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Samples from the Devon Island ice cap (Nunavut, Canada) were used to calculate the annual input of atmospheric formed perchlorate. Depth samples collected in the spring of 2006 were dated between 1996 and 2005. An optimized ion chromatography tandem mass spectrometry (IC-MS/MS) method with direct injection allowed detection of perchlorate in all analyzed samples. Concentrations varied between 1 and 18 ng L(-1), showed seasonality, and were correlated with the total ozone levels from the area. A significant correlation was observed between chloride and perchlorate only for data sets corresponding to peak perchlorate concentrations. Data available suggests that perchlorate from the Arctic snow was formed in the atmosphere following two different mechanisms. Stratospheric chlorine radicals reacted with ozone year around, producing concentrations of perchlorate correlated with the total ozone level. The second pathway was specific to the summer months, when the amounts of perchlorate were correlated with the chloride concentrations, suggesting a possible tropospheric formation. Analysis of a deep ice core sample confirmed that perchlorate was present in precipitation at similar concentration more than 2000 years ago. Perchlorate ion represents a sink for the stratospheric chlorine, being removed via precipitation. The estimated amount of perchlorate that reached the Arctic in 2005 was 41-86 t.

Summary Potassium efflux is a useful experimental quantity for assessing damage to lichens exposed to SO2. This SO2‐induced K+ efflux is biphasic in response to increasing concentrations of aqueous SO2. The first phase can be extrapolated to identify the SO2 concentration at which no K+ release occurred above the control values. This threshold concentration was used to determine the relative sensitivities of various lichen species. Good agreement was observed between the total K+ lost and the reduction in the total photosynthetic 14C‐fixation rates. The magnitude of the SO2‐induced K+ efflux indicated that release occurred from intra‐cellular sources. The kinetics of the release process and the effects of SO2 on membrane integrity are discussed.

X-ray fluorescence was adapted to the analysis of 22 terricolous lichen species from 14 sites in the Mackenzie Valley, Northwest Territories, and 7 species from the Sudbury District of Northern Ontario. X-ray fluorescence (XRF) proved to be faster and exhibited better sensitivity and reproducibility than conventional analytical techniques; also, the samples were not destroyed in the analysis. Procedural details of the XRF method are given. The levels of copper, iron, nickel, and sulphur in Arctic lichens were similar to those found in lichens growing on the periphery of the Sudbury pollution zone but very much lower than in specimens nearer the nickel smelter. A linear relationship between concentration and the reciprocal of the distance from the Copper Cliff smelter was confirmed for the occurrence of these four elements in samples collected along a 60-mi NNW transect.

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