Technical basis for narcotic chemicals and polycyclic aromatic hydrocarbon criteria. II. Mixtures and sediments

A method is presented for developing sediment quality guidelines (SQG) for narcotic chemicals in general and polycyclic aromatic hydrocarbons (PAHs) in particular. The guidelines can be applied to any individual or mixture of narcotic chemicals including PAHs using only the chemical's octanol/water partition coefficient. They are derived using the final chronic values for type I narcotics developed from a database consisting of LC50s for 145 chemicals and 33 species, including fish, amphibians, arthropods. mollusks, polychaetes, coelenterates, and protozoans. The target lipid model is used that accounts for the variations in toxicity due to differing species sensitivities as well as chemical differences. The SQGs are derived using the equilibrium partitioning model (EqP), and the results are compared to other sediment quality guidelines. The criterion for a mixture of PAHs is based on the known additivity of narcotic chemicals. The toxic unit concentration corrected for solubility is calculated for each chemical in the mixture and then summed. A total toxic unit greater than one indicates a toxic mixture. The prediction is compared to the results from an experiment using sediment spiked singly and with a mixture of PAHs. The toxicity and amphipod abundance of field-collected sediments are also examined.