Simple, continuous-flow systems for dissolving the water-soluble components of crude oil into sea-water for acute or chronic exposure of marine organisms

A continuous flow apparatus, referred to as a solubilizer, was constructed to dissolve the water-soluble fraction (WSF) of crude oil into water for short and long-term experiments with marine organisms. The basic solubilizer system consists of an oil reservoir, oil pump, modified glass bottle, and oil waste reservoir. This system dissolves the water-soluble components of crude oil without the loss of the more volatile compounds and without the formation of emulsions or oil droplets. Four solubilizer systems (two continuous flow and two recirculating) were evaluated for their efficiency in extracting the water-soluble components from Cook Inlet crude oil by analyzing for six monoaromatics over a 96-h period of continuous operation. When a solubilizer system was started, a stable concentration of the monocyclic aromatics in the water-soluble fraction was reached within 24 h. The water quality of the WSF effluent was not altered markedly in the continuous (open) flow systems, but there was a substantial reduction in dissolved oxygen in the recirculated (closed) systems. A single solubilizer system (open flow) with a 3 ml min⁻¹ oil flow and a 1 l min⁻¹ sea-water flow generated approx. 1.4 ppm of the total monoaromatics, which includes benzene, toluene, ethylbenzene and the three xylene isomers. This concentration varied depending on physical parameters and the chemical composition of the crude oil and water. With only slight modifications of the basic continuous flow system, a higher concentration (> 3.4 ppm total monoaromatics) of the water-soluble fraction of crude oil was achieved. By recirculating the water supply, concentrations of 6.7–11 ppm total monoaromatics in the WSF were produced. The stability, reproducibility, and reliability of the four systems were demonstrated in several experiments. Researchers working in aquatic systems with crude oil can well appreciate a simple system that is easily cleaned, relatively maintenance-free, and which produces stable, reproducible concentrations of the WSF over extended periods of time. The increasing demands for ecological studies on aquatic organisms with crude oil, a difficult mixture of chemicals with which to work, precipitated the development of these solubilizer systems.