The use of lichens in atmospheric deposition studies with an emphasis on the Arctic

Abstract

Lichens are well known to accumulate and retain a variety of contaminants and therefore are very useful in documenting relative temporal and spatial deposition patterns of contaminants. As one of the dominant and most widespread groups of arctic plants, they have been used frequently in deposition studies, particularly as related to redionuclides and metals. Many lichens are highly dependent on atmospheric sources of nutrients. It is assumed that deposition and accumulation processes related to contaminants occur in ways analogous to nutrient deposition and accumulation. As receptors of atmospheric deposition, lichens have advantages over vascular plants due to the lichens' relative lack of morphological variability with time, their lack of a cuticle and associated stomates and their lack of roots. Mechanisms by which contaminants are accumulated and tolerated by lichens are briefly reviewed. Data regarding elevated elemental concentrations associated with certain industrial activities in relation to putative background levels are tabulated. The use of enrichment factors and multivariate analyses provide two procedures by which patterns in complex data sets can be discerned where pollution is minimal. Such analyses are presented as a case study from the Northwest Territories of Canada. Finally, arctic lichens may also be useful in documenting deposition patterns of persistent organic contaminants, particularly in relation to the lichen-caribou-human food chain, as was previously documented for radionuclides.