2002 Elemental Analysis of Boundary Waters Canoe Area Lichens of the Superior National Forest, Minnesota: Final report.

Abstract

In the 1986 report on the lichens and air quality in the Boundary Waters Canoe Area it was recommended that a restudy of the elemental analyses of lichens be done every five years. A restudy was done in 1992 and 1997. The present report is on the third restudy done in 2002 using the same methods, species and localities. The most significant finding of the fourth sampling is a dramatic decrease in Ph content in the lichens, which continues to decline and not level off. There is also a consistent upward trend in alkali and alkaline earth metals which is unexplained. Sodium shows a significant decrease from west to east, suggesting a source near Lac La Croix.

Isabella Lake continues to show high concentrations of some elements. Hypogymnia physodes, an important biomonitoring species in this study, continues to show elevated levels of Ca, Mg and Mn.