Rodney L. Stevens¹, Laila T. Johannesson²

(1) Göteborg University, Göteborg, Sweden
(2) Göteborg University

ABSTRACT: What Do You Mean by Bioavailability?

Environmental risks are often set in relation to contaminant accumulation in organisms. "Bioavailability" is an attractive term, referring to an important net effect of contamination. An increasing interest for bioassay testing further emphasises the need for site-specific relevance of sediment toxicity. But focusing upon this end result begs the question of how biological, geochemical and sedimentological processes interrelate, and "bioavailability" needs further specification to account for the spatial and temporal variability of most environments. Our conclusion is that the sediment environmental relationships relevant for characterizing bioavailability can be integrated using the facies concept, which has a long tradition in sedimentology. Toward this goal, a classification using "Integrated Facies" of the sediment system will be presented and illustrated with examples from Göteborg Harbor, Sweden. These facies are initially based upon visual descriptions of physical, geochemical and biological attributes, but provide an open framework necessary for the details provided by future analyses, particularly the specialised information from detailed geochemistry, microfaunal or toxicity analyses. The facies divisions should balance the value of site-specific measures with the need for obtaining sufficient data for statistical definitions of parameter relationships, contaminant background distributions and spatial variability within each facies. The connection of this classification to an open database structure should also be favourable for techniques using stochastic or deterministic modelling. Simple geochemical threshold levels or enrichment factors should be considered suspect until comprehensive and site-specific evaluations have established the relationships necessary to justify these widely applied classifications.

AAPG Search and Discovery Article #90906©2001 AAPG Annual Convention, Denver, Colorado