Lichen metal contents as correlates of air filter measurements

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Abstract
Lichens and air-borne particulates were analysed for Pb, Zn and Cu content at sites for which air quality data and traffic flow were known. Three localities were sampled: SHU, HP and BW, which were 20, 100 and 500 km from New York City. The foliose lichen Parmelia caperata was found at all three localities, and the fruticose Cladina rangiferina at the two rural localities only. Particulates collected on air filters at each locality contained 1.7× as much Pb as Cu and 4–20× as much Pb as Zn. Lichens selectively accumulated Zn at all sites, and Pb at roadside sites, but not at forest sites. Filters had ratios of Pb/Zn twice as high as those in P. caperata, and 10× higher than C. rangiferina. Differences in lichen response to Pb, Cu and Zn suggest that when using lichen metal content to assess ecosystem impacts including effects on human health, adjustments should be made for accumulation rates of metals by the lichens used for biomonitoring.