» Air Resources Division-Did You Know Archive

Did You Know Archive

Aspen leaf affected by ozone.

Ground-level ozone can affect vegetation in national parks, causing leaf injury and reduced growth in sensitive plants. Many plant species are affected, from pines in Yosemite and Sequoia National Parks to milkweed and black cherry in Shenandoah and Great Smoky Mountains National Parks. Ozone can even reach levels high enough to affect the health of park visitors and employees.

Milkweed leaf affected by ozone.

Health advisories are routinely issued in parks when ozone is expected to be high and visitors may be advised to limit their physical activity during such times. Most ozone forms outside park boundaries when emissions from cars, oil and gas development, power plants, and other sources combine in the atmosphere in the presence of sunlight. The National Park Service is partnering with the Environmental Protection Agency and States to monitor ozone in parks and to develop strategies to reduce ozone pollution.

Norris Geyser Basin in Yellowstone National Park, WY Photo: Bryan Harry, 1964

Yellowstone National Park is actually a volcanic area that emits mercury into the air. We hear a lot in the news about man-made sources of mercury such as trash burning and coal-burning power plants, but there are natural sources too, such as volcanoes and volcanic areas. Recent measurements have shown that mercury is being emitted to the air from the Norris and Mammoth thermal areas at the rate of 205 - 450 lbs/year. Mercury is a toxic metal that is hazardous to the health of wildlife and people. The atmospheric transport of mercury from all sources, natural and man-made, is a huge research area. These measurements in Yellowstone National Park are helping scientists understand how mercury moves through the environment.

Too much nitrogen can be a bad thing. Farmers use nitrogen to fertilize crops, but too much nitrogen can harm natural ecosystems. In Rocky Mountain National Park, nitrogen pollution from car exhaust, industrial emissions, and agricultural sources has caused changes in water, soil, and tree chemistry. Increasing nitrogen has altered algae communities in some lakes and favors certain plant species over others, a change that could reduce habitat for some animals and diminish alpine flowers in the park. More information on the effects of nitrogen deposition at Rocky Mountain National Park is available in this fact sheet (PDF .2 mb).

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Human activities have altered the chemical composition of the atmosphere through the buildup of greenhouse gases - primarily carbon dioxide, methane, and nitrous oxide. This is known as the greenhouse effect. Fossil fuels burned to run cars and trucks, heat homes and businesses, and power factories are responsible for about 98% of U.S. carbon dioxide emissions, 24% of methane emissions, and 18% of nitrous oxide emissions. Increased agriculture, deforestation, landfills, industrial production, and mining also contribute a significant share of emissions. The United States alone emits about one-fifth of total anthropogenic (man-made) greenhouse gases globally.

Photo of biodiesel-powered bus in Acadia National Park

Parks are not immune to air pollution. And while most of the pollution detected in parks comes from outside park boundaries, some of the pollution comes from activities and operations within parks. Many parks have taken steps to reduce and prevent air pollution. Over 675 pieces of equipment and vehicles in at least twenty parks are using biodiesel fuel (or biodiesel blends), a cleaner form of fuel than normal gasoline or diesel fuel. Other parks use alternative fuels, renewable energy, and environmentally-friendly cleaning products to minimize contributions to air pollution. The National Park Service Green Energy website provides information about what parks are doing to reduce or prevent pollution and conserve resources.

Image courtesy of Earth Sciences and Image Analysis Laboratory,
NASA Johnson Space Center
http://eol.jsc.nasa.gov

Our earth is unlike other planets in many ways. Perhaps the most important difference is that it is surrounded by air. Compared to the size of the earth (diameter of almost 8000 miles), this layer is not very thick. It goes upward from the earth's surface for only a few hundred miles. About half of all the earth's air is pulled into the 5 miles closest to the surface. This blanket of air doesn't vent into space. Everything that goes into the air mixes in this thin layer and deposits into our lungs, lakes and streams, or onto plants or soil. The National Park Service monitors atmospheric deposition in many parks across the country and studies the effect on park resources.

The cleaner the air is, the more likely you are to notice a small increase in pollution. Adding just 1 microgram of fine particles per cubic meter of air to a clean atmosphere will reduce how far you can see by 30 percent, from 243 miles (392 km) to 167 miles (270 km).

The National Park Service operates digital cameras at many parks. These cameras often show the effects of air pollution such as visibility impairment. Because these cameras are typically located near air quality monitoring sites, the camera web pages display other information along with the photo such as current levels of ozone, particulate matter, or sulfur dioxide air pollutants, visual range, and weather conditions. more »

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