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A spatially and bioenergetically explicit terrestrial ecological exposure modelOregon Department of Environmental Quality, 811 SW Sixth Avenue, Portland, Oregon 97204, USA, hope.bruce{at}deq.state.or.us 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 nor ingestion rate is limited. This is unlikely to be true in the field. Poor habitat quality (expressed as limited or lacking 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. To explore this possibility, an existing spatially explicit exposure model (SE3M) was enhanced to: 1) express habitat quality in terms of gross energy available from a suite of habitat-specific food types, 2) track fulfillment of a receptors daily energy needs as it traverses habitat patches with varying gross energy levels, 3) link intake of contaminants to food consumed to meet daily energy needs, and 4) track contaminant doses and resulting tissue residue levels as a receptor moves through habitat patches with differing levels of contamination. A feedback term through which chemical stressors affect a receptors ability to intake and process energy was not considered at this time. The now spatially and energetically explicit exposure model, SE4M, provides a platform for exploring spatial and bioenergetic factors that may influence a receptors acquisition of energy and contaminant tissue residues as it moves through space and time. An application of this model would be to provide predictions of tissue residue levels that are accessible to calibration or validation with empirical field data.
Key Words: bioenergetic model ecological risk assessment spatially explicit model
Toxicology and Industrial Health, Vol. 17, No. 5-10,
322-332 (2001) |
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