600284067A
FINAL REPORT
RESPONSE OF CRUDE OIL SLICKS TO DISPERSANT TREATMENT AT SEA:
1978 TESTS
JBF Scientific Corporation
Wilmington, Massachusetts 01887
Grant No. R806056
Project Officer
Leo T. McCarthy, Jr.
Oil and Hazardous Materials Spill Branch
Municipal Environmental Research Laboratory
Cincinnati, Ohio 45268
This study was conducted
in cooperation with
American Petroleum Institute
Task Force on Dispersed Oil
Washington, D.C. 20037
MUNICIPAL ENVIRONMENTAL RESEARCH LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
CINCINNATI, OHIO 45268
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DISCLAIMER
This report has been reviewed by the Municipal Environmental Research
Laboratory, U.S. Environmental Protection Agency, and approved for publica-
tion. Approval does not signify that the contents necessarily reflect the
views and policies of the U.S. Environmental Protection Agency, nor does
mention of trade names or commercial products constitute endorsement or
recommendation for use.
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FOREWORD
The U.S. Environmental Protection Agency was created because of increas-
ing public and government concern about the dangers of pollution to the
health and welfare of the American people. Noxious air, foul water, and
spoiled land are tragic testimonies to the deterioration of our natural
environment. The complexity of that environment and the interplay of its
components require a concentrated and integrated attack on the problem.
Research and development is that necessary first step in problem solu-
tion; it involves defining the problem, measuring its impact, and searching
for solutions. The Municipal Environmental Research Laboratory develops new
and improved technology and systems to prevent, treat, and manage wastewater
and solid and hazardous waste pollutant discharges from municipal and com-
munity sources, to preserve and treat public drinking water supplies, and to
minimize the adverse economic, social, health, and aesthetic effects of
pollution. This publication is one of the products of that research and
provides a most vital communications link between the researcher and the
user community.
This report describes field tests in which a chemical dispersant was
applied to controlled oil spills. The findings will assist in predicting
the effects of dispersant use.
Francis T. Mayo, Director
Municipal Environmental Research
Laboratory
m
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ABSTRACT
Four small research oil spills (1.67 m3 (440 gal) each) were made to
determine the physical and chemical behavior of crude oil slicks on the sea
after treatment with a dispersant. Work was performed offshore New Jersey
under a research ocean dumping permit from the U.S. Environmental Protection
Agency. Each spill was made from a research vessel and was then tracked by
vessel and aircraft for several hr. Two crude oils were used; one spill of
each oil was treated with dispersant immediately, and one after 2 hr. A
self-mix dispersant was sprayed on each spill from a helicopter that had
been fitted with a spray system delivering droplets whose mean diameter was
approximately 1 mm. More than 1000 samples of background water, water under
the slicks, and of the surface water were taken with time for chemical
analysis. Aerial photographs were also taken, and representative photographs
are presented in this report. Currents and winds were measured, so that
physical transport of the oil could be interpreted.
Chemical analyses and visual observations showed immediate treatment to
be much more effective than dispersant treatment after 2 hr. Factors con-
tributing to this varying effectiveness include weathering of the oil and
the higher dose rate (dispersant volume per unit area) achieved with imme-
diate treatment. Comparison of the 2 crude oils showed Murban to be more
effectively dispersed than La Rosa, with other factors held constant.
Murban is lighter and less viscous than La Rosa. Vector analyses relating
the oil's movement across the sea surface to the wind and current vectors
showed that dispersed oil plumes follow the current. Oil that remains on,
or returns to, the sea surface is affected by both wind and current.
This report was submitted in fulfillment of Grant No. R806056 by JBF
Scientific Corporation and the American Petroleum Institute under the Spon-
sorship of the U.S. Environmental Protection Agency. This report covers the
period January 1, 1978 to December 1, 1980, .and work was completed as of
December 1, 1980.
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CONTENTS
Foreword i i i
Abstract iv
Figures vi
Tables viii
Acknowledgments ix
1. Introduction 1
Purpose 1
Scope 2
2. Conclusions 3
3. Recommendations 5
4. Experimental Methods 6
Participating Organizations 6
Research Permit (EPA Region II) 6
Remote Sensing (NASA) 6
Spill Locations and General Conditions 8
General Operations 8
Navigation 8
Current Measurement 8
Air Control and Photography 10
Spilling Oil 10
Spraying Dispersant 11
Sampling and Sample Handling 12
Chemical Analysis 14
5. Results and Discussion 15
Physical Behavior 15
Visual and Photographic Observations 15
Slick Spreading 23
Slick Drift 23
Chemical Analyses 29
Total Extractable Organics 29
Petroleum Hydrocarbons 38
Low-Molecular-Weight Hydrocarbons 39
References 41
Appendices
A. Analytical Support to the API Investigation of the
Effectiveness of a Surface-Active Agent in Combating
Open Ocean Spills (Exxon Research and Engineering Co.) .... 42
B. Data From Chevron Oil Field Research Co 51
C. The Dispersion and Weathering of Chemically Treated
Crude Oils on the Sea Surface 58
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FIGURES
Number Page
1 Relationships among participating organizations 7
2 Chart showing test area 9
3 Sketch of four-vane drogue 10
4 Schematic of immediately dispersed oil slick and location
of sample stations for typical 10-station sample run .... 13
5 First Murban spill after 53 min, showing water-in-oil
emulsion near downwind edge of slick 16
6 First Murban spill after 2 hr and 22 min (22 min after
dispersant was sprayed) 17
7 First La Rosa spill after 54 min 18
8 First La Rosa spill after 1 hr and 54 min (20 min after
dispersant was sprayed) 19
9 Second La Rosa spill, 26 min after spill (21 min after
dispersant was sprayed) 20
10 Second Murban spill, 29 min after spill (22 min after
dispersant was sprayed) 21
11 Second Murban spill, 46 min after spill (39 min after
dispersant was sprayed) 22
12 Slick area growth with time, La Rosa spills 24
13 Slick area growth with time, Murban spills 24
14 Effect of wind and current on slick position: Spill No. 1,
Murban treated after 2 hr 25
15 Effect of wind and current on slick position: Spill No. 2,
La Rosa treated after 2 hr 26
16 Effect of wind and current on slick position: Spill No. 3,
La Rosa immediately treated 27
VI
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FIGURES
Number Page
17 Effect of wind and current on slick position: Spill No. 4,
Murban immediately treated 28
18 Total extractable organic matter (ppm) in water samples
collected during first sample run through La Rosa crude
oil spill immediately dispersed (oil spilled 1019, dis-
persed 1028-1035) 30
19 Total extractable organic matter in water samples collected
during second sample run through La Rosa crude oil spill
immediately dispersed 31
20 Schematic view of surface slick and subsurface plume's
spreading and transport as affected by wind and current ... 32
21 Comparison of concentration - depth profiles at one station
for various times under the immediately dispersed La Rosa
crude oil spill 33
22 Total extractable organic matter (ppm) in water samples
collected during first sample run through immediately
dispersed Murban crude oil spill (oil spilled 1404,
dispersed 1411-1416 33
23 Total extractable organic matter (ppm) in water samples
collected during second sample run through immediately
treated Murban crude oil spill 34
24 Comparison of concentration-depth profiles at one station
for various times under the immediately dispersed Murban
crude oil spill 35
25 Comparisons of concentration - depth profiles for La Rosa
and Murban crude oils at about the same time following
discharge and dispersion 36
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TABLES
Number Page
1 General experimental conditions 8
2 Dispersant application specifications 11
3 Comparison of wind effect vectors with wind vectors 29
4 Summary of carbon tetrachloride extractable organic matter
in water from under four research oil spills (ppm) 37
5 Approximate volume of extractable organics accounted for
in water samples under each spill 38
6 Comparison of total low-molecular-weight hydrocarbon
concentrations from stations at center of plumes,
after immediately treated spills 40
vm
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ACKNOWLEDGMENTS
Many extraordinary efforts were made by API task force members and EPA
staff to assist in the successful execution of this study. Clayton
McAuliffe of Chevron Oil Field Research Company worked with JBF on many
aspects of test design and provided the subsurface sampling system that was
used. In addition, he took primary responsibility for preparing a technical
paper summarizing the results. The paper is Appendix C of this report, and
several of its passages were used for descriptions in the main text of the
report.
Within JBF, acknowledgment must be made of Stephen Greene's persistence and
problem-solving in accomplishing the work aboard ship. Jaret Johnson was
Project Manager and coordinated the sea trials from the air.
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SECTION 1
INTRODUCTION
In 1975, the American Petroleum Institute (API) began to sponsor con-
trolled field tests to determine the physical and chemical fate of crude
oils spilled at sea. These test programs have been in response to a lack of
scientific information regarding several aspects of the behavior of spilled
oil under actual conditions in the field. Laboratory work at its best is
still only a simulation of field conditions, and much of the field work on
spills of opportunity has not achieved its potential because of the diffi-
culty of mounting a scientific response immediately after a spill occurs(l).
The API field program includes the following elements in chronological
order:
Four research spills in the Gulf of Maine in 1975, each followed by
aerial photography, navigational tracking, and sampling of water
and surface oil. These projects were described in API Publication
4290(2) and in papers by McAuliffe(3), and Johnson, McAuliffe,
and Brown(4).
Several research spills off Southern California in 1978. Some of
these were tracked scientifically, as above, and others were sub-
jected to a variety of attempts at skimming or dispersant applica-
tion^).
Four research spills in the outer New York Bight in 1978, each of
which was treated with a dispersant. These are the subject of this
report.
Several research spills off Southern California in 1979.
Four research spills in the outer New York Bight in 1979. These
will be the subject of a separate report.
PURPOSE
The 1978 east coast tests were made to determine the physical and chem-
ical behavior of two crude oils spilled at sea, as affected by the appli-
cation of a dispersant. Independent variables included time of slick
weathering before dispersant application and oil type. So that comparisons
could be made with the 1975 tests in which no dispersants were applied, the
same crude oils were used. In addition, biological tests were performed
inside and outside the spill areas by the Virginia Institute of Marine
Science (VIMS) and by Dr. David Boyles, British Petroleum Company, Ltd.
1
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SCOPE
This report describes the methods, observations, results, and conclu-
sions of the four research oil spill experiments conducted by JBF Scientific
Corporation in the outer New York Bight in 1978. Although JBF closely
coordinated its efforts with those of the biological researchers, the biolo-
gical results and their reporting are outside the scope of this report. All
data and interpretations relating to physical and chemical fate are provided
here.
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SECTION 2
CONCLUSIONS
Average total oil concentrations under the immediately dispersed slicks
at 1, 3, 6, and 9 m were, respectively: La Rosa - 0.7, 0.7, 0.3 and 0.2
mg/1; Murban - 3.1, 2.4, 0.5, and 0.4 mg/1. The highest concentrations (30
to 90 min after dispersion) were La Rosa, 3 mg/1 at 3 m depth; Murban, 18
mg/1 at 1 m depth. Because the dispersant:oil volume ratio for these imme-
diately dispersed slicks was about 1:11, the concentrations of dispersant in
the water should be less than 10% of these values.
Maximum oil concentrations for dispersion delayed 2 hr were lower (<1.1
mg/1), and only slightly higher than those found under nondispersed oil
(highest concentration for La Rosa was 0.5 mg/1; for Murban, 0.9). The less
effective dispersion after delayed treatment reflects less efficient dis-
persant application for these spills, as well as increased oil viscosities
due to weathering.
Dispersant treatment of Murban and La Rosa crude oil slicks within 10
min of spilling the oil yielded several differences relative to slicks that
were not treated (in 1975) or treated after 2 hr (in 1978). These differ-
ences included very thin surface oils in contrast to the thick, viscous
appearance of untreated slicks; comparatively high concentrations of oil in
the water column; spreading of thin surface films to larger areas than
untreated slicks; and, in the case of Murban crude, a readily visible sub-
surface oil plume.
Subsurface oil plumes moved with the current, whereas surface oil,
whether treated or not, moved as the vector sum of current and 1% to 2% of
the wind speed.
Below the immediately treated spills, extractable organics concentra-
tions several times higher than background penetrated at least 9 m below the
sea surface. Dilution to concentrations at or near background took place in
2 to 3 hr, however, for these spills of 1.67 m3(440 gal).
The amounts of oil accounted for in the water samples, although very
approximate, show that very little oil (<2.4%) was dispersed by the treat-
ments 2 hr after spillage for both crudes. This low percentage of oil
dispersed was probably caused by the spraying of dispersant at a uniform
dose per unit area, after the oil had had time to become separated into
areas of different thickness. For this reason, most of the area of the
slick (thin oil) received most of the dispersant, while most of the oil (in
thicker patches at the downwind edge of the slick) received an inadequate
amount of dispersant.
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Approximately 40% to 70% of the Murban crude, immediately treated, was
computed to be in the water column. The amount of La Rosa crude was approx-
imately half as much. Visual observations of the immediately treated Murban
spill indicated that almost all of the oil entered the water immediately,
but that some of it returned to the surface before samples were taken.
Low-molecular-weight (C]_ to CIQ) hydrocarbon concentrations under
the immediately treated Murban spill were much higher than under the immedi-
ately treated La Rosa spill. Spills treated after 2 hr had low concentra-
tions of C]_ - do hydrocarbons in the water.
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SECTION 3
RECOMMENDATIONS
Data from this report should be compared with data from laboratory
effectiveness tests. If the laboratory tests are valid and if reliable
scaling relationships can be derived, other oils and other dispersants
should be tested. Thus a data base could be developed to guide dispersant
selection and fate predictions for accidental spills.
The relative importance of several variables affecting dispersant effec-
tiveness should be elucidated. Poor dispersant effectiveness with oil that
weathered for two hours in these tests may be caused by the weathering
itself or by the homogeneous treatment of a non-homogeneous weathered slick.
That is, the thicker oil at the downwind edge of the slicks was treated at
the same dose as the thinner oil at the upwind edge.
Because this report will be followed by another on the 1979 New York
Bight test series, no other recommendations are made at this time. Issues
that remain unresolved after analysis of the 1979 data will be identified
and recommended for further study in the report on 1979 tests.
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SECTION 4
EXPERIMENTAL METHODS
PARTICIPATING ORGANIZATIONS
After JBF and the API had contracted for this project, the U.S. Environ-
mental Protection Agency's Office of Research and Development (EPA/ORD)
became sufficiently interested to participate in funding the project by
means of a grant to the API for part of the cost. In addition to the re-
search interest by EPA/ORD, EPA's Region II was involved in the regulatory
function of reviewing JBF's application for a research permit under PL92-
532, the Marine Protection, Research, and Sanctuaries Act of 1972.
These and other relationships among the administrative and technical
participating organizations are outlined in Figure 1. Some of the groups
shown in Figure 1 will be discussed later in this section with regard to
test methods; other groups' activities are described here.
Research Permit (EPA Region II)
An application for a research permit was submitted to the Surveillance
and Analysis Division, Marine Protection Program, of EPA Region II on July
19, 1977. A request for clarification and expansion on 18 issues was sent
to JBF by Region II on October 27, 1977. JBF's response, amending the
original application, was sent to Region II on December 19, 1977. Permit
No. II-MA-143-Research was granted by Region II, after public notice and
comment, on June 30, 1978. The permit's effective period was October 1,
1978 through March 31, 1980. JBF's work in both 1978 and 1979 was under
this permit.
Remote Sensing (NASA)
The National Aeronautics and Space Administration (NASA) is developing
technology to monitor various environmental phenomena, including oil spills,
from satellites. Development and testing of the equipment is being per-
formed from aircraft. JBF learned of NASA's desire to monitor planned oil
spills, and contacted the NASA Langley Research Center in August 1978 to
discuss possible cooperation. Subsequent discussions led to several under-
standings:
NASA would deploy up to four aircraft to fly over the 1978 test
spills for testing various remote sensing techniques.
After a detailed coordinating session at NASA's Wallops Flight
Center, further questions regarding air safety and potential
6
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Chemical Analyses
Chevron Oil Field
Research Co.
La Habra, CA
and
Exxon Research &
Engineering Co.
Linden, NJ
Primary Sponsor
American Petroleum Institute
Washington, D.C.
Permitting Authority
U.S. EPA/Region II
Edison, NJ
Biological Work
Virginia Institute
of Marine Sciences
and
BP Research Centre
Middlesex, TJK
Contributing Sponsor
U.S. EPA/ORD
Edison, NJ
Prime Contractor
JBF Scientific Corp.
Wilmington, MA
Subcontractors
Ship (R/V Annandale)
Marine Science Consortium
Wallops Island, VA
Command/Photographic
Aircraft
Aero-Marine Surveys, Inc.
New London, CT
Administrative Authority
Reporting Channels
Field Command (Primarily for Safety)
Remote Sensing
National Aeronautics
& Space Administration
Hampton, VA
Dispersant Application
Island Helicopters, Inc.
Garden City, NY
Figure 1. Relationships among participating organizations.
interference with the JBF test mission would be decided by the JBF
test director either before or during each test.
NASA would provide for JBF's use in spilling and sampling, the
Research Vessel Annandale, which was under contract to NASA at the
time. Coincidentally,JBF had been negotiating with the Marine
Science Consortium to lease the Annandale after its NASA contract
expired. This cooperative effort enabled JBF to use the Annandale
at an early date and without charge, and afforded NASA ~aunique
opportunity to test its remote sensing systems.
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SPILL LOCATIONS AND GENERAL CONDITIONS
The area permitted for the tests, and the actual locations of the four
test spills, are shown in Figure 2. These sites were selected because their
distance from shore and prevailing currents made it unlikely that any oil
would approach shore. In addition, all spills were made where the water
depth was greater than 40 m to minimize the likelihood of oil contacting
resuspended bottom material. Finally, no spills were made when wind was
blowing toward shore.
Table 1 shows the general experimental and environmental conditions for
the tests. These conditions appear sufficiently similar that weather is not
considered a variable affecting test results.
TABLE 1. GENERAL EXPERIMENTAL CONDITIONS
Date
Nov.
Nov.
Nov.
Nov.
2
3
9
9
Time Before
Dispersant
Oil Application
Murban 2 hr
La Rosa 2 hr
(a.m. ) La Rosa 4 min
(p.m. ) Murban 5 min
Wind Speed
(m/sec)
4-6
4-6
3-6
3-6
Seas
(m)--
0.3-1
0.3-1
0.3-1
0.3-1
Water Temp.
(°C)
14
14
13
13
Air Temp
(°C)
15-20
15-20
12-17
12-17
GENERAL OPERATIONS
Navigation
Both the Annandale and the control aircraft used Loran-C for navigation.
Positions wererecorded for all sampling stations, for all aerial photo-
graphs, and for any other events of significance. The precision of the
Loran-C readings is approximately + 100 ft in the test area.
Current Measurement
Currents were measured by tracking drogues from the ship and from the
air. Loran-C positions and times were plotted in the office to derive
current vectors. These drogues were of the customary four-vane configur-
ation, presenting a square drag area to the water (1.2 m on a side), with a
small staff and flag above the waterline for ease in sighting (Figure 3).
The drogues' buoyancy was such that they followed currents approximately 1
to 2 m below the surface.
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SCALE
I I I I
0 10 20 30
NAVIGATIONAL LANE
FOUR TESTS CONDUCTED HERE
, APPROVED
TEST SITE
NEW JERSEY
ATLANTIC.^**
SOUNDINGS IN METERS
Figure 2. Chart showing test area,
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Figure 3. Sketch of four-vane drogue.
Air Control and Photography
The aircraft for operational control and photography was provided by
Aero-Marine Surveys, Inc., of New London, CT. A Cessna Model 3376 Skymaster
was used, carrying the Aero-Marine Surveys pilot and photographer, and the
JBF Project Director. The JBF Project Director guided the research vessel
to its sampling stations and guided the dispersant-spraying helicopter from
this aircraft.
Vertical color photographs were made with two belly-mounted Hasselblad
MK-70 mm cameras. Color positive exposures were made on Kodak 11 Color
Safety Film and color negative exposures were made on Kodak 8 Color Safety
Film. A third camera recorded readings on a data panel for Loran-C posi-
tion, time, altitude, and heading. All three cameras were activated simul-
taneously for each exposure. Altitudes for photography varied from 160 to
1300 m.
Spi Hing Oil
Each spill was 1.67 m3 (440 gal) of one of the crude oils (Murban from
Abu Dhabi and La Rosa from Venezuela). These were the same crudes used in
the 1975 test spills that were not dispersed(2).
Each spill was discharged from a 1.9 m3 tank mounted on the stern of
the research vessel through two 7.6 cm diameter hoses. Each hose was 7 m
10
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long, extending over the side to the water surface. The ends of the hoses
were on floats, causing the oil to discharge horizontally on the water
surface. This minimized both evaporation losses due to discharge above the
water, and vertical descent of the oil into the water. The less viscous
Murban (0.83 specific gravity, 39° API) discharged in approximately 3 min;
the La Rosa (0.91 specific gravity, 23.9° API), in 6 min. All "time after
spill" data in this report are based on the beginning of the spill. The
research vessel was not moved by its propeller during the spills, but the
wind moved the ship and freshly spilled oil slightly. Oil surrounded the
stern while the valves were open, but an equiaxed and uniform slick was
always in place after the spill was complete and the vessel moved away.
Spraying Dispersant
A self-mix dispersant, suitable for application without added mixing
energy (e.g., prop wash or breaker board agitation), was used for all tests.
When dispersant is applied from the air, care is required to produce
droplets that are large enough not to drift from the target, but not so
large that they plunge through the oil film or do not achieve even coverage
of the area. Extensive discussions between JBF and Island Helicopters, Inc.
led to a series of dry-land field tests in which various spray nozzles,
aircraft altitudes, and flight speeds were checked. Several members of the
API Task Force on dispersed oil participated in these field tests. The
result was the set of dispersant application specifications listed in
Table 2.
TABLE 2. DISPERSANT APPLICATION SPECIFICATIONS
Aircraft:
Spray System:
Nozzles: Type
: Number
Mean Droplet
Di ameter:
Coverage:
Bell 206 B Jet Ranger
Belly-mounted Simplex unit with
10-meter boom mounted above skids
Spraying Systems Co. No. D1256
Cone-type teejets
15
Approximately 1 mm
Approximately 94 £/hectare (10 gal/acre)
11
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Because the dispersant manufacturer recommended the same coverage, or
area! dose rate, regardless of the spill's age, different volumetric dose
rates resulted. For the spills dispersed immediately, approximately 152 &
(40 gal) were sprayed and the volumetric dose rate was approximately 1:11
(dispersant:oil spilled). For the spills dispersed after 2 hr of spreading
and weathering, approximately 360 £ (95 gal) were sprayed and the volumetric
dose rate was approximately 1:4.6.
For the last three tests, dispersant was discharged while the helicoper
flew crosswind in a rapid back-and-forth pattern. In the first test, the
helicopter sprayed only while flying upwind, because this was expected to be
the most effective method. However, after each downwind leg (not spraying),
it was not possible to discern the treated from untreated areas. The pilot
then noted that, in a back-and-forth spraying pattern, remnants of the spray
could be seen in the air after a fast 180° turn. This pattern was fol-
lowed for the remaining work.
Another problem with the first test was the pilot's estimation that the
slick area was approximately 16 ha (40 acres), meaning that the intended
areal dose could not be achieved (the helicopter payload was selected for an
expected area of 8 ha and any excess load would have compromised safety).
Therefore, only the downwind half of the first slick was treated. Since the
downwind portion of an oil slick contains most of the oil(6) this approach
should have left only the thin trailing sheen untreated.
SAMPLING AND SAMPLE HANDLING
The sampling program was designed to obtain water samples at approx-
imately equally spaced stations on transects through the surface slicks and
emulsion plumes. Figure 4 is a schematic diagram of a typical sample run.
Samples on all runs through dispersed or non-dispersed oil were taken at
1- and 3-m depths at all 10 stations, and at 6 and 9 m at Stations 3 and 8.
Surface samples were taken, with a small bucket, at all stations during
sampling runs through dispersed oil. No surface samples were taken in
non-dispersed oil. A sampling run took about 45 min. Between stations, the
ship moved at approximately 0.5 m/sec (1 knot).
For the immediately dispersed slicks, the first run was started a few
minutes after dispersion, and the second after about 1.3 hr. For the two
delayed dispersion tests, one sampling run was made before dispersion (un-
treated oil), and two after. The two sampling runs after dispersion were
immediate and after about 1 hr.
For all of the spills a few samples were also taken 2, 3, and 4 hr after
dispersion, at Stations 3 and 8.
The subsurface samples were collected with small submersible pumps with
internals of glass-filled polypropylene (Tee! Model 1P681). These pumps
discharged through polypropylene tubing, at approximately 4 1/min. The
pumps were attached approximately 0.5 m below a floating 115-liter (30-gal)
steel drum towed 3 m lateral to the bow of the research vessel. In this
position, the ship's bow wave did not cause water mixing at the sample
inlets. These inlets were 1, 3, 6 and 9 m below the water surface, along a
taut vertical line suspending a 23 kg weight from the bottom of the float.
12
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Wind Direction
Vessel Track
Figure 4. Schematic of immediately dispersed oil slick and location
of sample stations for typical 10-station sample run.
From McAuliffe, et al. .^Appendix C).
The sample gear was lowered and removed from the water outside the observed
slicks to avoid surface oil contamination.
Two types of samples were collected at each station and depth: one
1.5-1 sample in 1.9-1 (0.5-gal) flint glass jug, and duplicate completely
filled 300-ml (10-oz) "soft drink" bottles with crown caps. The 1.9-1 jugs
had been cleaned by rinsing three times with distilled-in-glass carbon
tetrachloride (CC14) that was checked for purity by infrared (IR) spec-
troscopy. Immediately after collection, 50 ml of this CC14 was added to
each jug from an all-glass dispensing pipet. The jugs were sealed with
teflon-lined metal screw caps, and hand-shaken for about 10 sec to initiate
the solvent extraction of organic matter including the dispersed oil. The
CC14 also prevented bacterial degradation of the hydrocarbons. In the
laboratory, the samples were shaken 2 min to complete the extraction.
Prior to sample collection, about 30 mg of mercuric chloride (HgCl2)
was added to each 300 ml bottle to prevent biodegradation prior to analysis.
Each bottle was then flushed with reactor-grade helium and sealed with a
crown cap (polyvinyl chloride seal). At time of sample collection, each
bottle was uncapped, filled to within 3 mm of the top, and resealed with a
crown cap. The small air space minimized loss of volatile hydrocarbons to
this gas space and possible contamination of sample by hydrocarbons (as well
as CC14 vapors) that may have been in the atmosphere during sample collection.
13
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Samples of each crude oil were taken from the spill tank in glass bot-
tles with Teflon-lined screw caps.
Chemical Analysis
Total extractable organic matter was measured on the single 50-ml por-
tion of CC14, with an IR instrument, as absorbancy at 2930 cnr1. This
method measures other CC14 soluble compounds such as organic acids,
esters, and alcohols in addition to the crude oil. The CC14 extracts of a
few samples were further analyzed for total nonvolatile (C]4+) hydrocar-
bons, by removing polar organic compounds with a silica gel column and
reanalysis by IR. Details of these techniques are given in Reference 7.
These analyses were performed by Exxon Research and Engineering Co., Linden,
N.J.
Volatile hydrocarbons (C] to CIQ fraction) in the water samples were
analyzed by a gas equilibrium method (8) at Chevron Oil Field Research Co.,
La Habra, CA. Forty ml of Murban and La Rosa oil samples were equilibrated
with 140 ml of sea water collected before the oil spills. The oil and water
were hand shaken gently and periodically for 24 hr or more. Mercuric
chloride added at the time of water collection prevented possible biodegra-
dation of dissolved hydrocarbons during equilibration and prior to analysis.
This water was filtered (from one 50-ml glass syringe into a second) to
remove any separate-phase oil that may have been dispersed during oil-water
mixing. Twenty-five ml of this water was gas equilibrated five times.
These successive analyses were used to measure the equilibrium concen-
trations of individual C] to C]Q hydrocarbons for the two crude oils,
and to calculate individual hydrocarbon distribution coefficients.
The water samples collected at the various stations and depths were then
analyzed with a single equilibration using the measured distribution coeffi-
cients to calculate concentrations. This gives sufficient accuracy and
saves time and cost of multiple equilibrations. For those samples that
contained significant separate phase oil, the duplicate sample was filtered
and analyzed. Separate-phase oil contributes hydrocarbons to the gas phase
in concentrations higher than if the hydrocarbons were only in solution.
Method details are given in References 8 and 9.
14
-------
SECTION 5
RESULTS AND DISCUSSION
PHYSICAL BEHAVIOR
Visual and Photographic Observations
General observations of the spills' physical behavior are discussed here
in preparation for the more detailed data presentations and analyses.
Spill 1, Murban Treated After 2 hr--
This spill showed the behavior of Murban as seen in the 1975 test series
in the rapid formation of a thick brown water-in-oil emulsion. This mater-
ial formed a large patch near the downwind edge of the slick (Figure 5).
After treatment of this slick with dispersant, the visible appearance of the
slick did not change significantly. As described in the previous section,
only the downwind half of this slick was treated. An opportunity to compare
treated and untreated areas at the same time was thus available. Other than
the normally observed differences between upwind and downwind sections, no
difference between treated and untreated areas was detectable (Figure 6).
Spill 2, La Rosa Treated After 2 hr--
The downwind, thicker portion of this slick in the untreated condition
was dark blue as seen from the air, and quite viscous as seen from ship-
board. The overall slick before treatment is shown in Figure 7. Dispersant
application produced some immediate, visual changes: in the treated area,
iridescence and blue surface oil disappeared, and foam streaks appeared.
Within 15 to 20 min after treatment, however, the visual appearance of the
slick was similar to its condition before treatment, as shown in Figure 8.
Spill 3, La Rosa Treated Immediately--
No subsurface plume of oil was visible after treatment. The primary
difference between this spill's appearance and that of untreated La Rosa
slicks was seen from shipboard: the surface oil was thin and transparent,
in contrast to the normal opaque, viscous slicks resulting from La Rosa
spills. A typical aerial view of this slick is shown in Figure 9.
Spill 4, Murban Treated Immediately--
Dispersant spraying of the freshly spilled Murban caused apparently
total entry of the oil into the water as a light brown plume (Figure 10).
As time passed, some oil returned to the surface as a thin sheen, and the
subsurface plume became diluted and less visible (Figure 11). The sub-
surface plume after 1 hr was in the upwind part of the area of the surface
slick.
15
-------
Figure 5. First Murban spill after 53 min, showing water-
in-oil emulsion near downwind edge of slick.
Scale: 1 cm = 32 m
Neg. No. 36
16
-------
Figure 6. First Murban spill after 2 hr and 22 min
(22 min after dispersant was sprayed).
Neg. No. 45, 47 and 48
Scale: 1 cm = 36 m
17
-------
Figure?. First La Rosa spill after 54 min,
Neg. No. 152
Scale: 1 cm = 32 m
18
-------
Figure 8. First La Rosa spill after 1 hr and 54 min
(20 min after dispersant was sprayed).
Neg. No. 174
Scale: 1 cm = 32 m
19
-------
Figure 9. Second La Rosa spill, 32 min after spill
(23 min after dispersant spraying began)
Neg. No. 258
Scale: 1 cm = 19 m
20
-------
Figure 10. Second Murban spill, 29 min after spill
(22 min after dispersant was sprayed).
Neg. No. 338
Scale: 1 cm = 19 m
21
-------
Figure 11. Second Murban spill, 46 min after spill
(39 min after dispersant was sprayed).
Neg. No. 342
Scale: 1 cm = 19 m
22
-------
Slick Spreading
Areas of all four slicks were measured by olanimeter techniques on
photographs taken at various times. Results for the two La Rosa spills are
shown in Figure 12, with 1975 La Rosa data (no dispersant) shown for compar-
ison. Figure 13 shows similar data from the Murban spills of 1975 and 1978.
Several observations can be made, based on these plots and on a review
of the aerial photographs.
The spreading of the 1978 slicks that weathered for 2 hr before
treatment was similar to that of the 1975 slicks (untreated).
The application of dispersant at 2 hr had no apparent effect on
spreading rates.
For the immediately treated La Rosa spill, the spreading rate and
area of the slick were both greater than for untreated or delayed-
treated La Rosa slicks. To attain such a large area, the slick
must have been very thin.
The immediately dispersed Murban spill spread at a slower rate than
untreated Murban slicks for approximately the first 30 min. Ulti-
mately, however, the area of the treated slick became much larger
than that of untreated or delayed-treated Murban slicks.
The observed greater spreading tendency of the immediately treated oils
is caused, in part, by the reduction in the oil/water interfacial tension
achieved by the dispersant. Reduction in viscosity may also contribute. In
the case of the Murban spills, the initially slower rate of spreading can be
related to the observation that very little oil was on the surface for the
first 30 min after dispersant application, as discussed previously. The
visible dispersed plume's horizontal rate of spreading below the surface was
lower than the rate observed for surface slick spreading with untreated
oils. However, as the oil returned to the surface, it formed a slick that
spread rapidly into a large, thin sheen.
Slick Drift
Winds and currents affect the transport of oil slicks across the sea
surface. The 1975 work confirmed several literature findings in that those
spills moved as the vector sum of current and approximately 1% to 3% of the
wind vector.
Figures 14 through 17 show the transport of surface oil, as well as wind
and current vectors, for the four 1978 spills. During the time of obser-
vation for each spill, winds were fairly consistent. Current direction
changed on each test day, however. During Spill No. 1 (Figure 14), the
current heading changed from ESE to NNE, producing a change in the direction
of surface oil transport. Spill No. 2 (Figure 15) showed an even more
pronounced shift in current and oil directions. On the third test day,
23
-------
1000 2000
Figure 12. Slick area growth with time, La Rosa spills,
1000 2000
Figure 13. Slick area growth with time, Murban spills,
24
-------
True
North
1556
1
(Local Time)
1207
1248. --'
SCALE:
1853 m
(1 Naut. Mi.)
LEGEND:
Wind Vector
p 1 1*
1 segment = 2.6 m/sec (5 knots)
Current Vector
1 segment = 0.13 m/sec (0.25 knots)
Slick position (Leading Edge)
Figure 14. Effect of wind and current on slick position:
Spill No. 1, Murban treated after 2 hr.
25
-------
True
North
N
1412
1225
(Local
Time)
1044 A.
I *<
SCALE:
1853 m
(1 Naut. Mi.)
I I
LEGEND:
Wind Vector
,O-
1 segment = 2.6 m/sec (5 knots)
Current Vector
.1 segment = 0.13 m/sec (0.25 knots)
Slick Position (Leading Edge)
Figure 15. Effect of wind and current on slick position:
Spill No. 2, La Rosa treated after 2 hr.
26
-------
True
North
\
SCALE:
1853 m
(1 Naut. Mi.)
1322,0
«f!245
i
122!
1052
(Local
Time)
LEGEND:
Wind Vector
O 1 1 *>
1 segment = 2.6 m/sec (5 knots)
Current Vector
-1 segment = 0.13 m/sec (0.25 knots)
1
Slick Position (Leading Edge)
Figure 16. Effect of wind and current on slick position;
Spill No. 3, La Rosa immediately treated.
27
-------
which Included two test spills, current was consistent during each spill but
shifted directions between spills, contributing to the different headings of
the surface oils from these spills.
Analysis of the velocity vectors for oil, current, and wind showed
results similar to those from the 1975 tests: the effect of the wind on all
surface slicks was a vector whose magnitude was 1% to 2% of the wind vector,
and roughly parallel to the wind vector. These effects on surface oil
movement, summarized in Table 3, were independent of whether the oil had
been treated with dispersant. The direction of movement of subsurface oil
is discussed later, where the subsurface plume's fate is inferred through
chemical analyses for known sample positions.
TABLE 3. COMPARISON OF WIND EFFECT VECTORS WITH'WIND VECTORS
Wind effect compared
to wind vector
Spill
Time Interval
Approximate
Heading
Ve locity
Ratio
Murban - 2 hr
Before treatment
After treatment
parallel
30° to
Right of wind
1%
1%
La Rosa - 2 hr
La Rosa - immed.
Murban - immed.
Before treatment
After treatment
After treatment
After treatment
200 to
Right of wind
200 to
Left of wind
200 to
Right of wind
parallel
2%
1%
2%
1%
CHEMICAL ANALYSES
that
of the
o i i L_J i A >nL. nn/ii_i^L-*J
Analyses of the water samples provided information
complements the physical observations for overall indications of fate o-
oil and some of its specific fractions.
Total-Extractable-Qrganics
Analyses of the CC14 extracts by infrared
spectroscopy were performed by Exxon Research and Engineering Co. (ER & E).
ER & E's findings are presented as Appendix A, and the interpretations of
those data are developed in this section. As the discussion will show,
highest oil concentrations and most interesting patterns were found in the
water samples from the spills that were treated immediately. These spills
(No's 3 and 4) are therefore discussed first.
29
-------
The crossed transects of a sampling run permit a three-dimensional
analysis of plumes of dispersed oil (i.e., in crossed vertical planes).
However, the limited sampling at 6 and 9 m (only at Stations 3 and 8) gives
a limited view of dispers'on at these depths. The 1975 work (2) showed that
these two crude oils dispersed only slightly to depths up to 3 m without
dispersarit treatment, even in rough seas. In addition, McAuliffe et al. (9)
found no oil at 6 m below the sea surface near a platform blowout theit was
treated with dispersant. Therefore, significant dispersion of oil down to 6
not expected. These depths were added only to verify the ear-
but the detection of measurable oil at 6 and 9 m in this work
In subsequent studies conducted in October 1979, all stations
and 9 m was
lier results,
was frequent.
were sampled through 9 m, and all samples were analyzed.
La Rosa Spill, Immediately Dispersed--
Figure 18 shows the total extractable organic matter concentrations with
depth along the two transects of the first sampling run following the imme-
diate dispersion of La Rosa crude oil. The vertical scale exaggeration is
about 45X. The contour for 0.25 ppm was at approximately 9 m at its deepest
point; for the 1.0 ppm contour, 4 to 5 m.
The shape of the 2.0 ppm contour
10 is interesting in its asymmetry.
for its asymmetric shape, this might
fact. However, the second
on the transect of Stations 6 through
Relying as it does on one data point
be suspected as an experimental arti-
ract. However, tne second set of transects, approximately 1 hr later
(Figure 19) produced the same type of contour. An unexplained, but real,
hydrodynamic effect appears responsible for this unusually shaped isopleth.
.25 19.1 10.8 4.06 .18
-.03 3^1:
h-.09
.10
Stations (\J (2) (3
Time after +24 +29 +32
spill (min)
(5)
+41
.44
-09
(6)
+57
WIND
4.69 7.05
(7)
+61
(8)
+64
.52
1.76
(Intersect)
(9)
+70
Figure 18. Total extractable organic matter (ppm) in water samples
collected during first sample run through La Rosa crude
oil spill immediately dispersed (oil spilled 1019, dis-
persed 1028-1035). Vertical scale exaggeration about 45x,
From McAuliffe et al. (Appendix C).
30
-------
i3
ti>
S6
o
.10
1.05
.11
.18
.06
.16
.06
.05
.11
.08
Stations (T)
Time after spill (min) +84
.09 1.63 1.44
+87 +89 +92
(5)
+95
WIND
Stations (&
Time after +104
spill (min)
+127
Figure 19. Total extractable organic matter in water samples collected
during second sample run through La Rosa crude oil spill
immediately dispersed. Vertical scale exaggeration about
45x. From McAuliffe et al. (Appendix C).
Another observation based on Figures 18 and 19 is that the plume of
dispersed oil extended much more in the direction parallel to the wind
(transect 6 - 10) than in the crosswind direction. In addition, the plume
remained beneath the visible surface slick. Figure 16 showed that the
current was at approximately 90° from the wind direction during this
spill's period of observation (current to the northwest, wind to the north-
east). One can postulate that the immediately dispersed subsurface oil
should be advected only by the current vector. The oil behavior that should
result from this condition is shown schematically in Figure 20. In Figures
18 and 19, subsurface oil was shown to be more heavily concentrated at the
upwind end of the slick, indicating that the behavior suggested in Figure 20
did occur.
If the subsurface plume's buoyancy is effectively neutral because of
small droplet size, water circulation should cause a large number of drop-
lets to be at the surface at any time. While at the sea surface, droplets
may coalesce with residual surface oil or with each other. This phenomenon
31
-------
Surface Slick
Subsurface Plume-^ ^x"~~" ^""^x True
North
OH
(Leading Edge)
Initial Spill and
Dispersant Spray
Figure 20. Schematic view of surface slick and subsurface plume's
spreading and transport as affected by wind and current.
may be another reason for the observed rapid spreading rates of the immedi-
ately dispersed oils. Such a mechanism could cause dispersed plumes to be
in contact with thin surface slicks as long as both are detectable. If this
hypothesis is correct, an on-scene vector analysis, coupled with visual
observation of the surface sheen, may make the tracking of dispersed plumes
for extended periods an easy task, even if the subsurface oil cannot be seen.
Comparing Figures 18 and 19 shows the effect of dilution as the subsur-
face plume dispersed. Another way to view the dilution is shown in Figure
21 for the immediately dispersed La Rosa spill. Concentrations at the
center of the plume are plotted with depth over time. Because each depth
concentration is a single analysis, great reliance should not be placed on
an individual point. As expected, a steady decrease in concentrations
toward background values occurred over time.
Murban Spill, Immediately Treated--
The subsurface plume shape for the immediately treated Murban spill is
shown for the first sampling transects in Figure 22. Comparison with Figure
18, representing a similar time span for similarly treated La Rosa crude,
32
-------
^^^^
Total Extractable Organic Matter,ppm
Figure 21. Comparison of concentration - depth profiles at
one station for various times under the immediately
dispersed La Rosa crude oil spill.
-WIND
u
1
S3
£
&6
Q
9
Stations
\^ ^
- .09 6.10
^N
-.11 1.20
Horizontal
scale
0 50100
m
(D ©
Time after +25 +28
spill (mini
11
17.83.17 .17
s. | jy- 8 ppm
10.2 1.07
\^J 4 PPm
.05
© 0 ©
u
1
3
6
9
- .07
- .08
b
c
c
3.80 3.07 I
j
2.54 2££//
\V i99^ ^
\
;
3
\.95
-------
-.'. ~-;S"Vs^sr^.V'vT..
shows generally higher concentrations for Murban. Dispersed oil was
found in higher concentrations at greater depths (almost 1 mg/1 at 9m).
also
Figure 23 shows the subsurface plume shape for the second set of tran-
sects on this spill. Because only a few samples for the station 1 to 5
transect were analyzed, that transect is poorly characterized. The plume
appears centered beneath the surface slick, however. As Figure 17 showed,
the wind and current were approximately parallel during this test, so that
the subsurface plume and surface oil would be expected to remain together.
The dilution of this plume with time, as expected, proceeded similarly to
that of the plume from the immediately treated La Rosa spill. Comparison of
Figure 24 (Murban) with Figure 21 (La Rosa) shows this similar time pattern.
2
15
5
3.40 7.29
1.55 3.81
3.72
1 ppm
0.30
0,35
Stations
Time after
spill (min)
+ 81
1.82
£ 6
Q
9
Stations
f84 +88
0.96
+ 94
+ 98
0.41
WIND
0.14
0.08
0.10
0.09
0.25 ppm
0.20 0.07
0.08
0 50 100
m
0.18
& d>
Time after +108
spill (min)
H16
+ 122
+ 126
(\0)
+ 131
Figure 23. Total extractable organic matter (ppm) in water
samples collected during second sample run through
immediately treated Murban crude oil spill. Vertical
scale exaggeration about 45x.
34
-------
Total Extractabla Organic Matter, ppm
0.03 0.10 1.0
Figure 24. Comparison of concentration-depth profiles
at one station for various times under the
immediately dispersed Murban crude oil spill,
Spills Treated After Two Hr--
The data for the two spills that were allowed to weather for 2 hr before
dispersion do not allow such clear graphical display. Most values for total
extractable organic matter were much lower than those from the immediately
dispersed spills. One explanation is-tfee larger area to be treated after 2
hr, with a consequently larger water volume available to dilute an equiva-
lent amount of oil.
Another problem is the nonhomogeneity of the oil slicks after 2 hr.
Most of the oil was concentrated in the leading (downwind) part of the
slick, in perhaps only 10% of the total slick area, as observed by Hollinger
and Mennel1a(6). The dispersant was applied uniformly over the whole
slick rather than concentrated on the area of heavy oil. If a "lens" com-
prising 10% to 20% of the slick area contained 80% to 90% of the oil, the
volumetric application rate of dispersant to the oil in the lens would be
approximately 1:25, in contrast to the gross rate of 1:4.6.
Therefore the dispersant to oil volumetric application rate for most of
the oil was not as high as for the immediately dispersed spills, which were
treated before appreciable spreading had occurred. Weathering also would
have increased oil viscosities, and thereby should have decreased dispersant
effectiveness.
Comparisons Among Tests--
Extractable Qrganics Concentrations--Concentration lines for the immedi-
ately treated Murban spill (Figures 22 and 23) show higher values than with
La Rosa Figures 18 and 19). Dispersed oil was also found in higher concen-
trations at greater depths (almost 1 ppm at 9m).
35
-------
:«t«^^ " -*
Figure 25 compares concentration-depth profiles of the two crude oils,
for samples from the center of the plume at similar times after oil dis-
charge and dispersion. Again, each concentration is a single data point.
Total Extractable Organic Matter, ppm
0.10 1.0 10.0 20.0
Depth profile
88 min
after spill
Figure 25. Comparison of concentration - depth profiles for
La Rosa and Murba/fxrude oils at about the same time
following discharge and dispersion. From McAuliffe
etal. (Appendix C).
A summary of the total extractable organic matter in water under the
four research oil spills is shown in Table 4. It includes only values
exceeding 0.10 ppm (approximately two times background). Untreated oil
dispersed naturally in the water to a lesser extent than chemically treated
oil. Immediate treatment was more effective than treatment after 2 hr.
The greatest difference between oils was evident when they were dis-
persed immediately. Murban oil concentrations were higher at all water
depths than for La Rosa. The slightly higher concentrations for La Rosa
compared with Murban following delayed dispersion may reflect differences in
chemical application and/or sampling locations.
Amount of oil accounted forComputation of the amount of oil in the
water was performed with the following procedure and simplifying assumptions:
f
For the figures showing reliable isopleths of extractable organics
(Figures 18, 19, and 22), the volume inside each isopleth was
approximated as an inverted pyramid, bounded by plane surfaces
extending from the nadir of the pyramid, near the isopleth lines to
the sea surface.
36
-------
TABLE 4. SUMMARY OF CARBON TETRACHLORIDE EXTRACTABLE ORGANIC
MATTER IN WATER FROM UNDER FOUR RESEARCH OIL SPILLS
(ppm)*
Sample Description
n**
La Rosa
Maximum
Mean
Murban
n** Maximum
Mean
Not dispersed
1 m 4
3m 3
Dispersed at 2 hr
1 m 7
3m 7
6 m 2
9 m 1
Dispersed within 10 min
0.22
.51
.23
1.05
.65
.29
0.13
.26
.15
.27
.38
1
2
8
4
1
1
0.95
.16
.18
.11
.14
.12
0.14
.13
.10
1
3
6
9
m
m
m
m
16
14
5
1
2.
2.
24
96
50
25
.69
.67
.31
-
13
9
4
4
17
10
1
.80
.20
.00
.95
3.
2.
.
10
45
45
40
*Background concentrations (ppm); 1 m, 0.061; 3 m, 0.050; 6 m, 0.048;
9 m, 0.051
**Number of samples
The volumes of the pyramids thus described were calculated and the
amount of extractable organic matter was determined by multiplying
by the concentration, with appropriate dimensional conversions.
Double accounting was avoided by using the incremental volumes and
concentrations for each pyramid, and summing the results.
The results should be used with great caution as to absolute quantities
of oil in the water, but the relative amounts for different oils and treat-
ments should be useful for comparison because all computations used the same
assumptions. The reasons for the approximate nature of the absolute oil
quantities include:
37
-------
The isopleths are not "snapshots", but represent changes in time as
well as position. Therefore average extent (area and volume of
each plume during each transect) was roughly approximated.
The isopleths do not in fact describe pyramids or even cones, but
the pyramid shape was selected because of simplicity. Given the
amount of judgment used in drawing the isopleths among the sparse
data points, a more sophisticated approach to volume computations
was not justified.
Results are shown in Table 5.
TABLE 5. APPROXIMATE VOLUME OF EXTRACTABLE ORGANICS
ACCOUNTED FOR IN WATER SAMPLES UNDER EACH SPILL
Time to dispersant Approximate
Oil Spraying Amount oil in water (a)*
Murban Immediate 680
Murban 2 Hr 40
La Rosa Immediate 340
La Rosa 2 Hr 40
* Spilled oil volume was 1665 £.
The many judgments and other sources of error leading to these results
could possibly cause these values to be off in absolute terms by as much as 50
to 60%. The relative amounts, which are more reliable, clearly show the
advantage of applying dispersant to these oils as soon as possible. The
relative ease of dispersing Murban crude compared to La Rosa crude is also
evident. These relative findings concur with visual observations of effec-
tiveness.
Petroleum Hydrocarbons
Petroleum hydrocarbons (C]4+) were determined on three of the extracts.
Extractable organic matter was 2.24, 1.25, and 2.54 mg/1; C]4+ hydrocarbons
were respectively 1.43, 0.72, and 1.97 mg/1. Petroleum hydrocarbons averaged
76% of the total extractable organic matter. This is in the range previously
observed (7) for a much larger number of analyses. However, the actual crude
oil content of the original CC14 extracts is higher because hydrocarbons
38
-------
5 ppm).
The polar organic compounds removed by silica gel appear to exceed the
extractable organic matter from background water samples outside the oil spill
areas (particularly noticeable when the extractable organic material ranges
from 0.2 to 1 ppm). A possible explanation is that crude oil acts as an
organic solvent, extracting and concentrating natural organic compounds in sea
water.
Low-Molecular-Weight Hydrocarbons
As described in Section 4, individual hydrocarbons in the C] to C]Q
fraction were measured by gas chromatography. The raw data are provided as
Appendix B. Interpretation of these data, as developed by Clayton McAuliffe
of Chevron Oil Field Research Company, is detailed in Appendix C, pages 8
through 16. A brief summary of the data and findings is presented below.
To compare the two oils, representative data shown in Table 6 can be used.
Review of Table 6 yields the following observations:
Of all the La Rosa samples from 6 and 9 m, only one showed detectable
C] to C]Q hydrocarbons.
C] - C]o concentrations under Murban spills were much higher than
those under La Rosa spills for similar locations and times. Two
factors contribute to this difference: the better dispersion of
Murban and the fact that, when fresh crude oil was equilibrated with
clean sea water in the laboratory, the C] - CIQ fraction's con-
centration was nearly twice as high for Murban as for La Rosa.
In addition, review of all the data in Appendix B shows that, although
similar numbers of samples were collected from all four spills, the numbers of
samples with detectable C] - CIQ hydrocarbons were (not counting duplicate
samples):
Murban, 2 hr weathering -8(6 before spray, 2 after)
La Rosa, 2 hr weathering - none
Murban, immediate spray - 38
La Rosa, immediate spray - 17
The more effective dispersion of Murban is obvious.
39
-------
TABLE 6. COMPARISON OF TOTAL LOW-MOLECULAR-WEIGHT HYDROCARBON
CONCENTRATIONS FROM STATIONS AT CENTER OF PLUMES,
IMMEDIATELY AFTER IMMEDIATELY TREATED SPILLS*
Time
after spill
(min)
33
30
33
30
33
30
33
58
58
66
58
58
58
88
88
90
88
88
88
Depth (m)
0
0
1
1
3
3
6
0
1
1
3
6
9
0
1
1
3
6
9
Oil
La Rosa
Murban
La Rosa
Murban
La Rosa
Murban
La Rosa
Murban
Murban
La Rosa
Murban
Murban
Murban
Murban
Murban
La Rosa
Murban
Murban
Murban
Total C] - C]0
hydrocarbons (ppb)
8.46
3693
2.62
72.1
1.67
16.6
1.22
46.2
16.5
3.56
24.8
4.00
3.29
25.3
25.3
1.41
19.5
13.0
5.45
*Where no entry appears (e.g., 33 min, 6 m,
carbons were less than 0.4 ppb.
Murban), C] - CIQ hydro-
40
-------
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1.
2.
3.
4.
5.
6.
7.
8.
9.
Pollack, A.M., and K.D. Stolzenbach. Crisis Science: Investigations in
Response to the Argo Merchant Oil Spill. MITSG 78-8, Massachusetts
Institute of Technology, Cambridge, June 1978. 328 pp.
JBF Scientific Corporation. Physical and Chemical Behavior of Crude Oil
Slicks on the Ocean. Publication 4290, American Petroleum Institute,
Washington, D.C., April 1976. 98 pp.
McAuliffe, C.D. Evaporation and Solution of C2 to C]Q
from Crude Oils on the Sea Surface. In: Fate and Effects
Hydrocarbons in Marine Ecosystems and Organisms, D.A.
Pergamon Press, New York, 1977. pp. 363-372.
Hydrocarbons
of Petroleum
Wolfe, ed.,
Johnson, J.C., C.D. McAuliffe, and R.A. Brown. Physical and Chemical
Behavior of Small Crude Oil Slicks on the Ocean. In: Chemical Disper-
sants for the Control of Oil Spills, ASTM STP 659, L.T. McCarthy, Jr.,
G.P. Lindblom, and H.F. Walter, eds., American Society for Testing and
Materials, 1978. pp. 141-158.
Smith, D.D., and G.H. Holliday. API/SC-PCO Southern California 1978 Oil
Spill Test Program. In: Proceedings of the 1979 Oil Spill Conference,
Publication 4308, American Petroleum Institute, Washington, D. C.
pp 475-482.
Hollinger, J.P., and R.A. Mennella. Oil Spills: Measurements of their
Distributions and Volumes by Multifrequency Microwave Radiometry.
Science, 181: 54-56, July 6, 1973.
and T.D. Searl. Sampling and
Ocean Water. In: Advances in
ed., American Chemical Society,
Brown, R.A., J.J. Elliott, J.M. Kelliher,
Analysis of Nonvolatile Hydrocarbons in
Chemistry Series, 147, T.R.P. Gibb, Jr.,
Washington, 1975. pp. 172-187 .
McAuliffe, C.D. GC Determination of Solutes by Multiple Phase Equili-
bration. Chemical Technology, 1: 46-51, 1971.
McAuliffe, C.D., et al. The Chevron Main Pass Block 41 Oil Spill:
Chemical and Biological Investigations. In: Proceedings of the 1975
Conference on Prevention and Control of Oil Pollution, American Petro-
leum Institute, Washington, pp. 555-566
41
-------
APPENDIX A
ANALYTICAL SUPPORT TO THE API INVESTIGATION
OF THE EFFECTIVENESS OF SURFACE-ACTIVE AGENT
IN COMBATING OPEN OCEAN SPILLS
R. A. Brown
T. D. Searl*
SUMMARY
Four hundred samples for four planned oil spills were collected and half
of them were analyzed for extractable organic content (includes hydrocarbons
and higher molecular weight alcohols, esters, and organic acids). A few
samples were analyzed for total nonvolatile hydrocarbons. An average value
of 0.68 was observed for the ratio nonvolatile hydrocarbons/extractable
organics.
INTRODUCTION
In November 1978 the JBF Scientific Corporation conducted a series of
four planned oil spills for the API in the Atlantic Ocean about 30 miles off
the New Jersey coast. These spills were to investigate the effectiveness of
a surface-active agent in combating open ocean spills. The role of the Ana-
lytical and Information Division of Exxon Research was to determine the oil
content of samples collected from a spill using the carbon tetrachloride-
infrared techniques developed for measuring parts per billion of oil in
seawater.
EXPERIMENTAL
Sampling
A major goal of the program was to make quantitative measurements of the
total oil, and the distribution of its fractions, in the water column.
Requirements included background water samples, samples of the oil spilled,
and the oil and water under the slick.
*This work was done under contract with the American Petroleum Institute in
support of a study to evaluate chemical dispersants in oil spill control.
42
-------
Because the concentration of individual oil fractions in the water were
likely to be very low, extreme caution was exercised to minimize contamina-
tion. Therefore, the 400 one-half gallon sample bottles for the determina-
tion of oil in water were fitted with teflon-lined caps and rinsed three
times with carbon tetrachloride (CC14) before being sent to the research
vessel. The cases of Burdick and Jackson, distilled in glass CC14 were
all tested for purity by infrared (IR) before going to the vessel. Conveni-
ent apparatus for dispensing 25 ml of CC14 were also provided the sampling
team.
On the ship, the surface water was sampled by bucket and the subsurface
water with submersible pumps discharging through polypropylene tubing into
the precleaned sample bottles which were aboard ship. The intake tubing was
deployed before entering the oily area and retrieved outside the oil. The
sample pumps operated continuously, so that the system was constantly
flushed to help ensure the integrity of the sample.
Twenty-five ml of the special CC14 was added to each bottle as soon as
possible after sampling and all of the samples were sent to Exxon Research
at Linden when the research vessel docked. Personnel of Exxon Research were
not involved in the sampling operations.
Method of Analysis
The basic analytical technique applied to this study is described in
detail*. Figure A-l is a schematic description of the method. The 1.5
liters of water were extracted with one 50-ml portion of CC14. The ex-
tract was placed in a 5 cm cell and scanned by a FT-IR instrument. The
absorbance of the peak at 2930 crrr^ was measured and converted to micro-
grams of oil by means of a calibration factor based on over 30 different
crude oils. This IR value measures other CC14 soluble lipids such as
organic acids, esters, and alcohols in addition to petroleum.
In order to measure total nonvolatile (C]4+) hydrocarbons, the CC14
extract was evaporated to 2 ml and then separated in a silica gel column
into a total hydrocarbon fraction as shown in Figure A-l. An infrared
measurement of the final silica gel fraction provided a measure of the
hydrocarbons.
RESULTS
Exxon Research agreed to provide 400 bottles and analyze 133 samples for
extractable organics and 10 for nonvolatile hydrocarbons. Jay Johnson of
JBF requested that 185 samples be analyzed for extractable organics. The
results are presented in Tables A-2 through A-5. The background oil content
of the testing area taken before the oil spills are not available, for these
samples never reached the Linden laboratory. Backgrounds taken after the
first and third oil spills are presented in Tables A-3 and A-5, respectively.
*R.A.Brown,J.J. Elliott, J.M. Kelliher, and T.D. Searl, "Sampling and
Analysis of Nonvolatile Hydrocarbons in ocean Water," Adv. in Chem., No.
147, 172-187 (1975).
43
-------
Obtain 3 to 20 Liter Sample
Extract Sample with
25 to 125 ml Carbon Tetrachloride
IR Measurement of
Extractable Organics
\
Reduce Sample to 2 ml by
Controlled Evaporation
of Carbon Tetrachloride,
Add 0.1 ml of n-Pentane
Silica Gel Column Separation
I
I
Carbon Tetrachloride
+ n-Pentane
Saturate Hydrocarbons
Chloroform
+ Benzene
Aromatic Hydrocarbons
Evaporate Chloroform, n-Pentane
and Benzene, Replacing with
Carbon Tetrachloride
I
IR Measurement of
Total Hydrocarbons
Figure A-l. Analytical method for nonvolatile hydrocarbons
in ocean water.
44
-------
In 1972, as part of Exxon's program on the measurement of hydrocarbons
in the oceans of the world, tankers passing through this same area took
surface and 10 m samples of seawater. The extractable organic values ob-
tained for five samples are presented in Table A-6 and summarized in Table
A-l with the values obtained on the current tests.
The background values for surface and subsurface extractable organics
obtained before the second spill are considerably higher than the values
obtained before the fourth spill. Possibly some oil from Test I was still
present in the water column. The agreement between the background data for
the fourth spill and the tanker data obtained 6 years before are good: They
are statistically similar.
The data for nonvolatile hydrocarbons obtained at three stations are
given in Tables A-4 and A-5. A mean value of 0.68 is given by the ratio
nonvolatile hydrocarbons/extractable organics. This is in the range nor-
mally observed.
TABLE A-l. COMPARISON OF BACKGROUND LEVELS OF EXTRACTABLE
ORGANICS AT SPILL SITE
Surface Subsurface
Description EQ Std. Dev. E0_ Std. Dev. Depth, M
ug/1
1972, Tanker 47 16 42 7 10
1978, Before 2nd Spill 517, 151 71 12 1,3,6,9
1978, Before 4th Spill 62 36 6,9
45
-------
TABLE A-2. EXTRACTABLE ORGANICS IN WATER BY IR FIRST ATLANTIC OIL
SPILL OF 11/2/78 WITH MURBAN CRUDE
Dispersant
Added
No
No
Yes
II
It
Yes
II
M
Yes
II
M
TABLE
Dispersant
Appl led
No
No
Yes
II
Yes
It
11
Yes
Yes
Nominal Time
after Spill ,
min. Station
T + 15 1
8
T + 120 1
2
3
5
7
9
T + 180 1
3
4
T + 240 3
4
5
Actual
Time
12:13
12:26
14:23
14:25
14:28
14:33
14:38
14:44
15:01
15:07
15:10
16:37
16:42
16:46
Extractable Orgam'cs in Water,
Surface
26,900
105
92
51
63
479,000
1,950
230
80
199
270
927
A-3. EXTRACTABLE ORGANICS IN WATER BY
SPILL OF 11/3/78 WITH LAROSA
Nominal Time
after Spill , Actual
min. Time
Background
0 10:32
T + 30 10:54
T + 120 12:19
12:28
12:35
T + 180 13:20
13:24
13:33
13:39
T + 225 14:00
T + 300 15:33
Statfon
3
3
1
3
5
3
4
6
7
3
9
1m
951
24
119
45
92
113
41
104
65
142
125
180
3m 6m
29
158 51
49
29
107 137
48
48
72
46
87 42
85
IR SECOND ATLANTIC
CRUDE
Extractable Organics in Water^
Surface
517
151
144
223
146
1,245
135
96
52
111
67
1m
77
58
220
116
219
86
13
95
93
39
81
59
3m 6m
76 67
93 56
507 116
147 194
65
89 103
108
1 ,049 649
102
45
79
49
ug/i
9m
54
119
39
OIL
uq/1
9m
69
73
34
116
67
294
42
46
-------
TABLE A-4. EXTRACTABLE ORGANICS IN WATER BY IB THIRD ATLANTIC OIL
SPILL OF 11/9/78 WITH LAROSA CRUDE
Nominal Time
Oispersant after Spill, Actual
Applied min.
Yes T + 30
1
i
1
1
1
M
Yes T'+ 90
I
1
I
1
I
1
I
1
Yes T + 180
(1 M
(a) Nonvolatile hydrocarbon
(b) Nonvolatile hydrocarbon
Time
10:43
10:51
10:58
11:20
11:23
11:29
11:34
11:43
11:46
11:48
11:51
11:54
12:03
12:07
12:11
12:18
13:10
13:15
= V.430 vg/1.
= 718 yg/1.
Station
1
3
4
7
8
9
10
1
2
3
4
5
6
7
8
9
3
8
TABLE A-5. EXTRACTABLE ORGANICS IN
Nominal Time
Dispersant after Spill,
Applied min.
Background
Yes T + 30
II II
n II
11 II
II II
II II
Yes T + 75
It
"
it
n
il
n
Yes T + 150
II
SPILL OF 11/
Actual
Time
14:32
14:34
14:40
14:59
15:02
15:07
15:28
15:32
15:54
16:01
16:06
16:11
16:15
17:05
17:15
- ~ -
_
Extractable Organics in Water, _yg/l
Surface
252
10,800
4,060
4,690
7,050
521
1,760
100
lost
1,050
106
92
1,630
1,410
125
385
WATE3 BT
rR MJRBAN
1m
26
1,950
957
1,650
2,240(a)
691
64
180
320
297
64
642
1 ,250 (b)
52
158
3m 6m
90
2,750 498
668
2,960
433 490
69
45
62
161
297 109
185
50
1,130
288 305
148
36 53
101 146
9m
99
245
79
45
IR FOURTH ATLANTIC OIL
CRUDE
Extractable Organics in Water, jjg/1
Station
2
3
4
7
8
9
2
3
6
7
8
9
10
3
8
Surface
62
20,500
}, 360, 000
123
11,000
3,400
7,290
1,820
960
409
140
no
339
1m
121
6,100
17,800
3,170
3,800
3,070
1,550
3,810
81
98
294
201
66
129
138
3m 6m
28
45
84
2,540(a) 972
3,720 302
91
310 329
75
36 39
147 119
9m
43
948
352
182
73
128
(a) Nonvolatile hydrocarbons = 1,968 ug/1.
47
-------
TABLE A-6. EXTRACTABLE ORGANICS IN COASTAL WATER BY TANKER
Extractable Organics pg/1
Date
11/2/79
3/19/72
3/28/72
4/12/72
4/14/72
4/20/72
Ship Lat.
Present Study 40°
Esso Lexington 40°
39°
Esso Puerto Rico 39°
39°
Esso Lexington 40°
10'
07'
35'
54'
38'
06'
73° 35'
73°
73°
73°
73°
73°
44'
36'
44'
45'
39'
Average
Surface
63
42
24
60
45
47
10 M
42
--
46
32
47
42
48.
-------
RESEARCH AND ENGINEERING COMPANY
P.O. BOX 121. LINDEN. N. J. 07036
ANALYTICAL AND INFORMATION DIVISION
J. K. PATTERSON
Director
May 23, 1979
Analytical Support to the
API Investigation of the
Effectiveness of Surface-
Active Agent in Combatting
Open Ocean Spills
Ref. No. 79AN 541
Dr. J. R. Gould
American Petroleum Institute
2101 L Street, NW
Washington, D. C. 20037
Dear Dr. Gould: 4r- -
Our report on the above subject dated 4/2/79 presented analy-
tical data on the extractable organics content of over 180 sea water
samples, thus fulfilling the provisions of Exxon Research and Engineering
Company's contract with the American Petroleum Institute. The Oil Spill
Task Force, after receiving the report, requested that we analyze an
additional 50 samples. The results of these analyses are presented in
the attached table.
Very truly yours,
T. D. Sear!
TDSrpjs
Attachment
cc: J. Johnson - JBF Corp.
G. P. Canevari
49
-------
ADDITIONAL ANALYSES OF ATLANTIC OCEAN
PLANNED OIL SPILL SAMPLES - NOVEMBER, 1978
Test
1
2
3
4
Crude
Murban
11
11
n
it
"
"
11
"
LaRosa
11
u
n
u
M
ii
n
n
n
11
H
n
n
u
n
u
n
LaRosa ^
H
H
II
II
II
II
It
H
II
Murbatr'
M
»
It
n
M
H
H
U
II
II
II
n
Sample
21
22
32
33
194
195
196
235
236
239
357
414
413
205
347
431
432
502
501
500
503
504
505
560
561
566
568
^ 911
910
909
920
921
923
924
925
765
339
^ 973
974
975
708
705
996
732
720
727
733
977
736
735
Station
7
7
9
9
2
2
2
5
5
6
6
6
6
7
2
2
2
1
1
1
2
2
2
2
2
4
4
2
2
2
5
5
6
6
6
2
10
1
1
1
2
3
4
4
5
9
9
10
10
10
T
T
T
T
T
T
T
T
T
T
T
T
T
T
T
T
T
T
T
T
T
T
T
T +
T +
T +
T +
T
T
T
T
T
T
T
T
T +
T +
T
T
T
.T
T
T
T
T
T
T
T
T
T
Approx.
Time
+ 15 min.
+ 15 rain.
+15 min.
+15 min.
+ 3 hrs.
+ 3 hrs.
+ 3 hrs.
+ 3 hrs.
+ 3 hrs.
+ 30 min.
+ 30 min.
+ 30 min.
+ 30 min.
+ 30 min.
+ 2 hrs.
+ 2 hrs.
+ 2 hrs.
+ 3 hrs.
+ 3 hrs.
+ 3 hrs.
+ 3 hrs.
+ 3 hrs.
+ 3 hrs.
3-3/4 hrs.
3-3/4 hrs.
3-3/4 hrs.
3-3/4 hrs.
+ ^30 min.
+ 30 min.
+ 30- min.
+ 30 min.
+ 30 min.
+ 30 min.
+ 30 min.
+ 30 min.
1-1/2 hrs.
1-1/2 hrs.
+ 30 min.
+ 30 min.
+ 30 min.
+ 30 min.
+ 30 min.
+ 30 min.
+ 30 min.
+ 30 min.
+ 30 min.
+ 30 min.
+ 30 min.
+ 30 min.
+ 30 min.
Extractable
0 m
665
527
557
131
198
2,760
300
118
132
19,100
178
440
307
23,200
6,400
218
1 m
122
79
102
93
117
227
180
132
125
87
165
91
147
279
88
168
202
Organics in Hater, ppb
3m 6m 9m
119
50
107
126
68
63
161
255
163
105
92
m
1 ,200
10,200
1,070
2,690
143
'a'Dispersant added immediately after spill.
50
-------
APPENDIX B
DATA FROM CHEVRON OIL FIELD RESEARCH CO.
Chevron Oil Field Research Company
A Standard Oil Company of California Subsidiary
P.O. Box 446, La Habra, CA 90631, U.S.A.
April 24, 1980
Mr. Jaret C. Johnson
JBF Scientific Corp.
2 Jewel Drive
Wilmington, MA 01887
Dear Jay:
Enclosed are the low-molecular-weight hydrocarbon analyses
for the 1978 East Coast tests. Because of errors in electronic
integration of the gas chrqmatograms, we measured peak heights
and recalculated all the acamatic hydrocarbons. The tables
include only those samples that had measurable concentrations
over background values. All.samples contained some GC peaks,
but when measuring at a few' parts per trillion sensitivity, it
is easy to obtain contamination - from the air during sampling,
from the containers, or during laboratory analysis.
These data can be included as an appendix to the report you
prepare for API. You can also attach a copy of our paper and
refer to it for an explanation of how the data were obtained.
Refer also to the paper for use of the analysis in interpreting
weathering of the Murban and La- Rosa crude oils that occurred
following discharge of these oils.
Sincerely,
Clayton D. McAuliffe
Attach: Analyses
cc: J. R. Gould, API w/attach
G. P. Canevari, Exxon Research
J. P. Marum, AMOCO
51
-------
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57
-------
APPENDIX C
THE DISPERSION AND WEATHERING OF CHEMICALLY TREATED CRUDE OILS
ON THE SEA SURFACE
Clayton D. McAuliffe
Chevron Oil Field Research Company
La Habra, California 90631
Gerard P. Canevari
Exxon Research and Engineering Company
Florham Park, New Jersey 09732
Thomas D. Sear!
Exxon Research and Engineering Company
Linden, New Jersey 07036
Jaret C. Johnson
Stephen H. Greene
JBF Scientific Corporation
Wilmington, Massachusetts 01887
Four research crude oil spills discharged on the open ocean were chemi-
cally treated with a dispersant. The underlying water was then analyzed to
determine (1) the dispersion of oil into the water column, and (2) the
rate of loss (weathering) of low-molecular-weight hydrocarbons from the
dispersed oil. These tests, funded by the American Petroleum Institute and
the U. S. Environmental Protection Agency, were conducted in a manner
similar to those for untreated spills conducted in 1975 (Ref. 1, 2). The
current tests were designed to compare the dispersion and weathering of
chemically treated and naturally dispersed oils.
The untreated oils (Ref. 1, 2) showed relatively low concentrations of
nonvolatile hydrocarbons in the water column under the slicks, generally
less than 1 mg/L. These samples containing naturally dispersed oil showed
very rapid weathering of the C-, to C,Q hydrocarbons (<30 min). The C-J-C-.Q
hydrocarbons detected were residual In the oil droplets, and truly dis-
solved hydrocarbons were apparently not present. Samples of oil collected
over time from the surface slicks showed slower weathering (>7 hrs for
trimethyl benzenes).
Chemical dispersion is thought to accelerate the natural weathering
processes. This would result in higher concentrations of oil penetrating
58
-------
to greater depths, and accelerated escape of volatile hydrocarbons to the
atmosphere. The mechanism for this behavior was expected to be the mixing
of dispersed droplets having high specific surface areas in near-surface
water, causing rapid loss of volatile hydrocarbons. An untreated slick,
although constantly exposed to the atmosphere, may be less susceptible to
evaporation than dispersed oil because its lower surface-to-volume ratio
tends to retard transport (by diffusion) of volatile hydrocarbons.
Oil emulsified in water is removed from most of the wind's influence,
so that it does not travel as far as a surface slick. This minimizes the
possibility of oil stranding or entering biologically sensitive areas. A
review and discussion of the alteration of oil on a water surface is given
in Reference 3.
The current study also involved extensive aerial remote sensing, and a
limited biology program. This report, however, covers mainly the chemical
results, plus limited observations made visually and from aerial photographs.
EXPERIMENTAL METHODS
General Operations
In November 1978, four spills were conducted approximately 40 km (25 mi)
off New Jersey and 96 km (60 mi) south of Long Island, New York. Each spill
was approximately 1.67 m3 (440 gal) of one of two crude oils (Murban from
Abu Dhabi and La Rosa from Venezuela). These were the same crudes used for
the 1975 untreated tests. Composition of the naphtha fraction is given in
Reference 2.
Each spill was discharged from a 1.9 m3 (500 gal) tank mounted on the
research vessel through two 7.6 cm (3 in) hoses. The ends of the hoses
were on floats, causing the oil to discharge horizontally on the water
surface. This minimized both evaporation losses due to discharge above the
water, and vertical descent of the oil into the water. The less viscous
Murban (0.83 specific gravity, 39° API) discharged in approximately 3 min;
the La Rosa (0.91 specific gravity, 23.9° API), in 6 min.
The oils were treated by aerially spraying a self-mix dispersant from
a pod and spray booms mounted above the skids of a helicopter. The heli-
copter flew approximately 10 m above the water surface. One slick of each
oil was dispersed immediately, and one each after 2 hr.
The immediately dispersed slicks were sprayed with 150 L (40 gal) of
chemical dispersant; the slicks sprayed after 2 hr with 360 L (95 gal). In
all cases, there was over-spraying (outside the slick) and a percentage
loss due to wind drift. The major experimental conditions are summarized
in Table C-l.
Sample collection
The sampling program was designed to obtain water samples at approxi-
mately equally spaced stations on transects through the surface slicks and
59
-------
TABLE C-l
GENERAL EXPERIMENTAL SUMMARY
Item
Date of spill
Time of spill
Time of dispersion
Spill location
latitude
longitude
Conditions
wave height, m
wind (m/s)
(knots)
air temp. , °C
water temp. , °C
Murban 1
2 Nov. 1978
1153
1350
40°09'09"N
73°30'39"W
0.3 to 1.0
4.0 to 5.5
8 to 11
15-20
14
La Rosa 1
3 Nov. 1978
1014
1200
40°09I12"N
39°33'40"W
0.3 to 1.0
4.0 to 5.5
8 to 11
15-20
14
La Rosa 2
9 Nov. 1978
1019
1028
40°09'18"N
73°32'00"W
0.3 to 1.0
2.5 to 6.0
5 to 12
12-14
13
Murban 2
9 Nov. 1978
1404
1411
40°09'30"N
73°34'45"N
0.3 to 1.0
2.5 to 6.0
5 to 12
14-17
13
emulsion plumes. Figure C-l is a schematic diagram of a typical sample run.
Samples of all four tests were taken at 1 and 3 m depths at all 10 stations,
and at 6 and 9 m at Stations 3 and 8. Surface samples were taken, with
a small bucket, at all stations during sampling runs through dispersed oil.
A sampling run took about 45 min.
6)V_ (8V 43)-(9 (10
Vessel Track
Fig. C-1 Schematic of immediately dispersed oil slick and location of sample stations for typical
10station sample run.
For the immediately dispersed slicks, the first run was started a few
minutes after dispersion, and the second after about 1.3 hr. For the two
delayed dispersion tests, one sampling run was made before dispersion (un-
treated oil), and two after. The two sampling runs after dispersion were
immediate and after about 1 hr.
For all of the spills a few samples were also taken 2, 3 and 4 hr
after dispersion, at Stations 3 and 8.
60
-------
The subsurface samples were collected with small submersible pumps
discharging through polypropylene tubing, at approximately 4 L/min. The
pumps were attached approximately 0.5 m below a floating 115 L (30 gal)
steel drum towed 3 m lateral to the bow of the research vessel. In this
position, the ship's bow wave did not cause water mixing at the sample
inlets. These were 1, 3, 6 and 9 m below the water surface, along a line
suspending a 23 kg weight from the bottom of the float. The sample gear
was lowered and removed from the water outside the observed slicks to avoid
surface oil contamination.
Two types of samples were collected at each station and depth: one
1.5 L sample in 1.9 L (0.5 gal) flint glass jug and duplicate completely
filled 300 ml (10 oz) "soft drink" bottles with crown caps. The 1.9 L jugs
had been cleaned by rinsing three times with distilled-in-glass carbon
tetrachloride (CC1,) that was checked for purity by infrared (IR) spectro-
scopy. Immediately after collection, 50 ml of this CC1, was added to each
jug from an all-glass dispensing pipet. The jugs were sealed with teflon-
lined metal screw caps, and hand-shaken for about 10 sec to initiate the
solvent extraction of organic matter including the dispersed oil. The CC1,
also prevented bacterial degradation of the hydrocarbons. In the labora-
tory, the samples were shaken 2 min to complete the extraction.
Prior to sample collection, about 30 mg of mercuric chloride (HgCl?)
was added to each 300 ml bottle to prevent biodegradation prior to analysis.
Each bottle was then flushed with reactor-grade helium and sealed with a
crown cap (polyvinyl chloride seal). At time of sample collection, each
bottle was uncapped, filled to within 3 mm of the top, and resealed with a
crown cap. The small air space minimized loss of volatile hydrocarbons to
this gas space and possible contamination of sample by hydrocarbons (as
well as CC1, vapors) that may have been in the atmosphere during sample
col lection.
Samples of each crude oil were taken from the spill tank in glass
bottles with teflon-lined screw caps. In the laboratory these oil samples
were equilibrated with sea water collected outside the spill area, to
provide equilibrium dissolved hydrocarbon concentrations in sea water.
Aerial control and photography
A small twin-engine high-wing aircraft served as a control platform
from which to direct the dispersant-spraying helicopter, to direct the
research vessel to each sampling station, and to provide visual and photo-
graphic documentation of the oil slicks and their chemical dispersion.
Periodic color photographic runs were made over each slick using a verti-
cally mounted camera in the floor of the aircraft. Each exposure recorded
the time and Loran C coordinates.
Chemical analysis
Total extractable organic matter was measured on the single 50 ml
portion of CC1., with an IR instrument, as absorbancy at 2930 cm 1. This
method measures other CC1* soluble compounds such as organic acids, esters,
61
-------
and alcohols in addition to the crude oil. The CC1, extracts of a few
samples were further analyzed for total nonvolatile (C-,4+) hydrocarbons,
by removing polar organic compounds with a silica gel column and reanalysis
by IR. Details of these techniques are given in Reference 4.
Volatile hydrocarbons (C, to C,Q fraction) in the water samples were
analyzed by a gas equilibrium methoa (Ref. 5). Forty millilitres of Murban
and La Rosa oil samples were equilibrated with 140 ml of sea water collected
prior to the oil spills. The oil and water were hand shaken gently and
periodically for 24 hr or more. Mercuric chloride added at the time of
water collection prevented possible biodegradation of dissolved hydrocarbons
during equilibration and prior to analysis. This water was filtered (from
one 50 ml glass syringe into a second) to remove any separate-phase oil
that may have been dispersed during oil-water mixing. Twenty-five milli-
litres of this water was gas equilibrated five times.
These successive analysis were used to measure the equilibrium concen-
trations of individual C-. to C-,n hydrocarbons for the two crude oils, and
to calculate individual Hydrocarbon distribution coefficients.
The water samples collected at the various stations and depths were
then analyzed with a single equilibration using the measured distribution
coefficients to calculate concentrations. This gives sufficient accuracy
and saves time and cost of multiple equilibrations. For those samples that
contained significant separate phase oil, the duplicate sample was filtered
and analyzed. Separate-phase oil contributes hydrocarbons to the gas phase
in concentrations higher than if the hydrocarbons were only in solution.
Method details are given in References 1 and 5.
RESULTS AND DISCUSSION
Visual and photographic observations
Application of dispersant after two hours of weathering appeared to
have little effect on Murban crude oil, based on visual and photographic
observations. Dispersal of weathered La Rosa crude oil did appear effec-
tive. However, some oil reappeared within 10 to 15 min after dispersant
application.
When dispersant was applied to fresh La Rosa, no sudden change was
apparent. However, in time this oil became a thin sheen, as contrasted
with the thick, black, asphaltic appearance of untreated La Rosa. Also,
the track of the research vessel remained visible for a considerable period
of time as contrasted with the quick closing behind the vessel with the
untreated oil.
Murban crude oil changed dramatically when dispersant was immediately
applied. A distinct whitish-brown subsurface plume appeared quickly. Over
several hours, this plume dispersed in the water column, growing in area
and diminishing in color and visibility. A thin-transparent surface oil
sheen gradually appeared during this time period as some of the emulsion
62
-------
droplets resurfaced and broke. These visual observations give qualitative
indication of the dispersion of crude oils by chemical treatment, but
chemical analysis is needed for quantitative interpretation.
Oil dispersion as determined by infrared analysis
The large number of chemical analyses prevents a complete tabulation of
the results for total extractable organic matter (OM). Some of the analyses
will be presented in graphical form to document chemical dispersion of
these crude oils. As expected, the highest concentrations in the water
column were attained after immediate dispersion as compared with dispersion
after two hours. Interpretation will concentrate on immediate dispersion
results.
The crossed transects of a sampling run permit a three-dimensional
analysis of plumes of dispersed oil (i.e., in crossed vertical planes).
However, the limited sampling at 6 and 9 m (only at Stations 3 and 8) may
give a distorted (narrow) view of dispersion at these depths. Based upon
natural dispersion of oil into the water column (Ref. 2) and the lack of
chemically dispersed oil at 6 m (Ref. 6), significant dispersion of oil
down to 6 and 9 m was not expected. These depths were added only to verify
the prior results, but we were surprised to find measurable oil at 6 and
9 m. In subsequent studies conducted in September and October 1979, all
stations were sampled through 9 m.
Fig. C-2 shows the extractable OM concentrations with depth along the
two transects of the first sampling run following the immediate dispersion
of La Rosa crude oil. The vertical scale exaggeration is about 45X. The
contour for 0.25 ppm was at approximately 9 m at its deepest point; for the
1.0 ppm contour, 4 to 5 m.
" o
CD 3
JZ
*^
a
.25 19.1 10.8 4.06 .18
.44
.10
-.09
4.69
7.05
.52
1.76
.05
0 50100
m
Stations CD (2) (3
Time after +24 +29 +32
spill (min)
(4)
+39
(5)
+41
(6)
+57
(7)
+61
(Intersect)
(9)
+70
(10)
+75
Fig. C~2 Total extractable organic matter (ppm) in water samples collected during first sample run through La Rosa
crude oil spill immediately dispersed (oil spilled 1019, dispersed 1028-1035).
The shape of the 2.0 ppm contour on the transect of Stations 6 through
10 is interesting in its asymmetry. Relying as it does on one data point
63
-------
for its asymmetric shape, this might be suspected as an experimental arti-
fact. However, the second set of transects, approximately 1 hr later
(Fig. C-3) produced the same type of contour. Fig. C-3 also shows the
lower concentrations brought about by dilution of the plume in a larger
volume of water.
0
1
I3
E
.10
1.05
.11
.18
.06
.11
.08
.06
.16 V30 /19 .05
Stations (?)
Time after spill {min) +84
, .09 1.63
(2) (3) (4) (5)"
r87 +89 +92 +95
1.44
Stations _
Time after +104
spill (min)
Fig. C-3 Total extractable organic matter in water samples collected during second sample run through
La Rosa crude oil spill immediately dispersed.
Petroleum hydrocarbons (C-,»+) were determined on three of the extracts.
Extractable OM was 2.24, 1.25, and 2.54 mg/L; C-..+ hydrocarbons were respec-
tively 1.43, 0.72, and 1.97 mg/L. Petroleum hydrocarbons averaged 76% of
the total extractable OM. This is in the range previously observed for
a much larger number of analyses (Ref. 8). However, the actual crude oil
content of the original CC1, extracts is higher because hydrocarbons < C,,
-,-... .., j.,.- ^-, .js evap0rated to 1 ml prior to adding to the top of
are lost when the CC1
the silica gel column?
Thus, the C10 and C,, with lesser amounts of Cc
to
ount
percent
oil may be even higher for those samples with the highest oil content
(>5 ppm).
Olid O I 1 I 1>U y *- I WU I UHII I . IMUO} 1^1 1C ^"]O C1MVU ^-l O " ' '-I ' ICOO<=I Cll|[*JUI I V^O Ul UQ
C,-, hydrocarbons are present in the original CC1, extract. This may am
to 10 to 15%, thereby raising the oil content to 85 to 90%. The percen
The polar organic compounds removed by silica gel appear to exceed the
extractable OM from background water samples outside the oil spill areas
64
-------
(particularly noticeable when the extractable OM ranges from 0.2 to 1 ppm).
A possible explanation is that crude oil acts as an organic solvent, extrac-
ting and concentrating natural organic compounds in sea water.
Another way to view the dilution is shown in Fig. C-4 for the immedi-
ately dispersed La Rosa spill. Concentrations at Station 3 in the center
of the plume, are plotted with depth over time. Because each depth concen-
tration is a single analysis, great reliance should not be placed on an
individual point. As expected, a steady decrease in concentrations toward
background values occurred over time.
Concentration lines for the immediately dispersed Murban spill
(Fig. C-5) show higher values than with La Rosa (Fig. C-2). Dispersed oil
was also found in higher concentrations at greater depths (almost 1 ppm at
9 m).
Total Extractable Organic Matter, ppm
Total Extractable Organic Matter, ppm
0.10 1.0 10.0 20.0
Depth profile
88 min
after spill
Fig. C-4 Comparison of concentration depth profiles
at one station for various times under the
immediately dispersed La Rosa crude oil spill.
Fig. C-6 Comparison of concentration depth profiles
for La Rosa and Murban crude oils at about the
same time following discharge and dispersion.
Fig. C-6 compares concentration-depth profiles of the two crude oils,
for samples from the center of the plume at similar times after oil dis-
charge and dispersion. Again, each concentration is a single data point.
A rough material balance calculation indicates that the Murban crude oil
was almost completely dispersed, whereas the La Rosa was about half dis-
persed. These evaluations concur with visual impressions of effectiveness,
The data for the two spills that were allowed to weather for 2 hr
before dispersion do not allow such clear graphical display. Most values
for total extractable OM were much lower than those from the immediately
dispersed spills. One explanation is the larger area to be treated after
two hours, with a consequently larger water volume available to dilute an
65
-------
0
1
CL3 *J
0)
f
cj 6
Q
g
.31 20.5
\"**^^llfc^
- .09 6,10
X
-.11 1.20
Horizontal
scale
0 50100
m
Stations (T) (2)
Time after +25 +28
spill (min)
136023.2
1 /
17.83.17 .17
v | [j 8 ppm
10.2 1.07
1 I 4 ppm
05
\J+J
0
1
3
6
q
.12 11.0
- .07
- .08
A 1
3.80, |
M
2 54 |i
\^-' 1
- °\1^
tfl I
! !
H 1
\ i
\.95 I
(3)(1) (5) (Z) d)(3
+30+36 +39 +55 +58 j
,_ j
6.40
/
/ 3.07
"S1
7 2.eay
'**#
) (£)
+64
.22
||
.20
7.14
4
+66
(Intersect)
Fig. C-5 Total extractable organic matter (ppm) in water samples collected during first sample run through
immediately dispersed M urban crude oil spill (oil spilled 1404, dispersed 14111416). The dashed
contour for 4 ppm is based on the station 1 to 5 transect.
equivalent amount of oil. Most of the oil was concentrated in the leading
(downwind) part of the slick, in perhaps only 10% of the total slick area,
as observed by Hollinger and Mennella (Ref. 8). The dispersant was applied
uniformily over the whole slick rather than concentrated on the area of
heavy oil. Therefore the dispersant to oil application rate was not as
high as for the immediately dispersed spills, which were treated before
appreciable spreading had occurred. Weathering also would have increased
oil viscosities, and thereby would have decreased dispersant effectiveness.
A summary of the total extractable OM in water under the four research
oil spills is shown in Table C-2. It includes only values exceeding
0.10 ppm (approximately two times background). Untreated oil dispersed
naturally in the water to a lesser extent than chemically treated oil.
Immediate dispersion was more effective than after two hours, but most of
the difference may be attributed to differences in application rate of
dispersant to the oil.
The greatest difference between oils was evident when they were dis-
persed immediately. Murban oil concentrations were higher at all water
depths than for La Rosa. The slightly higher concentrations for La Rosa
compared with Murban following delayed dispersion may reflect differences
in chemical application and/or sampling locations.
Oil Weathering as Measured by C-. to C,n Analysis
Infrared analysis of CC1, extracts provides a measure of total oil in
water samples, but is relatively insensitive. It is also complicated by
the presence of background hydrocarbons and CC1. extractable organic com-
pounds such as acids, alcohols, and esters in sea water. As used in this
study, the method had a limit of detection of about 0.02 mg/L. The method
also does not give information on individual hydrocarbons, classes of
66
-------
hydrocarbons,
carbons).
or degree of weathering (loss of low-molecular-weight hydro-
TABLE C-2 SUMMARY OF CARBON TETRACHLORIDE EXTRACTABLE ORGANIC
MATTER IN WATER FROM UNDER FOUR RESEARCH OIL SPILLS (CONCENTRATIONS
IN MG/L, PPM)*
n**
La Rosa
Maximum
Mean
n
Murban
Maximum
Mean
Not dispersed
Di
Di
1 m
3 m
spersed at 2 hr
1 m
3 m
6 m
9 m
spersed within 10 min
1 m
3 m
6 m
9 m
4
3
7
7
2
1
16
14
5
1
0.22
.51
.23
1.05
.65
.29
2.24
2.96
.50
.25
0.13
.26
.15
.27
.38
-
.69
.67
.31
-
1
2
8
4
1
1
13
9
4
4
0.95
.16
.18
.11
.14
.12
17.80
10.20
1.00
.95
-
0.14
.13
.10
-
-
3.10
2.45
.45
.40
^Background concentrations (ppm); 1 m, 0.061; 3 m, 0.050; 6 m, 0.048;
9 m, 0.051
**Number of samples
A gas equilibrium method (Ref. 1, 5) using gas chromatography permits
the measurement of most individual hydrocarbons in the C-,, to C-,Q fraction
with a limit of detection of 2 ng/L (ppt) for alkanes ana cycloaTkanes and
10 ppt for aromatic hydrocarbons. This analysis permits the loss of low-
molecular-weight hydrocarbons (weathering) to be followed with time (Ref.
1-3).
If adverse biological effects (immediate toxicity) result from oil
spills, they are thought to be produced principally by the more soluble
low-molecular-weight hydrocarbons (principally aromatics such as benzene
and toluene). Of importance, therefore, are the concentrations of the
dissolved hydrocarbons and the duration of organism exposure to them. When
water is equilibrated with crude oils, the C-. to C,Q soluble fraction
comprises over 98% of the total soluble hydrocarbons (Ref. 9). For typical
crude oils, benzene plus toluene constitute 70 to 80% of the aromatic
hydrocarbons, and 62 to 78% of the total C.-+ hydrocarbons (saturates plus
aromatics).
Gas Chromatograms. Gas chromatograms of (1) dissolved hydrocarbons in
sea water equilibrated with an excess of Murban crude oil from the spill
tank; and (2) C, to C-,Q hydrocarbons residual in dispersed oil droplets in
a water sample collected under the chemically treated Murban oil spill are
shown in Fig. C-7.
67
-------
Attenuation 1 x
Number Over Each Peak is Relative
Retention Time in Hundreths of Minutes
(1074= 10.74 mini
Fig. C-7 Gas Chromatograms: (A) Equilibrium concentrations of dissolved hydrocarbons in sea water mixed
with an excess of Murban crude oil from the spill tank. Inset is from second chromatogram with less
attenuation to show more clearly the di and trimethylbenzenes. (B) C-] to C-|Q hydrocarbons found
in 1 m water sample collected 49 min after immediate dispersion of Murban crude oil spill (total
extractable organic matter was 3.8 ppm). See text for details of analytical procedures.
68
-------
The GC column was 6 m of 3.2 mm stainless steel tubing packed with 10%
UCW-98 silicone fluid on chromosorb W-HP. The column was temperature pro-
grammed from 60° to 145°C at 6°C/min. A 30 cm precut (backflush) column
was in a sample valve oven at 100°C. The column was backflushed at 4 min
which prevented >Cin hydrocarbons from entering the 6 m column. A 2.0 ml
(1.6 mm, diameter) sample loop in the sample valve oven introduced 1.5 mL
(at 100°C) of the 20 to 23 ml of gas flowed from the 50 ml equilibration
syringe through the sample loop.
The numbers over or near the individual hydrocarbon peaks are the
relative retention times in hundredths of minutes. Each principal hydro-
carbon peak has been named, and the GC amplifier attenuation is given.
Fig. C-7A is the gas chromatogram (GC) of dissolved hydrocarbons in sea
water equilibrated with Murban crude oil at attenuations of 1 x 10^
(methane through pentanes) and 500 x 10^ for the remaining hydrocarbons.
The partial GC (Fig. C-7A) is from another analysis with less attenuation,
to better show the characteristic di- and trimethylbenzene peaks.
Fig. C-7A shows the marked decrease in concentration of hydrocarbons
with increase in molecular weight (carbon number), and the much greater
solubility of aromatic hydrocarbons relative to the saturated hydrocarbons
of the same carbon number (cycloalkanes are more soluble than alkane hydro-
carbons). In particular, note the large benzene and toluene peaks. The
decrease is due to not only lower solubility with an increase in carbon
number, but also to the lower concentrations of individual hydrocarbons in
crude oils (higher carbon numbers than toluene for aromatics) as carbon
number increases. An increase in number of isomers occurs with an increase
in carbon number.
For pure hydrocarbons, normal alkane solubility decreases six to seven
orders of magnitude between carbon numbers 1 and 12. For aromatics, the
solubility decreases similarly between carbon numbers 6 and 24 (Ref. 9,
10). For example, hexane, cyclohexane, and benzene, each with six carbon
atoms in the molecule, have respective solubilities of 9.5, 60, and 1,750
mg/L (Ref. 10, 11). Thus benzene and cyclohexane are respectively 185 and
6 times more soluble than hexane. The aromatic to n-alkane solubility
ratio increases (Ref. 9), so that dimethyl naphthalenes are over 600 times
more soluble than n-C-,2.
Most of the gas was separated from the crude oil. Thus, the peaks in
Fig. C-7A for methane through pentanes (particularly methane, ethane, and
propane) are lower than if the crude oil was "live" (gas not removed).
Figure C-7B represents the C-, to C,Q hydrocarbons in a water sample collected
at 1 m near the center of the immediately treated Murban spill 46 min after
dispersion. The attenuation is 500 times less (1000 times for C, to Cg)
than in Fig. C-7A, and the peak areas (concentrations) are entirely reversed
(methane through the trimethylbenzenes). This qualitatively shows not only
the very low concentrations of these low-molecular-weight hydrocarbons
(Fig. 7B), but progressively greater loss with decrease in carbon number.
Weathering of these low-molecular-weight hydrocarbons was very rapid.
Quantitative data are presented in tables that follow.
69
-------
Weathering of Murban crude oil. Table C-3 shows C, to C,Q hydro-
carbons in water samples from 0 to 9 m depths at the center or the Murban
slick 46 min after spraying with a self-mix dispersant. The first numeri-
cal column "Oil max." gives the equilibrium concentrations of dissolved
hydrocarbons in sea water that was thoroughly mixed with an excess of
Murban crude oil from the spill tank. Note, as discussed above, the de-
crease in concentration with increase in carbon number, and the high concen-
trations of benzene and toluene. The alkane and cycloalkane hydrocarbons
( >7 carbon atoms) have become so low that they are difficult to identify
and separate from aromatic hydrocarbons (Fig. C-7). Thus n-heptane and
methylcyclohexane are the highest carbon number saturate hydrocarbons shown
in Table C-3. Methane-through-pentane hydrocarbons (Oil max.) are lower
than if the gas had not been separated. In essence, only aromatic hydro-
carbons were measured in solution from toluene through trimethylbenzenes.
In addition to those peaks designated as alkane or cycloalkane (Fig. C-7b),
peaks 870 and 1141 are also nonaromatic (compare Fig. O7A and C-7B).
These peaks arise from presence of nondispersed oil and presumably droplets
smaller than the filter used to remove most of the separate phase oil.
The concentrations of the individual hydrocarbons found in the dis-
persed (emulsion) plume of the Murban crude oil confirm the distribution
and values indicated in Fig. C-7B. They are very low, and the lowest carbon
numbers are present in the lowest concentrations. This is the opposite of
that expected if solution were an important process.
Consider the hypothetical situation of oil on a water surface with
(1) evaporation prevented, and (2) a limited volume of water maintained in
contact with the oil (i.e., the laboratory conditions for mixing a sample
of crude oil from the spill tank with sea water in a sealed glass bottle).
Under equilibrium conditions, one would expect to find the concentrations
and relative concentrations as shown in Oil max., Table C-3. Removing the
restriction on water movement, but preventing evaporative loss would result
in nonequilibrium solution of hydrocarbons into the water, and the rate of
solution of individual hydrocarbons would become important (just as for
evaporation).
The rate of solution increases with decrease in carbon number, and
with class of hydrocarbon (i.e., aromatic vs alkane for the same carbon
number). Under nonequilibrium conditions, methane would go into solution
faster than ethane, ethane faster than propane, etc. Similarly, benzene
would go into solution faster than toluene, toluene faster than xylenes,
etc.
The concentration of each hydrocarbon becomes progressively lower as
the degree of departure from equilibrium increases. Thus, the shorter the
contact time of oil and water, the lower the concentration of each hydro-
carbon in water, and the higher the relative concentrations for those
hydrocarbons having the lowest carbon numbers for each class of hydro-
carbons (alkane, cycloalkane, and aromatic). Because this was not observed
in the water samples under the slick, leads to the conclusion that solution
is apparently not a very important process, even when crude oil is chemi-
cally dispersed and emulsion droplets penetrate the water column.
70
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TABLE C-3 LOW-MOLECULAR-WEIGHT HYDROCARBONS IN WATER SAMPLES
FROM VARIOUS DEPTHS COLLECTED 45 MIN AFTER IMMEDIATE DISPERSION
OF MURBAN CRUDE OIL
Depth, m
Extractable Of
4, mg/L
0
11.0
1
3.8
3
2.54
6
0.97
9
0.95
Hydrocarbons, ug/L (Oil max.)1
Methane
Ethane
Propane
Isobutane
n-Butane
Isopentane
n-Pentane
Cyclopentane
3-Methylpentane
n-Hexane
Methylcyclopentane
Benzene
Cyclohexane
n-Heptane
Methylcyclohexane
Toluene
Ethyl benzene
m, p-Xylene
o-Xylene
926*** Trimethylbenzene
1027 Trimethylbenzene
1077 Trimethylbenzene
1,2,4-Trimethylbenzene
1197 Trimethylbenzene
102
1560
2360
940
2720
870
1080
510
125
290
280
6080
270
65
140
5630
610
1550
900
68
800
370
920
300
.077
.004
.009
.006
.004
.002
.007
.026
.023
.072
.092
.260
.205
.34
.59
3.75
2.25
7.70
5.45
.42
6.50
2.75
6.20
3.20
.0003**
ToooT
.0006
TOW
.0002
.0006
7DOl~
70~TF
7075"
7033"
TIJ04
7076"
752~
747
TM7
7TT
7%J
76T
767
7ST
77?
757
1T07
Total saturates
Total aromatics
11,300 1.46
17,200 38.5
Total hydrocarbons 28,500 40
.070
.002
.004
.003
.002
.002
.005
.012
.006
.022
.027
.095
.066
.067
.135
1.40
.80
2.55
1.85
.12
1.55
.65
1.40
.66
.42
11.1
11.5
.0001
TOODT
.0003
7DW
70007
Tools'
7007~
.072 .070 .073
7m
TOC
70S
7TO3"
T09T
T025"
TIT"
7W
7TT
718"
719"
7TS
7T5"
722
.041
.011
.008
.040
.395
.285
1.05
.75
.050
.74
.30
.75
.38
.041
.018
.020
.022
.48
.23
.95
.57
.035
.50
.16
.31
.13
.13 .13
4.75 3.41
.26
.075
.50
.24
.023
.27
.035
.065
.040
.07
1.51
4.90 3.54 1.58
*Equilibrium concentrations of dissolved hydrocarbons when an excess of Murban
crude oil from the spill tank was mixed with sea water
**Underscored value is percent hydrocarbon found in water sample compared
with equilibrium concentration of dissolved hydrocarbon (Oil max.)
***Number is relative retention time (see Fig. C-7)
It appears that evaporation is the dominant process. The low-molecular-
weight hydrocarbons that do dissolve apparently quickly evaporate to the
atmosphere or dilute to very low concentrations. The hydrocarbons in solu-
tion measured in the water samples (Table C-3) apparently were not in true
solution at the time of collection, but residual in separate-phase oil
droplets. After collection, they equilibrated between the oil droplets and
water. The equilibrium solubility of C-.Q+ hydrocarbons in crude oils is
71
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very low, probably less than 10 ppb. Thus, the separate oil phase in the
samples ranged from about 11,000 ppb in the surface sample to 940 ppb in
the 9 m sample, 300 to 600 times the total dissolved hydrocarbon concentra-
tions.
The data in Table C-3 show that the residual hydrocarbons are low in
concentration, even for the surface-collected sample. Thus, the biologically
toxic low-molecular-weight hydrocarbons have been quickly lost. The concen-
tration of the least volatile, trimethylbenzene (1197), is only 1.07% of
the equilibrium solubility for unweathered oil (Oil max.). The remaining
percentages (Column 3) show a generally progressive decrease with carbon
number (0.0002 to 0.0006% for ethane through pentane hydrocarbons).
The percentages found at 1 m (Column 5) are even lower, showing that
oil emulsion at this depth is more weathered than oil droplets at the
surface. Accelerated weathering is noted with increasing depths as shown
by decreasing concentrations and by percentages if calculated for 3, 6 and
9 m. For example, 1,2,4-trimethylbenzene concentrations in the dispersed
oil droplets for 0, 1, 3, 6, and 9 m are respectively 0.67, 0.15, 0.08,
0.03, and 0.007%.
Because the samples were collected simultaneously, the accelerated
weathering with increasing depth apparently relates to smaller droplet
sizes. Evaporation and solution are diffusion processes; and the shorter
the diffusion pathway, the higher the rate. As droplet size decreases, the
surface-to-volume ratio increases, with resulting faster loss of volatile
and soluble hydrocarbons.
It seems reasonable to expect smaller droplets at greater depth.
Oil-in-water emulsions have a size distribution that ranges from 0.1 to 100
mm (Ref. 12). The larger droplets (some may be even larger than 100 mm,
Ref. 13) will be buoyant (Murban crude oil has a specific gravity of 0.83),
and will rise toward the water surface after mixing downward by wave action.
However, below diameters of about 2-3 mm, gravitational effects are balanced
by Brownian forces. These small droplets move by Brownian motion and will
disperse in all directions, just as clay-sized (<2 mm) mineral particles
stay indefinitely suspended in water.
The percents for the aromatics benzene and toluene in Column 3,
Table C-3 are 0.004 and 0.067 whereas methylcyclopentane, cyclohexane,
n-heptane, and methylcyclohexane are 0.033, 0.076, 0.52, and 0.42 respec-
tively. Thus benzene and toluene are very much lower. This is also shown
to a lesser extent for the percents of these hydrocarbons in Column 5.
This also suggests that the hydrocarbons found in waters associated with
the dispersed slick were residual in the droplets and not in true solution
at the time of collection. These data indicate that benzene and toluene
were lost more rapidly by solution (although evaporation greatly predomi-
nates) than the corresponding carbon-number-saturates; and that once lost,
were subsequently evaporated or quickly diluted. Had these aromatics been
in true solution at time of collection, their concentrations should have
been higher than the corresponding-carbon-number alkane and cycloalkane
hydrocarbons.
72
-------
The concentration of methane (Table C-3) is constant at about 70 ppt.
This reflects the expected equilibrium concentration of methane in sea
water with that in the atmosphere for this region of the Atlantic Ocean
(Ref. 14).
Table C-4 presents the concentrations of C-, to CIQ hydrocarbons in
water samples collected at 1 m over the time (18 to lio min) that measurable
oil could be detected. These data show the rapid loss of volatile hydro-
carbons with time. Even at 18 min, the trimethylbenzenes average a little
over 1% remaining in the dispersed oil droplets. This 18 min sample had
the highest observed oil content (17.8 ppm) of all the subsurface samples
collected.
TABLE C-4 LOW-MOLECULAR-WEIGHT HYDROCARBONS IN WATER SAMPLES
COLLECTED OVER INCREASING TIME AT 1 MM UNDER THE
IMMEDIATELY DISPERSED MURBAN CRUDE OIL SPILL
Time after dispersion,
Extractable OM, mg/L
mm
18
17.8
46
3.8
72
1.55
no
0.31
Hydrocarbons, g/L
Ethane .004 .0003* .002
Propane .016 .0007 .004
Isobutane .008 .0008 .003
n-Butane .006 .0002 .002
Isopentane .003 .0003 .002 - .008
n-Pentane .007 .0006 .005 - .006
Cyclopentane .004 .0008 .012 - .004
3-Methylpentane .010 .008 .006 .008 .008
n-Hexane .024 .008 .022 .006 .008
Methyl cyclopentane .036 .013 .027 .018 .006
Benzene .117 .002 .095 .020 .024
Cyclohexane .139 .051 .066 .041 .040
n-Heptane .128 .196 .067
Methyl cyclohexane .315 .225 .135 .014
Toluene 3.50 .062 1.40 .55 .150
Ethylbenzene 2.20 .360 .80 .42 .090
m, p-Xylene 8.85 .57 2.55 1.80 .429
o-Xylene 5.65 .63 1.85 1.13 .300
926 Trimethylbenzene .50 .73 .12 .07 .029
1027 Trimethylbenzene 8.95 1.12 1.55 1.06 .051
1077 Trimethylbenzene 3.90 1.05 .65 .51 .078
1,2,4-Trimethylbenzene 7.52 .82 1.40 1.13 .175
1197 Trimethylbenzene 4.60 1.53 .66 .68 .120
Total saturates .70 .35 .09 .08
Total aromatics 45.8 11.1 7.4 1.45
Total hydrocarbons _ 46.5 _ 11.5 _ 7_J5 _ 1.53 _
*Underscored value is percent hydrocarbon found in water sample compared
with equilibrium concentration of dissolved hydrocarbon (Table 3, Oil max.)
The decreasing percentage with decrease in carbon number (Column 3)
confirms data in Table C-3 showing that these measured hydrocarbons are
73
-------
residual in the emulsion droplets. Note again that solution preferentially
removed benzene and toluene (and probably the higher aromatic hydrocarbons,
but to a lesser extent) from these droplets compared with corresponding
carbon number saturates.
Weathering of La Rosa crude oil. Table C-5, for immediately dispersed
La Rosa crude oil, shows the concentrations of low-molecular-weight hydro-
carbons in water samples collected at 0 and 3 m, and 47 and 94 min after
dispersion. Also shown are the equilibrium concentrations of dissolved
hydrocarbons attainable when an excess of La Rosa crude oil was thoroughly
mixed with sea water (Column 1, Oil max.), and the percent of hydrocarbons
remaining in the dispersed droplets (Columns 4 and 7).
The equilibrium concentrations (Oil max) for La Rosa are somewhat dif-
ferent from Murban, reflecting the differences in specific gravities and
viscosities. La Rosa has less Cr+ hydrocarbons than Murban, but comparable
C-, to C-. The lower Cr+ concentrations reflect the lower naphtha fraction
(La Rosa, 11 volume %; Murban, 19%, Ref. 2). The comparable C, to C. con-
centrations are probably related to less complete separation of gas from
the more viscous La Rosa.
The hydrocarbons in water samples also reflect the apparently slower
diffusion (evaporation and solution) from the more viscous La Rosa crude
oil, particularly for the C-, to C- fraction. There also was a slower
change in concentration witn time and depth, compared with Murban.
This slower weathering may be due not only to higher viscosity, but
also to larger droplet sizes. Observations and extractable oil reported
previously show La Rosa to have been less effectively dispersed, compared
with the almost complete dispersion of Murban. However, the generally
lower concentrations were more uniformly dispersed to 6 m (Table C-2). The
larger La Rosa droplets being less buoyant may well have mixed downward by
wave action more easily than Murban.
Although the weathering of La Rosa was slower, it should also be noted
that the concentrations of low-molecular-weight hydrocarbons were very low
in the water samples. The highest concentrations of an individual hydro-
carbon was 1.5 ppb toluene at 3 m, 47 min after dispersion; and 0.6 ppb at
3 m, 94 min after dispersion. Total low-molecular-weight hydrocarbons were
less than 15 ppb for all samples.
The percent benzene and toluene (Columns 4 and 7) show as for Murban
crude oil, that these aromatics were preferentially removed by solution
from the oil droplets. However, once removed, they apparently very quickly
diluted or evaporated to the atmosphere, as previously discussed.
SUMMARY AND CONCLUSIONS
Four research oil spills (1.7 m3 each) of two crude oils (Murban, 0.83
specific gravity; and La Rosa, 0.91) were made 40 km off New Jersey. Two
spills were immediately sprayed by helicopter with a self-mix dispersant;
two, after 2 hr.
74
-------
TABLE C-5 LOW-MOLECULAR-WEIGHT HYDROCARBONS IN WATER SAMPLES
COLLECTED AT TWO DEPTHS AND AT TWO TIMES FOLLOWING IMMEDIATE
DISPERSION OF LA ROSA CRUDE OIL
Depth, m
Time after dispersion,
Extractable OM, mg/L
mi n
0
47
4.70
3
47
2.96
0
94
1.63
3
94
1.13
Hydrocarbons, g/L (Oil Max.)*
Methane
Ethane
Propane
Isobutane
n-Butane
Isopentane
n-Pentane
Cyclopentane
3-Methylpentane
n-Hexane
Methy!cyclopentane
Benzene
Cyclohexane
n-Heptane
Methylcyclohexane
Toluene
Ethylbenzene
m, p-Xylene
o-Xylene
926 Trimethylbenzene
1027 Trimethylbenzene
1077 Trimethylbenzene
1,2,4-Trimethylbenzene
1197 Trimethylbenzene
Total saturates
Total aromatics
Total Hydrocarbons
170
1740
2360
620
1510
470
480
330
72
125
230
2870
270
23
120
2370
300
680
360
24
170
55
125
75
8520
7030
.073
.070
.38
.25
,57
.47
,35
,43
,13
,13
,46
.60
,63
,09
.49
,80
66
,75
,30
,15
,94
,35
15
,90
4.52
9.60
15.500 14.1
.053
.083
.36
.25
.59
.53
.45
.52
.18
.23
.57
.50
.76
.09
.51
1.50
.59
1.40
1.05
. 14
.66
.20
.65
.47
5.18
7.16
12.3
015
040
039
113
094
6
_25
_L§
_25
017
077
064
30
20
48
38
33
34
12
17
34
37
37
07
_ 36
063 1.10
41
05
.77
.08
.61
.18
.67
.51
_
_39
43
20
_
_29
_58
_39
J16
52
1
_
63
3.60
5.75
9.3
.076
.045
.19
.12
.26
.21
.17
.17
.05
.07
.18
.20
.19
.03
.17
.57
.20
.51
.40
.04
.43
.10
.34
.27
1.93
3.06
5.0
.003
.008
019
017
.045
035
051
078
007
070
13
14
024
067
075
110
17
25
18
27
36
^Equilibrium concentrations of dissolved hydrocarbons when an excess of
La Rosa crude oil from the spill tank was mixed with sea water
**Underscored value is percent hydrocarbon found in water sample compared
with equilibrium concentration of dissolved hydrocarbon (Oil max.)
Water samples were collected over time at 1, 3, 6, and 9 m under the
nontreated slicks and following dispersion. The dispersant application and
the sampling were directed from another aircraft. This plane also provided
a platform for observation of dispersant effectiveness and taking of color
photographs.
Water samples were analyzed by IR for total oil content of a carbon
75
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tetrachloride extract; and for weathering of the C-, to C,Q hydrocarbon
fraction, by gas chromatography.
Total oil under the immediately dispersed slicks at 1, 3, 6, and 9 m
were respectively: La Rosa - 0.7, 0.7, 0.3 and 0.2 mg/L; Murban - 3.1,
2.4, 0.5, and 0.4 mg/L. The highest concentrations (30 to 90 min after
dispersion) were La Rosa, 3 mg/L; Murban, 18 mg/L.
Oil concentrations for dispersion delayed 2 hr were lower (<_!.! mg/L),
and only slightly higher than found under nondispersed oil (highest concen-
tration for La Rosa was 0.5 mg/L; for Murban, 0.9. The less effective dis-
persion after delayed treatment reflects lower and less efficient dispersant
application for these small spills, as well as increased oil viscosities
due to weathering.
Samples collected 2 to 4 hr after dispersion contained no more than 2
to 3 times background concentrations of about 0.06 mg/L.
Rough material balance calculations, supported by visual and photo-
graphic evidence, indicate that Murban crude oil treated immediately was
almost completely dispersed; for La Rosa, about half was dispersed. It
follows that oil removed from the influence of wind will not travel as far,
and thereby reduce the likelihood of oil stranding or entering biologically
sensitive areas.
The dispersed oil in the water column weathered very rapidly. Evapora-
tion of C-, to C,Q hydrocarbons greatly exceeded solution. Relative concen-
trations of the individual C, to C,0 hydrocarbons show that dissolved
hydrocarbons (including benzene ana toluene) were not present at <0.01
yg/L detection limit. Apparently the more soluble hydrocarbons quickly
evaporate or dilute to even lower concentrations.
The measured C-, to C-,n hydrocarbons were residual in dispersed oil
droplets, and did not exceed 50 pg/L, even for samples collected at 1 m and
18 min after dispersion. After 2 hr this had decreased to < 2 vg/L.
Weathering increased from the surface to 9 m depth for samples collec-
ted at the same time, indicating decreasing droplet sizes with increasing
depth. Weathering also increased with time for samples collected at the
same depth.
Murban crude oil dispersions weathered more rapidly than La Rosa,
reflecting Murban's lower viscosity (and possibly smaller droplet sizes).
The rapid weathering of low-molecular weight hydrocarbons from dis-
persed crude oil droplets should quickly reduce biological toxicity from
hydrocarbons such as benzene and toluene.
The observed changes in concentrations and weathering of chemically-
dispersed crude oils provide real-world data that can assist in the design
of initial concentrations and dilutions for realistic laboratory bioassays.
76
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ACKNOWLEDGEMENT
The work reported here was conducted under contracts from the American
Petroleum Institute, Financial assistance from the U. S. Environmental
Protection Agency under grant number R806056 is gratefully acknowledged.
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77
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Preprint of photoready copy of paper prepared for Petroleum and the Marine
Environment, International Conference and Exhibition, Monaco, 27-30 May
1980.
UBRARY U.S.
78
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