EFFECTS OF SEDIMENT HOMOGENIZATION ON INTERSTITIAL WATER PCB GEOCHEMISTRY

Sediment homogenization is a common practice in many contaminated sedi ment toxicity testing and chemical analysis protocols. A primary goal of sediment homogenization is to reduce inter-replicate variability. I n this study, the geochemical effects of sediment homogenization were evaluated by measuring the concentration and distribution of polychlor inated biphenyls (PCBs) in environmentally contaminated marine sedimen t interstitial waters. Sediment homogenization, prior to isolation of interstitial waters, was found to significantly increase the concentra tion of PCBs in the dissolved and colloidal phases-generally by a fact or of two. Long-term storage (i.e., several months) of sediments follo wing mixing appeared to allow interstitial water distributions of PCBs to return to ''normal,'' although a storage artifact may also be pres ent. This study indicates that homogenization results in significant c hanges in the concentration of PCBs in environmentally contaminated se diment interstitial waters. Consequences of these changes on inference s made based on toxicity tests or chemical analyses using homogenized sediments need to be considered and studied further.