Preparation of water soluble fractions of crude oils for toxicity studies.

Abstract

W. A. Maher Water Research Centre, School of Applied Science, Canberra College of Advanced Education, PO Box 1, Belconnen, ACT Australia 2616 Petroleum hydrocarbons (oils) are major contaminants of estuarine and coastal environments (Connell and Miller 1981; Knap et al 1979). Marine organisms accumulate hydrocarbons (Lee et al 1976; Morris 1974) but little is known about the effects of repeated exposures of organisms to low concentrations of hydrocarbons. The most immediate toxic and subtoxic fractions of oils are those soluble in water (Hufford 1971), toxicity of oils to organisms usually being related to the content of non-volatile persistent aromatic hydrocarbons (Neff and Anderson 1975; Zikto and Carson 1970). A widely used procedure for producing water soluble fractions of oils for toxicity studies is the slow stlrring method of Anderson et al (1974), in which an oil is layered on to water and mixed by means of a magnetic stirring bead. This paper examines the factors affecting the preparation of water soluble fractions of oils by this method. The water soluble fractions were also examined after filtration through membranes of varying pore sizes to establish the importance of particulate matter in the process of solubilization. MATERIALS AND METHODS Crude oils were obtained from commercial sources. Sea water was collected from a pr8 environment, passed through a 0.45 Bm filter and sterilized by steaming. Water extracts of oils were prepared using a mixing flask that has been previously descr8 (Maher 1982); 400 mi of sea water was poured into the flask and 1-3 g of oil layered onto the surface. The flask was placed into a thermostated water bath (200C) and magnetic stirring used to produce a turbulent layer of less than 0.5 cm depth. The water soluble fraction was removed through a tube located below the oil layer. Ai1 experiments were performed in the dark. Aliquots of water soluble fractions (I0 ml) were extracted with 5 ml of n-hexane using vortex mixing. The organic layers were