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Quantitative monitoring of airborne lead pollution by a foliose lichen |
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| Authors: | David Schwartzman Margaret Kasim Lorin Stieff James H Johnson Jr |
| Institution: | 1. Department of Geology and Geography, Howard University, 20059, Washington, D.C., USA 2. Stieff Research and Development Inc., P.O. Box 263, 20795, Kensington, Md., USA 3. Department of Civil Engineering, Howard University, 20059, Washington, D.C., USA |
| Abstract: | The potential use of lichens as quantitative monitors of airborne heavy metal pollution has been demonstrated by measurements of Po210, Pb, Cd, Zn, and V levels in sequential growth of the foliose lichen Pseudoparmelia baltimorensis from three localities in the greater Washington, D.C. area. Samples were dated using the growth rate measured by Lawrey and Hale (1977). Po210, Pb, and V increase with age in a given colony. Higher levels of Pb, V, Cd, and Zn are present in samples from the two more polluted sites. The retention of heavy metals is consistent with trapping by an ion exchange mechanism. Since Po210 is the daughter product of in situ decay of Pb210, accumulated from atmospheric fallout of known rate, its levels can be used to calculate trapping efficiencies of Pb and retrospective fallout rates. These rates are similar to published data from rural and urban areas. |
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