Oil in the Sea IV Inputs, Fates, and Effects (2022) / Chapter Skim
Currently Skimming:
5 Fates of Oil in the Sea
5 Fates of Oil in the Sea
Pages 161-262
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From page 161... ...
modeling of oil spills in the oceans, critical • There is an expanded appreciation of processes and oil fates to understanding the behavior of oil in the sea. unique to cold water and sea ice in deep sea and Arctic environ • Dissolution, long known as a relevant fate process for oil spilled ments, and new recognition that oil biodegradation can occur at at the sea surface, recently has been recognized as potentially rates faster than previously assumed at near-freezing temperatures.
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From page 162... ...
Whereas one marine compartment to another (e.g., moving from a sur- the 2003 report did not thoroughly examine biodegradation face slick to dispersion in the water column or stranding on as a fate of spilled oil, extraordinary technological and conthe shoreline) , transformation of oil components to partially ceptual advances made in analysis of microbial communioxidized products (e.g., by photo-oxidation or biodegrada- ties in the ocean (‘omics techniques)
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From page 163... ...
more difficult than it sounds because the marine environ- Section 5.5 summarizes the uses of oil spill models for prement is heterogeneous over many size and time scales, from dicting the fates of marine oil spills. Section 5.6 summarizes micrometer-sized oil droplets in millimeter-sized pore spaces conclusions and research needs arising from the literature in beach sand to many square miles of evaporating oil slick review.
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Because the oil and gas mon forms of petroleum in the marine environment. Oil and from the DWH oil spill was emitted as a live mixture, oil gas properties depend on the composition of the petroleum spill science now recognizes the important implications fluid and on the thermodynamic state, normally defined by of the live oil state, and significant new research has been a given temperature and pressure.
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TABLE 5.1 Summary of Processes Affecting the Fate of Oil in the Sea Process; Chapter Section Definition Promoting Conditions Surface spreading; Movement of oil on the sea surface that cre- Low viscosity oils spread more quickly than those with high Sections 5.2.2.1, 5.3.1 ates thin, floating pools of slicks and sheens viscosity Bubble and droplet Breakup of immiscible oil and gas into Turbulence, shear, low interfacial tension, mixing of oil or gas formation; droplets and bubbles suspended in the ocean with water Sections 5.2.2.2–5.2.2.4, water column 5.3.3.2 Mixing, dispersion, Changes in concentrations of spilled hydro- Concentrations decrease when hydrocarbons are mixed with and dilution; carbons by incorporation of those com- greater volumes of seawater, caused by turbulence and ocean Sections 5.2.2.3, 5.2.4, pounds in different volumes of seawater currents. Concentrations increase when oil droplets accumu 5.3.1.3, 5.3.2 late at the sea surface, caused by oil droplet rise and boundary interaction with the sea surface (see also surface spreading)
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From page 166... ...
fundamental dynamics occurring at the bubble or droplet Hence, the extent and thickness of sheens and slicks and scale, including the parameters affecting breakup and the the size distributions of oil droplets and gas bubbles are effects of chemical dispersants. Here, the discussion is thus key parameters controlling the fate of spilled oil in the limited to universal behavior of oil and gas interacting with marine environment, ultimately determining the affected the sea.
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the U.S. Coast Guard describes oil slicks for spill response operations using Streamers: Oil or sheen oriented in lines, windrows, or streaks.
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. Breakup of gas bubbles is fundamentally different from Other information that can be obtained from the appear- that of oil droplets due to the low dynamic viscosity and low ance of an oil slick include coverage and distribution on density of gas compared to oil.
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or as surface floating oil is entrained into the water column through a process normally referred to as dispersion. In either case, turbulent motion in the seawater is responsible for the from experiments on gas jets into a large laboratory tank.
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When the interfacial tension let sizes using these parameters must be fitted to experimenis very low, however, the viscosity, a form of fluid friction, tal data, and are expected to have different fit coefficients in BOX 5.3 Parameters Controlling Droplet Breakup Empirical Parameters: Hinze (1955) utilized scaling laws from the characteristic oil droplet sizes should encapsulate some version of canonical model of turbulence with properties of immiscible liquids to Equation B.3, adapted to the specific scales of turbulence in a given develop an empirical relationship for the maximum stable droplet size flow field.
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mote smaller droplet sizes because smaller droplets help While bubble and droplet breakup has been a topic increase biodegradation rates in the water column and reof chemical engineering for years, the past 10 years have duce the amount of oil on the water surface, thus reducing seen a tremendous increase in models adapted to oil spill the amount of oil that can reach the shoreline. Dispersants scenarios and in laboratory data relevant to oil spills may be applied at the sea surface to promote breakup of which can be used to calibrate and validate such models.
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horizontal direction than the vertical direction, largely due Gas bubbles and oil droplets can also be mixed by ocean to the density stratification, which promotes lateral motion currents, much like tracer clouds of dissolved material. The and inhibits vertical motion.
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Also, known about the generation and potential deposition of oil droplets that reach the sea surface will accumulate there, atmospheric gas-phase and aerosol pollutants to and from not passing entirely into the atmosphere nor resuspending marine oil sources. immediately into the ocean water column.
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. One of the largest uncertainties from atmospheric linearly related to primary particulate matter emissions SOx emissions has been attributed to the international ship- (Streets et al., 2000; Corbett, 2003; Endresen, 2003; Perraud ping operations in marine environments (Smith et al., 2011)
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whether they are has been shown to directly emit oil droplets into the atmo- primary (e.g., methane) or secondary (e.g., CO2, N2O)
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+ RH Æ XH• + R• in our understanding of the role of photochemical reactions in the fate of spilled oil, and perhaps by extension to some XH• + O2 Æ X + HO2• of the other types of petroleum or oil inputs to the marine R• + O2 Æ RO2• environment. Renewed appreciation of photochemical RO2• + RH Æ RO2H + R• reactions has resulted in a paradigm shift, causing us to consider photochemical reactions as one of the major RO2• + XH• Æ RO2H + X factors influencing the fate of spilled oil at the sea surface.
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The statement lates to the fate of spilled oil in the marine environment is about "from a mass balance consideration" seems to be based presented by Ward and Overton (2020)
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surrogate oil spread on a thin film of pre-irradiated sea water The evidence for both direct and indirect photo-oxidation and exposed to simulated sunlight in a laboratory experiment of oil components is summarized by Ward and Overton (Zito et al., 2020)
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FIGURE 5.13 van Krevelen diagrams of the molecular formula unique to each fraction (oil soluble, interfacial material, dissolved organic matter or DOMHC) showing the progression of higher oxygenated species from each fraction after simulated sunlight exposure.
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At the same time, dissolution may be or liquid-phase petroleum fluid are transferred to an aqueous occurring at the petroleum–water interface of the surface dissolved state in seawater. The solubility is the maximum slick and for oil droplets suspended in the water column amount of a given compound that may be dissolved in water by natural dispersion.
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and Oil Because of the ubiquitous nature of surfactants in the Unlike for floating oil, suspended oil droplets and gas environment, dirty bubble dynamics are expected in most bubbles are not exposed to the atmosphere, and all mass natural systems; however, several studies in the oceans inditransfer from the petroleum to the aqueous phase must be by cate that clean bubble mass transfer rates may be appropriate dissolution -- evaporation, or volatilization, does not occur. early after release of a droplet or bubble.
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to degrade because of its high viscosity and reduced surface After some time, mass transfer reduces to dirty bubble mass area. In addition, emulsified oil exhibits reduced evaporation, transfer rates, either due to surfactant contamination (Olsen dissolution, entrainment into the water column and transport et al., 2019)
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Different oils exhibit different tendencies Initially, dispersed oil moves down into the water column to depths to emulsify, and emulsification of surface oil spills (slick) is likely to ranging from 1 to 10 meters (about 3 to 30 feet)
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the viscosity increasing from 1,000 mPa to over 11,600 mPa to the water column. In this case, the oil droplets will rise to over 12 days (Daling et al., 2014)
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depth of the water column; shallow and deep sediments of the The greatest value in the new techniques is that microbial seafloor; hydrothermal vents and natural oil and gas seeps; identity and activity now can be studied without having to habitable oil reservoirs beneath the seafloor; and beaches, cultivate organisms or separate them from their community estuaries, and salt marshes. Microbes form associations with partners.
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com- Although these caveats might appear to discredit ‘omics prises four gene catalogs of microbial community sequences output, environmental microbiologists have learned not to acquired from global ocean water surveys, currently pro- consider sequence identification as a permanent label but viding access to more than 110 million functional and rather as the best interpretation at the time of analysis, partictaxonomic gene sequences that enable study of microbial ularly for uncultivated environmental microbes. Despite the biodiversity and ecosystem activity.
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this case, some or most of the original chemical structure remains, even though the product may no longer be detected directly using a Note that the term bioavailability, when used in the context of microbial bio conventional analytical techniques (see Box 5.8 later in the chapter for degradation, is synonymous with "accessible to microbial cells," whether dispersed or emulsified in the water column, sorbed to sediments or organic material, or the analytical consequences of transformation)
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Introduction of oil at the surface or from the subsurface produces dispersed oil droplets in the water column. Hydrocarbon-degrading bacteria colonize the droplets to form marine oil snow (MOS)
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Another natural continuous source An obvious question is how they persist in the ocean in the of hydrocarbons is contemporary biological production in the absence of spilled oil. The selective pressure likely is con- "short hydrocarbon cycle" (see Box 5.6 and Section 2.1.5)
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efficient proportions and physical orientations at the correct phase Species compete for access to the oil, for example at the oil–water of oil biodegradation may take some time. This process may explain interface of dispersed oil droplets, and for nutrients and electron accep- in part the acclimation period ("lag time")
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. This implies that chemical been observed to be transported from seafloor sediments to dispersion of oil droplets is not the main factor limiting oil the water column by attachment to gas bubble surfaces dur- biodegradation in deep Gulf waters, and that other nuances ing ebullition (Schmale et al., 2015)
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. oil slicks, its impacts on biodegradation of spilled oil, whether at the surface or subsurface, should be resolved.
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Naphthenic acids are natural components of heavy crude enter the marine environment. Olefin biodiodegradation is oils such as bitumen, and spills of dilbit (see Chapter 2)
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This approach ignores the surface-area intermediate (>~40° API) , through medium oils like Alaska dependent nature of biodegradation of oil droplets (Brakstad North Slope and North Sea oils, to shale oils and waxy crudes et al., 2015; Thrift-Viveros et al., 2015; Wang et al., 2016)
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. that include liquid oil because this may affect the oil droplet size, hence, the surface area of the oil–water interface.
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to be detected by GC. Thus, caution is required when using routine GC methods to infer the degree of loss of oil components.
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have been used with oil droplets or slicks at the oil-water interface (Abbasnefor short-term incubations, for example, until the n-alkanes zhad et al., 2011)
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These factors are important for oil in the support various anaerobic processes. Because seawater has sea because it is relatively easy and fast for free-living aerobic a relatively high concentration of dissolved sulfate, sulfate hydrocarbon-degraders to begin metabolizing oil near the reduction is common in anaerobic marine environments, ocean surface within hours or days, but it may take weeks, generating end products including hydrogen sulfide (H2S)
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. biodegradation of liquid oil components is a widespread and The toxicity of such mixtures of aromatic acids to marine well-studied phenomenon in marine systems, and metabolism fauna is not yet known, as dilution in the water column or of saturates and aromatics by diverse species has been known distributed metabolism may reduce any potential effects.
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. Concentrations of dissolved nitrate, ni- Salinity may also be a factor in Arctic sea ice, where brine chantrite, ammonium and phosphate from terrestrial runoff may nels containing oil and microbes have higher salinity than the ice be adequate for oil biodegradation in near-shore waters and (see Section 5.3.5.3)
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Laboratory studies at high pressure and low temperature microbial communities and therefore oil biodegradation. Mahave varied considerably in their methodology, including rine oil snow, for example, is a hotspot of microbial activity the hydrostatic pressure applied (6–50 Mpa [megaPascal]
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mental level, an oil spill budget reports the amount of spilled • Sunlight can transform oil components. oil entering different environmental compartments (e.g., water • Chemical changes in the oil affect the physical features column, sediments, sea surface, atmosphere, etc.)
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Estimates of viscosity, and water content of an oil or refined product, natural dispersion and droplet formation are very uncertain as and the rates at which it evaporates from the sea surface, they depend significantly on the energy from wind and waves disperses into the water column, and forms oil droplets that on the surface being transferred to the floating oil. Although become emulsified, or suspended, in the water (NOAA, natural dispersion and droplet formation are mechanisms that 2021c)
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Bottom: Oil fate (weathering) view from WebGNOME, showing an oil budget for a simulated spill.
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The best and worst cases defined in the report are the combinations of values of the seven variables depicted in each stack that correspond to the lower and upper endpoints of a 95% confidence interval for the volume of "Other Oil." The Oil Budget Calculator does not quantify the volume of oil that forms tar balls or surface slicks, sinks due to sedimentation, remains in the surf zone, or impacts the shore and is subsequently cleaned up. These are instead grouped together as "other oil." The amount of oil listed as "other" is quite large in the DWH oil budget.
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Dispersed oil droplet size: A major improvement in containment ("direct recovery from wellhead") being the most estimating dispersant efficiency would be possible effective method, and chemical dispersant applications at sur- if practical operational tools and methods existed to face and subsurface dispersing a substantial fraction (National characterize droplet size distribution of subsurface Commission, 2011a)
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reported fates for different compound groups and in the water column as tiny oil droplets. From Figure 5.24, environmental compartments and performed simulations only French-McCay et al.
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absolute values to use. The most reliable number was the total As can be seen by these different approaches to calculating amount released, as that was able to be calculated from the voloil budgets: it is difficult to compare different types of calcula ume loaded into the hold and the amount pumped out after the tions and models; there are very large/rough/round numbers spill.
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This section addresses processes immediately at the ocean surface or originating at the 5.3.1.2 Wind Drift and Stokes Drift ocean surface and potentially affecting transport over the upper mixed layer of the ocean, extending to depths of order ~10 m. Oil transport modelers have observed for decades that Most oils are lighter than seawater, so newly spilled oil tends floating oil tends to move by a combination of the nearto rise toward the surface and accumulate, at least temporarily, surface ocean currents and the wind vector.
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The rate of natural dispersion may also Entrainment of oil from the sea surface into near-surface decrease with increasing ice coverage. The presence of ice on water occurs when oil droplets separate from the oil slick water reduces water surface and wave activity; thus, mixing and enter the water column -- a process commonly referred and energy dissipation could be very low.
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. Hence, when breakup reduce the droplet sizes of oil droplets forming under waves occurs by turbulent eddies, predictions using the Hinze and increase the volume of entrained, dispersed oil.
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of dispersed oil in the water column affect the impact of photo-oxidation. Dissolution occurs between the petro 5.3.2 Processes Affecting Oil in the Water Column leum–water interface of surface floating oil and suspended water droplets.
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Marine snow refers to one or more oil droplets with mineral particles attached to organic matter aggregates that form naturally in the upper their surface only. The size of the oil droplets ranges from water column even in the absence of oil, settle by gravity into less than 1 mm to tens of mm.
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OMAs consist of solid aggregates that are a the DWH oil spill, SOAs were considered under the broad category mixture of oil and minerals blended into microscopic bodies of various of tar balls and were referred to as tar mats. After the DWH spill, the shapes.
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From page 215... ...
and nutrients available to the organisms in the activity converts the organic matter into non-sinking DOM, upper water column and, furthermore, responds to the presforming plumes of DOM and soluble nutrients (nitrogen, ence of dispersed oil and chemical dispersants. The color phosphorus, and iron)
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From page 216... ...
forms when naturally or chemi- droplets in water results in increased collision rates between cally dispersed oil droplets attach to marine snow and droplets and marine particles and, therefore, increases the mineral particles (Brakstad et al., 2018c) (see Figure 5.29)
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From page 217... ...
Changes in the oil biodegradation either directly as primary and secondary surface water microbial community composition that occur oil-degraders (e.g., by mineralizing, transforming, and/or after oil spills (see Section 5.2.8.2) can affect the produc- assimilating hydrocarbons and degradation products)
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From page 218... ...
MOS on the seafloor are influenced by the dynamic interac Fundamental physical chemical properties of medium to tions of benthic fauna (bioturbation, resuspension, feeding) ; higher molecular weight material predict adsorption/absorp- presence of oil and dispersants (petrogenic hydrocarbons, tion to marine snow/extracellular polymeric organic material smaller oil droplets, pyrogenic material generated from in (see Chapter 2)
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surface but was not reclaimed at the surface, plus an elevated and extended discharge from the Mississippi River during unknown proportion of the subsea dispersed oil plume that sedimented the spill generated high concentrations of suspended sediments in the as MOS and OPAs. The oil that reached the sea floor was chemically water column.
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. Boom cores from the Arctic Central Basin, North and South Atlanmaterial used for oil absorption of oil spills is made of tic, Southern Ocean, Mediterranean Sea, and Indian Ocean plastic compounds.
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Microplastics can be incorpolyamide, and acrylic) are found in intertidal and subtidal porated into aggregates that form during coagulation of sediments, as well as locations with periodic polystyrene organic matter and oil droplets.
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, and seawater to form buoyant jets, which rise as buoyant plumes presence/absence of suspended sediments (OPA formation; through the ocean water column, and depending on the see Section 5.3.2.1)
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When a plume forms, these regimes. Within the ZFE, the turbulent dissipation rate it can transport small oil droplets or gas bubbles at plume is constant and depends on the release velocity and orifice dispeeds of about 0.5 to 1.0 m/s (Gros et al., 2020)
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. Second, the presence of bubbles or droplets in the flow important contributions to the turbulence production term breaks down the assumptions used to derive solutions for arising from the wakes of the oil droplets and gas bubbles single-phase buoyant; namely, self-similarity is no longer (Fraga et al., 2016; Zhao et al., 2016, 2017; Lai et al., 2019)
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The oil droplet size from weak sources, assuming no chemical parameter space of the DWH oil spill is also shown as the dispersants are used, which is reasonable for these slow or shaded region in the figure along with extrapolated predicdistributed sources. As a result, for diffuse or weak sources, tions for the droplet size of untreated DWH oil using the millimeter-scale droplets and bubbles are expected to form empirical equations of Johansen et al.
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These data are needed for oil droplet breakup with but includes breakup within the viscous subrange; the LES
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From page 227... ...
This into droplets. A distinguishing feature of the formed droplets indicates that the breakup process is largely self-similar and was the inclusion of smaller water droplets within individual that the approach in VDROP-J, which uses uniform distribu- oil droplets for the experiments with jet Reynolds numbers of tions of velocity and size distribution, is appropriate.
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From page 228... ...
, creating filaments and blobs of oil and subsequently break up into individual droplets. The insets show the details of the formed oil droplets, which include many compound droplets composed of water droplets suspended in oil droplets and sometimes cascading as in a set of Russian dolls.
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When the gas arrives at sufficient blowout, pipeline leak, or diffuse seepage through the sea- atmospheric concentration, the gas may ignite and burn. This floor, is expected to enter the ocean water column as live was the case for the gas released in the Ixtoc I blowout and for petroleum droplets and bubbles.
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Corresponding theoretical simulations in an open mounted both on the hull of the research vessel and on ocean with background methane concentration showed that the ROV. They simulated the gas bubble evolution using degassing is a negligible process for oil droplets over a wide the measured bubble size distributions at the sea floor usrange of initial conditions for all but potentially the final ing TAMOC and applied acoustic models to convert the few meters of rise through the ocean water column (Gros simulated bubble properties to acoustic backscatter.
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(2017) model com- undergo breakup as they traverse the ocean water column.
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Section 4.2.3 summarizes three phases of SSDI several years between initial entrainment of oil in suspended sampling and monitoring, which includes observation of the particles and their deposition in deep sea sediments, as well source conditions and surface slicks, characterization of the as sediment resuspension and transportation events (Diercks oil droplet size distributions near the source, and chemical et al., 2021)
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oil biodegradation, rapidly shifting from methane, ethane, Aerobic oil biodegradation may occur after deposition of and propane gas utilization during the active spill to biodeg- OMA and MOS and during burial but will become limited radation of liquid oil components post-spill. In addition to by diffusion of dissolved oxygen to replenish that consumed MOS that formed near the ocean surface, microbial biomass during oxidation of hydrocarbons.
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. High and low tides as well as tidal currents seafloor sediments at least four years after the DWH oil spill can shift the shoreline and transfer sediment.
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oil released into the Gulf of Mexico from the DWH spill At intertidal areas with exposed shorelines including rocky reaching low-relief beaches of sand and shell aggregates in shores, rocky banks, solid man-made structures, and rocky Louisiana, United States, showed that these aggregates can cliffs with boulder talus bases, oil is generally held offshore be mobilized from the subtidal and intertidal zone of the by waves or rapidly removed from the exposed surface by beach during more energetic events such as storms and high wave action. However, oil can penetrate to the wet rock tides (Curtis et al., 2018)
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. The hydrodynamic conditions in coastal areas exposed In contrast, the half-lives of aliphatic and aromatic hydroto recurrent contamination result in long-term persistence of carbons in Macondo oil from the DWH spill that impacted deep oil spills from wrecks by burying and resurfacing the Pensacola Beach (Florida)
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As described by Michel in sediment cores 18–36 months after the DWH oil spill, et al.
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The decrease in 5.3.5 Arctic Marine Systems and Sea Ice seawater infiltration can have adverse effects on chemical transformation processes (e.g., nutrient recycle and redox Polar oceans historically have not been impacted greatly condition) in beaches, and subsequently on receiving water by accidental oil spills (see Chapter 3)
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Bacteria and plankton form biofilms on the underside of sea ice by attaching via extracellular polymers, and also may become entrained in brine channels. They may encounter oil in the water column, at the seawater:ice interface, or within ice masses.
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Unlike freshwater ice, sea ice is porous, having an internal Thicker slicks and cold air temperatures decrease evapora- network of fluid-filled channels as a consequence of brine tion rates, allowing toxic low molecular weight components exclusion while the ice is forming. The bottommost pores are to persist longer in the oil where they may be available to directly in contact with the underlying seawater and permit dissolve into the water column.
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light crude oil applied to first-year ice surface migrated to Recent x-ray micro-computerized tomography (CT) studies the underlying water column via dissolution.
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. Oil 5.3.5.2 Effect of Low Temperature on Oil Biodegradation may persist in multiyear ice for up to 5 years or seasonal melting may release the oil from first-year ice to impact the In the event of an oil spill, the remoteness of some food web at a distance from the original location, since sea Arctic regions would delay and alter spill response options ice movement can be a major pathway for long-distance some of which, furthermore, would be less effective due cryptic transport of entrained oil (Wang et al., 2017)
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They found that conventional Q10 constantly cold environments such as deep oceans and polar scaling was adequate for predicting biodegradation rates for regions. Oil-degrading genera that are commonly detected by the more water-soluble, lighter oil components, but were less polar marine studies during low-temperature biodegradation accurate for poorly water-soluble, higher molecular weight include members of the family Oceanospirillaceae such as oil components, possibly because Q10 does not capture temthe psychrophilic obligate hydrocarbon-degraders Oleispira perature effects on oil behavior (e.g., increased viscosity antarctica, Oleiphilus, and Thalassolituus; psychrotolerant and decreased water solubility of PAHs at low temperature; heterotrophs Polaribacter, Colwellia, and Cycloclasticus reviewed by Margesin and Schinner, 2001)
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cells such as algae or with inorganic particles or ice crystal The oil was depleted by a combination of evaporation, FIGURE 5.41 Photographs of oil migrating through columnar sea ice grown in experimental tanks. Left panel: oil distribution in a brine channel ~10 cm above oil:water interface, with fanning into "feeder: brine channels; Right panel: vertical section of ice showing mechanically dispersed oil droplets entrained in the bulk ice.
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. By sequestering those in temperate waters but degradation within the sea ice the cells near the top of the water column, they are optimally was negligible.
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. In another study, biodegradation proceeded only good biodegradation of oil by melted sea ice (indicating that after biofilms had formed on the surface of the oil droplets; appropriate organisms and sufficient nutrients were present in fact, agitating the culture to decrease adherence delayed in the ice)
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They 5.4 FATES IN SPECIFIC MARINE ENVIRONMENTS: found the genes to be ubiquitous, along with nanomolar CHRONIC INPUTS concentrations of short-chain alkanes even in sediments considered pristine. Taken together, the studies suggest that In addition to the episodic oil spills described in Section 5.3 the potential for both aerobic and anaerobic alkane biodeg- that have a defined onset and finite duration of oil input, radation is widespread in cold seafloor sediments, and there there are numerous long-term sources of oils that enter the is cosmopolitan distribution of species and genes associated marine environment (see Chapter 3)
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From page 248... ...
5.4.1 Fates of Oil and Gas from Natural Seeps ultimate fates of the contaminants in the sea. For the most part, the fates of oil from continuing inputs are assumed to Natural seeps are ubiquitous on the continental margins be similar to those of episodic spills (refer to Section 5.3 for and are sources of natural gas and liquid-phase petroleum to episodic inputs and Section 5.2 for fundamental hydrocarbon the ocean water column (Ruppel and Kessler, 2017; see also fate processes in the oceans)
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From page 249... ...
might little dissolution on transiting the ocean water column. The amplify aerobic biodegradation by free-living and MOS oil often reaches the sea surface and, depending on the sea microbes in the water column, in addition to serving as livstate, may form a distinct slick that extends many kilometers ing markers of produced water plume movement via ‘omics from the seep source.
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From page 250... ...
In contrast, containers were observed, indicating that components of oil from sunken wrecks (described in Section 3.5.4) may produced water from this offshore field are biodegrad- impact the water column as the oil rises and/or the sediment, able relatively rapidly under simulated in situ conditions.
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The longer the exposure, that sediments from the water column or is re-mobilized the longer the release time once the exposure is reduced from beaches. Direct measurement of hydrocarbons in or eliminated.
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From page 252... ...
To predict the trajectories and fates for real spills include forecasting models to help direct the of spilled oil, the currents, temperature, and salinity dynamics response and injury assessment models to help understand of these ocean–atmosphere hydrodynamic models are used. the impacts of different response decisions and the ultimate Initial conditions for an oil spill include the flow rate, injury to the environment resulting from the spill.
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From page 253... ...
Pictures of spilled oil show a different the total amount of oil considered, its centroid location, and characteristic: oil slicks can be highly localized compared its spatial extent. Because oil may be transported in different to the kilometer-scale resolution of ocean circulation mod- directions from the surrounding ocean water, concentrations els, breaking up into slicks a few 100 meters in diameter to of dissolved chemical species within a Lagrangian parcel patches of dispersed oil droplets on scales set by the surface are not directly predicted.
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From page 254... ...
Because these there is no longer a need to track liquid droplets separately models keep track of the oil mass and its characteristic state from the atmospheric dynamics. As a result, atmospheric within the ocean water column (i.e., number and size of oil dispersion models do track component concentrations and droplets)
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From page 255... ...
, a spatial average, or filter, is applied. This filtering has the including the interactions of oil droplets with Langmuir effect of removing turbulent motions that occur below the circulations (Yang et al., 2014, 2015)
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From page 256... ...
. Injury assessment modeling only a few sub-models related to oil fate; others require fully may rely on very similar simulations of fate and transport to integrated operational models; and others involve specific, those used in spill response modeling, but these simulation purpose-build research models.
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From page 257... ...
physics, chemistry, and thermodynamics controlling oil fate This is often difficult to achieve because natural processes and transport. Hence, the accuracy of their approximations undergo periodic variability over large ranges of absolute should be evaluated.
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From page 258... ...
The magnitude of oil biodegradation in cold, deep focused on the fate of oil spilled at the surface, but the DWH ocean water. Samples from the deep dispersed oil oil spill in the deep subsurface focused attention on addi- plume from the DWH spill revealed that the natural tional processes affecting oil behavior and fate.
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From page 259... ...
However, utilizing this information in model- though models are imperfect, they are an important tool for ing or response still requires additional work. guiding response and damage assessments for oil spills.
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From page 260... ...
Conclusion -- Oil spill budget shortcomings: Calculating and Conclusion -- Monitoring PAH profiles in sediments and reporting on the mass balance/oil budget from mitigation bivalves: The NOAA National Status and Trends Program activities and natural processes is often required during an oil (Kimbrough et al., 2008) has provided a unique, nationwide spill response.
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. 5.2 Chemical reactions affecting the fates of oil: With the renewed appreciation of photo-oxidation as a significant process affecting oil chemistry, more research is needed to focus on interactions of photo-chemical products with the physical and chemical properties of oil, its behavior in the water column and on shorelines (e.g., emulsification and adherence to mineral surfaces)
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From page 262... ...
This includes the need to develop new modeling algorithms, add these algorithms to models, and validate their predictions, ideally using in situ observations. Some of the new insights that are currently being developed or still need to be parameterized for oil spill models include photo-oxidation, MOSSFA, temperature effects on biodegradation kinetics, and anaerobic biodegradation, among others.
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Key Terms
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