DYNAMIC COMPARTMENT MODELING OF HEAVY METAL ACCUMULATION IN MOSSES

Epiphytic mosses and lichens have been utilized in numerous studies to reconstruct temporal and spatial heavy metal deposition patterns. However, the relationship between atmospheric metal deposition and moss and lichen tissue metal concentrations is not well understood. The development of accurate models to describe this relationship depends on understanding all parameters impacting accumulation of atmospheric deposition. Limited understanding of this relationship restricts the use of mosses and lichens as biomonitors. Accumulation of atmospheric deposition occurs within extra-cellular, intra-cellular and inter-cellular compartments. Each compartment concentration is dependent on input and output fluxes determined by ambient, physiological, and biological parameters. An improved understanding of the relationship between atmospheric deposition and metal accumulation in mosses and lichens will improve the viability of this tool in assessing atmospheric metal concentrations.

This study will develop a dynamic compartment model for ectohydric mosses that describes cycling of metals through moss tissue and develops accurate correlations between tissue concentrations and atmospheric metal deposition. Results will be reported for the first series of conceptualized experiments. This includes the evaluation of annual metal cellular compartment concentrations in moss from three sites selected to represent an urban environment, a site impacted by a point source, and a relatively natural site. Annual metal cellular compartment concentrations will be evaluated by sequential elution. Concentrations for moss collected from the site impacted by the point source will be compared to Oregon DEQ air monitor data. Correlations between annual compartmental tissue concentrations and atmospheric concentrations will be evaluated. Modeling external and internal fluxes will allow mosses to be used as accurate depictions of atmospheric metal deposition rates. Spatially-intensive monitoring using mosses can supplement existing direct monitoring networks. Tissue concentrations could be used to create fine-scale pollution concentration maps, ultimately, facilitating the identification of metal hotspots and emission sources.