COMPARISON OF METHODS FOR CONDUCTING MARINE AND ESTUARINE SEDIMENT POREWATER TOXICITY TESTS - EXTRACTION, STORAGE, AND HANDLING TECHNIQUES

A series of studies was conducted to compare different porewater extra ction techniques and to evaluate the effects of sediment and porewater storage conditions on the toxicity of pore water, using assays with t he sea urchin Arbacia punctulata. If care is taken in the selection of materials, several different porewater extraction techniques (pressur ized squeezing, centrifugation, vacuum) yield samples with similar tox icity. Where the primary contaminants of concern are highly hydrophobi c organic compounds, centrifugation is the method of choice for minimi zing the loss of contaminants during the extraction procedure. No diff erence was found in the toxicity of pore water obtained with the Teflo n(R) and polyvinyl chloride pressurized extraction devices. Different types of filters in the squeeze extraction devices apparently adsorbed soluble contaminants to varying degrees. The amount of fine suspended particulate material remaining in the pore water after the initial ex traction varied among the methods. For most of the sediments tested, f reezing and thawing did not affect the toxicity of porewater samples o btained by the pressurized squeeze extraction method. Pore water obtai ned by other methods (centrifugation, vacuum) and frozen without addit ional removal of suspended particulates by centrifugation may exhibit increased toxicity compared with the unfrozen sample. The toxicity of pore water extracted from refrigerated (4 degrees C) sediments exhibit ed substantial short-term (days, weeks) changes. Similarly, sediment p ore water extracted over time from a simulated amphipod solid-phase to xicity test changed substantially in toxicity. For the sediments teste d, the direction and magnitude of change in toxicity of pore water ext racted from both refrigerated and solid-phase test sediments was unpre dictable.