Biomonitoring Heavy Metal Pollution with Lichens
Certain characteristics of lichens and bryophytes meet the specifications required for biological monitors. These include large geographical ranges, allowing the comparison of metal content in diverse regions, and a morphology that does not vary with seas
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PROTOCOL
Biomonitoring Heavy Metal Pollution with lichens JACOB GARTY
Introduction Certain characteristics of lichens and bryophytes meet the specifications required for biological monitors. These include large geographical ranges, allowing the comparison of metal content in diverse regions, and a morphology that does not vary with season, thus enabling accumulation to occur throughout the year (Puckett 1988). Lichens integrate long-term deposition patterns and do not reflect necessarily short-term patterns, measured by most atmospheric scientists. The advantages of biomonitoring with lichens over instrumental monitoring are that lichens accumulate most of the elements of the periodic table, are usable at low expense, do not depend on electricity for their operation, do not need treatment and are easy to hide, thus discouraging vandalism. Inexpensive biomonito ring systems also provide much information on the impact of airborne heavy metals on physiological processes. Expensive automatic instrumental air monitoring, on the other hand, provides detailed information on the concentration of gases (e.g S02, NO x , CO, 0 3 ) in the air, whereas airborne heavy metals are often not documented. Of the large number of lichen species, only a few have been used as biomonitors of trace-element deposition, to assess the degree of atmospheric contamination. However, the study of these few species has yielded hundreds of publications. In this chapter, the term "passive biomonitoring" will be used to denote monitoring that involves analysing lichens in situ. In "active biomonitoring" lichens are collected from an area with clean air, exposed to polluted area and then analysed for metal accumulation.
Jacob Garty, Tei Aviv University, Department of Plant Sciences and Institute for Nature Conservation Research, The George S. Wise Faculty of Life Sciences, Tel Aviv, 69978, Israel (phone +972-3-6407468; fax +972-3-6409380; e-mail [email protected])
I. C. Kranner et al. (eds .), Protocols in Lichenology © Springer-Verlag Berlin Heidelberg 2002
27 Biomonitoring Heavy Metal Pollution with Lichens
Lichens accumulate metals both by particulate trapping and via ion exchange. Heavy metal containing particles may be detected in close association with mycobiont hyphae, e.g. in Caloplaca aurantia sampled in a contaminated site in Tel Aviv (Garty et al. 1979). The particles appeared in a variety of shapes and sizes and were found to consist ofTi, Cr, Fe, Ni, Mn and Zn. Scanning electron micrographs of Parmelia chlorochroa rhizinae produced by Gough and Erdman (1977) show the presence of irregularly shaped foreign matter and fly-ash micro spheres. The assumption that metal-containing particles are enclosed in the thallus was put forward based on the coefficient of variation (CV) obtained by SD/mean values of heavy metal content (Garty et aI. 1977). These authors assumed that CV s indicate the mode of aerial dispersion of particles containing heavy metals. Very low CV s were assumed to indicate a low variation due to an even suspension of
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