ABSTRACT
Historically the standard approach for assessing the quality or potential toxicity of marine or estuarine sediments has been to expose macrobenthic organisms directly to the whole sediments for a specified period of time after which the survival of the test species is determined. Equilibrium-partitioning theory predicts that porewater is the controlling exposure medium in the toxicity of sediments to infaunal organisms. Centrifugation is the most commonly employed method for extracting porewater from sediments. One of the most commonly employed methods for extracting porewater is squeezing sediments using either mechanical or pneumatic pressure. Collection devices containing a dialysis membrane or filter sometimes referred to as "peepers", have been used to obtain porewater by means of passive diffusion. In sediment quality assessment surveys in bays and estuaries particularly, it is not uncommon to obtain porewater with a wide range of salinities, pH, dissolved oxygen levels, and varying concentrations of ammonia and sulfide.
