Accumulation of airborne pollutants by lichens is, in part, the basis for their use as bioindicators of air quality. However, direct correlations between emission sources and pollutant element accumulation by lichens are often difficult to document. In this study copper accumulation patterns by lichens, along a copper pollution gradient, were examined. Data from four locations, along a 1500-km, north-south transect, with increasing distance from copper smelting activity (southeastern Arizona, southwestern New Mexico, and adjacent parts of Mexico), were collected. Lichens, representing two growth forms (foliose and fruticose), were collected from each study site. Copper and zinc concentrations were determined for all samples using PIXE analysis. In addition, ambient air concentrations of copper and zinc for all sites were obtained from the AQG web site ( Correlation of copper concentrations in lichen samples and ambient air along the transect showed a highly significant positive linear relationship (R2=.97). Data also showed that foliose lichens accumulated approximately twice as much copper as fruticose species. Cu/Zn ratios from lichen samples and ambient air were correlated along the transect and also showed a highly significant positive linear relationship (R2=.98). Background Cu/Zn ratios are < 0.5. Values from the two sites nearest the copper smelting operations ranged between 0.6 and 1.45, while the “clean” sites had values between 0.1 and 0.35. Substrate Cu/Zn ratios from the Arizona location were all below 0.5. These patterns support the use of element ratios in accurately predicting elevated element concentrations in lichen thalli and making more effective decisions relative to possible sources of pollutant elements.

Key words: Bioindicators, Copper, Element Ratios, Lichens, Zinc