Development of Methodology and Apparatus for the Bioassay of Oil

Abstract

ABSTRACT Bioassay of petroleum or its components presents technical problems not encountered in testing of soluble and less volatile materials. The literature includes numerous accounts of toxicity for both crude and refined oil. In most instances, the indices of toxicity are based on metered inflow. Few such studies, however, consider the concentrations of oil in the water column to which the test organism is exposed. Essentially oil and water form a two-phase system. Even on a continuous flow basis, oil cannot be maintained as a homogeneous oil-water mixture within a bioassay test system. Homogenization techniques produce a totally artificial environment dissimilar to natural conditions characterized by a slick of floating oil. Furthermore, since subsurface oil concentrations may represent a small fraction of the metered inflow, currently applied indices of toxicity based on metered inflow may be erroneous. This presentation summarizes techniques that may be applied in the bioassay of oil and other non-miscible materials. Special attention is directed to the above problems. Bioassay procedures are described that are conducted in flow-through tanks equipped with gravity oil metering systems and static mixers to equilibrate diluent water. Oil concentrations measured at different depths are utilized to calculate the mean level of exposure of the test organisms in the water column. Habitat preference and behavior of the test organism during bioassay were assessed in relationship to toxicity. This work was performed under contract to the American Petroleum Institute, Committee on Environmental Affairs.