Petroleum-Derived and Indigenous Hydrocarbonsin Recent Sediments of Lake Zug, Switzerland Walter Giger,' Martin Reinhard, Christian Schaffner, and Werner Stumm Institute for Water Resources and Water Pollution Control, Swiss Federal Institute of Technology, CH-8600 Dubendorf, Switzerland
H Presented are hydrocarbon analyses of recent sediments from Lake Zug, Switzerland. The sediments near the densely populated northern shores of the lake contain large amounts of hydrocarbons, predominantly derived from fossil fuels; indigenous hydrocarbons, presumably derived from aquatic organisms, predominate in the middle part of the lake, adjacent to less densely populated areas.
The ubiquity of hydrocarbons in recent sediments and in living organisms is well established. Some of these compounds have biological origin, whereas others are derived from pollution by petroleum products (Blumer and Snyder, 1965; Blumer e t al., 1972a,b,c; Han et al. 1968, 1969; Meinschein, 1969). If petroleum products are spilled into rivers, lakes, or the sea, much of the higher boiling material is taken up by the sediments. There, biodegradation is retarded, especially below the water sediment interface (Blumer and Sass, 1972b). With repeated chronic pollution, hydrocarbons may therefore accumulate in the sediments. Some petroleum-derived hydrocarbons may show biological effects even a t very low concentration levels. T o anticipate and assess the degradation of natural waterways, their sediments must be analyzed in detail, and a distinction must be made between indigenous and petroleum hydrocarbons. Here we report an investigation by infrared spectroscopy and gas chromatography of sediment extracts from Lake Zug, Switzerland (Figure 1). To whom correspondence should be addressed
Experimental Samples of the sediment surface were taken a t six locations near the shores of Lake Zug (Figure l ) in water depths varying from 2-9 meters. Samples 1, 5, and 6 were taken by a diver, whereas at stations 2, 3, and 4 a grab sampler was used. For infrared analyses, 50 grams of the wet sediment were shaken with 50 ml of CC14 for 20 min. The extracts were dried with Na2S04. The spectrum was recorded between 3500 and 2500 c m - l in a Beckman-IR-8 spectrometer. After percolation through basic A1203 (Merck, activity I) the spectrum was measured again. The amounts of total extractables and of hydrocarbons were determined by measuring the C-H bands according to API Method 733-58 (1957). For gas chromatography 50-200 grams of the wet sediment were shaken with 100 ml of pentane. The extracts were dried with Na2S04, percolated through basic A1203 (Merck, activity I) and concentrated at room temperature to 1 ml. Aliquots (1-2 pl.) of the solutions were injected into a Carlo Erba-GI gas chromatograph, equipped with a flame ionization detector and a glass capillary column (25m, OV-101, purchased from H. J. Jaeggi, Trogen AR. Switzerland). Helium was used as a carrier gas a t a flow rate of 3 ml/min and the column temperature was programmed at 3"/min from 30-230°C.
Results and Discussion The results of the infrared determinations (Table I) must be considered as only estimates, however the concentrations of hydrocarbons a t stations 1, 2, 3, and 4 are significantly higher than a t locations 5 and 6. The hydrocarbon concentrations a t stations 1, 2, and 4 exceed the maximum concentration (320 pg/g dry weight) determined by Unger (1971) in a similar study of Lake Constance. At stations 5 and 6 the hydrocarbon concentrations are in the same range as the lower values found in Lake Constance. In the msrine sediments of Buzzards Bay, Mass., the background of biochemically derived hydrocarbons lies close to 50-70 pg/g dry sediment (Blumer and Sass, 1 9 7 2 ~ ) The . hydrocarbon concentrations in the sediments of the northern part of Lake Zug exceed this value, whereas stations 5 and 6 resemble the unpolluted marine sediments. Table I. Organic Matter of Lake Zug Sediments Determined by Infrared Spectroscopy and Gas Chromatography Station n0.a
CCl, extractable, p g / g dry wt
Hydrocarbons, p g l g dry wt
n-C -HsL/ pristane
1
2350
900
1.8
2 3 4
1590b
610h
570 2470
5 6
lolob
240 860 140b 50
1.0 2.8 2.0
300
Pristane/ phytane
0.8 1.0 1.0 1.3
S t a t i o n n,urnbers refer t o Figure 1. b Average value of t w o i n d e p e n d e n t determinations. c N o t determinable. (1
Figure 1.
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Lake Zug, locations of sampling stations
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1
1
Figure 2. Gas chromatograms of sediment extracts a. Station 4 . b. Station 6. Numbers indicate carbon numbers of n-alkanes
The infrared determination of total extractable and hydrocarbon concentrations permits no clear distinction between indigenous and pollution-derived material. Still, it suggests that the sediments near the densely populated shores of the lake are contaminated with petroleum hydrocarbons. For a better insight into the compositions of these hydrocarbons, the pentane extracts of the sediments were studied by gas chromatography. Stations 4 and 6 (Figure 2) are representative of the northern and middle part of the lake, respectively. Correspondingly, the gas chromatograms demonstrate a considerable difference in their hydrocarbon chemistry. The main four features are described as follows: The hydrocarbons a t station 4 show a continuous distribution curve of n-alkanes in the range of carbon numbers n = 10-24; while a t station 6 n-heptadecane dominates all other n-alkanes by a factor of a t least 5. A smooth chain length distribution of the n-alkanes is typical for petroleum and petroleum products (Philippi, 1965; Zafiriou et al., 1972). T h e predominance of n-heptadecane in Figure 2b is attributed to hydrocarbons produced by algae and other photosynthetic organisms. It is very often the dominant compound in biogenic hydrocarbon mixtures ( H a n and Calvin, 1969; Youngblood et al. 1971). The n-Cl7 alkane in Figure 2a is also more abundant than the adjacent straight chain alkanes, explained by a superposition of indigenous and polluting hydrocarbons. The concentration of odd-numbered n-alkanes increases again in the range from n-CZ3 to n-Cz7. This feature is common for unpolluted recent sediments (Stevens, 1956; Han et al., 1968; Tissier and Oudin, 1973) and is often observed in terrestrial plants (Clark 1966). In station 4, material transported by the river Lorze may be the reason for the large increase toward n-Cz7. The isoprenoid hydrocarbons pristane ( C z o ) and phytane ((221) are among the major constituents in station.4, whereas in station 6 they are absent or present only in trace amounts. These two compounds are also major constituents of many crude oils (Speers and Whitehead, 1969; Zafiriou et al., 1972). The n-C17/pristane ratio of the stations from the north-
ern shore varies between 2.8 and 1.0 (Table I). This may be attributed either to different sources or to different degrees of biodegradation of the fossil fuels (Blumer and Sass, 1972b). The pristane/phytane ratio, however, remains remarkably constant, close to unity. In unpolluted marine sediments, phytane is absent or present in a much lower amount than pristane (Blumer and Snyder, 1965). The very distinct differences in the hydrocarbon compositions are best explained by the presence of fossil fuels in the northern part of Lag Zug. These pollution-derived hydrocarbons are superimposed over a background of indigenous compounds presumably derived from aquatic organisms and from land material transported by the river Lorze. The sediments near the less populated shores, however, seem to contain almost only indigenous hydrocarbons. It does not seem very likely that the contribution by recent metabolic activities changes so much throughout the lake. T o find the sources of those high hydrocarbon concentrations and t o estimate the effects of these compounds on the surrounding biota, a more detailed study of sediment extracts and comparisons with possible sources is being pursued. Ac knouledgment This study was supported in part by the Swiss Department of Commerce (Common Market Project COST 64b) and by the Canton of Zug. The authors would like to thank Max Blumer, Woods Hole Oceanographic Institution, Woods Hole, Mass., for very valuable discussions.
Literature Cited American Petroleum Institute. “Manual on Disuosal of Refinery Wastes,” Vol. IV, API Method I, 733-58, 1957. Blumer. M.. Sass, J., Mar. Pollut. Bull., 3, 92-4 (1972a). Blumer. M.. Sass. J.. Science. 176. 1120-2 (1972133. Blumer, M . , Sass, J., Woods Hole Oceanographic Institution, Tech. Rept. No. 72-19, 1972c. Blumer. MI,Snyder. W . D., Science, 150, 1588-89 (1965). Clark, R. C., Jr., Woods Hole Oceanographic Institution, Tech. Rept. No. 66-34, 1966. H a n , J.. Calvin, M., Proc. Nat. Acad. Sei. C.S., 64, 436-43 (1969). Han. J.. McCarthy, E. D., Van Hoeven, W., Calvin, >I Bradley, .. W. H.. ibid., 59,29-33 (1968). Meinschein, W. G.. in “Organic Geochemistry,” p p 330-56, e d . by G . Eglinton and M . T . J. Murphy. Springer Verlag, S e w York, S . Y . , 1969. Philippi. G. T.. Geochim. Cosmochim. Acta, 29, 1021-49 (1965). Speers, G. C., Whitehead, E . V. in ”Organic Geochemistry,” p p 638-75, ed. by G. Eglinton a n d M . T. J . Murphy. Springer Verlag, N e a Y o r k . N.Y.. 1969. Stevens. K, P., Bray, E. E.. Evans, E . D.. Amer. A s s . Petrol. Geol. Bull., 40,975-83 (1956). Tissier, M., Oudin. J. L., Prev. Cont. Oil Suills Joint Conf.. Proc., pp 205-14, 1973. Unger. L., Gas Wasserjach, Wasser Abxasser, 112, 256-61 (1971). Youngblood, W. W..Blumer, M., Guillard, R . L.. Fiore, F., Mar. Bioi., 8, 190-201 (1971). Zafiriou. O., Blumer, M . , Myers, J., Woods Hole Oceanographic Institution, Tech. Rept. No, 72-55, 1972. Receiced for recieu: Julj 9, 1973. Accepted ,Vocem ber I , 1973.
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