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Normal paraffin profiles of pelagic tar samples from the marmap survey
Marine Chemistry, 3(1975) 1--7 © Elsevier Scientific Publishing Company, Amsterdam -- Printed in The Netherlands
Research Papers NORMAL PARAFFIN PROFILES OF PELAGIC TAR SAMPLES FROM THE MARMAP SURVEY
JAMES N. BUTLER and JUDITH C. HARRIS Harvard University, Division of Engineering and Applied Physics, Cambridge, Mass. (U.S.A.) (Received September 3, 1974; accepted January 9, 1975)
ABSTRACT Butler, J. N. and Harris, J. C., 1975. Normal paraffin profiles of pelagic tar samples from the MARMAP survey. Mar. Chem., 3: 1--7. Pelagic tar samples from twenty stations on cruises of the research vessels ALBATROSS IV (72-6) and DELAWARE II (72-19 ) were analyzed by gas chromatography to obtain semi-quantitative profiles of normal paraffins in the range from C 10 to C35 and a qualitative indication of the relative amount of other compounds having a volatility in that same range. These samples are essentially all weathered residues of waxy paraffinic crude oils, and are similar (with respect to the parameters measured) to numerous samples collected in the Sargasso Sea near Bermuda. INTRODUCTION Pelagic t a r was o b t a i n e d in m a n y n e u s t o n s a m p l e s d u r i n g the first operational t e s t p h a s e o f t h e M A R M A P survey ( S h e r m a n et al., 1973). Cruise 72-6 o f t h e A L B A T R O S S IV o b t a i n e d at 32 s t a t i o n s s a m p l e s o f t a r ranging in w e i g h t f r o m 15 m g t o 3 g. On Cruise 72-19 o f t h e D E L A W A R E II, t a r was o b t a i n e d at 1 0 6 stations, w i t h s a m p l e s ranging in w e i g h t f r o m 1 m g t o approxim a t e l y I g. T h e s e s a m p l e s o f t a r w e r e s e p a r a t e d f r o m t h e o t h e r m a t e r i a l c o l l e c t e d in t h e n e u s t o n t o w s b y p e r s o n n e l o f t h e M A R M A P p r o g r a m . Visually, t h e t a r l u m p s w e r e black t o grey, s o f t in t e x t u r e , a n d r a n g e d f r o m d r y to s t i c k y in c o n s i s t e n c y . A f e w s a m p l e s w e r e so fluid t h a t t h e y m e l t e d o v e r t h e inside o f t h e vials, b u t m o s t w e r e in the f o r m o f l u m p s ranging in size f r o m a b o u t 1--5 m m in d i a m e t e r . T h e s a m p l e s c h o s e n f o r this p r e l i m i n a r y analysis w e r e t a k e n f r o m 20 s t a t i o n s ( T a b l e I) w h e r e a relatively large a m o u n t o f t a r was c o l l e c t e d , so t h a t t h e smaller s a m p l e s c o u l d be reserved f o r l a t e r w o r k w i t h m o r e r e f i n e d t e c h n i q u e s , including analysis f o r metallic e l e m e n t s a n d specific classes o f organic c o m p o u n d s .
2 TABLE I Index of samples Station No. Location
*1
Visual appearance, texture
N~/2
Chromatogram type* 2
a) hard grey-black crumbly b) hard grey-black crumbly a) crumbly light grey b) black sticky soft black sticky black sticky dry surface, sticky inside brown-black, sticky very soft (melted) grey black pasty brown-black sticky a) soft black sticky b) soft black sticky a) soft black sticky b) soft black sticky c) crumbly black
20 19.5 15 17 16.5 18 18 18 18 16.5 19.5 18.5 19--22 16.5 16
D D B E A B B B A B A B B B B
crumbly black soft black dry soft black dry soft black dry crumbly black with grey surface a) soft black sticky b) soft black sticky a) soft black dry b) crumbly grey dry crumbly black sticky soft black crumbly light grey dry
16 14.5 15--16 15.5
B F B B
15.5 17.5 17 17.5 16 14.5 16 18
A A B B B A A C
DELAWARE II (72-19) (East Coast of U.S.) 12
37°N
70°W
15
39°30'N
70°W
23 38 60 66 68 72 88
39°N 70°30'W 39°N 72°W 38°30'N 74°W 38°N 73°W 38°N 71°W 37°30'N 74°W 35°30'N 72°W
112
33°30'N
77°W
ALBATROSS IV (72-6) (North of West Indies) 1 3 13 15 57
23 °N 21 °N 23°N 24°N 24°N
6 l°W 6l ° w 63°W 65°w 72°W
61
27°N
7'3°W
63
26°N
74°W
65 71 75
24°N 27°N 30°N
74°W 77°W 78°W
*1
*2
N,/2 is the retention index where the unresolved background reaches half its maximum height, expressed as the carbon number of a normal paraffin with the same retention index. A, Weathered paraffinic crude. Single maximum in envelope of paraffins. B, Crude oil sludge. Bimodal envelope of paraffins. C, Wax. Essentially all paraffins. D, Isoprenoids (Pristane, phytane) large but no normal paraffins below about C27. E, Other: Sample 15b shows an unusual (biogenic?) peak near C~9. F, Other: Sample 3 shows large isoprenoids, almost no paraffins above C24.
METHODS Samples were analyzed at Harvard on a Hewlett-Packard Model 5711 temperature-programmed gas chromatograph with flame-ionization detector. The procedure used was similar to that developed by Blumer's group at Woods Hole Oceanographic Institution (Erhardt and Blumer, 1972). Approximately 1--5 mg of tar was placed in a glass tube (1 mm i.d.) in an electrically heated probe ( " P y r o p r o b e " ) which could be inserted into the injector port of the gas chromatograph. Volatile material from the sample was distilled at approximately 250°C for 10 minutes and accumulated on the cold (30--50°C) column. During this period, two pulses of 20 sec each at approximately 330°C were applied. The probe was then removed from the injector port. The column was 1/8 inch × 10 feet stainless steel, packed with 3% Apiezon L on Chromosorb. Carrier gas (N:) flow was.60 ml/min. Temperature was programmed from 80 ° to 300°C at 4°/min, and held at 300 ° until no more peaks were observed to elute from the column. A blank was run each day to insure that there was no contamination of the column or injector port by residual material of low volatility. (A sample chromatogram is displayed in Fig.1.) In addition, five samples were analyzed at the Bermuda Biological Station using a Varian Aerograph Model 1400 with flame ionization detector and a 1/16 in × 10 ft column packed with 3% SE-30 on Varaport 30 100/120 mesh. Carrier gas (N2) flow rate was 30 ml/min. Temperature was programmed from 50 ° to 300 ° at 6°/min. This analysis protocol was identical to that used for samples from the Sargasso Sea and allowed direct visual comparison with a large number of published chromatograms (Butler et al., 1973).
I
S~a~ion61 soft sticky black
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11124 25
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Fig.1. Sample gas chromato~ram of a pelagic tar lump obtained at Station 61 of the ALBATROSS IV cruise, 27 N, 73°W., northeast of the Bahama islands. For this sample N1/2 = 17.5.
RESULTS AND DISCUSSION
Chromatograms made during this study are schematically summarized in Figs.2 and 3. All show distinct peaks for normal paraffins in the range from 12 to 35 carbons, a number of smaller peaks probably corresponding to branched chain paraffins, and an unresolved background of naphthenic, aromatic, heterocyclic and other c o m p o u n d s characteristic of crude oils. Although each chromatogram is unique, and even different tar lumps from the same station (indicated by a, b, c, in Table I) show distinct chromatograms, there are a number of general features which appear significant in all. The chromatogram type has been indicated as a simple weathered paraffinic crude (A), a crude-oil sludge with a bimodal paraffin distribution (B), pure paraffinic wax (C), a sample with high-carbon paraffins and substantial 1.0 f
20
3,0
'
~
120
40
112b
I 15b
25
150 ,Ipr "'"'",,
38
/ z "'\
6O
66
68
/
72
880
8Bb
112o
112b
112c
DELAWARE IT 72-19 NORMALPARAFFINS, PRISTANE AND PHYTANE, SHOWN AS BARS. . . . . . UNRESOLVED BACKGROUND, (SAME SCALE)
Fig.2. S c h e m a t i c s u m m a r i e s of t h e gas c h r o m a t o g r a m s o f samples f r o m t h e D E L A W A R E II cruise, s h o w i n g n o r m a l paraffins, p r i s t a n e , a n d p h y t a n e as vertical bars, a n d t h e unresolved e n v e l o p e as a d a s h e d line o n t h e same scale.
I0
20
Y-'"'"',,
%
30
40
/."".,
. ..--...,
15
57
61a
61 b
630
63b
65
71
75 f
....
,
ALBATROSS ~ 7 2 - 6 NORMAL PARAFFINS, PRISTANE AND PHYTANE, SHOWN AS BARS. ..... UNRESOLVED BACKGROUND, (SAME SCALE)
Fig.3. S c h e m a t i c s u m m a r i e s of t h e gas c h r o m a t o g r a m s of samples f r o m t h e A L B A T R O S S IV cruise.
pristane and phytane but no low-carbon paraffins (D), and other relatively unusual types. Numerous examples of types A and B will be found in other Sargasso Sea samples, and several samples of types C and D are also d o c u m e n t e d (Butler et al., 1973). O n e important parameter which would be desirable is the age of the tar lumps. Unfortunately, no technique has yet been developed which will unambiguously give the chronological age of a pelagic tar lump (Butler, 1975, this issue, pp. 9--21). Evaporation during weathering tends to diminish the low-boiling hydrocarbons at a rate proportional to their vapor pressure with the result that the unresolved envelope of the chromatogram moves to higher retention index values as the weathering process continues. An index of the degree of weathering is N~/2, the equivalent normal paraffin carbon n u m b e r having a retention index equal to that where the unresolved background reaches half its maximum height (Table I). This index was used by Blumer et al. (1973) in their weathering studies of crude oil on rocky shores (symbol CS~) and has been related to chronological age by a semiquantitative evaporative weathering model (Butler, 1975). For pelagic tar, however, the relation between N~/2 obtained from the gas
chromatogram and the time the tar has been weathering is complicated by the high degree of fragmentation that crude oil residues appear to undergo on the surface of the open ocean. Chronological age cannot be obtained in terms of the evaporative weathering model unless the initial volume of the sample before fragmentation is known, and such information is at best speculative. For this reason, we have not attempted to calculate ages from the N~/~ values. In spite of this limitation, the samples listed in Table I may be grouped according to increasing degree of weathering. DELAWARE 15a, ALBATROSS 3, 13, 15, 57, and 65 all have N m in the range 14.5--15.5 and may be inferred to be quite fresh. DELAWARE 15b, 23, 7 2 , 1 1 2 b , 112c and ALBATROSS 1, 61, 63, and 71 have N, n in the range 16--17 and have probably been at sea for a longer time. DELAWARE 38, 60, 66, 68, and 88b and ALBATROSS 75 have N,12 in the range 18--18.5. The most heavily weathered samples are DELAWARE 12, 88a, and 112a, w i t h indices between 19 and 22. The distribution of these N,/2 values is approximately normal, with a median between 16.5 and 17.0, almost exactly the same as for a series of 40 samples (median 16.7) taken during the same period (summer of 1972) at Station S in Bermuda (Butler et al., 1973; Butler, 1975). This tends to confirm the idea that the MARMAP samples are from the same general population of pelagic tar lumps as the samples collected near Bermuda. More than half of the chromatograms showed bimodal paraffin distribution (type B), in the C20 to C3s range, characteristic of crude oil sludges (Brunnock et al., 1968). This is evidence that these tar lumps came from tanker wastes d u m p e d at sea. One sample (ALBATROSS IV, Station 75) was almost all paraffins (type C). Only one chromatogram (DELAWARE II, Station 15) showed an unusually large peak near the retention time of normal C,9 which might be biogenic in origin. However, another lump collected at the same station showed the usual pattern of a waxy, weathered crude oil. Extensive discussion of the possible sources and fates of these pelagic tar lumps has been published elsewhere (Blumer et al., 1973; Butler et al., 1973; National Academy of Sciences, 1975).
CONCLUSIONS (1) All the samples analyzed appear to be residues of paraffinic crude oil. (2) Many of the samples contain relatively large amounts of high-boiling paraffinic wax, indicating that their origin is from tanker wastes. (3) The qualitative character of the samples is indistinguishable from those obtained in neuston tows near Bermuda. Parameters considered in this comparison include: color, texture, size, shape, profile of normal paraffins, volatility of lowest-boiling components, relative amount of paraffins and isoprenoids, relative amount of paraffins and unresolved background material, and the absence (except for one sample) of isolated peaks indicative of biogenic components.
ACKNOWLEDGEMENTS
The enthusiastic assistance of Mr. Steven A. Gherini and Miss Karen E. Fine of Harvard University; and the cooperation of Drs. Kenneth Sherman, Robert L. Dryfoos, and Frederick D. Knapp of the MARMAP Field Office, National Marine Fisheries Service, are gratefully acknowledged. This work was supported by the National Science Foundation, International Decade of Ocean Exploration, the National Marine Fisheries Service, and the National Institutes of Environmental Health Sciences. This is Contribution No. 165 from the Bermuda Biological Station for Research. REFERENCES Blumer, M., Erhardt, M. and Jones, J. H., 1973. The.environmental fate of stranded crude oil. Deep-Sea Res., 20: 239--259. Brunnock, J. V., Duckworth, D. F. and Stephens, G. G., 1968. Analysis of beach pollutants. J. Inst. Petrol., 54: 310--325. Butler, J. N., 1975. Evaporative weathering of petroleum residues: the age of pelagic tar. Mar. Chem. 3 : 9 - - 2 1 (this issue). Butler, J. N., Morris, B. F. and Sass, J., 1973. Pelagic tar from Bermuda and the Sargasso Sea. Bermuda Biological Station for Research, St. George's West, Spec. Publ., 1 0 : 3 4 6 pp. Erhardt, M. and Blumer, M., 1972. The source identification of marine hydrocarbons by gas chromatography. Environ. Pollut., 3: 179--194. National Academy of Sciences, National Research Council, 1975. Petroleum in the marine environment. Washington, D.C. Sherman, K., Colton, J. B., Knapp, F. D., Dryfoos, R. L., Kinnear, B. S., 1973. Oil and plastics contamination and fish larvae in surface waters of the northwest Atlantic. Unpubl. Prelim. Rep., Marmap Field Office, Narragansett, Rhode Island. U.S. Dept. Commerce News, Feb. 13 (NOAA 73-17).
Research Papers NORMAL PARAFFIN PROFILES OF PELAGIC TAR SAMPLES FROM THE MARMAP SURVEY
JAMES N. BUTLER and JUDITH C. HARRIS Harvard University, Division of Engineering and Applied Physics, Cambridge, Mass. (U.S.A.) (Received September 3, 1974; accepted January 9, 1975)
ABSTRACT Butler, J. N. and Harris, J. C., 1975. Normal paraffin profiles of pelagic tar samples from the MARMAP survey. Mar. Chem., 3: 1--7. Pelagic tar samples from twenty stations on cruises of the research vessels ALBATROSS IV (72-6) and DELAWARE II (72-19 ) were analyzed by gas chromatography to obtain semi-quantitative profiles of normal paraffins in the range from C 10 to C35 and a qualitative indication of the relative amount of other compounds having a volatility in that same range. These samples are essentially all weathered residues of waxy paraffinic crude oils, and are similar (with respect to the parameters measured) to numerous samples collected in the Sargasso Sea near Bermuda. INTRODUCTION Pelagic t a r was o b t a i n e d in m a n y n e u s t o n s a m p l e s d u r i n g the first operational t e s t p h a s e o f t h e M A R M A P survey ( S h e r m a n et al., 1973). Cruise 72-6 o f t h e A L B A T R O S S IV o b t a i n e d at 32 s t a t i o n s s a m p l e s o f t a r ranging in w e i g h t f r o m 15 m g t o 3 g. On Cruise 72-19 o f t h e D E L A W A R E II, t a r was o b t a i n e d at 1 0 6 stations, w i t h s a m p l e s ranging in w e i g h t f r o m 1 m g t o approxim a t e l y I g. T h e s e s a m p l e s o f t a r w e r e s e p a r a t e d f r o m t h e o t h e r m a t e r i a l c o l l e c t e d in t h e n e u s t o n t o w s b y p e r s o n n e l o f t h e M A R M A P p r o g r a m . Visually, t h e t a r l u m p s w e r e black t o grey, s o f t in t e x t u r e , a n d r a n g e d f r o m d r y to s t i c k y in c o n s i s t e n c y . A f e w s a m p l e s w e r e so fluid t h a t t h e y m e l t e d o v e r t h e inside o f t h e vials, b u t m o s t w e r e in the f o r m o f l u m p s ranging in size f r o m a b o u t 1--5 m m in d i a m e t e r . T h e s a m p l e s c h o s e n f o r this p r e l i m i n a r y analysis w e r e t a k e n f r o m 20 s t a t i o n s ( T a b l e I) w h e r e a relatively large a m o u n t o f t a r was c o l l e c t e d , so t h a t t h e smaller s a m p l e s c o u l d be reserved f o r l a t e r w o r k w i t h m o r e r e f i n e d t e c h n i q u e s , including analysis f o r metallic e l e m e n t s a n d specific classes o f organic c o m p o u n d s .
2 TABLE I Index of samples Station No. Location
*1
Visual appearance, texture
N~/2
Chromatogram type* 2
a) hard grey-black crumbly b) hard grey-black crumbly a) crumbly light grey b) black sticky soft black sticky black sticky dry surface, sticky inside brown-black, sticky very soft (melted) grey black pasty brown-black sticky a) soft black sticky b) soft black sticky a) soft black sticky b) soft black sticky c) crumbly black
20 19.5 15 17 16.5 18 18 18 18 16.5 19.5 18.5 19--22 16.5 16
D D B E A B B B A B A B B B B
crumbly black soft black dry soft black dry soft black dry crumbly black with grey surface a) soft black sticky b) soft black sticky a) soft black dry b) crumbly grey dry crumbly black sticky soft black crumbly light grey dry
16 14.5 15--16 15.5
B F B B
15.5 17.5 17 17.5 16 14.5 16 18
A A B B B A A C
DELAWARE II (72-19) (East Coast of U.S.) 12
37°N
70°W
15
39°30'N
70°W
23 38 60 66 68 72 88
39°N 70°30'W 39°N 72°W 38°30'N 74°W 38°N 73°W 38°N 71°W 37°30'N 74°W 35°30'N 72°W
112
33°30'N
77°W
ALBATROSS IV (72-6) (North of West Indies) 1 3 13 15 57
23 °N 21 °N 23°N 24°N 24°N
6 l°W 6l ° w 63°W 65°w 72°W
61
27°N
7'3°W
63
26°N
74°W
65 71 75
24°N 27°N 30°N
74°W 77°W 78°W
*1
*2
N,/2 is the retention index where the unresolved background reaches half its maximum height, expressed as the carbon number of a normal paraffin with the same retention index. A, Weathered paraffinic crude. Single maximum in envelope of paraffins. B, Crude oil sludge. Bimodal envelope of paraffins. C, Wax. Essentially all paraffins. D, Isoprenoids (Pristane, phytane) large but no normal paraffins below about C27. E, Other: Sample 15b shows an unusual (biogenic?) peak near C~9. F, Other: Sample 3 shows large isoprenoids, almost no paraffins above C24.
METHODS Samples were analyzed at Harvard on a Hewlett-Packard Model 5711 temperature-programmed gas chromatograph with flame-ionization detector. The procedure used was similar to that developed by Blumer's group at Woods Hole Oceanographic Institution (Erhardt and Blumer, 1972). Approximately 1--5 mg of tar was placed in a glass tube (1 mm i.d.) in an electrically heated probe ( " P y r o p r o b e " ) which could be inserted into the injector port of the gas chromatograph. Volatile material from the sample was distilled at approximately 250°C for 10 minutes and accumulated on the cold (30--50°C) column. During this period, two pulses of 20 sec each at approximately 330°C were applied. The probe was then removed from the injector port. The column was 1/8 inch × 10 feet stainless steel, packed with 3% Apiezon L on Chromosorb. Carrier gas (N:) flow was.60 ml/min. Temperature was programmed from 80 ° to 300°C at 4°/min, and held at 300 ° until no more peaks were observed to elute from the column. A blank was run each day to insure that there was no contamination of the column or injector port by residual material of low volatility. (A sample chromatogram is displayed in Fig.1.) In addition, five samples were analyzed at the Bermuda Biological Station using a Varian Aerograph Model 1400 with flame ionization detector and a 1/16 in × 10 ft column packed with 3% SE-30 on Varaport 30 100/120 mesh. Carrier gas (N2) flow rate was 30 ml/min. Temperature was programmed from 50 ° to 300 ° at 6°/min. This analysis protocol was identical to that used for samples from the Sargasso Sea and allowed direct visual comparison with a large number of published chromatograms (Butler et al., 1973).
I
S~a~ion61 soft sticky black
o-lo
Iii
I
11124 25
B Di
!:2.
~
[
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[
;I'
i
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: t ,i:
4
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t,
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I ot
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+-
~ "
I .
.
.
.
.
.
.
.
I
. . . . . .
i
:
i
~
f ~ l : , I 25
-: ,
z
!
~
-
-
I
~
Fig.1. Sample gas chromato~ram of a pelagic tar lump obtained at Station 61 of the ALBATROSS IV cruise, 27 N, 73°W., northeast of the Bahama islands. For this sample N1/2 = 17.5.
RESULTS AND DISCUSSION
Chromatograms made during this study are schematically summarized in Figs.2 and 3. All show distinct peaks for normal paraffins in the range from 12 to 35 carbons, a number of smaller peaks probably corresponding to branched chain paraffins, and an unresolved background of naphthenic, aromatic, heterocyclic and other c o m p o u n d s characteristic of crude oils. Although each chromatogram is unique, and even different tar lumps from the same station (indicated by a, b, c, in Table I) show distinct chromatograms, there are a number of general features which appear significant in all. The chromatogram type has been indicated as a simple weathered paraffinic crude (A), a crude-oil sludge with a bimodal paraffin distribution (B), pure paraffinic wax (C), a sample with high-carbon paraffins and substantial 1.0 f
20
3,0
'
~
120
40
112b
I 15b
25
150 ,Ipr "'"'",,
38
/ z "'\
6O
66
68
/
72
880
8Bb
112o
112b
112c
DELAWARE IT 72-19 NORMALPARAFFINS, PRISTANE AND PHYTANE, SHOWN AS BARS. . . . . . UNRESOLVED BACKGROUND, (SAME SCALE)
Fig.2. S c h e m a t i c s u m m a r i e s of t h e gas c h r o m a t o g r a m s o f samples f r o m t h e D E L A W A R E II cruise, s h o w i n g n o r m a l paraffins, p r i s t a n e , a n d p h y t a n e as vertical bars, a n d t h e unresolved e n v e l o p e as a d a s h e d line o n t h e same scale.
I0
20
Y-'"'"',,
%
30
40
/."".,
. ..--...,
15
57
61a
61 b
630
63b
65
71
75 f
....
,
ALBATROSS ~ 7 2 - 6 NORMAL PARAFFINS, PRISTANE AND PHYTANE, SHOWN AS BARS. ..... UNRESOLVED BACKGROUND, (SAME SCALE)
Fig.3. S c h e m a t i c s u m m a r i e s of t h e gas c h r o m a t o g r a m s of samples f r o m t h e A L B A T R O S S IV cruise.
pristane and phytane but no low-carbon paraffins (D), and other relatively unusual types. Numerous examples of types A and B will be found in other Sargasso Sea samples, and several samples of types C and D are also d o c u m e n t e d (Butler et al., 1973). O n e important parameter which would be desirable is the age of the tar lumps. Unfortunately, no technique has yet been developed which will unambiguously give the chronological age of a pelagic tar lump (Butler, 1975, this issue, pp. 9--21). Evaporation during weathering tends to diminish the low-boiling hydrocarbons at a rate proportional to their vapor pressure with the result that the unresolved envelope of the chromatogram moves to higher retention index values as the weathering process continues. An index of the degree of weathering is N~/2, the equivalent normal paraffin carbon n u m b e r having a retention index equal to that where the unresolved background reaches half its maximum height (Table I). This index was used by Blumer et al. (1973) in their weathering studies of crude oil on rocky shores (symbol CS~) and has been related to chronological age by a semiquantitative evaporative weathering model (Butler, 1975). For pelagic tar, however, the relation between N~/2 obtained from the gas
chromatogram and the time the tar has been weathering is complicated by the high degree of fragmentation that crude oil residues appear to undergo on the surface of the open ocean. Chronological age cannot be obtained in terms of the evaporative weathering model unless the initial volume of the sample before fragmentation is known, and such information is at best speculative. For this reason, we have not attempted to calculate ages from the N~/~ values. In spite of this limitation, the samples listed in Table I may be grouped according to increasing degree of weathering. DELAWARE 15a, ALBATROSS 3, 13, 15, 57, and 65 all have N m in the range 14.5--15.5 and may be inferred to be quite fresh. DELAWARE 15b, 23, 7 2 , 1 1 2 b , 112c and ALBATROSS 1, 61, 63, and 71 have N, n in the range 16--17 and have probably been at sea for a longer time. DELAWARE 38, 60, 66, 68, and 88b and ALBATROSS 75 have N,12 in the range 18--18.5. The most heavily weathered samples are DELAWARE 12, 88a, and 112a, w i t h indices between 19 and 22. The distribution of these N,/2 values is approximately normal, with a median between 16.5 and 17.0, almost exactly the same as for a series of 40 samples (median 16.7) taken during the same period (summer of 1972) at Station S in Bermuda (Butler et al., 1973; Butler, 1975). This tends to confirm the idea that the MARMAP samples are from the same general population of pelagic tar lumps as the samples collected near Bermuda. More than half of the chromatograms showed bimodal paraffin distribution (type B), in the C20 to C3s range, characteristic of crude oil sludges (Brunnock et al., 1968). This is evidence that these tar lumps came from tanker wastes d u m p e d at sea. One sample (ALBATROSS IV, Station 75) was almost all paraffins (type C). Only one chromatogram (DELAWARE II, Station 15) showed an unusually large peak near the retention time of normal C,9 which might be biogenic in origin. However, another lump collected at the same station showed the usual pattern of a waxy, weathered crude oil. Extensive discussion of the possible sources and fates of these pelagic tar lumps has been published elsewhere (Blumer et al., 1973; Butler et al., 1973; National Academy of Sciences, 1975).
CONCLUSIONS (1) All the samples analyzed appear to be residues of paraffinic crude oil. (2) Many of the samples contain relatively large amounts of high-boiling paraffinic wax, indicating that their origin is from tanker wastes. (3) The qualitative character of the samples is indistinguishable from those obtained in neuston tows near Bermuda. Parameters considered in this comparison include: color, texture, size, shape, profile of normal paraffins, volatility of lowest-boiling components, relative amount of paraffins and isoprenoids, relative amount of paraffins and unresolved background material, and the absence (except for one sample) of isolated peaks indicative of biogenic components.
ACKNOWLEDGEMENTS
The enthusiastic assistance of Mr. Steven A. Gherini and Miss Karen E. Fine of Harvard University; and the cooperation of Drs. Kenneth Sherman, Robert L. Dryfoos, and Frederick D. Knapp of the MARMAP Field Office, National Marine Fisheries Service, are gratefully acknowledged. This work was supported by the National Science Foundation, International Decade of Ocean Exploration, the National Marine Fisheries Service, and the National Institutes of Environmental Health Sciences. This is Contribution No. 165 from the Bermuda Biological Station for Research. REFERENCES Blumer, M., Erhardt, M. and Jones, J. H., 1973. The.environmental fate of stranded crude oil. Deep-Sea Res., 20: 239--259. Brunnock, J. V., Duckworth, D. F. and Stephens, G. G., 1968. Analysis of beach pollutants. J. Inst. Petrol., 54: 310--325. Butler, J. N., 1975. Evaporative weathering of petroleum residues: the age of pelagic tar. Mar. Chem. 3 : 9 - - 2 1 (this issue). Butler, J. N., Morris, B. F. and Sass, J., 1973. Pelagic tar from Bermuda and the Sargasso Sea. Bermuda Biological Station for Research, St. George's West, Spec. Publ., 1 0 : 3 4 6 pp. Erhardt, M. and Blumer, M., 1972. The source identification of marine hydrocarbons by gas chromatography. Environ. Pollut., 3: 179--194. National Academy of Sciences, National Research Council, 1975. Petroleum in the marine environment. Washington, D.C. Sherman, K., Colton, J. B., Knapp, F. D., Dryfoos, R. L., Kinnear, B. S., 1973. Oil and plastics contamination and fish larvae in surface waters of the northwest Atlantic. Unpubl. Prelim. Rep., Marmap Field Office, Narragansett, Rhode Island. U.S. Dept. Commerce News, Feb. 13 (NOAA 73-17).