Hydrocarbons in surficial sediments from the Scotian Shelf

Geochimica et Cosmochimxa Acta.1978,Vol 42. pp. 165 10 172. Pergamon Press. Prmted in Great Britain

Hydrocarbons

in surficial sediments from the Scotian Shelfr

PAUL D. KEIZER, J. DALE and D. C. GORDON, JR.

Department of Fisheries and the Environment, Fisheries and Marine Service, Marine Ecology Laboratory, Bedford Institute of Oceanography, Dartmouth, Nova Scotia, Canada B2Y 4A2 (Received

3 June

1977; accepted

in revised form 27 September

1977)

Abstract-Surface sediments from 20 stations on the Scotian Shelf, collected on a transect from Halifax to Emerald Bank and around Sable Island, have been analyzed for hydrocarbon content and composition by gas chromatography and fluorescence spectrophotometry. Some samples were taken near abandoned exploratory drilling sites in the Sable Island area. Hydrocarbons appear to be mainly derived from biogenic terrestrial sources as evidenced by an inverse correlation of concentration with increasing distance from the mainland and a strong odd carbon preference in the n-alkanes. Contribution from petroleum sources, while minor, was most noticeable between Halifax and Emerald Bank. There is also evidence that the hydrocarbon composition at abandoned exploratory drilling sites has been slightly altered. INTRODUCTION SINCE the late 1960s a great deal of research has addressed the possible ecological impacts of oil pollution in the marine environment. Although the longterm effects of oil pollution are still not completely understood, it is generally recognized that oil resides in the water column for a relatively short time and that the area of greatest concern is the sediments, both intertidal and sublittoral, where a major fraction of released oil is deposited and may remain for many years (VANDERMEULENand GORDON, 1976). Exploratory drilling for oil off Canada’s east coast began in June of 1967 at Sable Island on the Scotian Shelf (Fig. 1). By January 1973, seven wells had been drilled on Sable Island and thirty-four wells offshore in the immediate vicinity (ANONYMOUS,1973). In the fall of 1973, we collected a number of sediment samples in this general area (Fig. 1). Some samples were taken adjacent to well sites which had been abandoned or capped and others were taken at intermediate sites. These samples were analyzed to determine the content, composition and probable origins of the hydrocarbons in this region. In particular, we were interested in determining if drilling operations had any measurable effect on the hydrocarbon content and composition of adjacent sediments. The information obtained would also serve as a baseline in the event of future oil and/or gas production in the Sable Island region.

The extraction procedure was a simplification of the method recommended by FARRINGTON and TR~PP (1975). Sediment samples were partially thawed and subsamples were transferred to pre-extracted glass Soxhlet thimbles. Samples and blanks were extracted for 18 h with 250 ml methanol-benzene (2:3 v/v). The extracts were extracted once with 85ml of pentane; the pentane-benzene extract was concentrated and an aliquot was dried at room temperature under a stream of nitrogen and weighed on a Cahn electrobalance to determine the extractable organic material (EOM). The remaining EOM of each sample was analyzed quantitatively and qualitatively by fluorescence (GORDON and KEIZER, 1974) using a Perkin-Elmer MPF-2A fluorescence spectrophotometer. Guanipa crude oil was used for calibration. “Oil” concentrations reported are estimates based on fluorescence with full consideration given to the limitations discussed by GORDONand KEIZER (1974). Samples were taken to dryness and the residue was redissolved in 0.5 ml of pentane. The aliphatic hydrocarbon fraction was obtained by eluting the sample from a column of silica gel under alumina (1 :l w/w) with 2 bed volumes of pentane. Aliquots of this fraction were analyzed on a Perkin-Elmer 3920 gas chromatograph with an MS-41 sampling accessory. The column was a 15 m x 0.5mm OV-1 SCOT column programmed from 100 to 280°C at 8”C/min. Injector temperature was 25O”C, detector temperature, 350°C. Peak areas were obtained with a HewlettPackard 3380A integrator; unresolved envelope areas were determined with a planimeter. Compounds were identified by retention times compared with standards. The aliphatic hydrocarbon fractions from Stations 1 and 13 were hydrogenated to check for the presence of alkenes. Hydrogen was bubbled through the pentane extract with stirring in the presence of platinum oxide at room temperature for 20 min. The sample was sealed under pressure with hydrogen in a Reacti-vial and placed in a hot water bath

at 50°C for 1 hr. To determine the effect of peak tailing on the area of the unresolved envelope, different amounts of a sample of Sediment samples were collected with a VanVeen grab Bunker C oil were injected, ranging from 0.1 to 2.Opg of at 20 locations on Cruise 73-030 of the C.S.S. Dawson in total n-alkanes. The area of the unresolved envelope was October of 1973 (Fig. 1). Subsamples were taken from the a linear function of the amount injected indicating a neglicentre of the grab sample and placed in solvent-cleaned glass bottles with foil-lined caps. Samples were frozen im- gible effect of peak tailing. Completeness of extraction was tested by extracting five mediately and kept at -20°C or colder until analysis in sediments with two portions of methanol-benzene. An December, 1976. average of 95.8 k 3.7% of the total recovered was in the first extract. Similarly, the methanol-benzene extracts were * Bedford Institute of Oceanography Contribution. extracted three times with pentane; 98.5 f 0.90, of the 165

MATERIALS AND METHODS

166

P. D.

KEIZER,

J. DALE and D. C.

GORDON,JR.

Ai0

2

4’ AQ

SABLE ,@I”_

,,4

&

12l

A’3

Y5 ‘16

17.

‘22

I

1

1

64O

63'

62O

61'

60"

59"

Fig. 1. Locations at which samples were collected. For purposes of comparison samples are divided into three groups: (m) A, Halifax transect; (A) B, stations at well sites; (m) C, intermediate stations.

total recovered was in the first extract. Samples were spiked with Bunker C fuel oil (2@-SOpg/g dry sediment) and extracted in the normal manner. Recoveries of fluorescing material averaged 96.5 +_8.5% and recoveries of the n-alkanes averaged 88%. The mean ~n~ntration of total n-alkanes in six subsamples from one sample was 125 rig/g sediment (SD. It 31). Methanol and benzene were redistilled reagent grade; pentane was twice distilled practical grade. All glassware was thoroughly cleaned with solvent immediately before use. Silica gel was Hi-Flosil, 60/200 mesh, activated at 250°C for 18 hr; alumina was Alcoa alumina F-20, SO/200 mesh activated at 400°C for 18 hr. Both supports were deactivated with 5% water.

RESULTS AND DISCUSSION

KING (1970) and MACLEAN and KING (1971) conducted extensive studies of the surficial geology of the Scotian Shelf. Their method of classification accurately describes the samples collected (Table 1). Ex-

ploratory drilling occurred at Stations 10, 12, 13, 15, 17 and 21 (Fig. 1) (ANONYMOUS,1973), all of which are in an area where Sable Island sand and gravel are dominant. Samples are divided into three groups. Group A includes all samples collected along the transect from Halifax Harbour to the south side of the Emerald Bank, including Stations 1, 2, 3, 5 and 24. All five sediment types (Table 1) are included in this area. Group B includes samples from stations at abandoned exploratory well sites, and Group C, the remaining samples. Samples from all stations in Groups B and C are Sable Island sand and gravel with the exception of Stations 9 and 11 which are Emerald silt. Concentrations of extractable organic material (EOM) varied from 19 to 64Opg per gram of dry sediment (Table 2). Concentrations of EOM and other parameters had a log normal frequency distribution, therefore reported means are geometric means. There is no significant difference among the concentrations of EOM from the three groups.

Hydrocarbons

167

in surficial sediments from the Scotian Shelf

Table 1. Type of sediment in samples collected. Sediment description from KING (1970) and MACLEANand KING (1971)

Sediment

Stations

description

Sambro

sand,

mainly

LaHave

clay,

silty

sandy

1

gravel

2

clay

3, 9 and 11

Emerald silt, poorly sorted, clayey and sandy silt Sable

Island

sand

and gravel

- with

less

than

50% sand

5 and 10

- with

less

than

50% gravel

7, 8, 12-22

Comparison with other data reported in the literature is complicated by the different areas in which the samples were collected and also by the variety of extraction methods employed. The extraction procedure employed here is most similar to that of FARR-

and 24

INGTONand TRIPP (1977). They report concentrations in the New York Bight of similar magnitude, but with a somewhat greater range (maximum of 275Opg/g) probably due to a greater pollution input. Values reported by GEARING et al. (1976) for sediments from

Table 2. Concentrations of various parameters extracted from Scotian Shelf sediments. Group A, transect from Halifax to Emerald Bank; Group B, abandoned exploratory drilling sites; Group C, sites intermediate to drilling sites Station no.

Group 1 2 3 5 24

‘GM

pristaneb

phytaneb

UCMb

b

b

"Oil"c

"Cl7

"C29

3 32 1 9 1

46 509 6 70 8

34 94 4 13 1

37 4,358

12 2,95

105 640 19 191 24

225 2298 26 312 79

7 44 1 10 2

90 15,554

201 25,1608

6 1.36

2 On7

1008 236,429O

3 0,27

59 153 118 105 48 53

263 202 171 37 180 55

10 12 13 6 2 7

7 3 7 2 1 1

2726 977 1723 830 240 132

6 4 8 3 2 2

41 42 36 70 3 4

8 14 10 2
7 3.15

2 1.6

703 208,2375

4 2,7

19 5,80

3 0.14

1 1 2

91 190 540 1456 299 19891 141 377 2070

1 1 96 87 1 __ 6 5 4

3 1 24 7 2 10 <1 2
81 49,135

LlfL2

L1eL2

b

2 10 1 2 1

880 4672 0 919 273

B

;;GM

Group 7 8 9 11 14 16 18 19 22

n-alkanes

A

;t GM L1cL2

Group 10 12 13 15 17 21

EOMa

122 53,282

C 102 19 491 251 50 259 47 54 157 102 46,228

15 8 466 417 10 308 60 43 47 59

18,199

,’mg/g dry sediment. h rig/g dry sediment. ’ pg/g dry sediment. ’ GM = geometric mean. LI,L2 = 95% confidence limits.

13 6 2 54 3 2 18 6 2,17

53
592 193,1812

<1 __ 9 10 1 18 2 3 2 3 1,9

6 1,27

2 lr7

168

P. D. KEIZER,J. DALE and D. C. GORDON,JR.

the Gulf of Mexico (4+232pg/g) are in the same range although a different extraction method and solvent were used. Using similar extraction methods, higher concentrations of EOM are reported for inshore areas (e.g. CLARK and BLUMER, 1967). Fluorescence analysis The limitations of the fluorescing technique as a means of analyzing for oil in sediments have been discussed (HARGRAVE and PHILLIPS, 1975). Briefly, quantitative fluorescence spectroscopy provides only an estimate of the possible “oil” concentrations in a sample. Due to the arbitrary nature of the standard and the complex mixture of fluorescing compounds in a sample, the estimate may not reflect the actual amount of petroleum-derived material in the sample. The most highly fluorescing compounds, under the analytical conditions used here, are the polycyclic aromatic hydrocarbons (PAH). The estimates of “oil” concentrations are therefore a measure of the relative concentrations of PAH in the samples. If the calibration standard and the extracted material are of the same composition, fluorescence analysis can be very accurate. A fluorescence contour diagram (HARGRAVE and PHILLIPS, 1975) provides a means of assessing the nature of the fluorescing material. Contour plots from Stations 2, 3 and 5 were similar to contour plots for crude oils; there was a distinctive excitation maximum near 300nm and an emission maximum near 400nm. The contribution of petroleum derived hydrocarbons in these samples is therefore probably substantial and estimates of “oil” concentrations at these stations should be more meaningful than those for the other stations. Concentrations of “oil” ranged from less than l-94/*g/g dry sediment (Table 2). HARGRAVE and PHILLIPS (1975) reported concentrations of 55405 pg oil/g wet sediment for samples taken from a variety of clean and polluted inshore areas. Concentrations of l-5 pg oil/g sediment were reported for the “unpolluted” subtidal sediments of Come-By-Chance Bay, Newfoundland (KEIZER, 1974). Assuming a water content of 20-30’4, the range of values reported here is greater than that of Come-By-Chance sediment but is much lower than the range of values for polluted sediments reported by HARGRAVE and PHILLIPS (1975). Samples in Group A had significantly higher concentrations of “oil” than those in Groups B and C, and within Group A there was a significant decrease in concentration with increasing distance from land. This suggests a terrestrial source for the petroleum derived fraction. River runoff, tidal flushing of polluted harbours, and atmospheric fallout of hydrocarbons from thermal electric plants and central heating units may be major contributors. Shipping activities are more concentrated in this area and may also contribute to the input of fluorescing hydrocarbons. A strong correlation (P < 0.01) between “oil” concentrations and EOM in Groups A and C suggests that

a relatively constant proportion of the sediment in these areas is fluorescing material. The exact origin of PAH in sediments is not clear (HITES, 1976). Accidental petroleum spills are one possible source. Natural petroleum seeps do not appear to be an important source as the Scotian Shelf region is reported to have low seepage potential (K~c~Ns and MONAGHAN, 1976). There is some disagreement as to whether or not organisms can synthesize PAH (HITES, 1976) but their presence in various organisms is well documented (e.g. ZITKO, 1975 and VANDERMEULENand GORDON, 1976). BLUMER et al. (1977) have recently published evidence which strongly supports the atmospheric rainout of combustion products from forest fires as a major contributor of PAH in sediments. n-Alkanes Concentrations of total n-alkanes ranged from 8 to 2298 rig/g dry sediment (Table 2). There is no significant difference between the concentrations in any of the groups due to the large variation within groups. However, if the concentrations are calculated per gram of EOM, the variability is much less and the mean concentration in Group A, 2236 @g/g, is significantly higher than in Group C, 574pg/g. The concentrations of total n-alkanes reported here are reasonably consistent with values reported elsewhere. CLARK and BLUMER (1967) report a total n-alkane concentration of 1680 rig/g dry sediment for a sample from inshore Massachusetts, while WHITTLE et al. (1974) reported concentrations of 610 rig/g sediment from inshore Scotland. Concentrations reported for Beaufort Sea sediments are much higher, ranging from 6000 to 23,6OOng/g (WONG et al., 1976). If concentrations of individual hydrocarbons are compared, the values reported here (Table 2) are very similar to that reported in the New York Bight by FARRINGTON and TRIPP (1977), O-88 rig/g for nC,, and 8.51050ng/g for nCz9. CLARK and BLUMER (1967) reported a concentration of 200 ng of nC,-i/g sediment and WHITTLE et al. (1974) 114 ng of nCz9/g sediment. Both the latter sets of sediment samples were from inshore areas. The values reported for the Beaufort Sea study (WONG et al., 1976) are generally higher; 17(X2800 ng of nC,, and 200 to 2430 ng of n& per gram of sediment. With the exception of the Beaufort Sea samples the range of concentrations reported from the different areas are very similar, particularly for specific n-alkanes. The composition of the n-alkanes extracted from sediments is also relatively consistent. In this study, the carbon preference index (CPI) ranged from 1.1 to 5.3 (Table 3) and there was no difference between the three groups. The CPI for sediments in the western North Atlantic (FARRINGTON and TRIPP, 1977) ranged from 1.1 to 3.5; in the Beaufort Sea (WONG et al., 1976) from 1.6 to 3.4; and, inshore Massachusetts (CLARK and BLUMER, 1967) 4.0. Sediment extracts from the Gulf of Mexico (GEARINGet al.,

1976) also exhibited a marked odd carbon preference. Variation in the CPI is the end product of the many sources of n-alkanes in the marine environment. A high CPI indicates that tHe major swurce of n-alkanes

is terrestrial plants, while a CPI approa~~n~ unity indicates greater input from marine organisms andjor petroleum hydrocarbons (FARRINGTONand Mums, 1975). lsoprenoitfs Two

isoprenoids,

pristane

and

phytane,

were

present in ail sediment extracts. The mean &ncentration of pristane was 60.1 @g/g EUM (6.0ng/g dry sediment, Concentrations of phytane were lower, averaging 20.5 pg/g EOM (1.9 rig/g dry sediment). There were no significant differences in concentrations of the isoprenoids among the three groups. The pristane EO phytane ratio varied from 1.03 at Station 16 to

10.21 at Station 21. Pristane was usually more abundant than n-octadecane (Table 3). The range af cwncentrations of pristane and phytane reported here are in agreement with other published reports (e.g. FARRINGTON and TRIPP, 1977; WHITTLEet al., 1974), again with the exception of values reported for the Beaufort

Sea which are up to an wrder of magnitude higher (WONG et al., 1976). Pristane has been identified in seawater and marine organisms; it is most likely a degradation product of phytol (Cox et al., 1974). The presence of phytane ia the marine enviro~ent is not as common; hwwever, it is fwund in petroleum at about an equal cwncentratian with pristane and therefore is generally used as an indicator of petroleum pollution It has not been found in any marine organisms except bacteria (HAN and Cntvr~, 1969). Its presence in sediments from a number of different areas has also been reported (GEARING et al., 1976; WoNc et al., 1976; FARRINQT~Nand TRIPP, 1977). The presence of phytane, if strongly correlated with other variables characteristic of petroleum, such as a large unresolved complex mixture, a CPI near unity, etc., is a strong indication that a major fraction of the hydrocarbwns detected are petroleum derived. Unresolved

complex

mixture

All of the chromatograms, with the exception of that frwm Station 3, had a measurable unresolved envelope. The material in this envelope is often

Table 3. Ratios of various parameters for Scotian Shelf sediments Station no.

"Tl.7 pristane

"-c18 -phytane

1

0.50

2

0.73 0.50 a.97 0.48

1.31 3.11 1.20 1.82 1.74 1.73 1.09,2*75

Group

Group B 10

21 H

GM

%lL2

%= 8

0.65 0.31. 0.65 0.55

1.19

1.17 0.28

1.33 0.68 1.09 1.94 1.23

0.54 0.31‘0.93

0.83,X.69

0.34

-__

1.19

0.99

16 18 19

0.35 0.33 0.68 1.02

22

0.92

0.80 2.46 1.89 1.02 0.94 1.95 2.46 1.01

0.64 0.39,1*04

l-37 0.97,1.94

9

11 14

%M %J2

resolved unresolved

CPP

2.90 4.58 2.00 5.25 2.48

0.50 0.62 k.4: 0.35

3.24 4.39 3.13 4.97 1.51

3.44b 1.70,5,18

Q.49b 0*32,0*66

3.20 1.80,5.68

Cl.14 0.37 0.20 0.10 0.12 0.42

2.65 3.65 3.71 3.80 2.61 1.42

3.82b 0.30,7_34

0.22b 0.08,0.36

2.82 1.90,4.19

1.22 _-_ 5.05 2.61 1.64 1.03 8.95 2.55 8.08

O.ZY. 0.10 1.04 0.37 0.08 0.05 0.56 0.15 0.04

1.65 I__ 5.32 4.52 1"65 ___ 1.48 1.76 J.14

3,88b 1.28.6.48

0.29b 0.04,0.54

2.12 1.23,3.67

phytane

A

3 5 24

12 13 15 If

pristana

0*7L 1.58

a carbon preference index. _”arithmetic mean. XGM = geometric mean. L,,L, = 95% confidence limits.

L.44 4.83 1.90 2.64 1.92 10.21

170

P. D. KEIZER.J. DALEand D. C.

referred to as the unresolved complex mixture (UCM). Concentrations of UCM (Table 2) averaged 6.9 mgig EOM (699 rig/g dry sediment). There was no significant difference between the means of the three groups. The ratio of resolved to unresolved hydrocarbons ranged from 0.04 to 1.04, and was significantly higher in the samples of Group A. It is important to note that the amount of UCM present is partly a function of the gas chromatographic parameters and therefore comparison with other reported values is of questionable value. Analysis of the UCM (BLUMERet al., 1970) has revealed a complex assemblage of principally naphthenic hydrocarbons. The presence of a UCM in organism extracts is indicative of petroleum pollution (FAKRIN~TONand MEYERS,1975). Its presence in sediment extracts may be more complicated due to the variety of sources of organic material in sediments, but again, if strongly correlated with other parameters indicative of a petroleum source it adds strength to arguments for such a source. Alkenes--cycloalkenes

In 14 of the 20 chromatograms there was a single peak and/or group of partially resolved peaks with retention indices between 2000 and 2100 (Fig. 2, peak 3). There was no apparent pattern to the variation in concentration. Their presence was affected by mild hydrogenation conditions indicating the presence of one or more unsaturations. Changes noted in the chromatograms were the dis-

SCOTIAN

GORDON, JR

appearance of the peak with retention index 2441, a decrease in the intensity of the 2050 peak and some apparent changes in the partially resolved peaks around n-heneicosane (C,,) indicating the compounds contained unsaturations (see Fig. 2). There was no apparent increase in the peak area of other resolved peaks indicating that the hydrogenated derivatives of these compounds were not resolved on this column under the conditions employed. Peaks with similar retention indices have been reported in sediments from a number of areas, more recently from the Gulf of Mexico by GEARINGet al. (1976) and in a number of offshore and coastal areas of the eastern North Atlantic (e.g. FARRINGTONand TRIPP, 1977). EHRHARDTand BLUIMER(1972) and GEARING et al. (1976), using GC-MS data, have tentatively identified these compounds as 25 carbon cycloalkenes with varying degrees of unsaturation. Possible hydrocarbon sources

The presence of a UCM, pbytane or a high “oil” concentration is not sufficient to indicate that the primary source of the extracted material is petroleum. However, a strong correlation between these and other variables makes a petroleum source more probable. Correlations between the various parameters in Group B and C samples are listed in Table 4. There was no significant correlation for any of the parameters in Group A, possibly due to the pronounced differences in sediment type and a greater diversity of hydrocarbon sources closer to the mainland.

SHELF

STATION I

Fig. 2. Gas-liquid chromatogram of sediment extract from Station 1. The odd carbon preference is very evident. Operating conditions for the analysis are given in the text. Dashed line is normal baseline. Pr = pristine, Ph = phytane, UCM = unresolved complex mixture. Peak 1 disappeared when sample was hydrogenated; peak 2 is an artifact of the separation procedure originating in the silica gel; peaks 3 are the compounds with retention indices between 2000 and 2100 mentioned in the text. Numbers 16-33 refer to the number of carbon atoms in the indicated n-alkane.

Hydrocarbons

in surficial sediments from the Scotian Shelf

171

Table 4. Results of linear regression analysis of various parameters

Group C

Group 3 Variable

P

n

c

< -05 *

8

.17

r .05

P

&f n-alkanes vs pristane

pristane

phytane

UCM

.61

vs phytane

.94

< .Ol *

9

.23

> .a5

vs UCM

.95

< -01*

9

.25

> .05

VB oil

.85

< .02*

9

.32

> .05

vs phytane

.69

> .05

8

.88

< .01*

v* UCM

.82

< .os *

8

.93

c .01*

vs UCM

.98

< .01*

9

.99

i .01*

vs oil

.8tJ

< -05 *

9

.20

> .05

vs oil

.80

< .os*

9

.09

z .05

* significant correlation.

While the concentration of the various parameters in Groups B and C are not significantly different, the correlation of various parameters indicates that there is a difference in the distribution of the measured parameters between these two groups. Results of linear regression analysis of the various parameters (Table 4) indicate that in samples from Group 3, the correlations between all the parameters associated with petroleum bydro~arbons are strong. Only the pristane-phytane correlation is not significant, perhaps due to the abundance of pristane from biogenic sources. In samples from Group C, the relationship between the various parameters is quite different. The strong correlation of pristane and phytane with the UCM remains and the correlation between pristane and phytane becomes significant. Removing the samples from Stations 9 and 11, which are a different sediment type, from Group C does not affect the results of the regression analyses. The only other known factor which could explain the difference between the two groups is the exploratory dri~iijlg which occurred at Group B stations. Deposition of drilling mud and tailings on the bottom as well as the release of petroleum hydroc~bons from the drihing rig and service vessels could have altered the composnion of suriicial sediments in the vicinity of the well sites. BEAN et al. (1974) have also noted an influence of production wells on the organic content of adjacent sediments.

the various parameters measured in samples collected along a transect from Halifax to Emerald Bank indicating a diversity of sources and/or ~veather~~~mechanisms in this region. Expression of concentrations relative to extractable organic material (EOM) removes some of the variability between sampies; it also expresses hydrocarbon concentrations in a manner which may be more realistic for judging the potential toxicity of polluted sediments. There is an apparent difference in the hydrocarbon composition of the sediment at abandoned exploratory drilling sites and from adjacent areas presumably unaffected by drilling. This cannot be accounted for by differences in sediment type or &I situ production of biogenic hydro~~bons. The change in &hehydrocarbon camposition is subtle but suggests that there may be changes in other parameters which were not analyzed, Acknowltdgements-The

authors wish to thank the Master and crew of the C.S.S. Dawsnn for their assistance, Messrs. W. R. HARDSTAFFand T. P. AHERN for their assistance in working up the laboratory procedures and Drs. B. T. HARGRAVE and E. M. LEVY for: critically reading the manuscript.

RE~R~NCES ANONYMOUS (1973) Offshore exploration.

Information and procedures for off shore operators. February 1973, 5th issue. Resource, management and conservation branch.

Department of Energy, Mines and Resources. M,, BLAYLOCK.I. W., SUTTONE. A., W~~DU~G R. E. and DAVIDXN F. M. (1974) Character~ation of sediments in the vicinity of offshort petroleum production, Paper presented at Symposium on chemistry of marine sediments, American Chemical Society, S-13 September, 1974, pp. 7X-735. BLUMERM.. DORSEYT. and SASS J. (1977) Azaarenes in

BEAN R.

CONCLUSIONS The hydrocarbon content of Scotian Shelf sediments appears to be primarily of terrestrial origin. This is documented by the strong odd carbon preference of the n-alkanes and the decreasing concentration of various parameters with increasing distance from the mainland. There is no correlation between

recent marine sediments.

Science

145, 283-285.

BLUMERM., SOUZA G. and SASS J. (1970) Hydrocarbon pollution of edible shellfish by an oil spill. Mau. Bial.

5, 195-202.

I72

P. D. KEIZER,J. DALE and D. C. GORDON,JR.

CLARK R. C. and BLUMERM. (1967) Distribution of nHITESR. A. (1976) Sources of polycyclic aromatic hydrocarbons in the aquatic environment. In Sources, Effects paraffins in marine organisms and sediment. Limnol. and Sinks of Hydrocarbons in the Aquatic Environment. Oceanogr. 12, 79-90. Cox R. E., MAXWELLJ. R., ACKMANR. G. and HOOPER Proceedings of the Symposium, 9-11 August, pp. S. N. (1974) Stereochemical studies of acyclic isoprenoid 326-332, American Institute of Biological Sciences, compounds--II. Microbial oxidation of 2,6,10,14-tetraWashington, D.C. methylpentadecane (pristane). Biochem. Eiophys. Acta KEIZER P. D. (1974) Estimation of hydrocarbon concen360. If%‘-173. trations in the sediments of Come-By-Chance BayEHRHARD~M. and BLUMERM. (1972) The source identifiFebruary 1974. Fisheries and Marine Service Technical cation of marine hydrocarbons by gas chromatography. Report No. 485. Enciron. P&t. 3, 179-194. KING L. H. (1970) Surficial geology of the Halifax-Sable FARRINGTON J. W. and MEYERSP. A. (1975) Hydrocarbons Island map area. Dept. Energy, Mines und Resources, in the marine environment. Chapter 5 in Environmental Marine Sciences Branch, marine science paper no. 1. Chemistry, Vol. I (editor G. Eglinton), Specialists PerioK~ONS C. B. and MONAGHAN P. H. (1976) Input of hydrodical Report, The Chemical Society, London. carbons from seeps and recent biogenic sources. In FARRINGTON J. W. and TRIPP B. W. (1975) A comoarison Sources, Effects and Sinks of Hydrocarbons in the Aquatic of analysis methods for hydrocardons in surfaie sediEnvironment. Proceedings of the Symposium, 9-11 ments. ACS Symposium Series, No. 18, Marine ChemisAugust, pp. 85-107, American Institute of Biological try in the Coastal Environment, pp. 267-284. Sciences, Washington, D.C. FARRINGTON J. W. and TRIPP B. W. (1977) Hydrocarbons MACLEANB. and KING L. H. (1971) Surficial geology of in western North Atlantic surface sediments. Geochim. the Banquereau and Misaine Bank map area. Dept. of Cosmochim. Acta 41, 1627-1641. Environment, Marine Sciences Branch, marine science GEARING P., GEARING J. N., LYTLE T. F. and LYTLE paper no. 3. VAUDFRMFULEX J. H. and GORDON D. C., JR. (1976) ReJ. S. (1976) Hydrocarbons in 60 northeast Gulf of Mexico shelf sediments: a preliminary survey. Geochim. entry of 5-year old stranded Bunker C fuel oil from a Cosmochim. Acta 40, 1005-1017. low-energy beach into the water, sediments and biota GORDON D. C., JR. and KEIZER P. D. (1974) Estimation of Chedabucto Bay, Nova Scotia. J. Fisheries Res. of petroleum hydrocarbons in seawater by fluorescence Board. Can. 33, 2002-2010. WHITTLEK., MACKIEP. R. and HARDYR. (1974) Hydrospectroscopy: improved sampling and analytical carbons in the marine eco-system. S. Aji. J. Sci. 70, methods. Fisheries and Marine Service Technical Report No. 481. 141-144. HAN J. and CALVINM. (1969) Hydrocarbon distribution WONG E. S., CRETNEYW. J., MACDONALDR. W. and of algae and bacteria, and microbiological activity in CHRISTENSEN P. (1976) Hydrocarbon levels in the marine sediments. Proc. Natl. Acad. Sci. 64, 436-443. environment of the southern Beaufort Sea. Beaufort Sea HARGRAVEB. T. and PHILLIPSG. A. (1975) Estimates of Technical Report No. 38. oil in aquatic sediments by fluorescence spectroscopy. ZITKOV. (1975) Aromatic hydrocarbons in aquatic fauna. Em,iro,t. Pollut. 8, 193-216. Bull. Environ. Contam. Toxicol. 14, 621-631.