A Preliminary Study On Monitoring Heavy Metal Atmospheric Deposition By Lichens In King George Island, Antarctica

Lichens are a symbiotic association of Fungi with algae or cyanobacteria; the lichenized fungi obtain potosynthetic substances from algae or cyanobacteria, and protects the photosynthetic symbionts. Because of their high sensitivity to air pollution, very slow growth rate, lacking of epidermis which are generally presented in higher plants, large permeability and strong enrichenment to heavy metals, lichens have been widely used in study of heavy metal atmospheric deposition by transplantation. Such studies are quite few in Antarctica, and therefore further study is badly needed.Taxonomic study on lichens collected from King George Island of Antarctic was conducted unsing routine morphological methods. The results show there are ten common foliose and fructicose lichens, viz.: Caloplaca regalis, Cladonia borealis, Himantormia lugubris, Placopsis contortuplicata, Ramalina terebrata, Sphaerophorus globosus, Stereocaulon alpinum, Umbilicaria antarctica, Usnea antarctica and Usnea aurantiacoatra. The morphological characteristics, habitats, geographical distribution were detailed described in the paper. Photoes of each lichens, and the key to the investigated species from Fildes peninsula, King George Island, Antarctica were also presented.The ecological distribution of the identified lichens was analyzed on the basis of specimen exmination, and information from litterature records. The results show that three groups can be found in the ten common lichens: widespread, saxicolous and terreicolous lichens.1) The widespread lichens includes three species, Usnea aurantiacoatra,Himantormia lugubris and Usnea antarctica. These lichens are most common in the investigated area, and do not show a perticular preference for substances. They are the main component of terrestrial vegation in Fildes peninsula and Ardley island.2) Saxicolous lichens include 4 species, Caloplaca regalis, Ramalina terebrata, Umbilicaria antarctica, Placopsis contortuplicata. These lichens were only found on rocks. Among which, Caloplaca regalis and Ramalina terebrata prefers the habitats with high distrubace from seabirds, and often grow together with Umbilicaria antarctica to form the important component of coastal lichen communities. While Placopsis contortuplicata often be found in scree microhabitats. 3) The terricolous lichens include 3 species: Cladonia borealis, Sphaerophorus globosus, Stereocaulon alpinum. They always grow on soil and form terricolous communities with mosses.Nine lichen species collected from King George Island, western Antarctica, viz. Usnea aurantiacoatra, Himantormia lugubris, Cladonia borealis, Caloplaca regalis, Sphaerophorus globosus, Stereocaulon alpinum, Placopsis contortuplicata, Ramalina terebrata and Umbilicaria antarctica were used to analyze differences in enrichment capability of Co, Cu , Cr, Al, Pb, Ni and Cd. After being exposed to air for a period of 2 months in Baoding, Hebei Province, heavy metal contents were measured by atom absorption spectrometry. The results show that different lichens have different ability to accumulate heavy metals in atmospheric deposition. Himantormia lugubris has strong enrichment ability on Pb, Co, Al and Cu in the atmospheric deposition. Umbilicaria antarctica has strong enrichment ability on Ni、Cr and Cd in the atmospheric deposition. And Usnea aurantiacoatra has strong enrichment ability on all the 7 elements in the atmospheric deposition. Therefore, when monitoring atmospheric Pb, Co, Al and Cu, Himantormia lugubris is a good choice; Umbilicaria antarctica should be given priority when detecting atmospheric Ni, Cr and Cd; Usnea aurantiacoatra is a good choice when we detect all the 7 heavy metal elements content of atmospheric deposition. Himantormia lugubris and Umbilicaria antarctica is the best combination while we detect Al, Pb, Ni, Co, Cu, Cr and Cd content of atmospheric deposition.By using inductively coupled plasma mass spectrometry (ICP-MS) and inductively coupled plasma optical emission spectrometry(ICP-OES), 13 metal elements (V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Cd, Pb, Al and Ti) in thallus of 6 lichens (Himantormia lugubris, Ramalina terebrata, Umbilicaria antarctica, Usnea aurantiacoatra, Caloplaca regalis and Sphaerophorus globosus) collected from Fildes Peninsula were measured. Difference in thallus metal content among 4 collection times (1983、1993、2006、2010) were analyzed, and the enrichment fators of metals were calculated. The results clearly show 1) most of the metal elements in Himantormia lugubris and Usnea aurantiacoatra derive from the attached substrates, while it is not true for Umbilicaria antarctica, Caloplaca regalis and Ramalina terebrata; 2) six metals, V, Co, As, Fe, Ti and Al, are mainly from the substrates, while Cr, Cu, Ni, Zn, Pb, Cd and Mn are mainly from other sources rather than from the substrates; 3) all measured metals are not significantly differed in thallus content among four collection times, regardless the source of metals. These results indicate that in the recent 20 years, atmospheric deposition is not the dominant source of heavy metals in lichen thallus. The atmospheric heavy metal pollution in Antarctica is minimal, and thus its variation is not sufficient to obscure the influence of substrate on heavy metal content in lichen thallus.