Lichen Evidence for Changes in Atmospheric Pollution in Shenandoah National Park, Virginia

Recently collected specimens of the lichen Flavoparmelia baltimorensis from Shen- andoah National Park in Virginia, especially those from higher elevations, contain higher concen- trations of sulfur, and lower concentrations of lead than specimens collected from the same sites at various times in the past. These results suggest long-term increases in regional sulfur pollution and a corresponding decline in lead pollution. The well-documented ability of some lichens to accumulate elements from the atmosphere has led to their frequent use as monitors of atmospheric pollution. In an on-going effort to assess levels of air pollutants in Shenandoah National Park in Vir- ginia, we have investigated lead and sulfur accu- mulation by specimens of the lichen, Flavoparmelia baltimorensis (Gyelnik & F6riss) Hale, a common species that has been collected in the park at various times during its 50-year history. Our objective was to compare sulfur and lead concentrations found in recently collected specimens to concentrations of the same elements in specimens collected in the past. Such a retrospective element analysis is valu- able because it provides information about changes in pollution deposition patterns with time.