Trend worsening for pollutant in 16 national parks

A pollutant that can slowly trigger changes in the lives of plants and animals is increasingly being found in 16 National Park Service sites, mostly in the western United States. Air quality data obtained by The Associated Press shows significant worsening trends for ammonium in several flagship parks, including Yellowstone, Mount Rainier and Utah's Canyonlands. At Colorado's Rocky Mountain National Park, researchers have already seen subtle shifts in the alpine tundra, where some of the park's trademark wildflowers are being replaced by grass. Scientists worry that increases in nitrogen-rich ammonium could gradually transform other national parks' sensitive ecosystems, affecting everything from microscopic algae and plants to fish, frogs and other wildlife. Ammonia is a mix of hydrogen and nitrogen. When it mixes with water, it becomes ammonium and acts as an extra dose of fertilizer when it reaches the ground. It's commonly associated with fertilizers, large animal feeding operations, vehicle exhaust and factory emissions. It also occurs naturally...AP