volatile liquid hydrocarbons in waters of the gulf of mexico and caribbean sea

Volatile Liquid Hydrocarbons in Waters of the Gulf of Mexico and Caribbean SeaAuthor(s): Theodor C. Sauer, Jr.Source: Limnology and Oceanography, Vol. 25, No. 2 (Mar., 1980), pp. 338-351Published by: American Society of Limnology and OceanographyStable URL: http://www.jstor.org/stable/2835430 .

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Limnol. Oceanogr, 25(2), 1980, 338-351 ? 1980, by the American Society of Limnology and Oceanography, Inc.

Volatile liquid hydrocarbons in waters of the Gulf of Mexico and Caribbean Sea'

Theodor C. Sauer, Jr.2 Department of Oceanography, Texas A&M University, College Station 77843

Abstract Concentrations of volatile liquid hydrocarbons (VLH), C6-C,4 hydrocarbons, were deter-

mined in 1977 in coastal, shelf, and open-ocean surface waters of the Gulf of Mexico and Caribbean Sea. In open-ocean, nonpetroleum-polluted surface water, VLH concentrations were -60 ng liter-' while in heavily polluted Louisiana shelf and coastal water values reached -500 ng liter-'. Caribbean surface samples had very low concentrations, :30 ng liter-'. The relationship between anthropogenic gaseous hydrocarbons and VLH was approximately linear. Aromatic VLH accounted for 60-85% of the total VLH in surface waters. Cycloalkane concentrations were <1.0 ng liter-1 in open ocean water, 60-100 ng liter-1 in polluted water (20% of total VLH). Alkanes were -15 ng liter-' in open ocean water, -40 ng liter-' in polluted water. The concentrations of five major VLH compounds (aromatics) in water samples-benzene, toluene, ethylbenzene, m-, p-xylenes, and o-xylene (called BTX)- were sufficient to predict the total VLH. The empirically determined relationship is VLH(ng liter-') = 1.42 BTX (ng liter-'); r = 0.96.

Subsurface VLH concentrations in samples of polluted waters collected from depths of 50 m were only 35-40 ng liter-' below surface concentrations. Open ocean subsurface samples had concentrations of only -30 ng liter-' at 30-50-m depths, comparable to those of Carib- bean surface water.

Research on hydrocarbons in water, sediment, and organisms has received considerable attention, largely because of problems associated with the discharge of these compounds into the ocean. Although analytical techniques have become increasingly available to re- solve complex mixtures of hydrocarbons, the types of hydrocarbons investigated are dictated by the methodology. Gas- eous (C1-C5) hydrocarbons and the higher-molecular-weight (>C14) hydrocarbons have been determined extensively because analytical methods for them are well developed. The C,-C,4 hydrocarbons have received comparatively little consideration even though many of them are the most toxic components of petroleum (Baker 1970; Anderson 1975; McAuliffe 1977a). Those of interest, called volatile liquid hydrocarbons (VLH), include the relatively highly soluble aromatics (benzene, toluene, meth- yl-, ethyl-, propyl-substituted benzene,

1 The experimental work was supported by NSF grant OCE76-8 1493. Preparation of this manuscript was made possible by NSF grant EAR77-21774 and ONR contract N00014-75-C-0537.

2 Present address: Exxon Production Research Company, P.O. Box 2189, Houston, Texas 77001.

and naphthalene), aliphatics (normal and branched C6-C,4 alkanes), and cycloalkanes (alkyl-substituted cyclopentanes and cyclohexanes).

Much of the research involving VLH has been concerned with laboratory studies of the exposure of marine organisms to the water-soluble fraction of petroleum (e.g. see Anderson et al. 1974; Natl. Acad. Sci. 1975; Vandermeulen and Ahern 1976). Although the data are incomplete, especially in the area of sublethal and chronic effects, VLH in seawater have been found to have greater effects on marine organisms at lower concentrations than any other fraction of petroleum. Unfortunately, few analyses of VLH in the ocean have been made to see whether concentrations there are in a range that would be detrimental to organisms. In fact, baseline distributions of VLH in marine waters have not been established.

Except for McAuliffe's studies of VLH concentrations in formation waters and oil spill slicks (e.g. McAuliffe 1966, 1974, 1977a, b), there has been little quantita- tive work on VLH in seawater and next to none at the ng liter-' level. Koons and Monaghan (1973) and Koons (1977) determined C5-C1o hydrocarbons in sam-

338



Volatile liquid hydrocarbons 339

ples taken with Niskin bottles and a gal- vanized bucket near oil platforms in the Gulf of Mexico and along tanker routes in the Pacific Ocean. Schwarzenbach et al. (1979) determined volatile constituents in a few samples from the coastal waters and marshland of southeast Mas- sachusetts.

The biological effects of VLH are of major concern, but the role played by VLH in the cycling of organic matter in the sea is also important. Duce and Duursma (1977, p. 328) stated that "the only way to answer most of the funda- mental questions concerning the processes involved in the cycling of organics in seawater is to know just what organic substances, with their characteristic reac- tivities, solutions, biological activities, etc. are present." Volatile liquid hydrocarbons have relatively high solubilities and vapor pressures: they make up the major constituents of anthropogenic organic material in the atmosphere (Duce 1978) and are discharged into marine coastal waters near industrial and urban areas in environmentally significant amounts (Sauer 1978). Almost all of these hydrocarbons are associated with the gas- oline and kerosene fractions of petroleum, which make up 30% of crude oil and 50% of refined oils (Natl. Acad. Sci. 1975). The lack of information about these hydrocarbons in the marine environment prompted this work.

I thank W. M. Sackett, L. M. Jeffrey, and J. W. Farrington for advice in pre- paring this manuscript, and J. M. Brooks for help in sampling and analyzing samples for gaseous hydrocarbons.

Procedures and sampling Analytical procedures-The dynamic

headspace stripping procedures used by Sauer et al. (1978) for determining volatile liquid hydrocarbons were modified in the desorbance system and GC analysis. The apparatus and conditions for stripping VLH from sample water and trapping them onto the adsorbent Tenax- GC remained unchanged.

After stripping VLH from the water sample, the Tenax-GC tube was placed

in a heating unit, on line with a 6-port valve and a gas chromatograph. A schematic diagram of the desorbance system in shown in Fig. 1. The heating unit con- sists of a cored solid aluminum cylinder with four 600-W symmetrically placed heating tubes. The valve is a 6-port stainless steel Carle valve. A Hewlett-Packard 5700A gas chromatograph with a flame ionization detector was modified to ac- commodate the desorbance system.

The Tenax-GC was heated to 250?C for 15 min to desorb the trapped components. The desorbed compounds passed through the 6-port valve and were then trapped on a liquid-nitrogen-cooled sample loop (precolumn). The precolumn is needed to trap the desorbed components because the compounds adsorbed on the Tenax-GC are not all released at the same time when heated. The gas flow rate through the Tenax-GC precolumn line was regulated at 40 ml min-'. Between the Tenax-GC tube and Carle valve is an injection port where standards were introduced. The entire desorbance line to the sample loop, including the valve, was heated to around 1250C with heating tape.

When the desorption process was com- pleted, the 6-port valve was switched so that the precolumn became online with the chromatographic column. The trapped components on the precolumn were then "injected" onto the column by replace- ment of the coolant with 1500C mineral oil. The chromatographic column carrier gas was regulated at 20 ml min-'.

Two chromatographic columns of different polarities were used to separate the volatiles; one was a copper chromatographic column (3.2 mm x 4.6 m) packed with nonpolar 10% SP-2100 on 80/100 Supelcoport. The column was temperature-programmed at 0?C for 2 min, 0?C to 1800C at 40C min-', and 1800C for 16 min. The 0?C temperature, achieved by introducing liquid nitrogen into the oven through a solenoid valve, is needed to re- solve cyclohexane from benzene ade- quately. The other column used-a more polar liquid phase-was a 3% OV-17 on 100/120 Gas-Chrom Q column (3.2 mm x



340 Sauer

Heating Unit

H,e

Tenox-GC Tube- 6-Port Valve Injection

0 Port

Gas Chromotogroph FID

Ssp-2loo 1 XCa~~~~~~~~~~rrier

a=<~~~~a

SP-2100[j j r

Pre- Column

Fig. 1. Schematic drawing of heating unit and precolumn used in desorbance of volatiles from Tenax-GC and "injection" onto gas chromatographic column.

4.0 m). The programming was - 10?C for 4 min, - 10?C to 150?C at 8C min-', and 150?C for 8 min. Samples were run in du- plicate on each different polarity column.

The flame ionization detector responses of all the components were measured relative to the responses of the standard normal alkanes, n-C6 through n- C14. The response factors of the aliphatic, alicyclic, and aromatic hydrocarbons relative to the n-alkanes are around 1.0. However, the small response differences for hydrocarbons were incorporated in the calculations of concentrations as given by Dietz (1967). Concentrations were determined by comparing ratios of peak areas to those of standard n-alkanes. Peak areas from the chromatograms were measured by a 3933A Hewlett-Packard inte- grator, peak height x 1/2 peak-height width, or planimetry.

The component sensitivity of the entire stripping and analytical method is < 1 ng liter-1. The VLH determined by this method range in boiling points from near n-hexane (69?C) to n-tetradecane (254?C), (pentadecane is also determined). Organ- ic compounds outside this range are not readily determined. However, some compounds with boiling points lower

than that of n-hexane, such as branched pentanes, can be qualitatively determined by this method.

Volatile components were identified on a Hewlett-Packard 5982A dodecapole mass spectrometer interfaced to a 5710A gas chromatograph with a single stage, glass jet separator and supported by a 5933A Data System. The SP-2100 chromatographic column from the desorbance system with the volatile components cry- ogenically trapped near the inlet part of the column was transferred to the GC/MS system. The trapped components were released for GC separation and MS iden- tification when the coolant-liquid nitrogen-was replaced with 150?C mineral oil. Mass spectra were recorded at the rate of one per 2.0 s from 40 to 350 amu with an electron ionization source volt- age and temperature of 70 eV and 170?C. Mass spectra were identified from the Eight peak index of mass spectra (Imp. Chem. Ind. Ltd. 1970) and Interpretation of mass spectra (McLafferty 1973). Many of the identifications were confirmed by standard GC retention times.

Since VLH in marine waters are present in ng per liter concentrations, thor- ough cleaning of glassware both for the stripping apparatus and the sample bottle is imperative. All glassware was acid- washed with a HF-HNO3 water mixture and rinsed with volatile-free water. Be- fore use, the stripping apparatus (Sauer et al. 1978: fig. 1, gas bubbler) was placed in a 2-liter sample bottle filled with clean, uncontaminated seawater, and allowed to strip for 1 h at -80?C and at a helium flow rate of 600 ml min-' to clean it. Sample bottles were purged and filled with helium or nitrogen for storage before sampling.

Use of the 2-liter bottle as both a sample bottle and stripping container mini- mized contamination from laboratory air. Unlike other methods where the sample is transferred from sample bottle to a separate stripping container, this method permitted stripping of VLH from water without transfer through laboratory air. Tests showed that transferring volatile- free water from one clean bottle to




another introduced many contaminants at concentrations high enough (1-10 ng liter-1) to interfere significantly with determinations.

The procedures of Sackett and Brooks (1975) were used to analyze methane and other gaseous hydrocarbons. Only gaseous hydrocarbons were collected with the VLH; no hydrographic parameters were measured.

Sampling-Sainpling for VLH at the ng per liter concentrations found in the sea requires that the sampling equipment be extremely clean. Conventional marine sampling methods (Niskin bottles) used aboard a research vessel contributed to VLH contamination of sample water (Sauer et al. 1978). To eliminate such contamination in surface water sampling, we took seawater samples from aboard a small rubber boat 200 m upwind and upcurrent of the research vessel and collected them in the same 2-liter volatile- free glass bottles used in the VLH stripping system. Over the bow of the small boat, closed glass bottles were lowered below the surface. The bottles were opened, filled at arms length and closed before they were raised. The stoppers were removed briefly and sodium azide was added to the sample to inhibit biodegradation of the hydrocarbons. The samples were stored in a refrigerator for later shipboard or laboratory analysis.

Sampling for VLH in the water column requires that the sampling bottles be closed while passing through both the air-sea interface and the water near the ship. A special sampler, similar to the one developed by Keizer et al. (1977) for solvent-extractable hydrocarbon sampling, was made for sampling below the surface (Fig. 2). Two sample bottles are fastened to a stainless steel frame with stainless steel wire. Both bottles are capped with Teflon stoppers which have stainless steel tubes centered in them and are con- nected to each other by Teflon tubing and a bent glass tube. The sampler is then attached to a KEVLAR or stainless steel hydrowire that is free of grease. Af- ter the sampler is lowered to the desired depth, a messenger is released which

Fig. 2. Photograph of VLH water column sampler.

breaks the glass tube and the bottles are allowed to fill for 10 min. When the bottles come to the surface, the sampler is removed from the wire and taken to a clean area, where the Teflon stoppers are removed, sodium azide is added to the samples, and the bottles are sealed with solid ground-glass stoppers. The samples are stored in a refrigerator for future analysis. Only steel, Teflon, and glass are used in constructing the sampler. The glass bottles, Teflon, and glass tubing are acid-washed and rinsed with volatile-free water before the sampler is assembled.

A major advantage of this sampling de- sign is that the water samples need not be transferred into other containers for storage or analysis, avoiding possible



342 Sauer

Table 1. Gaseous hydrocarbons (nl liter-') and total VLH (ng liter-') concentrations for cruises 77-G- 13 and 77-G-8 (-: not determined; nd: not detected).

Total

cYclo- aromatics Aromatics Station Methane Ethene Ethane Propene Propane alkanes alkanes (BTX)* VLH (%BTX)*

77-G-13 Caribbean Sea 7 Surf 39.4 4.4 0.3 - - nd nd 18.8(18.8) 18.8 100(100) 8 Surf 66.4 4.4 tr - - nd nd 12.2(12.2) 12.2 100(100)

10 Surf 43.5 3.7 tr - - nd nd 24.9(24.9) 24.9 100(100) 11 Surf 50.8 4.7 tr - - 14.3 3.4 45.5(40.5) 58.2 79(70)

77-G-13 Gulf of Mexico 13 Surf 54.9 3.8 tr - - 10.5 nd 55.5(53.1) 66.0 81(80)

30 m - - - - 7.0 nd 8.1(7.1) 15.1 54(48) 14 Surf 116.0 0.6 0.6 - - 17.9 0.1 30.0(26.8) 48.0 63(56) 15 Surf 83.6 3.2 tr - - 15.1 1.4 54.8(50.6) 71.3 77(71) 17 Surf 8,528.0 20.1 73.1 91.9 60.2 31.5 59.7 246.0(220.9) 336.2 73(66) 18 Surf >11,150 20.7 215.0 67.1 166.4 14.7 110.9 332.8(320.4) 458.4 73(70) 21 Surf 7,050 8.1 44.4 - - 10.3 34.3 138.3(129.4) 182.9 77(71)

25 m 1,800 1.7 2.5 - - (55) 0.0 125.0(117.0) 147.0t 83(80) 50 m 333 0.7 0.9 - - (35) 7.6 130.2(97.5) 152.8t 84(64)

24 Surf 280 2.9 2.5 - - 15.8 3.2 41.0(24.8) 60.0 69(41) 25 m 560 3.5 4.1 - - (30) 0.8 16.7(14.1) 26.2t 64(54) 50 m 144 3.8 1.5 - - (30) 0.1 10.0(3.5) 15.2t 66(23)

77-G-8 Gulf of Mexico Sackett's

Bank 2,060 3.7 2.2 1.5 0.5 15.2 1.8 42.5(39.3) 59.5 71(66) EFG 13 Sep

Surf 200 5.0 1.0 1.0 0.6 9.4 5.3 98.9(96.6) 113.2 85(83) EFG 15 Sep

Surf 200 5.0 1.0 1.0 0.6 12.6 1.5 66.2(40.4) 80.3 82(50) * BTX is an abbreviation for benzene, toluene, ethylbenzene, and m-, p-, o-xylenes. Only these concentrations are considered. t Total VLH concentrations do not include values listed under total al kanes in parentheses which represent concentrations of C1l, C12, C13,

and C14 n-alkanes.

contamination from the atmosphere or loss of volatiles through the transfer process. One disadvantage is its depth limi- tation: the 2-liter bottles implode at a depth of about 60 m.

Results and discussion Seawater samples were collected dur-

ing cruise 77-G-13 (November 1977, RV Gyre, Texas A&M University, Gulf of Mexico and Caribbean). Figure 3 shows the locations of the sample stations and the 77-G-2 cruise locations for reference to Sauer et al. (1978). Two other sets of samples were obtained on cruise 77-G-8 (September 1977) from Sackett's Bank (26032.0'N, 94004.0'W) and East Flower Garden (EFG: 27054.0'N, 93053.0'W). Ta- ble 1 shows total concentrations of gaseous hydrocarbons and VLH fractions: n- alkanes, cycloalkanes, and aromatics.

Specific VLH compound concentrations from these cruise samples were given elsewhere (Sauer 1978).

Gaseous and VLH distribution rela- tionships-In the Caribbean samples (Table 1) at stations 7, 8, and 10, the only VLH present were the aromatics; no n- alkanes or other volatiles were evident. These samples were taken just off Coz- umel and in the middle of the Cayman Sea and had the lowest concentrations found in this study. The water at these stations originates from surface waters of the Caribbean Sea.

Concentrations of methane at stations 7 and 10 were unusually low, 39-43 nl liter-1. The saturation methane concentration at station 11 (with essentially the same hydrographic conditions as stations 7 and 10) was calculated to be 38 nl liter- (T?C = 26.45 and S%0 = 35.815).




314 5 7 .@;- i '- --u

213 *-CRUISE 77-G-13 v s... *-CRUISE 77-G-2

/ I~~~~~~7 20't -<8 E B

II 95e 90e 85'

Fig. 3. Locations of sample stations taken during 77-G-13 and 77-G-2 (Sauer et al. 1978) cruises (------:100-fathom contour; -:1,000-fathom contour).

The water in this area may be upwelled subsurface water, but if it is not, the low methane concentrations like the VLH concentrations indicate that there is no contamination from anthropogenic sources. These VLH samples were analyzed on the same day aboard ship. An internal standard was run with one of the samples with almost complete recovery, indicating no unusual VLH loss or contamination during the processing at sea.

None of the surface samples from the Gulf of Mexico showed such low VLH concentrations: about 60 ng liter-1 typi- fied open ocean concentrations. The absence of any very low concentration of VLH (as in the Caribbean) in the surface water samples of the gulf suggested that perhaps the sample bottles had been contaminated during either processing or storage, but a deep water sample (1,000 m) analyzed a month after collection at the same time as other surface samples indicates that this is not true. All bottles were identically cleaned and samples stored under the same conditions. Table 2 shows the concentrations of VLH found in the deep water sample. The large unresolved component mixture is a result of the Niskin bottle used for sampling (cf. Sauer et al. 1978). The total organic vol-

Table 2. VLH concentrations of water sample (No. 1194) taken at 1,000 m (station 5: 77-G-13) with Niskin sampling bottle.

VLH RT* Compound (ng liter-')

600 Chloroform 24.5 630 690 Large unresolved

component mixture 650 Benzene 1.6 756 Toluene 1.5 834 2.7

1000 0.6 1204 0.7 1330 1.7

* Retention times from chromatographic column SP-2100.

atile concentration from the 1,000-m sample, excluding the RT No. 600 peak, is 8.8 ng liter-1. The No. 600 peak (24.5 ng liter-1) is believed to be contamination-most likely chloroform-from laboratory air. The No. 650 and 756 peaks are benzene and toluene. The No. 834, 1000, and 1204 peaks are found in glass bottle blanks at almost the same concentrations. The No. 1330 peak is never seen in glass bottle blanks. The absence of VLH concentrations as low as those in the Caribbean is probably the result of the selection of the sample sites coupled with the surface circulation patterns of the Gulf of Mexico.

The VLH distribution in marine surface waters of the gulf are influenced by both known anthropogenic sources and surface currents. VLH concentrations range from 48-458 ng-liter-' (Table 1). The concentrations in certain areas of the gulf fluctuate considerably depending on the locations of the anthropogenic inputs and the direction of surface currents.

The surface circulation of the Gulf of Mexico has significant influence on the direction of the Mississippi River outflow. Immediately south of the Mississip- pi River is a strong northerly current (Austin 1955) which causes the river outflow to be channeled east along the Flor- ida coast and across the Louisiana coast. Little of the outflow extends into the open ocean. This is evident from the transect of stations 13-17 (77-G-13: Table 1). Stations 13 and 14 have open ocean gaseous hy-



344 Sauer

*~~~~

Fig 4. Uoain folfedfrxainwtr(rn)dshre n apestos(-7G1

*FI ~ m 0 0 O_ 'E's

0-77-G-2: Sauer et al. 1978) on Louisiana shelf (adapted from Brooks 1975). Discharge was 45,800,000 liter d-l in O)cto}ber 1973. Solid symbols, > 160,0001liter-d-l; cross-hatched, 16,000-160,(0001iter^ d-l; open, < 16,000 liter -d-l. Rules indicate block boundaries. Contours (seaward) are about 30, 60, and 200 m.

drocarbon and VLH concentrations. Sta- tion 15, only 45 km away, still shows relatively little influence from the Mississippi River. Station 17, a few kilo- meters from the mouth, finally shows the hydrocarbon contribution of the Missis- Sippi .

Water samples taken near known anthropogenic sources have high concentrations of VLH and gaseous hydrocarbons. Extremely high VLH concentrations (>300 ng liter-') at stations 17 and 18 are attributable to the outflow of the Missis- sippi River and to the discharge of formation waters and hydrocarbon venting from offshore oil production. Conserva- tive estinmates for the amount of VLH discharged into Texas-Louisiana shelf surface waters from these sources are 5- 6x 108 g VLH per year for formation water discharges; 5-14x 108 gyr-', hydrocarbon venting; and 4-8 x 108 g- yr-1 Mississippi River runoff (Sauer 1978). Figure 4 shows the location of the stations with respect to known anthropogenic sources. Stations 17 and 18 are sur- rounded by known sources and have correspondingly high VLH concentrations while stations 15 and 21, farther

away from the sources, have lower concentrations. Station 15 has low enough VLH concentrations to be considered part of the group of open ocean stations (stations 13, 14, and 24). These concentrations (~60 ng liter-') are the lowest in the gulf and approximate open ocean or baseline concentrations of gaseous hydrocarbons (45 nl liter-' for methane and <1 nl liter-' for ethane and propane: Swinnerton and Linnenbom 1967; Swin- nerton et al. 1969). Station 21 has surface water VLH concentrations of 100-200 ng liter-', intermediate to open ocean and polluted concentrations. The East Flower Garden station (77-G-8) also ap- proximates this range. Both stations have VLH concentrations that correspond to intermediate values for gaseous hydrocarbons. The proximity of anthropogenic sources to the stations (Fig. 4) verifies these intermediate concentrations.

At most of the stations in Table 1, a direct correlation between VLH and gaseous hydrocarbons can be observed. This is especially good between VLH and the gaseous ethane and propane hydrocarbons. Values for methane, however, do not always parallel those of VLH, be-




cause methane has not only petrogenic sources but also biogenic sources which can contribute significantly to the amount in the water. These are either in situ production by microorganisms in the water column or diffusion out of delta and shelf sediments. Stations 13, 24 (77-G-13), and Sackett's Bank (77-G-8) have relatively high methane values, while ethane values are low and propane is very low or not detectable, suggesting that the methane there is of biogenic, not petrogenic, origin. The VLH concentrations at these stations are very close to the open ocean total VLH values of =60 ng-liter1. The lack of gaseous ethane and propane and the low VLH values indicate that these stations are not significantly contaminated by petroleum.

The relationship between VLH and gaseous ethane and propane from my data is shown in Fig. 5. The unlabeled points near the origin of the graph represent the remaining stations not indicat- ed in the figure. The relationship between these two parameters is approximately linear, but more data are needed to make statistically acceptable predictions of VLH concentrations in seawater from gaseous hydrocarbon concentrations. The relationship does however support the contention of Swinner- ton and Lamontagne (1974), Sackett and Brooks (1975), and Brooks et al. (1977) that C,-C, gaseous hydrocarbons are valuable indicators of petroleum pollution.

VLH fractions-Aromatics make up most of the VLH in seawater (Table 1). Toluene and many of the C2-C4 alkyl- substituLted benzenes were also the most abundant and consistently present group of organic volatiles in coastal samples taken by Schwarzenbach et al. (1979). In the Caribbean water samples, aromatics are the only volatile constituents in seawater. Toluene is present in all these samples and in those from the Gulf of Mexico. The persistence of toluene was also observed by Schwarzenbach et al. (1979) who suggested that perhaps toluene has a natural geochemical origin.

In the Gulf of Mexico, aromatics rep-

240

0 - Ethane STA

200 E 0- Propane

160 -18

20_

C,

V s - 017

0I7

40 0 D21

o m QEFG I

0 100 200 300 400 500 600 VLH (ng/liter)

Fig. 5. Graph of gaseous hydrocarbon concentrations (ethane and propane) vs. VLH concentrations.

resent from 63 to 85c of the total VLH with only slight differences between open ocean samples and anthropogenically polluted samples. Most open ocean samples (stations 11, 13, 15 and Sackett's Bank) show aromatics to be -71-81% of the total VLH, while heavily polluted samples (stations 17 and 18) have about 73% aromatics. The reason for the relative paucity of aromatics in polluted seawater is because of the considerable contribution of cycloalkanes to those samples: cycloalkane concentrations are close to zero in open ocean waters, while in polluted waters they increase to 60-110 ng liter-' (stations 17, 18)-about 20% of the total VLH. The n-alkanes do not seem to change appreciably, although contaminated waters do show doubled concentrations.

For simplicity in predicting VLH concentrations in seawater, I have summed up the five major components of VLH in seawater and compared the concentrations to the total VLH determined. These major components are the aromatics: benzene, toluene, ethylbenzene, -m-, p- xylene, and o-xylene. Their concentrations are listed in Table 1 (as BTX). The BTX fractions of total VLH are tabulated in the percent aromatics column. Except



346 Sauer

for station 24 surf (41%), the percent BTX in surface water ranges from 56 to 80%, with most percentages around 70%. From all of the Gulf of Mexico surface water analyses in Table 1 (cruises 77-G-13 and 77-G-8), an estimate of the amount of VLH in surface seawater can be deduced by determining the concentration of the BTX aromatics and using the relationship

VLH = 1.42 x BTX(ng liter-'). (1) The standard error of estimates is 18.6. The correlation coefficient for this equa- tion is 0.96 (linear least-squares best fit). The use of the VLH-BTX relationship re- duces the amount of effort needed to de- termine all the VLH in water samples. The major aromatics can easily be analyzed by GC alone, eliminating the need for difficult GC/MS analysis.

In heavily polluted seawater samples, chromatograms show unresolved component mixtures of unknown nature. Their contribution is usually 20-30% of the total resolvable VLH. The components in the mixtures are probably not all VLH but the relative amount of VLH is undeterminable. In samples where an unresolved mixture is evident, the VLH concentration predicted from Eq. 1 should be considered a lower limit.

At three stations (13, 21, and 24: Table 1), VLH seawater samples were taken at depth with the specially built sampler (Fig. 2). In the open ocean sample (station 13) taken at 30 m, the concentrations of VLH are very low (-15 ngiliter-'), comparable to the concentrations observed in the Caribbean. Station 21 shows considerably higher VLH concentrations at 25- and 50-m depths, quite close to those of the surface water sample. The location of station 21 (near the mouth of the Mississippi and among offshore platforms) and the intermediate VLH concentrations indicate polluted subsurface waters. The pollution influence is shown throughout almost the entire water column (bottom is 63 m), down to at least 50 m, with only a 30-40 ng liter-1 difference between surface and subsurface samples. The percentage of aromatics in these subsurface samples

is also like that in the surface water. The subsurface samples (25 and 50 m) at station 24 have concentrations similar to those of the Caribbean and the 30-m sample at station 13. The surface water concentration at station 24 indicates an open ocean type of water, similar to that of the surface waters at station 13. Generally, it seems that the subsurface VLH concentrations for stations 13, 21, and 24 reflect their respective surface concentrations.

An uncertain aspect of these subsurface samples, especially at stations 21 and 24, is their unusually high component concentrations around the C11, C12, C13, and C14 n-alkane retention times. At station 21 the 25-m sample has values for these n-alkanes of -55 ng liter-1. The 50-m samples are 35 ng liter-'. These n- alkane concentrations are anamolously high in comparison to the corresponding surface water values. The reason is not known, but it may be due to contamination during cleaning or assembly of the equipment. In any case, the values at these n-alkane retention times were not included in the totals.

VLH fluxes-Sauer (1978) determined that reservoir and material fluxes of VLH to and from marine surface waters can be most appropriately estimated by the stagnant film model (Treybal 1955; Kanwish- er 1963; Broecker and Peng 1974). This model simply predicts that the flux, F, of gas (VLH) from the ocean to the atmosphere is dependent on the molecular diffusivity of the gas and the thickness of the stagnant diffusion-controlled bound- ary layer, z:

F = Di dc (2) dz or simply

F = KiACi (3) where Ki = DI/z, Di = coefficient of molecular diffusion (cm2 s-1), z film thickness (cm), and ACi = concentration difference across the film layer, Cil - C,g (mol liter-1). [C,g is gas concentration at equilibrium with the overlaying air, Cig = ap, where a is the solubility of gas and p is the partial pressure of gas in the




atmosphere. (In these flux estimates, Cig is assumed to be negligible.) Cil = concentration of gas in aqueous mixed layer.] The film thickness, z, is dependent on the degree of water agitation from subsurface winds and turbulence in the water column.

Fluxes are determined on the assump- tion that there is no contribution from the atmosphere. If VLH are appreciable in the atmosphere, Cig = 0, and the flux from marine waters will be reduced due to the decrease in the concentration difference, Cil - Cig. Near urban areas atmospheric concentrations are usually significant enough to retard the flux from the water column and possibly in some near- shore areas can act as a source of VLH into the water column. In most urban areas, toluene ranges from 10 to 50 ppbv, benzene 10-50 ppbv, and xylenes 6-30 ppbv (Altshuller and Bufalini 1971; Bertsch et al. 1974; Holzer et al. 1977). Table 3 shows equilibrium concentrations of some VLH in marine waters as dictated by atmospheric concentrations ranging from 1 to 50 ppbv. From the equilibrium water concentrations (Table 3), the importance of the atmospheric contribution in flux calculations is more than evident even though marine water VLH are not in equilibrium with those in the atmosphere.

To estimate the reservoir and fluxes of VLH in the Gulf of Mexico, the VLH distribution in the water must be known. Since VLH concentrations in the water column are not known throughout the gulf, VLH in unknown areas will have to be approximated from known data; these are mostly from samples taken along the Louisiana-Texas shelf-an area of hydrocarbon pollution. There are, however, open ocean samples [stations 13, 14, 15, (77-G-13), and Sackett's Bank (77-G-8)] from outside the Louisiana-Texas shelf; these will be representative of other unknown areas proposed to be not significantly polluted. Areas in the gulf selected as VLH-polluted or nonpolluted waters are the same areas extensively surveyed for gaseous hydrocarbons by Brooks et al. (1977). The partially polluted shelf

waters east of the Mississippi River along the Mississippi, Alabama, and west Flor- ida coast will not be included in the flux estimates, however, since no VLH samples were taken in this region.

In the Louisiana-upper Texas shelf region, the flux of VLH from surface waters is estimated to be 4.7-6.3 x 10-2 g.m-2 yr-1, assuming that the VLH concentration range is 150-200 ng liter-', and the transfer velocity, K,, is lX 10-3 cm s-' (D = JXJ0-5 Cm2s-1); Z= 100 ,um, corresponding to mean wind speed of :450 cm s-'. The flux (g.m-2 yr-') from areas near heavy pollution inputs and the Mississippi River will be 3-6 times greater, however, because of the higher VLH water concentrations (assuming Cig = 0). The total flux from the Louisiana-Texas shelf becomes 7.1-9.4x 109 g.yr-' (mean surface area is 1.5xlO1l m2). If VLH are appreciable in the atmosphere over these waters, the flux will be less.

We could not estimate the reservoir of VLH in these shelf waters until we had proposed a depth of VLH extinction. Sta- tion 21 is the only subsurface station in the shelf typical of polluted waters; the other two (13 and 24) are characteristic of open ocean waters. We therefore needed additional subsurface information. The profiles of gaseous hydrocarbons that Brooks et al. (1974) took along the Texas- Louisiana coast suggest that a depth of 50 m is appropriate, and station 21 VLH concentrations showing pollution do exist to that depth. If we assume a 150-200 ng liter-' concentration to 50 m, and nothing beneath that, the reservoir value for VLH ranges from 1.1-1.5 x 109 g.

For the Gulf of Mexico except the shelf waters east of the Mississippi, the VLH concentrations will be those of the open ocean samples. Most of the central gulf estimate depends on the concentrations at station 13, although stations 14, 15, and 24 also indicate open ocean concentrations. Some question may arise as to whether station 13 is representative of open gulf surface waters, since we took only one group of samples in the area. Station 13 is supposedly far removed



348 Sauer

Table 3. Equilibrium concentrations (ng liter-') in marine waters equilibrated with atmospheric concentrations of 1 and 50 ppbv of VLH.

C,t (ng liter-')

VLH mol wt HiR* 1 ppbv 50 ppbv

n-hexane 86 47 0.063 3.8 n-decane 142 252 0.024 1.2

Methylcyclohexane 98 11.4 0.36 18.0

Benzene 78 0.12 27.0 1,370.0 Toluene 92 0.18 21.0 1,070.0 o-xylene 106 0.24 19.0 930.0 Ethylbenzene 106 0.25 18.0 890.0 1,2,4-trimethyl benzene 130 0.20 27.0 1,370.0 Naphthalene 128 8.4 x 10-3 640.0 32,000.0 * Effective Henry's Law constant derived from vapor pressure and solubility data (Chem. Rubber Co. 1972, McAuliffe 1966). t (P,IHiRRT) x (rnol wt,) x 109; C,-concentration in seawater (ng liter-'), P,-concentration in atmosphere (atm), R = 82.05x10-3 (atm liter g mol-h 'K-1), and T = 290?K.

from obvious anthropogenic sources; it has surface VLH concentrations higher than the Caribbean but the subsurface concentrations are similar. Possible rea- sons for this are considered below.

Surface currents passing through polluted waters bring VLH to the central gulf. The Stagnant-Filin model suggests that the mean residence time (i-) of a VLH in the mixed layer of surface water is r = hz/D, where h = water column height. Modeling calculations give a mean residence time for aromatics (benzene) in 1 m of water of -15 h, or, in 50 m of -30 days. This is enough time for a 50 cm s-' current from the Louisiana shelf to carry 150 ng liter-' of shelf water 300 km to station 13 and retain a concentration of -60 ngliter-'. This simple calculation assumes that the changes in advection and horizontal mixing are unidirectional with vertical and cross-horizontal mixing and advection changes negligible.

The atmosphere acts as a source of surface water VLH. A 1 ppbv concentration of an aromatic in air could conceivably yield a single component equilibrium concentration of 20 ng liter-' in surface water (Table 3). Winds from the north containing polluted coastal and industrial air could result in atmospheric concentrations sufficient for air-sea exchange to surface waters. The prevailing winds in the gulf are, however, from the south.

Open ocean discharges from tankers

and other ships are sufficient to produce detectable VLH concentrations. About 185x 1012 g yr-1 of crude oil and petroleum products are transported by tankers in the Gulf of Mexico (U.S. Dep. Interior 1976), of which 0.008-0.11% is discharged as VLH from tanker cleaning operations at sea. About 10% of the amount discharged can be assumed to dissolve in the surface water (90% is immediately lost to the atmosphere). Therefore, the input by tankers at sea to the surface waters of the Gulf of Mexico is 0.15- 2.0x101' g yr-', an order of magnitude larger than the VLH discharged into the surface waters of the Texas-Louisiana shelf from the Mississippi River, offshore hydrocarbon venting, and formation water discharges combined (Sauer 1978).

The VLH found in open ocean surface waters are truly residual concentrations. VLH concentrations are extremely low (parts per trillion) and may represent the amount of VLH that cannot transfer across the air-sea interface. Aromatic VLH do have higher solubilities than gases. Caribbean surface waters with ab- normally low VLH concentrations are perhaps subsurface or surface waters that have not come in contact with VLH contamination.

The VLH concentrations in station 13 samples are due to contamination. The deep (1,000 m) sample (Table 2) indicates that the sampling, storage, and an-




alytical procedure produce at the most a total 8 ng liter-' error of mostly uniden- tifiable compounds.

In open ocean surface waters and other nonpolluted shelf waters, the concentration of VLH is assumed to be 45 ng liter-', based on concentrations at stations 13, 14, 15, 24, and Sackett's Bank. The flux is therefore estimated to be 1.4x10-2 g m-2 yr-1 (transfer velocity, K,, of 1x 10-3 cm s-1) with the total flux for the area becoming 2 x 1010 g yr-', using 14 x 1011 m2 as the surface area for the gulf (less Louisiana-upper Texas shelf). If the concentration of VLH in the atmosphere over these waters is appreciable, the flux will be less. An aromatic concentration of 1 ppbv in the atmosphere would decrease the flux by almost half (1 ppbv aromatic in the atmosphere = 20 ng liter-' in water). The reservoir of VLH in the open ocean gulf area is estimated to be 2.Ox 109 g. This assumes 45 ng liter-' VLH for the upper 20 m of water (1.3x109 g), and 10 ng liter-1 for the remaining 50 m to the thermocline (0.7x 109 g). No VLH are expected below the thermocline (cf. the deep water, 1,000 m, sample: Table 2). The 10 ngKliter-1 value for the water between 20 m and the thermoline was estimated from subsurface samples at stations 13 and 24.

The total VLH flux for the entire Gulf of Mexico (less the Alabama, Mississippi, and western Florida shelf waters, which make up <5% of the total area) is estimated to be 28.0x109 g yr-1. The reservoir of VLH is 33.Ox 108 g. The flux and reservoir of VLH for methane from the entire Gulf of Mexico are 370 x 109 g* yr-1 and 38.5x 109 g (Brooks 1975). A residence time in the gulf for VLH estimated from these data is 0.12 years (40 days).

I did not consider biological degradation of VLH in the water in these estimates because rates of microbial degradation for VLH have not been established due to the lack of standardization of test- ing and the absence of units for express- ing rates of degradation. Considerable work on microbial mechanisms of metab- olizing VLH has been done (Van der Lin- den and Thijsse 1965; Doelle 1975; Gib-

son 1977), but unfortunately, there have been no conclusive in situ studies of rates of petroleum degradation in estuarine or marine environments, although such rates have been estimated from field or laboratory experiments (Floodgate 1972; Walker et al. 1976).

VLH biological effects-Extensive research has been done on the toxic effects of the higher molecular weight (solvent- extractable) hydrocarbons of petroleum on marine organisms, but comparatively little on VLH. Almost all the work that has included VLH has been concerned only with acute effects (Anderson et al. 1974; Atkinson et al. 1977; Malins 1977; Wolfe 1977). The short term studies of le- thal effects at high dosages do not address the realistic stress that may be encoun- tered by organisms from waters polluted by VLH. The sublethal effects are most important and include those which cause damage to physiology, growth, develop- ment, reproduction, and behavior. Be- havioral activities especially are mediat- ed by chemoreception (Kohn 1961) and are sensitive to low concentrations of hydrocarbons.

Those petroleum hydrocarbons that may have the most disruptive effect in chemoreception are those which most easily mimic chemical species that me- diate a organism's behavioral reaction. The compounds that initiate behavioral responses are usually very soluble and intermediate in size, such as 1,3,5-octa- triene (Cook and Elvidge 1951) and tau- rine (Takahashi and Kittredge 1973). The petroleum hydrocarbons with similar phys- ical characteristics are the VLH. Very few publications report behavioral or chemoreception effects with VLH. The response of snails and crabs to chemical substances that normally initiate feeding behavior was eliminated by 1 jug liter-' concentrations of the water-soluble fraction of kerosene-mostly benzenes (Ja- cobson and Boylan 1973; Takahashi and Kittredge 1973; Johnson 1977). Fertiliza- tion of macroalgae was completely inhibited by 0.2 ,ug liter-' of No. 2 fuel oil (Steele 1977). Chemoreception in marine bacteria was inhibited by 100 ,utg liter-'



350 Sauer

of benzene (Walsh and Mitchell 1973). These observations suggest that concentrations of VLH (aromatics) of the order of a couple of micrograms per liter are enough to disrupt chemosensory behavior.

Apparently concentrations of VLH of about 1 ugg liter-' could be detrimental to the life processes of many marine organisms. Especially in many coastal urban and industrial area waters, VLH concentrations are in this damaging range. The potential of these subtle behavioral effects on organisms from VLH should be carefully reviewed and additional behavioral pollution research should be done. Long term (chronic) sublethal exposure to VLH is regarded by many investigators (Colwell and Walker 1977; Steele 1977; Lee 1978; Rossi and Anderson 1978) to induce harmful behavioral effects at lower concentrations than those of severe, acute contamination. The polluted coastal waters, especially, have reached high enough steady state concentrations of VLH to make detrimental long term effects on marine organisms probable.

References ALTSHULLER, A. P., AND J. J. BUFALINI. 1971. Pho-

tochemical aspects of air pollution: A review. Environ. Sci. Technol. 5: 39-64.

ANDERSON, J. W. 1975. Laboratory studies on the effects of oil on marine organisms: An over- view. Am. Pet. Inst. Pub. 4249, p. 1-70.

, J. M. NEFF, B. A. Cox, H. E. TATUM, AND G. M. HIGHTOWER. 1974. Characteristics of dispersions and water-soluble extracts of crude and refined oils and their toxicity to estuarine crustaceans and fish. Mar. Biol. 27: 75-84.

ATKINSON, L. P., W. M. DUNSTAN, AND J. G. NA- TOLI. 1977. The analysis and control of volatile hydrocarbon concentration (e.g. benzene) during oil bioassays. Water Air Soil Pollut. 8: 235- 242.

AUSTIN, G. B., JR. 1955. Some recent oceanograph- ic surveys of the Gulf of Mexico. Trans. Am. Geophys. Union 36: 885-892.

BAKER, J. M. 1970. The effect of oil on plants. En- viron. Pollut. 1: 27-44.

BERTSCH, W., R. C. CHANG, AND A. ZLATKIS. 1974. The determination of organic volatiles in air pollution studies: Characterization of profiles. J. Chromatogr. Sci. 12: 175-182.

BROECKER, W. S., AND T. H. PENG. 1974. Gas exchange rates between air and sea. Tellus 26: 21-35.

BROOKS, J. M. 1975. Sources, sinks, concentrations

and sublethal effects of light aliphatic and aromatic hydrocarbons in the Gulf of Mexico. Ph.D. thesis, Texas A&M Univ. 342 p.

, B. B. BERNARD, AND W. M. SACKETT. 1977. Input of low-molecular-weight hydrocarbons from petroleum operations into the Gulf of Mexico, p. 373-384. In D. A. Wolfe [ed.], Fate and effects of petroleum hydrocarbons in marine organisms and ecosystems. Pergamon.

, J. R. GORMLY, AND W. M. SACKETT. 1974. Molecular and isotopic composition of two seep gases from the Gulf of Mexico. Geophys. Res. Lett. 1: 312-316.

CHEMICAL RUBBER COMPANY. 1972. Handbook of chemistry and physics, 53rd ed. CRC.

COLWELL, R. R., AND J. D. WALKER. 1977. Eco- logical aspects of microbial degradation of petroleum in the marine environment, p. 423- 445. In Critical reviews in microbiology. CRC.

COOK, A. H., AND J. A. ELVIDGE. 1951. Fertiliza- tion in the Fucaceae: Investigations on the nature of the chemotactic substance produced by eggs of Fucus serratus and F. t5esiculosus. Proc. R. Soc. Lond. Ser. B 138: 97-114.

DIETZ, W. A. 1967. Response factors for gas chromatographic analysis. J. Gas Chromatogr. 5: 68-72.

DOELLE, H. W. 1975. Bacterial metabolism. Aca- demic.

DUCE, R. A. 1978. Speculations on the budget of particulate and vapor phase non-methane organic carbon in the global troposhere. Pure Appl. Geophys. 116: 244-273.

, AND E. K. DUURSMA. 1977. Inputs of organic matter to the ocean. Mar. Chem. 5: 319- 339.

FLOODGATE, G. C. 1972. Microbial degradation of oil. Mar. Pollut. Bull. 3: 41-43.

GIBSON, D. T. 1977. Biodegradation of aromatic petroleum hydrocarbons, p. 36-46. In D. A. Wolfe [ed.], Fate and effects of petroleum hydrocarbons in marine organisms and ecosystems. Pergamon.

HOLZER, G., AND OTHERS. 1977. Collection and analysis of trace organic emissions from natural sources. J. Chromatogr. 142: 755-764.

IMPERIAL CHEMICAL INDUSTRIAL LTD. 1970. Eight peak index of mass spectra, v. 1 and 2. London.

JACOBSON, S. M., AND D. B. BOYLAN. 1973. Effect of seawater soluble fraction of kerosene on chemotaxis in a marine snail, Nassarius obso- letus. Nature 241: 213-215.

JOHNSON, F. G. 1977. Sublethal biological effects of petroleum hydrocarbon exposure: Bacteria, algae and invertebrates, p. 271-318. In D. C. Malins [ed.], Effects of petroleum on arctic and subarctic marine environments and organisms, v. 2. Academic.

KANWISHER, J. 1963. On the exchange of gases between the atmosphere and the sea. Deep-Sea Res. 10: 195-207.

KEIZER, P. D., D. C. GORDON, AND J. DALE. 1977. Hydrocarbons in eastern Canadian marine waters determined by fluorescence spec-




troscopy and gas-liquid chromatography. J. Fish. Res. Bd. Can. 34: 347-353.

KOHN, A. J. 1961. Chemoreception in gastropods. Am. Zool. 1: 291-308.

KoONS, C. B. 1977. Distribution of volatile hydrocarbons in some Pacific Ocean waters, p. 589- 592. In Proceedings of the 1977 Oil Spill Con- ference, New Orleans. Am. Pet. Inst. Publ. 4284.

, AND P. H. MONAGHAN. 1973. Petroleum derived hydrocarbons in Gulf of Mexico waters. Trans. Gulf Coast Assoc. Geol. Soc. 16: 170- 181.

LEE, W. Y. 1978. Chronic sublethal effects of the water soluble fraction of No. 2 fuel oil on the marine isopod, Sphaeroma quadridentatumn. Mar. Environ. Res. 1: 5-19.

McAULIFFE, C. D. 1966. Solubility in water of par- affin, cycloparaffin, olefin, acetylene, cycloole- fin and aromatic hydrocarbons. J. Phys. Chem. 70: 1267-1275.

. 1974. Determination of C1-Cl0 hydrocarbons in water, p. 121-125. In Marine pollution monitoring (petroleum). Natl. Bur. Std. Spec. Publ. 409. U.S. GPO.

. 1977a,b. Dispersal and alteration of oil discharged on a water surface, p. 19-35. Evapo- ration and solution of C2 to C,0 hydrocarbons from crude oils in the sea surface, p. 363-372. In D. A. Wolfe [ed.], Fate and effects of petroleum hydrocarbons in marine organisms and ecosystems. Pergamon.

McLAFFERTY, F. W. 1973. Interpretation of mass spectra. Benjamin.

MALINS, D. C. [Ed.] 1977. Effects of petroleum on arctic and subarctic marine environments and organisms, v. 1 and 2. Academic.

NATIONAL ACADEMY OF SCIENCES. 1975. Petro- leum in the marine environment. Washington, D.C.

RossI, S. S., AND J. W. ANDERSON. 1978. Effects of No. 2 fuel oil water-soluble-fractions on growth and reproduction in Neanthes asenaceodentata (Polychaeta: Annelida). Water Air Soil Pollut. 9: 155-170.

SACKETT, W. M., AND J. M. BROOKS. 1975. Origin and distribution of low-molecular-weight hydrocarbons in Gulf of Mexico coastal waters, p. 211-230. In T. M. Church [ed.], Marine chemistry in the coastal environment. Am. Chem. Soc. Symp. Ser. 18.

SAUER, T. C., JR. 1978. Volatile liquid hydrocarbons in the marine environment. Ph.D. thesis, Texas A&M Univ. 317 p. - W. M. SACKETT, AND L. M. JEFFREY. 1978. Volatile liquid carbons in the surface coastal waters of the Gulf of Mexico. Mar. Chem. 7: 1-16.

SCHWARZENBACH, R. P., R. H. BROMUND, P. M. GSCHWEND, AND D. C. ZAFIRIOU. 1979. Vol-

atile organic compounds in coastal seawater: Preliminary results. J. Org. Geochem. 1: 45-61.

STEELE, R. L. 1977. Effects of certain petroleum products on reproduction and growth of zygotes and juvenile stages of the alga Fucus edentatus De la Pyl (Phaeophyceae: Fucales), p. 115-128. In D. Wolfe [ed.], Fate and effects of petroleum hydrocarbons in marine ecosystems and organisms. Pergamon.

SWINNERTON, J. W., AND R. A. LAMONTAGNE. 1974. Oceanic distribution of low-molecular- weight hydrocarbons. Environ. Sci. Technol. 8: 657-663.

, AND V. J. LINNENBOM. 1967. Determina- tion of C1-C4 hydrocarbons in seawater by gas chromatography. J. Gas Chromatogr. 5: 570- 574.

, AND C. H. CHEEK. 1969. Distribu- tion of methane and carbon monoxide between the atmosphere and natural waters. Environ. Sci. Technol. 3: 838-842.

TAKAHASHI, F. T., AND J. S. KITTREDGE. 1973. Sublethal effects of the water soluble component of oil: Chemical communication in the marine environment, p. 259-264. In D. G. Ahern and S. P. Meyers [eds.], The microbial degradation of oil pollutants. Publ. LSU-SG-73- 01, Center Wetlands Resour., Louisiana State Univ.

TREYBAL, R. E. 1955. Mass-transfer operations. McGraw-Hill.

U.S. DEPARTMENT OF THE INTERIOR. 1976. Draft environment statement, outer-continental shelf, Gulf of Mexico. OCS 44. Bur. Land Manage.

VAN DER LINDEN, R., AND G. T. E. THIJSSE. 1965. The mechanisms of oxidation of petroleum hydrocarbons, p. 469-546. In F. F. Nord [ed.], Advances in enzymology, v. 27. Interscience.

VANDERMEULEN, J. H., AND T. P. AHERN. 1976. Effect of petroleum hydrocarbons on algal physiology; review and progress report, p. 107- 125. In A. P. Lockwood [ed.], Effects of pollutants on aquatic organisms. Cambridge.

WALKER, J. D., R. R. COLWELL, AND L. PETROKIS. 1976. Biodegradation rates of components of petroleum. Can. J. Microbiol. 22: 1209-1224.

WALSH, F., AND R. MITCHELL. 1973. Inihibition of bacterial chemoreception by hydrocarbons, p. 275-278. In D. G. Ahern and S. P. Meyers [eds.], The microbial degradation of oil pollutants. Publ. LSU-SG-73-01, Center Wetlands Resour., Louisiana State Univ.

WOLFE, D. A. [Ed.]. 1977. Fate and effects of petroleum hydrocarbons in marine organisms and ecosystems. Pergamon.

Submitted: 12 March 1979 Accepted: 15 October 1979



volatile liquid hydrocarbons in waters of the gulf of mexico and caribbean sea

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