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RESEARCH PRODUCT

Releasing rates of inorganic ions in lichens monitored by capillary zone electrophoresis as indicators of atmospheric pollution

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Abstract The releasing rates of inorganic ions in lichens when a thallus sample is sonicated under water, were studied. Ramalina farinacea samples taken from two locations exposed to atmospheric pollution sources at Els Ports (Castellon, Spain), and from three control locations, were used. Samples without visual symptoms of injuries were sonicated from 3 to 6 successive 10-min periods while renewing the water layer in between. Experiments with successive 2-min-sonication periods were also performed. The extracts were analysed by capillary zone electrophoresis, and K + , NH 4 + , Na + , Ca 2+ , Mg 2+ , Cl − , SO 4 2− and NO 3 − were detected. The apparently undamaged lichens sampled at locations exposed to SO 2 and ozone sources released high amounts of K + during the first sonication treatment and much lower amounts afterwards, whereas samples taken from control locations released approximately constant or increasing amounts of K + along the successive sonication treatments. The initial releasing rates of other ions showed no significant differences between samples from control and polluted locations. The initial releasing rates of K + and the SO 4 2− /Ca 2+ molar ratio were found to be useful as pollution indicators. The data were correlated with chlorophyll fluorescence quantum yield measurements, and with data obtained by visual evaluation of injury symptoms produced by pollution on representative lichen samples taken from the same locations.