Understanding the performance of different lichen species as biomonitors of atmospheric dioxins and furans: potential for intercalibration.

The aim of this study was to compare the performance of two lichen species--Xanthoria parietina and Ramalina canariensis--as biomonitors of the toxic organic compounds dioxins and furans (PCDD/Fs). For that purpose, the concentrations and profiles of PCDD/Fs found in samples of these two lichen species were compared. Results showed that R. canariensis presented higher concentrations than X. parietina and that the PCDD/F homologue profiles were substantially different between these species. Xanthoria parietina appeared to be a more efficient interceptor of more chlorinated PCDD/Fs and also of particles, whereas R. canariensis mainly reflected less chlorinated PCDD/Fs. Results also showed that the PCDD/F profile of X. parietina differed from the one found in other foliose and fruticose lichen species. Despite the differences observed between the profiles of R. canariensis and X. parietina, the calibration of PCDD/F concentrations between the two species was achieved, allowing the biomonitoring of PCDD/Fs at a regional scale using both species simultaneously.