Using Oil Spill Dispersants on the Sea (1989) / Chapter Skim
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4 Intermediate-Scale Experiments and Field Studies of Dispersants Applied to Oil Spills
4 Intermediate-Scale Experiments and Field Studies of Dispersants Applied to Oil Spills
Pages 165-214
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From page 165... ...
A number of experiments at scales larger than normal laboratory size (mesoscale) as well as field studies at sea have been conducted to determine the physical dispersion and the subsurface concentrations of of} components.
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From page 166... ...
, the function of Ekofisk crude oil suffering different fates was measured using tritium tracers. Only Q0037 percent of the oil was adsorbed in the plastic walls.
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From page 167... ...
Two pools were exposed to 20 ppm (average initial nominal concentration) North Sea Forties crude oil, two were exposed to 20 ppm oil with Corexit 9550 added, and two served as controls.
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From page 168... ...
Rough mass-balance calculations, supported by visual and photographic observations, indicated that Murban crude oil was almost completely dispersed (McAuliffe et al., 1980~. The highest total oil concentration measured under the lowviscosity Murban (39° API gravity)
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From page 169... ...
The highest dissolved hydrocarbon concentrations were 14 ppb at 47 min. and 9 ppb after 94 min.
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From page 170... ...
slicks during single sampling runs immediately after the control slicks were released. The highest amounts of naturally dispersed of} generally are found under fresh oil slicks.
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From page 171... ...
of oil in water under a 2~bbl crude oil slick that was sprayed immediately by DC-4 mrcra£t, September 26, 1979 (day 1~; second sample run. Source: McAuliffe et al., 1981.
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From page 172... ...
of oil in water under a 2~bU crude oil slick that WE sprayed immediately by DC-4 aircraft, September 26, 1979 (day 1~; third sample run through small downwind slick and then near drogue where dispersion occurred. Source: McAuliffe et al., 1981.
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From page 173... ...
in boat spraying of just the thick of} part of the fresh slick. (Laboratory testing with both fresh and weathered Pru~hoe Bay crude oil showed about this same difference.)
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From page 174... ...
card and GateHier, 1981~. For both chemical and natural dispersion, infrared analysis of water samples detected 0.!
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From page 175... ...
Ten percent Corex~t 9527 was applied by ship using the Warren Spring Laboratory system. Fluorometric monitoring of water samples showed as much as 75 percent dispersal.
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From page 176... ...
This study demonstrated that chemical dispersal of Tarsint crude oil in Beaufort Sea waters is feasible and it suggested improvements in the spray application system. More extensive arctic tests were held in the Beaufort Sea near Tuktoyaktuk, Northwest Territories in August 1986.
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From page 177... ...
. In addition to the field studies discussed above, a series of experimental spills were conducted on northern Baffin Island, Northwest Territories.
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From page 178... ...
spills of Statfjord crude oil and a light fuel of} in the North Sea. Five of the slicks were controls, one was crude oil premixed with dispersant Finaso} OSR-5 (used for ah tests)
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From page 179... ...
, in which unusuaDy complete distributions of petroleum hydrocarbons in the water column were measured, gives the clearest indication that chemical dispersion is more effective than natural dispersion in relatively calm seas; that dispersant treatment by air is superior in most cases to
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From page 183... ...
Three significant long-term field studies provide the bulk of this section: the Baffin Island Oil Spill study of an arctic environment; the Long Cove, Maine, study of a shadow north temperate environment; and the Panama study of a tropical mangrove environment. (These and related investigations are reviewed below and results are summarized in Table 4-6 at the end of this chapter.)
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From page 184... ...
Canada, Pumping to 1, 2, 4 Bottles not Sorbent Thickness St. John's fluorometer done, and bottles spoiled Norway, Sample bottle 1, 2.5, GC -- - North Sea 5, 9 Britain, Pumping to 1, 3, 6, GC, Sorbent Thickness North Sea bottles 9 fluorometer Skimmer Weathering France, Pumping to 0.5, 0.7, IR (bottles)
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From page 185... ...
INTERMEDIATE-SCALE EXPERIMENTS AND AFIELD STUDIES 185 Dispereant Remote Sensing Sampling Sensors Use References Kromekote -carde __ __ Pans Color Documentation photographs Photo Documentation Color photographs Color photographs and video IR Kromekote IR, UV cards Documentation Documentation Slick area Slick area surface tension Laser Documentation nuorosensor, photo __ Kromekote IR carafe _ Cormack and Nichols, 1977 McAuliffe et al., 1980 Green et al., 1982 Smith et al., 1979 McAuliffe et al., 1981 Bocard and Gatellier, 1982 Gill and Ross, 1982 IR Lichtenhaler and Dating, 1983 Documentation Cormack, 198Sb Documentation Bocard, 1985 Sorbent IR, UV Slick area Delvigne, 1983 paper GO analysis of recovered oil
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From page 186... ...
Both tanks were diluted to background levels by the fourth day, and resulting total exposure in the dispersed oil tank was approximately 80 ppm-hr. Acute effects were observed on numbers of heterotrophic bacteria, on abundance of zooplankton, and on community metabolism, but Tong-term ejects, such as decreased abundance and shifts in diversity, of untreated oil
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From page 187... ...
or dispersed oil on hydrocarbon turnover rates was small. Compared to laboratory experiments, hydrocarbon turnover rates were lower in the MERI' experiments, and apparently were inhibited because of decreased wad effects and larger water volumes.
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From page 188... ...
This condition probably reflects rapid loss washout of the dispersion or possibly adhesion of untreated oil to the zooplankton, but not the inability of zooplankters to graze the smaller dispersed oil particles. BIOS Arctic Studies A major study in the Arctic, the Baffin Island Oil Spill Project, is an excellent example of a large-scale field project with good con/
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From page 189... ...
Such low subsurface concentrations are consistent with the field studies described earlier. In bay 9, which received oil plus dispersant, 94 bbl of oil were premixed with 9.4 bbl of Correct 9527.
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From page 190... ...
—72°30~ ~ watt Bay 7 J ~~ ~ 1 c° :> ~ ~ Baffin~\ J Island _ FIGURE ~4 Baffin Island Oil Spill Project test sites. the 3- and 7-m depth contours.
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From page 191... ...
Elevated concentrations of volatile hydrocarbons in the water column were still measured the day after the spill, but by the second day they were at background levels of 30 to 50 ppb (Boehm et al., 1985, 1987~. Within 1 to 2 weeks, surfaced polychaetes and bivalves reburied themselves and the numbers of sea urchins, previously reduced, were near prespill levels (Cross and Thomson, 1982~.
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From page 192... ...
. The greater persistence in the untreated of} bay is evident and contrasts with the light initial levels in the sediments where oil was chemically dispersed.
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From page 193... ...
Temperate ShaBow Subtidal and Intertidal Habitats Studies of temperate subtidal habitats, like the mesocosm studies of microbes and plankton above, indicate that of} concentration and length of exposure to of} constituents appear to be the controlling factors, not whether the of! is dispersed.
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From page 194... ...
Reduced siphon activity was apparent on the first day, significant mortality occurred with the dispersed of} after 4 days, but mixing the dispersant with fresh water prior to use reduced mortality. No mortality occurred after 10 days with of]
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From page 195... ...
Intertidal Communities Although the primary focus of this report is the effectiveness of dispersants in open marine areas, a number of valuable intertidal studies have been conducted. They are noted here for the additional understanding they shed on the overall impact of dispersed oil compared with untreated oil.
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From page 196... ...
A major study in the United Kingdom compared effects of oil and dispersants for a variety of intertidal rocky shore, salt marsh, seagrass, sand, and mud flat habitats. Experimental plots were treated with oil, dispersants (BPllOOWD, BPllOOX, Corexit 8667, and Corexit 7664)
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From page 197... ...
In the latter case, there is considerably less long-term biological impact than would be observed with untreated oil. In summary, some experiments reveal more damage to organisms when dispersants are used directly on rocky shores, and some reveal
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From page 198... ...
Temperate ShaBow Subtidal Studies: I`ong Cove and Sequim Bay A controlled field study involving of} dispersal in a large volume of shallow water is not easy to plan and conduct especially in temperate areas, such as in the United States, where it is difficult to obtain permits to discharge of} for research studies. However, in 1981, such a field study was conducted in Long Cove, Searsport, Maine, comparing the fates and effects of two 6-lob} spins of Murban crude oil, one dispersed and one untreated (Gilfi~lan et al., 1983, 1984, 1985, 1986~.
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From page 199... ...
Following the discharge, significant amounts of Murban crude of} were found in sediments exposed to untreated oil, mostly in the upper intertidal zone, but not in sediments exposed to the cloud of dispersed of} (GilfiHan et al., 1983, 1984~. Differences between treatments were mostly within one standard deviation (Gilfi~lan et al., 1986~.
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From page 200... ...
Salmon have been studied because of their highly developed chemical sense, which might be disturbed by low concentrations of petroleum hydrocarbons (see Chapter 3~. The effects of untreated and chemically dispersed Pru~hoe Bay crude of!
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From page 201... ...
, forced brief exposure to whole Pru~hoe Bay crude of} or chemically dispersed oil at high concentrations did not prevent or delay homing. Topical Shallow Intertidal and Subtidal Habitats Seagrasses The potential impact of dispersing an of} spill over a shallow area with a seagrass-based benthic community is of considerable concern in tropical areas.
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From page 202... ...
As with laboratory studies, when effect threshold was based on total oil per unit volume (nominal concentration) , chemically dispersed oil apparently had a greater impact; when effect threshold was based on actual water-accommodated hydrocarbons, there was generally little difference in the toxicity of chemically and physically dispersed oils.
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From page 203... ...
Dispersant use is not recommended in shallow lagoons or areas of restricted flushing rates. Related field and ecological studies of the effects of o~l and dispersed oil on salt marshes were discussed earlier.
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From page 204... ...
slick in shallow water near or above a core] reef might cause greater damage than the untreated oil, because of the higher concentrations of hydrocarbons introduced into the water column.
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From page 205... ...
(1985) concluded that "in the long term, Diploria strigosa appears relatively tolerant to brief exposures to crude of} chemically dispersed in the water column." However, these experiments were limited to only one coral species, and other reef organisms, such as crustaceans, echinoderms, and other invertebrates, are known for their sensitivity to both chemically and physically dispersed oil.
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From page 206... ...
One site received 380 liters (2.4 bbl) of Prudhoe Bay crude oil, and the other site received the same quantity of oil mixed with 19 liters (5 gal)
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From page 207... ...
formed a slick over the enclosed area and eventually was pushed well into the mangrove forest by waves and rising tides, and was retained there, contaminating substrate, prop roots, beach wrack, intertidal algal mats, crab burrows, and depressions in the forest floor. Sediments and prop roots at the outer edge of the forest were cleaned of heavy of} contamination after several tidal cycles, but interior areas remained heavily oiled after 1 week.
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From page 208... ...
The distinction must be made between dispersed of} coming ashore, which generally did not penetrate sediment, and dispersant applied to an oiled intertidal sediment, where treated of} usually penetrated more deeply than the untreated oil. In subtidal areas, use of dispersants may increase toxicity to benthic fauna and plants, at least in the short term, but may reduce long-term effects of oil.
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From page 210... ...
210 m ~ r ~ al _` V ~ m 1 ~ m ~ ¢ ~ 00 — — 00 ~:5 to ~ ~ ~ ~— ~ ~ — - 00 _ ~ ~ I: ~ ~ ~ ~ D ~ — · U — a, E ~ !
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From page 214... ...
Experimental observations and results are scarce and often contradictory; in some field experiments, dispersed of} had no effects on Scolds, whereas in other exposures, red algae suffered tissue damage and inhibited growth when chronically exposed to dispersed crude oil. Only first-generation dispersants have been shown to cause major effects on seaweeds on shorelines.
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