Ammonium, a pollutant that can trigger ecological change, is increasingly showing up in National Park Service sites in the West, according to Mike Star of the Associated Press. Ammonium, which is often linked with agricultural operations and urban sources, can change soil and water chemistry. In large doses, it can affect the diversity of species. So far, scientists have been unable to pinpoint the source of the ammonium.
Pollutant worsens in 16 national parks
