Association of Hydrophobic Organic Compounds with Dissolved Organic Matter in Aquatic Systems John P. Hassett’” and Marc A. Anderson W a t e r Chemistry Program, University of Wisconsin, Madison, Wis. 53706
Radiolabeled cholesterol added to water samples was recovered less efficiently from river water than from distilled water by solvent extraction. However, if organic matter in river water was destroyed with UV radiation prior to cholesterol addition, recovery was equivalent to that from distilled water. This demonstrated that cholesterol could be bound by dissolved organic matter and stabilized in the aqueous phase. Water samples containing radiolabeled cholesterol or the PCB isomer 2,2’,5,5’-tetrachlorobiphenyl were fractionated by gel permeation chromatography. Results indicated that these compounds were associated with high molecular weight organic matter present in the samples.
Experimental
Water samples were collected from the Menomonee River upstream, downstream, and from the Memonomee Falls municipal sewage outfall. Organic matter in selected samples was concentrated by ultrafiltration using an Amicon UM05 ultrafilter (nominal molecular weight cutoff = 500). Sample volumes were reduced fivefold by this method. Samples collected upstream of the sewage outfall were pretreated to remove particulate matter by continuous flow centrifugation a t a force of 31 OOOg and a flow rate of 100 mL/min using a Sorvall Superspeed RC2-B refrigerated centrifuge. Some centrifuged samples were further treated to destroy organic matter by irradiating them in 2.7 cm (i.d.) quartz tubes for 6 h a t a distance of 8 cm from a 450-W highSeveral studies have demonstrated that dissolved organic pressure mercury vapor ultraviolet light source (Englehard matter can increase the apparent aqueous solubility of hyHanovia, Inc.). These samples were passed through glass fiber drophobic organic compounds. Wershaw et al. ( I ) found that filters (Reeve Angel 935 AH) before use. Ultraviolet oxidation 500 mg/L of humic material extracted from soil increased the has been found effective in destroying a variety of organic solubility of DDT 20 to 40 times. Poirrier et al. ( 2 )found that compounds, including humic material, in water ( 7 ) . DDT associated with iron-organic colloids in water and that [4-’*C]Cholesterol (ICN Pharmaceuticals, Inc.) was added it was concentrated in the colloids by a factor of 16000. to the water samples by placing benzene solutions containing Matsuda and Schnitzer ( 3 )showed that fulvic acid fractions 3.83 X lo3 cpm of cholesterol in 2-L Erlenmeyer flasks, of soil extracts increased the solubility of phthalate esters, but evaporating the solvent with a stream of nitrogen, adding 1.5 the effect decreased with decreasing molecular weight of the L of water sample to each flask, and stirring for 20 h on a phthalate ester. Boehm and Quinn ( 4 ) demonstrated that the magnetic stirrer a t 4 or 20 “C. All samples were then acidified fulvic acid fraction of a marine sediment increased the soluto pH
