Sediment quality assessment survey and toxicity identification evaluation studies in Lavaca Bay, Texas, a marine...

A sediment quality assessment survey was conducted in Lavaca Bay, Texas, in proximity to a marine Superfund National Priority List (NPL) site. Previous studies at this site had focused primarily on the degree and extent of mercury contamination. The purpose of this survey was to determine the potential ecotoxicological impacts of contaminants, using sensitive sediment toxicity tests in conjunction with a comprehensive chemical analysis of the sediments. In addition, phase I toxicity identification evaluation (TIE) studies were conducted at several of the more toxic sites. Sea urchin (Arbacia punctulata) fertilization and embryological development tests with sediment pore water were employed to assess the toxicity of the sediments. Elevated levels of mercury were found in a number of samples as much as 10-20 times that of background. Six stations had total polycyclic aromatic hydrocarbon (PAH) concentration above the probable effect level (PEL) guideline value, and some stations had concentrations as much as 1000 times above background levels. Eighteen of the 24 stations exhibited toxicity in one of the toxicity tests, while 14 stations were toxic in both tests. A number of stations within the fish closure area exceeded 8-16 of the PEl guidelines. Both aeration and the C18 column treatments were effective in reducing toxicity from the pore water of the two stations included in the TIE. This information, in conjunction with the fact that two of the four stations with the highest mercury concentrations were not toxic, suggests that the toxicity observed in this study is primarily due to organics, probably PAHs, and not mercury. We recommend that these other contaminants of concern be considered in any remedial actions that are planned for this NPL site and that impacts on the ecosystem, as well as human health issues, also be considered.