PARENT SESSION
PW17 - Problems of Scale in Assessment of Contaminant Fate & Transport
Wednesday, 20 November 2002
8:00 AM to 6:30 PM
Exhibit Hall
(P903) A SPATIALLY- AND BIOENERGETICALLY-EXPLICIT TERRESTRIAL ECOLOGICAL EXPOSURE MODEL.
Hope, Bruce*,1, 1 Oregon Department of Environmental Quality, Portland, OR, USA
ABSTRACT- In typical exposure models, dose is a function of ingestion rate, which is a function of field metabolic rate and food energy availability. It is implicitly assumed that neither food energy or ingestion rate are limited. This is unlikely to be true in the field. Poor habitat quality (expressed as limited or no food energy) or a physiologically-limited maximum ingestion rate may collectively limit energy intake. A receptor may thus be as much at risk from lack of energy as from toxicant effects as it moves through space and time. An existing spatially-explicit exposure model was enhanced to: express "habitat quality" in terms of gross energy available from a suite of habitat-specific food types, follow fulfillment of a receptor's daily energy needs as it traverses habitat patches with varying gross energy levels, link intake of contaminants to food consumed to meet these daily energy needs, and track contaminant doses and resulting tissue residue levels as a receptor moves through habitat patches with differing levels of contamination. Work with this spatially- and energetically-explicit model produced the following insights: (1) Relative spatial relationships between the locus of a receptor's foraging area and that of contaminated habitat do effect its degree of exposure; (2) But, owing to assimilation, depuration, and movement, there is no necessary strong linkage between residue levels in a receptor collected at a specific location and contaminant levels at that location should not be assumed; (3) The potential for contaminated individuals to transport contamination (as tissue residue) far from the source of that contamination should always be a consideration; (4) Any free living terrestrial receptor faces a constant demand for food energy, making the presence of poor quality (low metabolizable energy) habitat as great a potential threat as the presence of contamination.
Key words: spatially-explicit, bioenergetic, exposure model, ecological risk assessment