Oil is a general term that describes a wide variety of natural substances of plant, animal, or mineral origin, as well as a range of synthetic compounds. Crude oil is a naturally occurring oil generated by geological and geochemical processes. A variety of petroleum products are then derived from this natural resource. Because their compositions vary, each type of crude oil or petroleum product has unique characteristics or properties. These properties influence how petroleum will behave when it is released and determine its effects on biota and habitats.
Crude oil and derived petroleum products (collectively referred to here as petroleum) are made up of dozens of major hydrocarbon compounds and thousands of minor ones. Hydrocarbons occur naturally in great abundance and in a variety of forms. Although petroleum is overwhelmingly composed of hydrocarbon compounds, not all hydrocarbon compounds come from petroleum. Thus, it is appropriate to limit discussion here to that subset of compounds typically associated with the term petroleum hydrocarbon. For the purposes of this study, hydrocarbon compounds containing less than five carbon atoms (e.g., methane, ethane, and other gases) were not considered because they are abundant and widespread and because their behavior differs so greatly from liquid petroleum. Furthermore, non-petroleum oils (e.g., vegetable oils, animal fats) were not included, because spills of these materials, although not trivial, present unique fate and effect problems. Addressing these spills in an adequate manner was determined to be beyond the resources of the present study.
Crude oil, the naturally occurring liquid form of petroleum, is an important part of the current energy mix of fossil fuels. As this fossil fuel is extracted, refined, transported, distributed, or consumed, spills and other releases occur. In addition, natural processes can result in seepage of crude oil from geologic formations below the seafloor to the overlying water column (see Chapter 3 for greater detail about natural and anthropogenic inputs). Understanding the nature and distribution of sources and their inputs, as well as the behavior of petroleum in the environment, is key for understanding the potential effect on the marine environment (see Chapters 4 and 5 for more detail about fate and effects).
THE COMPOSITION OF PETROLEUM
Petroleum is composed principally of hydrocarbons (compounds containing only hydrogen and carbon); thus, the terms petroleum and hydrocarbons are often used interchangeably. In fact, the elements hydrogen and carbon together (occurring as hydrocarbons or related compounds) constitute about 97 percent of most petroleum, while the
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Oil in the Sea III: Inputs, Fates, and Effects 2 Understanding The Risk HIGHLIGHTS This chapter includes discussions of: The nature and composition of crude oil and petroleum products derived from it, The chemical, physical, and biological processes that affect how petroleum released into the marine environment behaves, Discussions of the principal sources of petroleum in the marine environment, Estimates of the mass of petroleum released to the marine environment each year from these sources, The potential environmental consequences of these petroleum releases, and A summary of the major findings and recommendations of the study. Oil is a general term that describes a wide variety of natural substances of plant, animal, or mineral origin, as well as a range of synthetic compounds. Crude oil is a naturally occurring oil generated by geological and geochemical processes. A variety of petroleum products are then derived from this natural resource. Because their compositions vary, each type of crude oil or petroleum product has unique characteristics or properties. These properties influence how petroleum will behave when it is released and determine its effects on biota and habitats. Crude oil and derived petroleum products (collectively referred to here as petroleum) are made up of dozens of major hydrocarbon compounds and thousands of minor ones. Hydrocarbons occur naturally in great abundance and in a variety of forms. Although petroleum is overwhelmingly composed of hydrocarbon compounds, not all hydrocarbon compounds come from petroleum. Thus, it is appropriate to limit discussion here to that subset of compounds typically associated with the term petroleum hydrocarbon. For the purposes of this study, hydrocarbon compounds containing less than five carbon atoms (e.g., methane, ethane, and other gases) were not considered because they are abundant and widespread and because their behavior differs so greatly from liquid petroleum. Furthermore, non-petroleum oils (e.g., vegetable oils, animal fats) were not included, because spills of these materials, although not trivial, present unique fate and effect problems. Addressing these spills in an adequate manner was determined to be beyond the resources of the present study. Crude oil, the naturally occurring liquid form of petroleum, is an important part of the current energy mix of fossil fuels. As this fossil fuel is extracted, refined, transported, distributed, or consumed, spills and other releases occur. In addition, natural processes can result in seepage of crude oil from geologic formations below the seafloor to the overlying water column (see Chapter 3 for greater detail about natural and anthropogenic inputs). Understanding the nature and distribution of sources and their inputs, as well as the behavior of petroleum in the environment, is key for understanding the potential effect on the marine environment (see Chapters 4 and 5 for more detail about fate and effects). THE COMPOSITION OF PETROLEUM Petroleum is composed principally of hydrocarbons (compounds containing only hydrogen and carbon); thus, the terms petroleum and hydrocarbons are often used interchangeably. In fact, the elements hydrogen and carbon together (occurring as hydrocarbons or related compounds) constitute about 97 percent of most petroleum, while the
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Oil in the Sea III: Inputs, Fates, and Effects minor elements nitrogen, sulfur, and oxygen make up the remaining 3 percent (NRC, 1985). Crude oil sometimes contains mineral salts, as well as trace metals such as nickel, vanadium, and chromium. In general, the hydrocarbon compounds found in crude oil are characterized by their structure (see Speight, 1991 for greater discussion of the classification of petroleum related compounds). These compounds include the saturates, olefins, aromatics, and polar compounds. Understanding these different compounds and their structures is important for understanding the fate and effect of releases of crude oil or products derived from it. The saturate group of compounds in various crude oils consists primarily of alkanes, which are composed of hydrogen and carbon with the maximum number of hydrogen atoms around each carbon (Speight, 1991). Thus, the term “saturate” is used because the carbons are saturated with hydrogen. The saturate group also includes cycloalkanes, which are compounds made up of the same carbon and hydrogen constituents, but with the carbon atoms bonded to each other in rings. Higher-molecular-weight saturate compounds are often referred to as “waxes.” Olefins, or unsaturated compounds, are those that contain fewer hydrogen atoms than the maximum possible. Olefins have at least one carbon-to-carbon double bond, which displaces two hydrogen atoms. Significant amounts of olefins are found only in refined products (NRC, 1985; Speight, 1991). Aromatic compounds include at least one benzene ring. Benzene rings are very stable, and therefore persistent in the environment, and can have toxic effects on organisms. The more volatile monoaromatic (single-ring) compounds found in crude oil are often referred to as BTEX, or benzene, toluene, ethylbenzene, and xylene (NRC, 1985; Speight, 1991). Aromatic hydrocarbons may account for about 1 to 20 percent of the total hydrocarbons in crude oil. Benzene and alkyl benzenes with one or two methyl or ethyl groups (toluene, xylenes, ethylbenzene), the BTEX compounds, may be present at a concentration of several percent in light crude oil, but more typically are present at concentrations of 1,000 to 10,000 mg/kg (Speight, 1991). Usually, toluene is the most abundant of the BTEX compounds, followed by benzene or one of the three xylene isomers. More highly alkylated benzenes usually are present at low concentrations in crude oils. Polycyclic aromatic (multiple-ring) hydrocarbons (PAH, also called polynuclear aromatic hydrocarbons, PNA) consist of at least two benzene rings. A typical crude oil may contain 0.2 percent to more than 7 percent total PAH. Some related aromatic compounds (not technically hydrocarbons because they may contain within their structure many elements such as sulfur, nitrogen, and oxygen) are detected with the same analytical techniques and often occur with true polycyclic aromatic hydrocarbons. Thus, these compounds are often grouped with, and discussed as, PAH. PAH includes those compounds that have the most serious environmental effects of the compounds in crude oil. PAH in the environment are derived largely from combustion of oil and coal, but are also produced by the burning of wood, forest fires, and a variety of other combustion sources. The abundance of aromatic hydrocarbons in petroleum usually decreases with increasing molecular weight. In most cases, one-ring (benzene) through three-ring (phenanthrene) aromatic hydrocarbons and related heterocyclic aromatic hydrocarbons, such as dibenzothiophene, account for at least 90 percent of the aromatic hydrocarbons that can be resolved in crude petroleum by conventional analytical methods (Neff, 1990). Four- through six-ring PAH (pyrene/fluoranthene through coronene), some of which are known mammalian carcinogens, usually are present at low or trace concentrations in crude oils (Kerr et al., 1999). The PAH in petroleum often contain one or more methyl, ethyl, or occasionally higher alkyl substituents on one or more aromatic carbons. As a general rule, these alkylated PAH are more abundant than the parent compounds in petroleum (Sporsol et al., 1983). Of the hydrocarbon compounds common in petroleum, PAH appear to pose the greatest toxicity to the environment (see Chapter 5 for greater discussion). Most of the PAH compounds in petroleum are not as toxic as those produced by certain combustion processes, but most groups are significant components of runoff from paved surfaces. Polar compounds are those that have a significant molecular charge as a result of bonding with elements such as sulfur, nitrogen, or oxygen. The polarity of the molecule results in behavior that differs from that of unpolarized compounds under some circumstances. In the petroleum industry, the smallest polar compounds are known as resins. The larger polar compounds are called asphaltenes and often make up the greatest percentage of the asphalt commonly used for road construction. Asphaltenes often are very large molecules, and if abundant in a specific volume of oil, they have a significant effect on oil behavior. PROPERTIES OF CRUDE OIL OR PETROLEUM PRODUCTS The properties of liquid petroleum, including crude oil or refined products, that are most important in understanding the behavior and fate of spills or other releases are viscosity, density, and solubility (see Chapter 4 for greater detail). Viscosity is the resistance to flow in a liquid. The lower the viscosity, the more readily the liquid flows. The viscosity of oil or petroleum products is determined largely by the proportion of lighter and heavier fractions that it contains. The greater the percentage of light components such as saturates and the lesser the amount of asphaltenes, the lower is the viscosity. Highly viscous oils tend to weather more slowly because they do not spread into thin slicks. Instead, they form tarballs, which can be transported long distances and accumulate in thick deposits on shorelines that can persist for decades.
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Oil in the Sea III: Inputs, Fates, and Effects Density is the mass of a given volume of oil or petroleum product and is typically expressed in grams per cubic centimeter.1 It is the property used by the petroleum industry to define light or heavy crude oils. Density is also important because it indicates whether a particular oil will float or sink in water. The density of pure water is 1.0 g/cm3 (at 15ºC) and the density of most oils ranges from 0.7 to 0.99 g/cm3 (at 15ºC), thus most oils will float on water. Since the density of seawater is 1.03 g/cm3 (at 15ºC), thus even heavier oils will usually float on it. Density is often used as a surrogate for predicting the relative rate of natural weathering when crude oil or other petroleum products are released to the environment. Light oils contain petroleum hydrocarbons that are readily lost via evaporation and microbial degradation. Heavy oils contain a greater percentage of the higher-molecular-weight petroleum hydrocarbons that are more resistant to weathering. Solubility in water is the measure of the amount of an oil or petroleum product that will dissolve in the water column on a molecular basis. Because the amount of dissolved oil is always small, this is not as significant a loss mechanism as evaporation. In fact, the solubility of oil in water is generally less than 100 parts per million (ppm). However, solubility is an important process because the water-soluble fractions of the oil are sometimes toxic to aquatic life. Thus, although solubilization represents a minor loss process, the concentration of toxic compounds dissolved in water from oil may be sufficient to have impacts on marine organisms. BEHAVIOR IN THE ENVIRONMENT Oil or petroleum products spilled on water undergo a series of changes in physical and chemical properties that, in combination, are termed “weathering.” Weathering processes occur at very different rates but begin immediately after oil is released into the environment. Weathering rates are not consistent and are usually highest immediately after the release. Both weathering processes and the rates at which they occur depend more on the type of oil than on environmental conditions. Most weathering processes are highly temperature dependent, however, and will often slow to insignificant rates as the temperature approaches zero. Table 2-1 is a summary of the processes that affect the fate of petroleum hydrocarbons from seven major input categories. Each input is ranked using a scale of high, medium, and low that indicates the relative importance of each process. The table is intended only to convey variability and is based on many assumptions. Nevertheless, it does provide a general idea of the relative importance of these processes. Clearly one of the biggest problems in developing such a table is that the importance of a particular process will depend on the details of the spill event or release. Table 2-1 attempts to account for this to a limited extent in the case of accidental spills by including subcategories for various oil types (see Chapter 4). This table emphasizes the role various environmental processes can play in spills of widely varying types. This in turn underscores how just one facet of the complex set of variables may vary from spill to spill, making each spill a unique event. Thus, the chemical and physical character of crude oils or refined products greatly influence how these compounds behave in the environment as well as the degree and duration of the environmental effects of their release. Relating Size of Release to Impact on Organisms This report attempts to compile and estimate total release (or loadings) of petroleum hydrocarbons to the marine environment from a variety of sources. These loading rates, in units of mass per unit time, are useful to compare the relative importance of various types of loadings and to explore the spatial distribution of loadings. Obviously, sources of petroleum that release significant amounts (whether through spills or chronic discharges) represent areas where policymakers, scientists, and engineers may want to focus greater attention. Attributing specific environmental responses to loadings calculated at worldwide or regional scales, however, is currently not possible. As discussed earlier, petroleum is a complex group of mixtures, and each group may contain widely varying relative amounts of hundreds (or more) compounds. Although many of the compounds are apparently benign, many other, such as some types of PAH, are known to cause toxic effects in some marine organisms. To further complicate this picture, marine organisms (even in the same taxa) vary greatly in their sensitivity to the same compound. Predicting the environmental response to a specific release of a known quantity of a refined petroleum product (which contains far fewer compounds than crude oil) requires much site-specific information about the nature of the receiving water body. Thus, the estimated loadings reported later in this chapter or in Chapter 3, are best used as a guide for future policymaking. In addition to identifying potential sources of concern, these estimates may have some value as performance metrics. Specifically, in those cases where reasonable comparisons can be made to estimates developed in earlier studies, they have value as a measure of the effectiveness of already implemented policies designed to reduce petroleum pollution. Much of what is known about the impacts of petroleum hydrocarbons comes from studies of catastrophic oil spills and chronic seeps. These two aspects of petroleum pollution (loading and impact) are distinct, and it is not possible to 1 The oil and gas industry, especially in the United States, often uses specific gravity instead of density. Specific gravity is used by the American Petroleum Institute (API) to classify various “weights” of oil. The density of a crude or refined product is thus measured as API gravity (ºAPI), which equals (141.5/specific gravity)—131.5.
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Oil in the Sea III: Inputs, Fates, and Effects TABLE 2-1 Processes That Move Petroleum Hydrocarbons Away from Point of Origin Input Type Persistence Evaporation Emulsification Dissolution Oxidation Horizontal Transport or Movement Vertical Transport or Movement Sedimentation Shoreline Stranding Tarballs Seeps years H M M M H M M H H Spills Gasoline days H NR M L L L NR NR NR Light Distillates days M L / L H L M H L L NR Crudes months M M M M M M M H M Heavy Distillates years L M L L H L H H H Produced water days M NR M M L L L L NR Vessel operational months M L M L M L L L M Two-stroke engines days H NR M L L L NR NR NR Atmospheric days H NR M M H NR / NR NR NR NR Land based U M L L L M M M NR U NOTE: H = high; L = low; M = moderate; NR = not relevant; U = unknown directly assess environmental damage from petroleum hydrocarbon mass loading rates. As discussed in Chapters 4 and 5 to a very large degree, loading rates reflect the intensity and location of societal use of petroleum, whereas effects tend to reflect the amount of toxic hydrocarbon compounds reaching a marine organism and the differing susceptibility of various organisms, populations, and ecosystems to the effects of these hydrocarbons. The reader is therefore strongly cautioned against inferring impacts from the mass loading rates. For instance, one might be tempted to calculate the “Exxon Valdez-equivalence” by comparing the quantity of petroleum released from a specific source to that released during the Exxon Valdez spill and then concluding that the impact of the petroleum release will be a corresponding multiple of the Exxon Valdez impact. This is a flawed analysis. Ecotoxicological responses are driven by the dose of petroleum hydrocarbons available to an organism, not the amount of petroleum released into the environment. Because of the complex environmental processes acting on the released petroleum, dose is rarely directly proportional to the amount released. In addition, one must consider the type of petroleum released and the susceptibility of the target organisms. Complex geochemical and pharmacokinetic models are required to translate petroleum release rates into environmental exposures. Even once these factors are accounted for, it is often difficult to reach consensus on the magnitude and duration of environmental effects (Box 2-1). The amount of petroleum made available to an organism through various environmental processes (whether for ingestion or absorption) is referred to as being biologically available, or simply “bioavailable.” Just as combustion during smoking makes nicotine in tobacco bioavailable to the smoker, physical, chemical, and even biological processes determine how bioavailable toxic compounds in oil and other petroleum products will be to marine organisms. It is understandable, therefore, that the release of equal amounts of the same substance at different times or locations may have dramatically different environmental impacts. Broadly speaking, the term “bioavailability” can therefore be used to describe the net result of physical, chemical, and biological processes that moderate the transport of hydrocarbon compounds from their release points to the target organisms. As the spill moves from the release point to the marine organism, these processes alter the chemical composition of the petroleum mixture, which in turn likely alters the toxicity by selectively enriching or depleting the toxic components (Bartha and Atlas, 1987). Physical weathering processes (Table 2-1) may encapsulate some or all of the petroleum in forms that are less available to organisms (e.g., tarballs). Various physiological and behavior processes moderate the movement of petroleum from the surrounding environment into marine organisms. Individual petroleum components pass into organisms at different rates, depending on their physical and chemical properties. Organisms respond to hydrocarbons in their surroundings and moderate or accentuate exposure. Incidental ingestion of oil by preening birds enhances exposure, while short-term cessation of filter feeding by bivalves in response to hydrocarbons in the water limits exposure. Once the hydrocarbons are in the organisms, there is a wide variation in the types and magnitudes of physiological responses. Many organisms readily metabolize and excrete hydrocarbons, although these pathways may create more toxic intermediates. In short, the processes of bioavailability, including petroleum fate and transport in the coastal ocean and disposition within marine organisms, are the most complex and least understood aspects of oil in the sea. Although there is a reasonable understanding of the amount of petroleum hydrocarbons released to the coastal ocean, and one can estimate the impact of spilled petroleum under previously studied conditions, generalizing these findings to predict hydrocarbon impacts from all sources on North American coastal waters is currently not possible.
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Oil in the Sea III: Inputs, Fates, and Effects BOX 2-1 Lessons from Exxon Valdez: Science in a Litigious Environment In addition to being the largest oil spill in U.S. waters, the Exxon Valdez Oil Spill (EVOS) has been a seminal event in the development of U.S. environmental policy. Efforts to ascertain the extent of the injury and the rate of recovery from the spill have been particularly divisive and opposing positions have been hotly debated. The relevant federal regulation (43 CFR 11.14) provides definitions of both injury and recovery, but does not specify how these are to be objectively measured. Thus, both the responsible party (Exxon) and the resource trustees (EVOS Trustee Council) developed different perspectives on how to define both injury and recovery, these differences reflecting very real differences in each group’s political, social, and financial objectives and responsibilities. These different perspectives and objectives led to differing technical and scientific approaches or methods for quantifying both the extent of the initial injury and the rate of recovery. These different approaches then led to different results and conflicting, and often incompatible, conclusions from two sets of studies. At the core of many disagreements centering on uncertainty in cause and effect were the questions of burden of proof and the application of the precautionary principle. In general, Exxon demanded a high level of proof to accept an injury, whereas the Trustees used a weight-of-evidence approach that accepted higher levels of uncertainty. Such situations are not uncommon in the world of science. Science is often divisive. In fact, the scientific method uses trial-and-error hypothesis testing and peer criticism to develop understanding in the form of a consensus opinion. Thus, scientific understanding is often best developed under a dynamic tension between consensus building and division. Litigation, however, offers a drastically different and somewhat incompatible set of rules. The purpose of litigation (from the latin litigāare, to dispute, quarrel, sue) is to resolve differences by determining which party has the stronger of two legal arguments. As in many instances where scientific or technical evidence forms the central tenant of either party’s argument, the dynamic tension between consensus building and division shifts perceptibly and inextricably toward division. Finding common ground in a litigious environment is not a priority, in fact it may even be considered to be antithetic to the purpose of litigation. Thus, while scientific and technical questions that arise within the litigious environment surrounding an event like EVOS may have broad implications for fundamental scientific understanding of the way systems respond to perturbations, the totality of the scientific effort expended during litigation cannot reasonably be expected to lead to a consensus opinion. This was recognized early on in the post-EVOS world, and a growing desire to inject new approaches or philosophies to facilitate cooperative approaches for developing natural resource damage assessments (NRDAs) began to emerge. Eventually, using authority granted under the Oil Pollution Act of 1990 (commonly referred to as OPA 90), NOAA instituted a new set of NRDA regulations that codified steps to develop cooperative assessment plans involving both the responsible party and the resource trustees. Under these regulations, responsible parties must be given the opportunity to participate in the damage assessment and, when appropriate, jointly conduct a coordinated and open damage assessment. The invitation to participate must be in writing and as early as practical, but no later than the completion of the preliminary assessment phase of the incident. There should be a formal agreement on how the cooperation is to be structured. The process should be open and all results available to the public. There are many benefits of cooperative assessments: cost savings because only one set of studies is being conducted; less potential for litigation because both sides are working with the same data and are more likely to reach common ground; and restoration can be accomplished more quickly because efforts can be shifted to designing restoration projects rather than preparing for litigation. Inherent in the cooperative process is trust. Each group has to trust the other to make a good faith effort to make the process succeed. Otherwise, there is the fear that cooperation will be abused: one side uses the knowledge gained in the process to build a better legal defense; studies are intentionally designed to provide data that are too weak for use in litigation; one side only pretends to be working cooperatively, or only agrees to cooperate on data collection and initial analysis, then the case changes to an uncooperative process for final negotiations and litigation, leaving the other side with a weaker case. Ongoing and future efforts to define the injury and recovery of the ecosystem in and around Prince William Sound due to EVOS will continue to raise important scientific questions and will contribute greatly to scientific understanding of the effect of releases of petroleum at a variety of scales. However, the development of a consensus opinion regarding the answers to these same questions most likely lies outside research efforts currently embroiled in the EVOS litigation. Understanding the Impacts of Spills and Other Releases Oil in the sea, whether from spills or chronic sources, is perceived as a major environmental problem. Occasional major oil spills receive considerable public attention because of the obvious attendant environmental damage, oil-coated shorelines, and dead or moribund wildlife, including, in particular, oiled seabirds and marine mammals (Box 2-2). These acute effects may be of short duration, or they may have long-term population- or community-level impacts depending on the circumstances of the spill and the numbers and types of organisms affected. Oil in the sea also occurs when small amounts are released over long periods of time, resulting in chronic exposure of organisms to oil and its component chemical compounds. Sources of chronic exposures include point sources, such as natural seeps, a leaking pipeline,
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Oil in the Sea III: Inputs, Fates, and Effects PHOTO 4 Each year since 1990, scientists studying shoreline recovery following the Exxon Valdez spill in Prince William Sound have taken photos of a prominent boulder, know commonly referred to as Mearns Rock. The photo series, available at http://response.restoration.noaa.gov/photos/mearns/mearns.html, demonstrates the complex changes that can take place year to year in the nature and abundance of marine organisms. (A) 1991 The entire boulder is covered with Fucus sp., a gold-brown algae. Notice the darker species of seaweed forming an apron around the base of the boulder. The beach area surrounding the boulder (the “beach face”) is also completely covered with other seaweed species. In the water behind the boulder, healthy eelgrass (Zostera marina) bed is visible. The boulder’s condition appears to be improving, shown by the heavier covering of seaweed. (B) 1993 Fucus now covers about 20 percent of the boulder’s surface. Large, older plants are gone apparently replaced by young plants. Mussels are growing on the front face of the boulder (black regions). (C) 1995 About half of the mussels have disappeared, leaving smaller dark regions on the right side of the boulder. Fucus is making a comeback on the left side and top surface of the boulder. Also visible is an apparent resurgence of algal growth on the beach face. The disappearance of the mussels may be the result of predation (perhaps by sea otters) or natural mortality. Regardless of whatever caused the boulder’s plant life to die back in 1993-94, the boulder now seems to be supporting new plant and animal life. (D) 1997 The boulder is once again covered (about 80 percent) with the seaweed Fucus. There are several age groups of Fucus on the boulder. Young Fucus is growing over the top section of the boulder and adult Fucus is growing around the mid-portion. The beach face is again rich with seaweed. No mussels are visible and the areas occupied by the barnacles have shrunk. Starfish and sea otters may have been preying on the mussels, and a predatory snail, Nucella, has likely been eating the barnacles.
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Oil in the Sea III: Inputs, Fates, and Effects (E) 2000 Mature Fucus now covers about 10 percent of the boulder’s surface. In addition, there is a heavy cover of a grayish, slimy seaweed (this could be any of three or four seaweed species that can look like this). The white areas on the beach face look to be large barnacle sets. Eelgrass is barely visible in the water. As in the 1993 photo, the mature Fucus plants are again dying back. However, at this time, there is no sign of a third new crop of young Fucus. (F) 2001 This year, the boulder has a 20-30 percent cover of Fucus. Older (brownish) plants are visible on the left section of the boulder and younger (greenish-brown) plants on the right. A whitish “bald” patch on the upper left is actually a patch of barnacles. Another bare-looking patch on the lower right corner contains barnacles (white) and small mussels (dark spots). A bright green algae, possibly “sea lettuce” (Ulva) droops down along the lower third of the rock face. Algae and barnacles also cover most of the cobble on the beach face. (Photo by Alan Mearns, courtesy of NOAA Office of Response and Restoration.) BOX 2-2 Environmental Sensitivity Index Mapping In 1979, as the oil from the Ixtoc II well blowout approached the U.S. coast, the Scientific Support Team from the Hazardous Materials Response Branch of the National Oceanic and Atmospheric Administration (NOAA) was advising the U.S. Coast Guard on protection priorities. The concept of ranking shorelines according to their oil spill sensitivity had recently been developed (Michel et al., 1978), and it was first applied in the days prior to oil landfall in south Texas. In 1980, the first Environmental Sensitivity Index (ESI) maps were produced for south Florida; by 1990, hardcopy ESI maps were available for most of the U.S. coastline. Since 1990, updated maps have been produced using Geographical Information System (GIS) technology, with both hard copy and digital products available. ESI maps and databases are comprised of three general types of information (Fig. 2-1; Halls et al., 1997): Shoreline Classification. The shoreline habitats are ranked according to a scale relating to sensitivity, natural persistence of oil, and ease of cleanup. A scale of 1 to 10 is used, with 1 being least sensitive and 10 the most sensitive. The classification system has been standardized nationwide, for estuaries, rivers, and lakes. The ranking scheme is based on extensive, empirical observations at oil spills, and it has become the basis for many spill response tools and strategies, such as protection prioritization, selection of response options, and determination of cleanup endpoints. Biological Resources. The maps display the spatial and temporal distributions of oil-sensitive animals, habitats, and rare plants that are used by oil-sensitive species or are themselves sensitive to oil spills. There are seven major biological groups (marine mammals, terrestrial mammals, birds, fish, invertebrates, reptiles and amphibians, and habitats and plants), which are further divided into groups of species with similar taxonomy, morphology, life history, and/or behavior relative to oil spill vulnerability and sensitivity. The maps show the locations of the highest concentrations, the most sensitive life-history stages or activities, and the most vulnerable and sensitive species. The maps link to data tables that include species name, legal status of each species (state and/ or federal threatened or endangered listing), concentration at that specific location, seasonal presence and/or abundance by month, and special life-history time periods (e.g., for birds, nesting, laying, hatching, and fledging dates). Human-Use Resources. The maps show four specific areas that have increased sensitivity and value because of their use: high-use recreational and shoreline access areas; management areas (e.g., marine sanctuaries and refuges); resource extraction locations (e.g., water intakes, subsistence areas); and archaeological, historical, and cultural resource locations. Sensitivity maps are used to identify protection priorities in vessel and facility response plans, and they are used in area contingency plans as part of the Sensitive Areas Annex. ESI maps use a standard set of colors and symbology so responders from any region can use the maps readily. The concept of sensitivity mapping has been adopted internationally as a key component of oil spill contingency planning (Baker et al., 1995). Sensitivity atlases have been produced for such diverse areas as Australia, Mauritius, South Africa, the Gaza Strip, the North Sea, most of Canada, and the Sakhalin Islands.
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Oil in the Sea III: Inputs, Fates, and Effects FIGURE 2-1 Environmental Sensitivity Index Map, with legend, for Provincetown Harbor, Cape Cod, Massachusetts (courtesy Research Planning, Inc.).
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Oil in the Sea III: Inputs, Fates, and Effects
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Oil in the Sea III: Inputs, Fates, and Effects production discharges, or a land-based facility. In these cases, there may be a strong gradient from high to low oil concentration as a function of distance from the source. In other cases, such as land-based runoff and atmospheric inputs, the origin of the oil is a non-point source, and environmental concentration gradients of oil compounds may be weak. Chronic exposures may also result from the incorporation of oil into sediments in which weathering of oil is slow and from which nearly fresh oil may be released to the water column over extended periods. In recent years, it is the long-term effects of acute and chronic oil contamination that have received increasing attention (Boesch et al., 1987) Petroleum Hydrocarbon Pollution and Its Possible Effects Petroleum hydrocarbon inputs into North American and worldwide marine waters were computed, based on various databases, for several major categories. Three activities— extraction, transportation, and consumption—are the main sources of anthropogenic petroleum hydrocarbon pollution in the sea. Each of these activities poses some risk of oil release, and as greater amounts of petroleum hydrocarbons are imported into North American waters, the risk increases. The categories are listed in Table 2-2. Details of the methods used, discussion of databases, and computation and distribution of sources are discussed in Appendixes C, D, E, F, G, H, and I. Table 2-2 and Figures 2-2A and 2-2B summarize the sources and inputs for North American and worldwide waters (see Chapter 3 for greater details). Table 2-3 summarizes conclusions about the intercomparability of the data, methods, and assumptions used develop these estimates with those reported by the NRC in 1985 and what significance if any, can be attached to changes in those estimates. The acute toxicity of petroleum hydrocarbons to marine organisms is dependent on the persistence and bioavailability of specific hydrocarbons. The ability of organisms to accumulate and metabolize various hydrocarbons, the fate of metabolized products, the interference of specific hydrocarbons (or metabolites) with normal metabolic processes that may alter an organism’s chances for survival and repro TABLE 2-2 Average, Annual Releases (1990-1999) of Petroleum by Source (in thousands of tonnes) North Americaa Worldwide Best Est. Regionsb Min. Max. Best Est. Min. Max. Natural Seeps 160 160 80 240 600 200 2000 Extraction of Petroleum 3.0 3.0 2.3 4.3 38 20 62 Platforms 0.16 0.15 0.15 0.18 0.86 0.29 1.4 Atmospheric deposition 0.12 0.12 0.07 0.45 1.3 0.38 2.6 Produced waters 2.7 2.7 2.1 3.7 36 19 58 Transportation of Petroleum 9.1 7.4 7.4 11 150 120 260 Pipeline spills 1.9 1.7 1.7 2.1 12 6.1 37 Tank vessel spills 5.3 4.0 4.0 6.4 100 93 130 Operational discharges (cargo washings) nac na na na 36 18 72 Coastal facility spills 1.9 1.7 1.7 2.2 4.9 2.4 15 Atmospheric deposition 0.01 0.01 traced 0.02 0.4 0.2 1 Consumption of Petroleum 84 83 19 2000 480 130 6000 Land-based (river and runoff) 54 54 2.6 1900 140 6.8 5000 Recreational marine vessel 5.6 5.6 2.2 9 nde nd nd Spills (non-tank vessels) 1.2 0.91 1.1 1.4 7.1 6.5 8.8 Operational discharges (vessels ≥100 GT) 0.10 0.10 0.03 0.30 270 90 810 Operational discharges (vessels<100 GT) 0.12 0.12 0.03 0.30 ndf nd nd Atmospheric deposition 21 21 9.1 81 52 23 200 Jettisoned aircraft fuel 1.5 1.5 1.0 4.4 7.5 5.0 22 Total 260 250 110 2300 1300 470 8300 aNumbers are reported to no more than two significant figures. b“Regions” refers to 17 zones or regions of North American waters for which estimates were prepared. These are discussed later in this chapter. cCargo washing is not allowed in U.S. waters, but is not restricted in international waters. Thus, it was assumed that this practice does not occur frequently in U.S. waters (see Chapter 3 and Appendix E). dEstimated loads of less than 10 tonnes per year reported as “trace.” eWorldwide populations of recreational vessels were not available (see Chapter 3 and Appendix F). fInsufficient data were available to develop estimates for this class of vessels (see Chapter 3 and Appendix E).
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Oil in the Sea III: Inputs, Fates, and Effects FIGURE 2-2 Relative contribution of average, annual releases (1990-1999) of petroleum hydrocarbons (in kilotonnes) from natural seeps and activities associated with the extraction, transportation, and consumption of crude oil or refined products to the marine environment. duction in the environment, and the narcotic effects of hydrocarbons on nerve transmission are major biological factors in determining the ecologic impact of any release. Weathering processes may alter oil composition and thus its toxicity (Burns et al., 2000; Neff et al., 2000). With weathering, there is a subsequent loss of monoaromatic compounds, and the polycyclic aromatic hydrocarbons become more important contributors to the toxicity of weathered oils. Other factors that may contribute to alterations in toxicity include photodegradation and photoactivation (Mallakin et al., 1999; Boese et al., 1999). Data gathered from several spills that occurred in the 1970s and 1980s demonstrated that the higher molecular weight aromatic compounds, such as the alkylated phenanthrenes and alkylated dibenzothiophenes, are among the most persistent compounds in both animal tissues and sediments (Capuzzo, 1987). Impairment of feeding mechanisms, growth rates, development rates, energetics, reproductive output, recruitment rates and increased susceptibility to disease and other histopathological disorders are some examples of the types of sublethal effects that may occur with exposure to petroleum hydrocarbons (Capuzzo, 1987). Early developmental stages can be especially vulnerable to hydrocarbon exposure, and recruitment failure in chronically contaminated habitats may be related to direct toxic effects of hydrocarbon-contaminated sediments (Krebs and Burns, 1977; Cabioch et al., 1980, Sanders et al., 1980; Elmgren et al., 1983). Marine birds and mammals may be especially vulnerable to oil spills if their habitats or prey become contaminated. In addition to acute effects such as high mortality, chronic, low-level exposures to hydrocarbons may affect survival and reproductive performance of seabirds and some marine mammals. Sublethal effects of oil on seabirds include reduced reproductive success and physiological impairment, including increased vulnerability to stress (reviewed in Hunt, 1987; Fry and Addiego, 1987, 1988; Briggs et al., 1996). In contrast, in marine mammals, sublethal exposure to petroleum hydrocarbons has been shown to cause minimal damage to pinnipeds and cetaceans (e.g., Geraci, 1990; St. Aubin, 1990), although sea otters appear to be more sensitive (Geraci and Williams, 1990; Monson et al., 2000). Oil can also indirectly affect the survival or reproductive success of marine birds and mammals by affecting the distribution, abundance, or availability of prey. Oil inputs from consumption activities vary widely in composition, persistence, loading rates by area and season, and effects. The single largest inputs of both petroleum hydrocarbons and PAH from this general source are land-based sources, which are composed of petroleum hydrocarbons that have already undergone considerable chemical and biological weathering during overland and riverine transport by the time they enter coastal waters. Further weathering rates will be slow. The hydrocarbons are mostly sorbed onto suspended sediments; thus their bioavailability is highly variable, depending on the feeding behavior of different organisms, sediment deposition patterns and rates, organic carbon content of the sediments, and the partitioning behavior of individual PAH. In contrast, although the input from the operation of recreational marine vessels in coastal waters is large, the bulk of the fuel is gasoline, which volatilizes from the surface water at rates that last on the order of several minutes to hours at 15ºC. The temporal and spatial discharge patterns are different from other sources, with most recreational boating being concentrated in the summer months and in coastal waters. Chronic contamination by petroleum hydrocarbons from sources other than oil spills may be found in many coastal urban areas as a result of non-point source petroleum spillage, the burning of fossil fuels, and municipal wastewater discharges. The persistence of some compounds such as PAH in sediments, especially in urban areas with multiple
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Oil in the Sea III: Inputs, Fates, and Effects FIGURE 2-13 Average, annual input (1990-1999) of petroleum hydrocarbons (kilotonnes) for Atlantic Seaboard of North America. (Additional data provided by EIA, EPA, USGS, and U.S. Coast Guard.)
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Oil in the Sea III: Inputs, Fates, and Effects TABLE 2-7 Average Annual Input (1990-1999) of Petroleum Hydrocarbons (tonnes) for the Gulf of Mexico and Puerto Rico ZONE (Coastal) F G H I Sum Seepsa na na na na Platforms traceb 90 ndc na Atmospheric trace trace ndc na Produced trace 590 trace na Sum Extraction trace 680 tracec nad Pipelines trace 890 trace trace Tank vessel 140 770 80 trace Coastal facilities 10 740 nde 130 Atmospheric trace trace trace trace Sum Transportation 160 2400 90 130 Land-based 1600 11000 1600 tracef Recreational vessels 770 770 ndg ndg Vessels >100GT (spills) 30 100 trace trace Vessel >100GT (op discharge) trace trace trace trace Vessel <100GT (op discharge) trace trace trace trace Atmospheric 60 90 100 50 Aircrafth na na na na Sum Consumption 2500 12000 1700 50 ZONE (Offshore) F G H I Sum Seeps 70000 70000 naa naa Platforms trace 50 61c na Atmospheric trace 60 40 na Produced trace 1700 130 na Sum Extraction trace 1800 231 nad Pipelines trace 60 ndi na Tank vessel 10 1500 ndi 490 Atmospheric trace trace trace trace Sum Transportation 10 1600 trace 490 Land-basedj na na na na Recreational vesselsk na na na na Vessels >100GT (spills) 70 120 trace 10 Vessel >100GT (op discharge) trace 25 trace trace Vessel <100GT (op discharge) trace trace trace trace Atmospheric 1600 1200 3600 70 Aircraft 80 80 20 20 Sum Consumption 1800 1400 3600 100 Grand Total 74000 91000 5600 790 Sum of Anthropogenic 4400 21000 5600 790 aNo known seeps in these regions bEstimated loads of less than 10 tonnes per year reported as “trace” cLack of precise locations for platforms in this zone precluded determining whether spills or other releases occurred less than 3 nmiles from shore (see Chapter 3 and Appendix D). Thus, all values for this zone reported as “offshore.” dNo known oil and gas production in this region eNo information on the existence of coastal facilities was available for this region (see Chapter 3 and Appendix G). fInsufficient water quality data exist to calculate input in this region, but existence of some urban landscape suggests it is a non-zero number (see Chapter 3 and Appendix I). gPopulations of recreational vessels were not available for these regions (see Chapter 3 and Appendix F) hPurposeful jettisoning of fuel not allowed within 3 nmiles of land (see Chapter 3 and Appendix E) iNo information on transportation-related spills was available for this region (see Chapter 3 and Appendixes D, E, and G) jLand-based inputs are defined in this study as being limited to the coastal zone (see Chapter 3 and Appendix I) kRecreational vessels are defined in this study as being limited to operations within 3 miles of the coast (see Chapter 3 and Appendix F)1 of magnitude, and the upper limit, if reasonable, would dominate all other inputs. This uncertainty reflects a variety of limitations, including a lack of adequate background data. To refine estimates associated with non-point sources, Federal agencies, especially EPA and the USGS, should work with state and local authorities to routinely collect and share data on the concentration of petroleum hydrocarbons in major river outflows and harbors in storm-and wastewater streams. The estimates presented here demonstrate the important role of air-sea exchange of hydrocarbons in (1) the persistence of petroleum hydrocarbons in surface waters and (2) the potential degradation of coastal air quality. These estimates are limited both by the lack of detailed field measurements of hydrocarbons in seawater and the coastal atmosphere under a variety of conditions and by the relatively poor knowledge of the fundamental physics of air-sea exchange. Directed research is needed that (1) conducts specific coupled field studies of air-sea interaction and (2) applies these studies to the modeling of petroleum hydrocarbon exchange at regional and global scales. On-going and growing investigations of air-sea exchange of carbon dioxide, conducted to better understand global climate change, provide a significant opportunity to improve the estimates of petroleum hydrocarbon exchange between the atmosphere and the surface ocean. During 1990-1999, spillage from vessels in U.S. waters was less than 40 percent of that during the prior decade, and it now represents less than 2 percent of the petroleum hydrocarbon inputs into North American waters. Significant reductions in spillage were also realized worldwide. Improvements in vessel operation and design and the introduction of related federal and international regulations contributed to this decline in oil spills. In U.S. marine waters, the largest spills come from vessels, followed by pipelines and facilities. Vessels have produced 109 spills of greater than 34 tonnes (10,000 gallons) in size since 1990, and these larger spills had an average size of about 400 tonnes. During the 1990s, tanker vessels were responsible for about 89 percent of the spillage from vessels. The comprehensive port control regime, administered by the U.S. Coast Guard, cooperative programs with ship owners and the boating community, and active participation of the International Maritime Organization in developing effective international regulatory standards have contributed to the decline in oil spills and operational discharges. These efforts and relationships should be continued and further strengthened where appropriate. Estimated operational discharges from vessels contribute very significant inputs. More than 99 percent of the estimated volume of operational discharge is related to non-compliance, because existing regulations restrict operational discharges of oil or limit them to not more than 15 ppm. The extent of non-compliance is difficult to assess, and therefore these estimates have a high level of uncertainty. Federal
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Oil in the Sea III: Inputs, Fates, and Effects FIGURE 2-14 Average, annual input (1990-1999) of petroleum hydrocarbons (kilotonnes) for the Gulf of Mexico and Puerto Rico. (Additional information provided by EIA, USGS, EPA, and McGraw Hill Higher Education.)
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Oil in the Sea III: Inputs, Fates, and Effects TABLE 2-8 Average Annual Input (1990-1999) of Petroleum Hydrocarbons (tonnes) for the Pacific Seaboard of North America (plus Hawaii) ZONE (Coastal) J K L M N O Sum Seepsa na na na na na na Platforms na traceb trace na na na Atmospheric na trace na na na na Produced na trace na na na na Sum Extraction nac trace trace nac nac nac Pipelines ndd 39 trace trace trace 0 Tank vessel nd 150 trace 10 trace 0 Coastal facilities trace 62 26 10 31 69 Atmospheric trace trace trace trace trace trace Sum Transportation trace 250 35 23 42 73 Land-based 860 1900 2300 1600 29 65 Recreational vessels nde 280 320 1600 36 nd Vessels >100GT (spills) ndf 28 trace 35 26 trace Vessel >100GT (op discharge) trace trace trace trace trace trace Vessel <100GT (op discharge) trace trace trace trace trace trace Atmospheric 420 14 44 120 150 280 Aircraftg na na na na na na Sum Consumption 1300 2200 2700 3400 240 350 ZONE (Offshore) J K L M N O Sum Seeps na 20000 na na na na Platforms na trace na na na na Atmospheric na trace na na na na Produced na 85 na na na na Sum Extraction nac 92 nac nac nac nac Pipelines ndh trace 0 0 0 0 Tank vessel trace 0 12 trace trace 0 Atmospheric trace trace trace trace trace trace Sum Transportation trace trace 12 trace trace trace Land-basedi na na na na na na Recreational vesselsj na na na na na na Vessels >100GT (spills) trace trace 16 13 87 52 Vessel >100GT (op discharge) trace trace trace trace trace trace Vessel <100GT (op discharge) trace trace trace trace trace trace Atmospheric 140 na 40 33 390 38 Aircraft 15 230 75 30 45 75 Sum Consumption 160 240 130 82 520 170 Grand Total 1500 23000 2800 3500 700 590 Sum of Anthropogenic 1500 2100 2800 2100 700 590 aNo known seeps in these regions bEstimated loads of less than 10 tonnes per year reported as “trace” cNo known oil and gas production in this region dNo information on transportation-related spills was available for this region (see Chapter 3 and Appendixes D, E, and G) ePopulations of recreational vessels were not available for these regions (see Chapter 3 and Appendix F) fInsufficient information on spills from cargo vessels was available for this region (see Chapter 3 and Appendix E) gPurposeful jettisoning of fuel not allowed within 3 nmiles of land (see Chapter 3 and Appendix E) hInsufficient information on spills from pipelines was available for this region (see Chapter 3 and Appendix E) iLand-based inputs are defined in this study as being limited to the coastal zone (see Chapter 3 and Appendix I) jRecreational vessels are defined in this study as being limited to operations within 3 nmiles of the coast (see Chapter 3 and Appendix F)
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Oil in the Sea III: Inputs, Fates, and Effects FIGURE 2-15 Average, annual input (1990-1999) of petroleum hydrocarbons (kilotonnes) for the Pacific Seaboard of North America (plus Hawaii). agencies, especially the U.S. Coast Guard, should work with the transportation industry to undertake a systematic assessment of the extent of noncompliance. If the estimates of noncompliance assumed in this report are essentially correct, more rigorous monitoring and enforcement policies should be developed and implemented. Gasoline and lube oil inputs from two-stroke recreational vessels are a large marine source of petroleum hydrocarbons. These discharges are primarily gasoline and lube oil, which have high evaporation rates and low PAH levels. However, these inputs frequently occur near ecologically sensitive areas (estuaries, mangroves) during vulnerable stages in the life cycle of organisms. Federal agencies, especially the EPA, should continue efforts to regulate and encourage the phase-out of inefficient two-stroke engines, and a coordinated enforcement policy should be established. Large quantities of VOC are discharged into the atmosphere from tank vessels and oil and gas operations. How
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Oil in the Sea III: Inputs, Fates, and Effects TABLE 2-9 Average Annual Input (1990-1999) of Petroleum Hydrocarbons (tonnes) for the Coastal and Territorial Waters of Alaska ZONE (Coastal) P Q Sum Seeps 400 tracea Platforms trace na Atmospheric trace na Produced 110 na Sum Extraction 120 nab Pipelines trace nac Tank vessel 20 trace Coastal facilities 30 10 Atmospheric trace trace Sum Transportation 60 20 Land-based 80 traced Recreational vessels 50 20 Vessels >100GT (spills) 70 trace Vessel >100GT (Op Discharge) trace trace Vessel <100GT (Op Discharge) trace trace Atmospheric 890 580 Aircrafte na na Sum Consumption 110 600 ZONE (Offshore) P Q Sum Seeps na na Platforms na na Atmospheric na na Produced na na Sum Extractionb na na Pipelinesc na na Tank vessel trace trace Atmospheric trace trace Sum Transportation trace trace Land-basedf na na Recreational vesselsg na na Vessels >100GT (spills) 30 50 Vessel >100GT (Op Discharge) trace trace Vessel <100GT (Op Discharge) trace trace Atmospheric 210 220 Aircraft 45 15 Sum Consumption 290 300 Grand Total 980 910 Sum of Anthropogenic 580 910 aEstimated loads of less than 10 tonnes per year reported as “trace” bNo known oil and gas production in this region (North Slope production is limited to terrestrial fields) cNo known coastal or offshore pipelines in this region (North Slope production is limited to terrestrial fields) dLoad in this region limited to petroleum hydrocarbons derived from eroded source rocks (see Chapter 3 and Appendix I) ePurposeful jettisoning of fuel not allowed within 3 nmiles of land (see Chapter 3 and Appendix E) fLand-based inputs are defined in this study as being limited to the coastal zone (see Chapter 3 and Appendix I) gRecreational vessels are defined in this study as being limited to operations within 3 nmiles of the coast (see Chapter 3 and Appendix F) ever, the VOC consist mostly of methane and ethane, which tend to oxidize rather than deposit in the oceans. These emissions may represent a “greenhouse gas” concern, but their atmospheric deposition into North American waters is less than 0.5 percent of all inputs, and inputs of VOC into the oceans worldwide are less than 4 percent of the estimated total. The U.S. Coast Guard should work with the International Maritime Organization to assess the overall impact on air quality of VOC from tank vessels and establish design and/or operational standards on VOC emissions where appropriate. On the basis of limited data, aircraft inputs from deliberate dumping of jet fuel in the sea appear to be locally significant. Federal agencies, especially the Federal Aeronautics Administration (FAA), should work with industry to more rigorously determine the amount of fuel dumping by aircraft and to formulate appropriate actions to limit this potential threat to the marine environment. Fates The effect of petroleum hydrocarbon is not directly related to the volume released. It is instead a complex function of the rate of release, the nature of the released hydrocarbon, and the local physical and biological ecosystem. Some progress has been made in understanding the basic processes affecting fates such as evaporation. Much more needs to be learned about oil-sediment interaction, vertical dispersion and entrainment, dissolution, Langmuir cells, and hydrate formation (as related to deep subsurface releases of gas). Furthermore, the priorities for research into petroleum hydrocarbon fate and transport have historically been driven by large spills. Thus, resource allocation to support these efforts tends to wane in periods during which a large spill has not recently occurred. Federal agencies, especially NOAA, MMS, the U.S. Coast Guard, and the USGS, should work with industry to develop and support a systematic and sustained research effort to further basic understanding of the processes that govern the fate and transport of petroleum hydrocarbons released into the marine environment from a variety of sources (not just spills). Response plans depend heavily on site-specific modeling predictions of the behavior of spills of various sizes and types, under a variety of environmental conditions. There is a need for both better baseline data, including ambient background levels of hydrocarbons in the sea, and better data for calibrating fate and behavior models. Because experimental release of petroleum is not feasible under most circumstances, comprehensive data on the fate of the oil must be collected during spills. Such efforts are generally neglected, because moving needed equipment and personnel to spill sites to collect data is of lower priority than containing the spill and minimizing damage to the environment and property. Federal agencies, especially the U.S. Coast Guard,
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Oil in the Sea III: Inputs, Fates, and Effects FIGURE 2-16 Average, annual input (1990-1999) of petroleum hydrocarbons (kilotonnes) for the coastal and territorial waters of Alaska. (Additional information provided by Alaska GIS Data Clearinghouse, Alaska Department of Natural Resources Division of Oil and Gas, EIA, EPA, and the U.S. Bureau of Land Management, Alaska.)
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Oil in the Sea III: Inputs, Fates, and Effects PHOTO 5 The brightest areas of the Earth are the most urbanized, but not necessarily the most populated. (Compare western Europe with China and India.) Cities tend to grow along coastlines and transportation networks. (Image courtesy of NASA.) NOAA, and EPA should work with industry to develop a more comprehensive database of environmental information and ambient hydrocarbon levels, and should develop and implement a rapid response system to collect in situ information about spill behavior and impacts. Natural seep systems and sites of historical spills offer good opportunities for field studies of the fate and effect of the release of crude oil and (in the case of spills) refined products, especially to understand dissolution and long-term weathering. Federal agencies, especially the USGS, NOAA, EPA, and MMS, should develop and support targeted research into the fate and behavior of hydrocarbons released to the environment naturally through seeps or past spills. Effects Ecosystems and their components vary at time scales ranging from seasons to decades and longer. Therefore, in the absence of ongoing monitoring, it is exceedingly difficult to quantify the effects of oil in the sea, or to establish when recovery from a pollution event is complete. The establishment of monitoring programs in selected regions with an elevated risk of petroleum spills or discharges would enhance the ability to determine effects and recovery and to understand the processes controlling ecosystem responses to pollution. Existing databases on the distribution, frequency, and size of petroleum spills and existing petroleum distribution routes could be used to identify locations most appropriate for monitoring. Federal agencies, especially the USGS and EPA, should work with state and local authorities to establish or expand efforts to monitor vulnerable components of ecosystems likely to be exposed to petroleum releases. The inputs and long-term fate of land-based sources (due both to runoff and to atmospheric deposition) are poorly understood. The range of uncertainty of land-based runoff of petroleum hydrocarbons is four orders of magnitude. The upper limit, if correct, would dwarf all other inputs. The loads from rivers and air inputs are not being monitored consistently, and the background inputs from rivers are virtually unknown. To assess the impacts attributable to different sources including oil spills and non-point sources, federal agencies, especially the USGS and EPA should work with state and local authorities to undertake regular monitoring of Total Petroleum Hydrocarbon (TPH) and PAH inputs from air and water (especially rivers and harbors) to determine background concentrations. There are demonstrable effects of acute oiling events at both small and large spatial scales. These effects result from physical fouling of organisms and physiological responses to the toxic components of oil. Although there is now considerable information on the toxicological effects of individual components of oil, there is a lack of information about the synergistic interactions in organisms between hydrocarbons and other classes of pollutants. This problem is particu
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Oil in the Sea III: Inputs, Fates, and Effects larly acute in areas subject to chronic pollution, (e.g., urban runoff). Research on the cumulative effects of multiple types of hydrocarbons in combination with other types of pollutants is needed to assess toxicity and organism response under conditions experienced by organisms in polluted coastal zones. Federal agencies, especially the USGS, MMS, NOAA, and EPA, should work with industry to develop or expand research efforts to understand the cumulative effects on marine organisms. Furthermore, such research efforts should also address the fates and effects of those fractions that are known or suspected to be toxic in geographic regions where their rate of input is high. There are demonstrable sublethal physiological effects of long-term, chronic releases of hydrocarbons into the marine environment. These have been found in areas affected by urban runoff, in areas where oil has been incorporated in sediments and then released back to the water column, and in production fields. Chronic sources of hydrocarbon pollution remain a concern, and their effects on populations and ecosystems require further assessment. Federal agencies, especially the USGS, EPA, and NOAA, should work with state and local authorities and industry to implement comprehensive laboratory and field based investigations of the impact of chronic releases of petroleum hydrocarbons. Biogenically structured habitats, such as coastal marshes and mangrove forests, are subject to destruction or alteration by acute oiling events. Because the structure of these habitats depends on living organisms, when they are killed, the structure of the habitat, and sometimes the substrate on which it grows, is lost. Depending on the severity of oiling, and particularly if oil is incorporated in the sediments or structure of the habitat, recovery of the habitat and the organisms dependent on it may be exceptionally slow. In areas of sensitive environments or at-risk organisms, federal, state, and local entities responsible for contingency plans should develop mechanisms for higher levels of prevention, such as avoidance, improved vessel tracking systems, escort tugs, and technology for tanker safety. Although there is now good evidence of the toxic effects of oil pollution on individual organisms and on the species composition of communities, there is little information on the effects of either acute or chronic oil pollution on populations or on the function of communities or ecosystems. The lack of understanding of population-level effects lies partly in the fact that the structure of populations of most marine organisms is poorly known because of the open nature of communities and the flow of recruits between regions. Also, in some populations (e.g., bony fish) the relationships between numbers of juveniles produced and recruitment to the spawning adult population are unknown. The U.S. Departments of Interior and Commerce should identify an agency, or combination of agencies, to develop priorities for continued research on the following: the structure of populations of marine organisms and the spatial extent of the regions from which recruitment occurs; the potential for cascades of effects when local populations of organisms that are key in structuring a community are removed by oiling; and the basic population biology of marine organisms, which may lead to breakthroughs in understanding the relationship between sublethal effects, individual mortality and population consequences. There is a tremendous need for timely dissemination of information across state, federal, and international boundaries about the environmental effects of oil in the sea. Although the United States has experience that might benefit the international community, this nation might benefit greatly from lessons learned in other countries with offshore oil production, heavy transportation usage, and diffuse inputs of petroleum from land- and air-based sources. Therefore, the federal agencies identified above, in collaboration with similar international institutions, should develop mechanisms to facilitate the transfer of information and experience.
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Oil in the Sea III: Inputs, Fates, and Effects II. Understanding Inputs, Fates, and Effects in Detail
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