THE APPLICATION OF CONTROLLED-RELEASE AND QSAR TECHNOLOGY TO SEDIMENTTOXICITY

Pharmacology and toxicology are two disciplines that often concentrate on different ends of the same dose-response curve. Two concepts from pharmacology have therefore been applied to the problem of understandi ng sediment toxicity. The first contribution is to consider sediment p articles as controlled release systems, that deliver a slower but more continual dose of toxicants to the sediment-associated fauna. Control led release systems have their effects because of surface coats (such as exopolymers) or surface erosion systems. The second approach that h as been widely applied in toxicology is the quantitative structure-ana lysis relationship (QSAR) that attempts to predict the biological acti vity 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-, SO32-) and inorganic crystal s with ion binding groups (PO43-). Particles were fed to the mussel My tilus edulis and shown to be sources of Zn-65 ions that were incorpora ted into the digestive gland. During digestion, particles are usually exposed to decreases in pH due to extracellular or intracellular (lyso somal) 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.