title: FT-Raman spectroscopy of lichens on dolomitic rocks: an assessment of metal oxalate formation.
abstract: The FT-Raman spectra of five epilithic lichen taxa growing on dolomite and magnesium-rich carbonate rocks have been analysed and interpreted for the key molecular marker bands associated with calcium oxalate monohydrate (whewellite), calcium oxalate dihydrate (weddelite) and magnesium oxalate dihydrate. From the results, it can be concluded that the biomineral product of lichen biodeterioration involves the calcareous part of the substratum only; no trace of magnesium oxalate has been found in the Raman spectra. Two of the species, Lecanora sulfurea and Aspicilia calcarea, produce calcium oxalate monohydrate exclusively, but Dirina massiliensis f. sorediata, D. massiliensis f. massiliensis and Tephromela atra produce significant quantities of the dihydrate. An explanation is advanced for the exclusive accumulation of calcium oxalate into the lichen thallus despite the significant presence of magnesium ions.
authors.affiliation: Department of Chemical and Forensic Sciences, University of Bradford, Bradford, UK BD7 1DP.
authors.forename: Howell G M
authors.initials: HG
authors.lastname: Edwards
authors.forename: Mark R D
authors.initials: MR
authors.lastname: Seaward
authors.forename: Stacey J
authors.initials: SJ
authors.lastname: Attwood
authors.forename: Samantha J
authors.initials: SJ
authors.lastname: Little
authors.forename: Luiz F C
authors.initials: LF
authors.lastname: de Oliveira
authors.forename: Mauro
authors.initials: M
authors.lastname: Tretiach
mesh_terms: D002129:Calcium Oxalate / Q000032:analysis; D019015:Geologic Sediments; D008011:Lichens / Q000737:chemistry* / Q000378:metabolism; D010070:Oxalates / Q000032:analysis*; D013059:Spectrum Analysis, Raman / Q000379:methods
chemical_list: D010070:Oxalates; D002129:Calcium Oxalate