Out of a Clear Blue Sky
Regional haze mars scenic vistas, even in Minnesota
A Forest Service IMPROVE automated monitoring station just outside the BWCA shows the distinct difference between a clear day (more than 125 miles visibility, above) and a hazy one (less than thirty, below).
Air pollution affects not only America?s urban areas, but its national parks and wilderness areas as well. On bad days, ?regional haze? cloaks some of our most treasured ?purple mountain majesties? in brown or white gauze. Many of the 280 million Americans who visit parks such as the Grand Canyon or Glacier National Parks annually are surprised to find they can?t get a clear view of the scenic wonders they?ve come to see.
The cause might surprise outdoor enthusiasts. It is fine particles similar to those that blight our urban skies. Some haze is natural, part of prevailing climate dynamics. After all, the Great Smoky Mountains were known by that name long before the mid-South industrialized. Dust, organic compounds, smoke from forest fires, and humidity figure into what?s considered natural (unpolluted) visibility.
In pre-settlement days, the farthest a person could expect to see on a clear day was between 60 and 80 miles in the Eastern U.S., and 110 to 115 miles in the West. Today, however, typical visual range in the West is 60 to 90 miles. In the East, it?s only 15 to 30 miles.
In Minnesota, sulfate is an important component of haze. Nitrate and organic carbon are significant in winter and summer, respectively.
One goal of the Clean Air Act is to restore the view of these national treasures to the clarity that onlookers enjoyed before the advent of man-made air pollution. Class I areas, as defined in the Act, are 156 national parks, monuments and wilderness areas in the United States. Two ? Voyageurs National Park and the Boundary Waters Canoe Area Wilderness (BWCA) ? are in Minnesota. Even remote, far-north Class I areas such as Voyageurs and the BWCA become hazy from transport of fine particles high in the atmosphere, where they can be carried long distances.
In 1999, the EPA issued regulations designed to further reduce haze and protect visibility, as well as specific programs to reduce particle air pollution overall. For example, the U.S. Department of Agriculture National Forest Service?s IMPROVE (Interagency Monitoring of Protected Visual Environments) network collects air samples and provides monitoring data on visibility and fine particulates at 163 Class I locations, including the BWCA and Voyageurs.
The equipment at IMPROVE sites includes samplers to measure airborne particles and particle mass, along with light-monitoring equipment and a camera. According to Trent Wickman of the Forest Service?s Duluth office, ?The contributions of pollutants at the [BWCA] are clear. A large portion is ammonium sulfates, which are pretty clearly tied to coal combustion.? He added there?s not sufficient data yet to provide trend analysis, but that ?we?re getting to that point.?
? Ralph Pribble