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Lipids in Shallow Bottom Sediments David G. Shawl Department of Chemistry, Harvard University, Cambridge, Mass. 021 38
Sediments from the bottom of Boston Harbor and vicinity were analyzed for lipids by gas chromatography. These analyses showed that a petroleum-like fraction was associated with sewage sludge dumped into the harbor and with bottom deposits of similar sludge-like mud. However, samples of silt and clay collected in adjacent areas showed no evidence of petroleum a t comparable concentrations. It is suggested that the difference in lipid content of the various sediments reflects the complexity of estuarine sedimentation processes and the mechanisms of absorption of organic materials onto sediments. As man recognizes the conflicts of his needs to use coastal waters for economic activities and a t the same time to maintain the ecological viability of these waters, detailed information about the natural processes which determine the environmental “equation of state” become increasingly important. This note reports the amounts and in part characterizes the lipids occurring in the surficia1 sediments in and adjacent to Boston Harbor, an estuarine area which has been subjected to heavy chronic pollution. (The term lipid is here used to denote, in addition to saponifiable compounds of biological origin, a variety of nonpolar organic substances including petroleum hydrocarbons .) Three principal sources of organic pollution in Boston Harbor are recognized (Ducsik, 1971): discharge of treated sewage a t the mouth of the harbor, raw sewage from malfunctioning and overflowing combined (sanitary waste and storm runoff) sewer relief points, and petroleum spillageparticularly during transfer from ship to shore. This note points out that a complex array of these major, as well as many other minor, sources of organic pollution have led not to a uniform fouling of the surficial sediments of Boston Harbor but to a complex pattern of accumulations of lipids.
fuel oil made under the same conditions is shown in Figure 1B. In these and other chromatograms, selected peaks were identified by the use of internal standards in separate runs. Normal alkane peaks identified in this way are marked with carbon numbers in the figure. Extraction of the raw sludge yielded a petroleum-like lipid fraction which amounted to approximately 2% of the wet weight of the sample. Station 1: Charles River. A black, foul-smelling mud was collected in the mouth of the Charles River, an area of weak currents. The gas chromatogram (Figure IC) of this extract differs in two ways from that of the sewage sludge or the fuel oil. Here a t relative attenuation 4 the resolved peaks are less intense relative to the unresolved envelope. Also, the envelope of unresolved peaks is open toward the upper end indicating the presence of a significant fraction of heavier materials. Station 2: Mystic River. A sample of mud was collected in the Mystic River near a dock at which petroleum is transferred. In the gas chromatogram (Figure 1D) of this extract (relative attenuation l), resolved n-alkane peaks are minor. The major feature is an unresolved envelope. This envelope, even more than that from Station 1, shows a predominance of heavier, unresolved materials. Station 3: Inner Harbor. A sample was taken from the channel of the Inner Harbor. The bottom material collected was a clay, compact, and containing coarse sand particles. The gas chromatogram (Figure 1E) prepared from this sample was different from those described above. At relative attenuation 1, this chromatogram contained only two peaks: one a t the retention time of n-docosane and one at a just shorter retention time. Station 4: Fore River. This sample of gray clay was not taken from the top of the sediment column. Rather, this clay had been overlain by a layer of dark oily mud, visually similar to that collected in the Mystic River. This sampling location was (like the Mystic River station) near a dock where fuel oil is transferred. Yet no lipids were de-
Results Samples of sludge, both raw and digested, from the Deer Island sewage treatment plant (a secondary treatment facility operated by the Boston Metropolitan District Commission) were extracted and analyzed by gas chromatography. The chromatograms of the two materials are qualitatively quite similar; that of the raw sludge is shown in Figure 1A (relative attenuation 40). The n-alkane peaks and unresolved envelope are characteristic of petroleum (Blumer and Sass, 1972). The chromatogram shown in Figure 1A was obtained using Dexsil 300-GC as stationary phase which does not resolve n-heptadecane and pristane (see Experimental). A gas chromatogram of the same material using Apiezon L as stationary phase resolved n-heptadecane and pristane and shows that the nalkane peaks decrease monotonically away from n-pentadecane-i.e., the extract does not show a predominance of odd over even n-alkanes. A chromatogram of Number 6 ~~~
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of M a r i n e Science, U n i v e r s i t y of
Alaska, Fairbanks, Alas. 99701.
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P r’ Figure 1. Gas chromatograms of sediment extracts A, sewage sludge, relative attenuation, 40; 8, fuel oil; C, Station 1, Charles River, relative attenuation, 4: D, Station 2, Mystic River, Relative attenuation, 1 ; E, Station 3, Inner Harbor, relative attenuation, 1 ; F, Station 4, Fore River, relative attenuation 0.01: G, Station 5, Strawberry Point, relative attenuation 0.01 : H , Station 6, Massachusetts Bay, relative attenuation, 2. See text for experimental conditions
tectable (Figure 1F) in the extract of this clay, even a t relative attenuation 0.01. Station 5: Strawberry Point. This sample came from an intertidal zone about 25 km southeast of Boston, outside the harbor. The sample collected was a mixture of organic matter, sand, and smaller mineral particles. Strawberry Point is in a surburban area where many of the homes are occupied only in the summer. It was hoped that this area (not pristine, but outside Metropolitan Boston) would yield a sample of marine organic muck of natural origin. Indeed, the extract of this material gave a chromatogram (Figure 1G) containing only a few discrete peaks a t relative attenuation 0.01. Station 6: Massachusetts Bay. This station, like Station 5, is outside Boston Harbor. In the present case the station is located about 3 km off Deer Island, the site of Boston's larger sewage treatment plant. The chromatogram (Figure 1H) made from sediment collected a t this station shows at relative attenuation 2 a complex pattern of peaks. Discussion The extract of sewage sludge (Figure 1A) shows an abundance of lipids. Similar results have been reported by others (Farrington, 1971 and references therein). The present gas chromatographic data suggest, but do not prove, that petroleum hydrocarbons are a significant part of these lipids. In the discussion that follows it is sufficient to regard sewage sludge as an important source of lipids entering the area of Boston Harbor. The extracts from Stations 1 and 2 (Figure 1C and 1D) each show that a mud occurring in an area of weak currents contains a significant quantity of lipids. The extracts from Stations 3, 4, and 5 show no indication of the broad spectrum of lipids associated with petroleum (Figure 1B) and sewage (Figure 1A). Undoubtedly lipids are present in these materials in lesser amounts and possibly with significant effects. However, these sediments have not accumulated lipids to the extent of Stations 1 and 2. The extract from Station 6 shows a lipid distribution which indicates that neither sewage sludge nor petroleum is the controlling factor. In a continuing study of hydrocarbon pollution of sediments following a single petroleum spill near Falmouth, Mass., Blumer and Sass (1972) report that sediment contamination gradually decreases away from the spill area. Likewise, in a study of benthic lipids in Narragansett Bay, Farrington (1971) noted a general decrease in hydrocarbons away from Providence, R.I. In Boston Harbor (and quite probably in the immediate vicinity of Providence), the situation is quite different. Highly fouled sediments are in close proximity to relatively clean ones. Part of the explanation for this uneven and irregular distribution must be the multiplicity of pollution sources in Boston Harbor. Each source tends to pollute sediments in its immediate vicinity. This probably accounts for much of the lipids found a t Station 2, near an oil dock. A second and perhaps more important factor in the distribution of lipids in the sediments is the tidal currents. In a thorough discussion of sediment transport and sedimentation in estuaries, Postma (1967) points out that in shallow coastal waters fine sediments such as sewage sludge and oil droplets usually are transported for many tidal cycles before coming to rest. Postma also discusses the mechanism by which each tidal cycle results in a net movement of fine sediments toward the land until sedimentation takes place in areas where currents are too weak to further move the sediments. This mechanism may explain why Station 1 in a landward area of weak currents contains lipids which resemble those from sewage sludge, while
Station 6 which is closer to Boston's sewage sludge outfall but to seaward of it, has a lipid composition quite different from that sludge. Strong tidal currents in the channel on the Inner Harbor explain the absence of lipid-containing sediments a t Station 3. The absence of heavy lipid contamination in the clay from Station 4 which had been closely overlain by oily mud is most interesting. It may be that the low permeability of the clay constitutes an effective barrier to the lipids preventing them from entering the clay. An alternative explanation is that lipids which entered this sediment were bound tightly enough to resist the extraction procedure used. The ability of clays to bind lipids is well known (Weiss, 1969). Humic acids, which are prevalent in coastal sediments, have also been shown t o strongly bind lipids including hydrocarbons (Khan and Schnitzer, 1972). However, when the capacity for this strong binding (which is probably small) is exhausted, the deposition of further lipid-containing particles on a compact clay will lead to the buildup of an organic rich mud over the clay. The low level of lipids observed at Station 5 (Figure 1G) support the belief that higher levels found within Boston Harbor are the result of contamination from petroleum and sewage.
Experimental
Sampling. Sediment samples, unless otherwise noted, were taken from the upper 5 cm of cores of bottom material during the fall and winter of 1971. Samples were stored below 0°C until extraction. Extraction. Extraction was carried out in a Soxhlet apparatus. A 10-gram (wet weight) sample of sediment was placed in a paper thimble and extracted for 24 hr with 100 ml of methanol. Prior to extraction, the apparatus was extracted with a separate charge of methanol for 24 hr. The methanolic sediment extract was extracted four times with 25-ml portions of hexane. If necessary, 10 ml of water were added to produce two phases in this liquid-liquid extraction. The hexane extract was filtered through magnesium sulfate and finally concentrated to 2 ml with a stream of filtered nitrogen. Organic solvents were reagent grade and were redistilled in glass before use. Water was refluxed with and distilled from potassium permangate before use. This extraction procedure quantitatively recovered 50 mg of a Number 6 fuel oil which had been mechanically coated onto 10 grams of washed and ignited sea sand. Chromatography of extraction blanks periodically demonstrated the absence of contamination. Gas Chromatography. Extracts were analyzed using a Varian Aerograph 1520B gas chromatograph operated in the single column mode. All sample extracts were chromatographed on a 10-ft x l/g-in. column of 2.5% Dexsil 300GC (Analabs, Inc.) on 60/80 mesh Chromosorb P. The gas chromatograph's oven was linearly programmed from 100-300°C a t lO"/min; the injector and detector were held a t 325°C. The carrier gas was helium flowing a t 15 ml/ min. The use of Dexsil 300-GC coated capillary columns for the analysis of petroleum has already been described (Novotny et al., 1972). The use of this stationary phase in packed columns for the analysis of such materials deserves comment, however. Under these conditions, column life was noticeably longer and more trouble free than with an Apiezon L column (Blumer et al., 1970) used to 300°C. However, resolution slightly inferior to that reported with Apiezon L is obtained with the Dexsil column. A peak (assumed to be pristane) that is just resolved from n-heptadecane on the Apiezon L column is coincident with nheptadecane on the Dexsil column. V o l u m e 7, N u m b e r 8, August 1973
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Acknowledgment
The author appreciates the aid of W. E. Doering and T.
R. Gilbert in this work. Literature Cited
Blumer, M., Sass, J., “The West Falmouth Oil Spill,” data available in November 1971; 11. “Chemistry,” Woods Hole Oceanographic Institution, unpublished manuscript, 1972. Available from National Technical Information Service, Springfield, Va. Blumer, M., Sousa, G., Sass, J., Mar. Biol., 5,195-202 (1970). Ducsik, D. W., Ed., “Power, Pollution and Public Policy,” p 243, MIT Press, Cambridge, Mass., 1971.
Farrington, J. W., “Benthic Lipids of Narragansett Bay-Fatty Acids and Hydrocarbons,” University of Rhode Island Thesis, 1971. Khan, S. U., Schnitzer, M., Geochirn. Cosrnochim. Acta, 36, 745-54 (1972). Novotny, M., Segura, R., Nooner, D. W., Gelpi, E., Anal. Chern., 44,9-13 (1972). Postma, H.. in Lauff, G. H., Ed., “Estuaries.” DV 158-79, AAAS publication No. 83, Washington, D.C., 1967. Weiss, A. in Eglinton, G., Murphy, M. T. J., Eds., “Organic Geochemistry Methods and Results,” pp 737-81, Springer Verlag, New York, N.Y., 1969.
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Received for review January 5, 1973. Accepted M a ) 3, 1973
DiphenyleneOxide and Cyclopentacenaphthylene(s)in Flame Soots Barry
D. Crittendenl and Ronald Long2
Chemical Engineering Department, University of Birmingham, England
w Soots from rich premixed flat flames of acetylene-oxygen and ethylene-oxygen, respectively, contain a range of polycyclic aromatic hydrocarbons, many of which have been identified by gas chromatography combined with high resolution mass spectrometry and/or uv spectrometry. A hitherto unidentified gas chromatographic peak lying between those of fluorene and anthracene + phenanthrene is considered to be due t o diphenylene oxide (dibenzofurane) and t o C ~ I H S probably , “pyracylene” (or cyclopentv,g]acenaphthylene) and possibly its isomer cyclopent[b, clacenaphthylene.
a1 deposited in the extraction filter. (Cold-trap samples were treated separately.) The extract was concentrated in a rotary evaporator, under vacuum, to a volume less than 1 ml. A 25-pl. sample of this was then injected into the sample column of the F and M 810 gas chromatograph with the operating conditions listed in Table I. A typical gas chromatogram (but in this case not extending to the benzopyrenes) is given in Figure 1. For the
Table I. Operating Conditions in Gas Chromatography
Column details: dual 12 ft 0.25 in. 10% SE 52 on 80-100 mesh Chromosorb G
It has been known for many years that benzo[a]pyrene and dibenzo[a,h]anthracene are potent carcinogens. More recently it has been shown that benzo[a]anthracene while only weakly carcinogenic can be metabolized in the animal liver through the 5,6-epoxide, which is extremely carcinogenic and mutagenic. Such polycyclic aromatic hydrocarbons are known t o be associated with smokes, soots, or particulate carbonaceous matter resulting from the incomplete combustion of fossil fuels, and essentially the same range of compounds results irrespective of source. Since some compounds present alongside the carcinogens in exhaust products appear to be tumor-promoting agents (to mouse epidermis, for example), while others show inhibiting effects, it is useful t o have information about the as yet unidentified compounds present. In a recent study by Crittenden and Long (1973) of the formation of polycyclic aromatic hydrocarbons in premixed rich flat flames of acetylene-oxygen and ethyleneoxygen operating at 40 m m Hg pressure, samples were taken via fused silica probes a t different heights above the burner. Soot and condensable materials were collected in a fritted glass extraction thimble (the “extraction filter”) and following this, in “cold traps.” A brief summary of the method of procedure in the analytical work follows: The probe and connecting lines were washed out with dichloromethane and the resulting solution was used for a 12-hr Soxhlet extraction of the materi-
Operating conditions
Helium flow rate, ml/min Hydrogen flow rate, ml/min Air flow rate, ml/min Injection port temperature, “C Detector block temperature, “ C Starting column oven temperature, “C Final column oven temperature, “ C Program rate, “C/min Electrometer sensitivity range Attenuation
10
20 Retention 1 me
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To whom correspondence should be addressed.
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50 35 220 300 300 150
295 6
10‘ 8
40
50
lmins I
Figure 1. Gas chromatogram of extraction filter sample collecte d from ethylene/oxygen flat flame, CzH4/0~ratio = 1.3 (not
extending to the benzopyrenes in this case)
