Abstract :
Pharmacology and toxicology are two disciplines that often concentrate on different ends of the same doseresponse curve. Two concepts from pharmacology have therefore been applied to the problem of understanding sediment toxicity. The first contribution is to consider sediment particles as controlled release systems, that deliver a slower but more continual dose of toxicants to the sediment-associated fauna. Controlled release systems have their effects because of surface coats (such as exopolymers) or surface erosion systems. The second approach that has been widely applied in toxicology is the quantitative structure-analysis relationship (QSAR) that attempts to predict the biological activity of certain groups of chemicals. In order to apply this concept to metal availability, model materials have been employed, based on ion exchange resins with known ligands (COO−, SO2−3) and inorganic crystals with ion binding groups (PO3−4). Particles were fed to the mussel Mytilus edulis and shown to be sources of 65Zn ions that were incorporated into the digestive gland. During digestion, particles are usually exposed to decreases in pH due to extracellular or intracellular (lysosomal) processes. It is suggested, therefore, that a change in pH from 8 to 5 probably simulates most accurately the QSAR for the unloading of metals from sediment surfaces with various binding features.
