Environ. Sci. Technol. 1990,24,208-214
only for extremely water-insoluble compounds such as DDT. The weak effect is much a result of the small size of the surfactant monomer and of the large polar group content of aquatic humic and fulvic acids. By comparison, the enhancement effect by micelles and oil emulsions is greater by 1.5-3 orders of magnitude because of their relatively large aggregate size, which makes them behave like a bulk organic phase. Accordingly, oil emulsions may be expected to exhibit much more pronounced and broader impacts than other dissolved organic matter at low concentrations on the transport and fate of organic pollutants, including many relatively water-soluble solutes such as TCB. In summary, the results of this study indicate that the emulsified solution of sulfonated hydrocarbons and free mineral oils can greatly enhance the water solubility of relatively water-insoluble compounds. The enhancement effect by such an oil emulsion approximates that by a relatively nonpolar organic solvent on a unit weight, water-free basis. Calculation of the partition coefficient with the emulsified system is facilitated by knowledge of the nonpolar hydrocarbon content of the emulsion and the solvent (octano1)-water partition coefficient of the solute. From the environmental standpoint, the results from this study illustrate the potential impact of oil emulsions on solute transport and fate in situations where spilled or waste oils may be emulsified by surfactants in natural waters, at landfill sites, and possibly in waste waters generated from oil-well drilling and tertiary oil recovery operations.
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Registry No. DDT, 50-29-3; TCB, 87-61-6;water, 7732-18-5; Petronate L, 63952-44-3;Petronate HL, 39412-55-0; Pyronate 40, 63952-48-7.
Literature Cited Chiou, C. T.; Malcolm, R. L.; Brinton, T. 1.; Kile, D. E. Environ. Sci. Technol. 1986, 20, 502. Chiou, C. T.; Kile, D. E.; Brinton, T. I.; Malcolm, R. L.; Leenheer, J. A,; MacCarthy, P. Environ. Sci. Technol. 1987, 21, 1231. Kile, D. E.; Chiou, C. T. Environ. Sci. Technol. 1989,23, 832. McBain, J. W.; Richards, P. H. Znd. Eng. Chem. 1946,38, 642. Shincda, K.; Hutchinson, E. J.Phys. Chem. 1962,66,577. Mukerjee, P.; Mysel, K. J. Critical Micelle Concentrations of Aqueous Surfactant Systems; NSRDS-NBS 36; U.S. Dept. of Commerce: Washington, DC, 1971. Schwartz, A. W.; Perry, J. W. Surface Active Agents-Their Chemistry and Technology; Robert E. Krieger Publishing Co.; Huntington, NY, 1978. Rosen, M. J. Surfactants and Interfacial Phenomena; John Wiley and Sons; New York, 1978. Chiou, C. T.; Peters, L. J.; Freed, V. H. Science (Washington, D.C.) 1979,206, 831. Chiou, C. T.;Schmedding,D. W.; Manes, M. Environ. Sci. Technol. 1982, 16, 4.
Received for review March 27,1989. Revised manuscript received August 28, 1989. Accepted October 3, 1989. The use of trade or product names in this paper is for identification purposes only and does not constitute endorsement by the US.Geological Survey.
Sedimentary Coprostanol as an Index of Sewage Addition in Santa Monica Basin, Southern Californiat Mahalakshmi I . Venkatesan" and Isaac R. Kaplan
Institute of Geophysics and Planetary Physics, University of California, Los Angeles, California 90024-1567 Sediment cores from Santa Monica Basin and effluent from two major municipal wastewater dischargers in southern California were analyzed for sterols. Specifically, the fecal sterols, coprostanols (coprostanol and epicoprostanol), were quantitated to determine the degree of sewage addition to the sediment. Although coprostanols are distributed throughout the Santa Monica Basin sediments in association with fine particles, some stations contain elevated levels, either due to their proximity to the outfalls or because of preferential advection of fine-grained sediments into their location where anoxicity aids in better preservation. The progressive seaward decline of coprostanols relative to total sterols from the outfalls represents dilution of sewage by biogenic sterols. The ratio of coprostanols to dinosterol appears to be a better indicator of the degree of sewage addition. A rapid increase in content of coprostanols from about 1935 coincides with the start of offshore wastewater discharge by JWPCP, the Los Angeles County Sanitation Districts on Palos Verdes Shelf, It is estimated that wastewater treatment plants release into southern California Bight 260 metric tons/yr of fecal sterols and 5 X lo4 metric tons/yr of sewage carbon. With growing population density in coastal urban centers,the need for disposal of sewage containing fecal wastes 'Institute of Geophysics and Planetary Physics Contribution No. 3199. 208
Environ. Sci. Technol., Vol. 24, No. 2, 1990
increases. Municipal wastes are often discharged into the marine environment and it therefore becomes important to determine the distribution and fate of these contaminants in the aquatic systems. Various reports have demonstrated that coprostanol (5&cholestan-3~-01),a fecal sterol of higher animals, can be used as a quantitative indicator of the presence of fecal material (ref 1-3 and references therein). Coprostanol concentration is unaffected by various treatments such as chlorination ( I ) or aeration of overlying water ( 4 ) and it persists in anoxic sediments (2,5,6). For the above reasons coprostanol can be a useful tracer of fecal pollution in the ocean or brackish waters where other tracers fail (3). This paper describes our investigations on the spatial and depth distribution of coprostanol in the sediments of Southern California Bight, with the main focus on the Santa Monica Basin. The Bight includes a network of continental shelf basins close to shore (7), which serve as efficient sediment traps. Because coprostanol can become associated with organic-rich solids (8), it can be easily deposited in nearshore basins and incorporated into (fine-grained) sediments. The onshore/offshore Santa Monica Basin is a target area for intense use by the large industrial and residential population. With the termination of sludge discharge from the Hyperion 7-mile plant as of November 1987, a decrease in the contaminant input levels from the outfalls is expected, and the present work should establish a benchmark for further comparisons in
0013-936X/90/0924-0208$02.50/0
0 1990 American Chemical Society
,
ANGELES
.,
Figure 1. Surface sediment and core locations in the Santa Monica Box core (Cross I, BC); 0, surface sediment (BLM); 1. Basin. Hyperion, 2. JWPCP, and 3. Orange County sewage outfalis.
the future. Our goal is therefore to determine the seaward transport of anthropogenic contaminants, from sewage outfalls. In view of our recent finding (9) that the ratio of coprostanol to its epimer epicoprostanol(50-cholestan-3a-ol) is an important factor in differentiating human waste from marine mammalian feces, we also determined the concentration of epicoprostanol. The ratio of coprostanol to epicoprostanol in the Santa Monica Basin sediments is very similar to that from sewage sludge but quite different from those measured in feces from marine animals such as toothed and baleen whales, pinnipeds, and penguin (9). Therefore, any contribution from marine mammalian feces, Le., from cetaceans (10) and pinnipeds, in the Basin must be trivial. These observations suggest that sewage effluents are the major source of fecal sterols in the Basin (9). The two isomers together will be referred to as coprostanols in the report. Several cores were examined for coprostanols to identify the principal areas of sewage contamination and to trace the historic record of sewage input in Santa Monica Basin. Sewage sludge as well as effluent filtrates from Los Angeles County and City Sanitation Districts wastewater dischargers (JWPCP and Hyperion, respectively) were also analyzed to relate to the sterol composition of sediments and to estimate the mass emission rates of sewage sterols and carbon into the Bight. The inputs from these two outfalls are the major sources of anthropogenic waste contaminants into the study area (11).
Methods Sample Location and Characteristics. Glass tube subcores were obtained from Soutar-type box cores, collected during Cross I cruise of October 1985 from Santa Monica Basin (Figure 1)along the northeast to southwest transect, onboard the R.V. New Horizon as part of the DOE CaBS (California Basin Study) program. Cores were stored frozen until the start of analysis. Surface sediment sample from station 364 is from a 1976 BLM cruise and was also stored frozen. The center of the Basin is -30 km from land and the maximum water depth is 910 m. The bottom water is anoxic below the sill depth of -730 m. The dominant particle sizes are in the fine silt range (5-10 pm in diameter) and the silt fraction can be as high as 60-70% of the sediment. Surface sediments from station 364 contain
coarse sand, while those from stations BC 40 and 113 contain fine sand (D. Gorsline, personal communication, 1989). Basin slope sediments (stations 40,113, and 12) are dark green and coarser than the deep basin sediments (stations 102 and 89). Clay percentages generally increase offshore (ref 12 and 13; D. Gorsline, personal communication, 1989). A general decrease in grain size away from shore toward the center of the basins, following the increasing water depth contours, is noted (7). Surface sediments (stations H5 and H7) at the 5-mile (Hyperion, primary and secondary treatment) and 7-mile (digested sludge and secondary treatment) pipeline outlets, respectively, were obtained from the City of Los Angeles, Bureau of Sanitation. Effluent sludge (H7S) entering the 7-mile pipeline was collected on a day different from H5 and H7 collection. Twenty-four-hour composite treated effluent (JWCPS, advanced and primary treatment) from the Los Angeles County Sanitation District was also analyzed for comparison with H7S. Analytical Procedures. Frozen sediment cores were partially thawed and discrete horizons (2-4 cm) were subsampled for lipid and total organic carbon (TOC) analysis. Sludge from effluents (4-16 L) were filtered on precombusted glass fiber (Whatman GF/A). Sediment samples and sludge were extracted with methanol and then methylene chloride in a V i i s homogenizer. The methanol, after dilution with nanopure water, was back-extracted into hexane, which was then combined with the methylene chloride phase. Extraction and subsequent fractionation into alcohol/sterol and other different compound classes were carried out according to the methods of Venkatesan et al. (14).Filtrates from effluents and an unfiltered effluent from Hyperion 5-mile were extracted three times with methylene chloride and analyzed for coprostanol as above. Only sterol profiles are discussed in this report. Derivatization into trimethylsilyl (TMS) ethers with BSTFA and quantitation by gas chromatography (GC) and GC/mass spectrometry (GC/MS) identification are the same as previously described (6). An external sterol standard mixture comprising coprostanol, epicoprostanol, cholesterol, cholestanol, campesterol, and &sitosterol was used in GC quantitation and GC/MS identification. Recoveries of these sterols ranged from 80 to 92% in the current procedure. Selected TMS ethers were also coinjected with derivatized coprostanol or epicoprostanol to confirm the identification. The following GC conditions were employed: HP 5840 gas chromatograph equipped with Grob-type splitless injector was used; 30-m DB5 (0.25-mm id., 0.25-pm film thickness) fused silica column was programmed from 40 "C at 4 "C/min up to 280 "C and 2 "C thereafter to 310 "C. Helium was the carrier gas at a flow rate of 20 cm/s. GC/MS (Finnigan 4OOO) conditions were the same as above with electron energy, 70 eV; source temperature, 240 "C; scan speed, 2 s sc8n-I from 50 to 550 amu.
Results and Discussion General Observations. The following sterols were measured in the Basin sediments: cholesterol, campesterol, @-sitosterol,dinosterol, coprostanol, epicoprostanol, cholestanol, and p-sitostanol. With the exception of coprostanols (coprostanol + epicoprostanol), all others are common in uncontaminated marine sediments (see ref 14-16, among others). Excluding dinosterol, all the sterols are also present in sewage sludge samples but in different proportions than in the sediments. The total sterols range in concentration from 1 to 81 pg/g (Table I) in the cores with the highest concentrations in the top 4 cm of deep water stations 102 and 89, in the anoxic zone. The sewage Environ. Sci. Technol., Voi. 24, No. 2, 1990 209
Table I. Coprostanols, Total Sterols, Dinosterol, and TOC Contents of Santa Monica Basin Sediments and Sewage Effluents (Concentration Based on Dry Sediment Weight)
sample
concn, pcglg TOC,” coprototal % stanolsb sterolse
dinosterol
1.36 1.20 1.15 1.13
1.6 (119)f 0.8 (70) 0.12 (10) 0.05 (5)
6.6(487)f 7.6 (631) 1.2 (104) 0.9 (79)
0.8 0.8 0.2 0.2
2.52 2.61 2.26 2.27
1.7 (67) 1.2 (46) 0.17 (8) 0.17 (8)
12.4 (491) 11.1 (425) 7.0 (309) 4.8 (212)
2.9 2.0 2.0 1.4
Table 11. Grain Size Characteristics of Surface Sediments from Santa Monica Basina
BC 40 (398 m)d 0-20 2-4
10-12 16-21 BC 113 (572 m) 0-2
2-4 12-14 20-23.5 BC 12 (750 m) 0-2 2-4 12-14 21-24.5 BC 102 (910 m) 0-2 2-4 14-16 22-25 BC 89 (908 m) 0-2 2-4 12-14 22-27.5 BLM 364 (57 m) 0-2 sewage effluents H5 (sediment, 6/87)” H7 (sediment, 6/87) H7S (sludge, 7/87) JWPCPS (sludge, 11/87) H5 (effluent, 6/87) H7 (EF, 6/87)j JWPCP (EF,11/87)
sand
silt/clay
BLM 364 (57 m) Seawatch BC 2 (297 m)b (=BC 40) Seawatch BC 4 (490 m)b (=BC 113) Seawatch BC 5 (750 m)b (=BC 12) CaBS 7 BC 1 (-900 m)b (sBC 102) CaBS 7 BC 2 (-900 mIb (=BC 89)
40
55
5
11
38
51
11
4.6
2
65
33
2
1
62
38
1.6
