Historical and current atmospheric deposition to the epilithic lichen Xanthoparmelia in Maricopa County, Arizona
Spatial variation of elemental deposition to lichen receptors across Maricopa County, Arizona, USA is documented for 1998 and historical trends relative to 1974 are documented. Spatial patterns of atmospheric deposition of trace elements to an epilithic lichen were assessed using a spatial grid of 2...
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Published in: | Environmental pollution (1987) Vol. 125; no. 1; pp. 21 - 30 |
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Main Authors: | , , , , , |
Format: | Journal Article Conference Proceeding |
Language: | English |
Published: |
Oxford
Elsevier Ltd
01-01-2003
Elsevier |
Subjects: | |
Online Access: | Get full text |
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Summary: | Spatial variation of elemental deposition to lichen receptors across Maricopa County, Arizona, USA is documented for 1998 and historical trends relative to 1974 are documented.
Spatial patterns of atmospheric deposition of trace elements to an epilithic lichen were assessed using a spatial grid of 28 field sites in 1998 throughout Maricopa County, Arizona, USA. In addition, samples of
Xanthoparmelia spp. from Arizona State University lichen herbarium material (1975–1976) was utilized for a limited number of sites in order to explore temporal trends. The lichen material was cleaned, wet digested and analyzed by ICP-MS for a suite of elemental concentrations [antimony (Sb), cadmium (Cd), cerium (Ce), chromium (Cr), cobalt (Co), copper (Cu), dysprosium (Dy), europium (Eu), gadolinium (Gd), gold (Au), holmium (Ho), lead (Pb), lutetium (Lu), neodymium (Nd), nickel (Ni), palladium (Pd), platinum (Pt), praseodymium (Pr), samarium (Sm), scandium (Sc), silver (Ag), terbium (Tb), thulium (Tm), tin (Sn), uranium (U), ytterbium (Yb), yttrium (Y), and zinc (Zn)]. Cluster analysis and principal component analysis suggest three major factors, which, depending on regional aerosol fractionation, explain most of the variation in elemental signatures: (1) a group of widely distributed rare earth elements (2) a highly homogenous Co, Cr, Ni, and Sc component representing the influence of mafic rocks, and (3) anthropogenic emissions. Elemental concentrations in Maricopa County lichens were generally comparable to those reported for relatively unpolluted areas. Only highly urbanized regions, such as the greater Phoenix Metropolitan Area and the NW corner of the county, exhibited elevated concentrations for Zn, Cu, Pb, and Cd. Lead levels in lichens have fallen over the last 30 years by 71%, while Zn concentrations for some regions have increased by as much as 245%. From the spatial pattern of elemental deposition for Cd, Cu, Ni, Pr, Pb, and Cu, we infer that agriculture, mining, industrial activities, and traffic probably are the major air pollutant sources in Maricopa County. |
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ISSN: | 0269-7491 1873-6424 |
DOI: | 10.1016/S0269-7491(03)00088-5 |