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Oil in the Sea III: Inputs, Fates, and Effects 1 Introduction In August of 1859, Colonel Drake drilled a well to a depth of 70 feet in Titusville, Pennsylvania, and discovered oil— an event that has changed the world. During the late 1800s, a number of small wells were drilled in Pennsylvania, Kentucky, and California, but the well that is generally credited with giving “birth to the modern oil industry” was the discovery at Spindletop in 1901 atop a salt dome near Beaumont, Texas (Knowles, 1983). From that time on, the nation’s, and indeed the world’s, demand for fossil fuel has continuously increased. Petroleum hydrocarbon extraction, transportation (pre- and post-refining), refining, and consumption by industry and the public account for a high percentage of the U.S. economy. Oil and natural gas are the dominant fuels in the U.S. economy, providing 62 percent of the nation’s energy and almost 100 percent of its transportation fuels (National Energy Policy Development Group, 2001). Similar trends are also present in many other nations. Expanding global economies, population increases, and a worldwide improvement in the standard of living have resulted in this increasing quest for fossil fuel. By the year 2020, the United States will need about 50 percent more natural gas and one-third more oil to meet the energy demands of a growing population (National Energy Policy Development Group, 2001). (While this trend is expected to continue in future years, it is subject to change based on future world geopolitical developments.) Liquid petroleum is the nation’s largest source of primary energy, accounting for approximately 40 percent of U.S. energy needs. In transportation alone the United States consumed an average of 19.5 million barrels (2.8 million tonnes1) of oil every day in 2000, compared to 9.8 million barrels per day (mb/d; 1.4 million tonnes per day; mt/d) in 1960; transportation fuels account for approximately 66 percent, the industrial sector accounts for 25 percent, and residential and commercial uses represent most of the remainder (National Energy Policy Development Group, 2001). Energy intensity, the amount of energy it takes to produce a dollar of gross domestic product (GDP), has declined steadily in the United States over the last 30 years. This decline is due to improvements in energy efficiency, as well as a shift from manufacturing to services. However, the rise in GDP has outpaced the declining energy intensity, resulting in an overall increase in energy consumption. Such widespread use, however, of any substance will inevitably lead to accidental and intentional releases. Liquid petroleum, whether crude oil or refined products such as tar, lubricating oil, gasoline, or kerosene, possesses many properties and contains many individual toxic compounds that can make such releases harmful to the environment. Thoughtful decisionmaking about the extent of petroleum extraction and use must therefore include a thorough understanding of the potential nature, location, and frequency of releases and the ecological risk they pose the environment. ENERGY NEEDS OF THE NATION Nearly 30 years have passed since the Arab oil embargo disrupted the U.S. oil supply, and at the time of the embargo, domestic oil production was in the middle of a 7-year decline (Riva, 1995). Our nation’s prosperity and way of life are sustained by energy use. Estimates indicate that over the next 20 years, U.S. oil consumption will increase by 33 percent, natural gas consumption by well over 50 percent, and the demand for electricity by 45 percent (National Energy Policy Development Group, 2001). Major reasons for this increased demand for energy have been a growing population and heavy increases in fuel for transportation. Table 1-1 shows the consumption of petroleum by end-use sector for 1973-1999. Whereas residential, commercial, and electric 1 On average, 42 U.S. gallons equal 1 barrel, and seven barrels equal roughly one metric ton (tonne) of crude oil. U.S. production and consumption figures are often discussed in barrels and gallons rather than in tonnes; thus, the text in this chapter makes use of all three units as appropriate.
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Oil in the Sea III: Inputs, Fates, and Effects TABLE 1-1 Consumption of Petroleum by End-Use Sector, 1973-1999 (quadrillion Btu) Year Transportation Percentage Residential & Commercial Percentage Industrial Percentage Electric Utilities Percentage Total 1973 17.83 51.2 4.39 12.6 9.1 26.1 3.52 10.1 34.84 1974 17.4 52.0 4 12.0 8.69 26.0 3.37 10.1 33.46 1975 17.61 53.8 3.81 11.6 8.15 24.9 3.17 9.7 32.74 1976 18.51 52.6 4.18 11.9 9.01 25.6 3.48 9.9 35.18 1977 19.24 51.8 4.21 11.3 9.77 26.3 3.9 10.5 37.12 1978 20.04 52.8 4.07 10.7 9.87 26.0 3.99 10.5 37.97 1979 19.83 53.4 3.45 9.3 10.57 28.5 3.28 8.8 37.13 1980 19.01 55.6 3.04 8.9 9.53 27.9 2.63 7.7 34.21 1981 18.81 58.9 2.63 8.2 8.29 26.0 2.2 6.9 31.93 1982 18.42 60.9 2.45 8.1 7.79 25.8 1.57 5.2 30.23 1983 18.59 61.9 2.5 8.3 7.42 24.7 1.54 5.1 30.05 1984 19.22 61.9 2.54 8.2 8.01 25.8 1.29 4.2 31.06 1985 19.5 63.1 2.52 8.2 7.81 25.3 1.09 3.5 30.92 1986 20.27 63.0 2.56 8.0 7.92 24.6 1.45 4.5 32.2 1987 20.87 63.5 2.59 7.9 8.15 24.8 1.26 3.8 32.87 1988 21.63 63.2 2.6 7.6 8.43 24.6 1.56 4.6 34.22 1989 21.87 63.9 2.53 7.4 8.13 23.8 1.69 4.9 34.22 1990 21.81 65.0 2.17 6.5 8.32 24.8 1.25 3.7 33.55 1991 21.46 65.3 2.15 6.5 8.06 24.5 1.18 3.6 32.85 1992 21.81 65.0 2.13 6.4 8.64 25.8 0.95 2.8 33.53 1993 22.2 65.6 2.14 6.3 8.45 25.0 1.05 3.1 33.84 1994 22.76 65.6 2.09 6.0 8.85 25.5 0.97 2.8 34.67 1995 23.2 67.1 2.08 6.0 8.62 24.9 0.66 1.9 34.56 1996 23.74 66.4 2.2 6.2 9.1 25.4 0.73 2.0 35.77 1997 24 66.2 2.14 5.9 9.31 25.7 0.82 2.3 36.27 1988 24.64 66.7 1.97 5.3 9.15 24.8 1.17 3.2 36.93 1999 25.21 66.9 2.07 5.5 9.45 25.1 0.97 2.6 37.7 SOURCE: U.S. Department of Energy, Energy Information Administration, Monthly Energy Review, March 2000, pp. 27, 29, 31, 33. utilities consumption has decreased, and industrial consumption has remained nearly constant, consumption by transportation has increased substantially. The U.S. population has increased from 180.7 million to 272.7 million in the past 40 years, an increase of 92 million people. Figure 1-1 illustrates U.S. oil production and consumption for 1960 through 1997 (Davis, 2000). Consumption increased from 9.8 mb/d (1.4 mt/d) in 1960 to 18.6 (2.8 mt/d) mb/d in 1997, an increase of 8.8 mb/d, and it has continued to increase during the past decade. U.S. oil production, however, has remained rather constant and since 1985 has been declining (Figure 1-1). As a result, U.S. consumption is presently nearly three times U.S. production. Figures 1-2 and 1-3 illustrate projections of consumption and production of oil and natural gas in the United States for the next 20 years (National Energy Policy Development Group, 2001). Note that oil consumption will exceed production by 19 mb/d (2.7 mt/d) in the year 2020, and natural gas consumption will exceed production by 13.5 trillion cubic feet in the same time. Today, the United States produces 39 percent less oil than it did in 1970, leaving us ever more reliant on foreign suppliers. As consumption increases and production decreases, net imports will have to increase to meet this demand (Figure 1-4). The United States has been a net importer of oil since the 1950s, and today oil accounts for 89 percent of net U.S. energy imports (National Energy Policy Development Group, 2001). If the projections of oil consumption are correct, the United States will have to import nearly 20 mb/d (2.9 mt/d) by the year 2020—double its current amount. WORLD ENERGY NEEDS AND RESOURCE AVAILABILITY As the population of the world increases and developing nations become more industrialized, the demand for energy will increase. Oil is currently the dominant energy fuel and is expected to remain so over the next several decades (see Figure 1-5). There is general agreement that the availability of oil will not be a significant constraint on oil demand through 2020, because the reserve-to-production ratio for Persian Gulf producers currently exceeds 85 years. Worldwide petroleum consumption is projected to increase by 44.7 mb/d (6.4 mt/d), from 74.9 mb/d (10.7 mt/d) in 1999 to 119.6
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Oil in the Sea III: Inputs, Fates, and Effects FIGURE 1-1 Worldwide petroleum production and consumption 1960-1997 (data from Davis, 2000). FIGURE 1-2 Projected oil field U.S. production (millions of barrels per day) at 1990-2000 growth rates (Energy Information Administration, 2000; National Energy Policy Group, 2001). FIGURE 1-3 Projected natural gas U.S. production (trillion cubic feet) at 1990-2000 growth rates (Energy Information Administration, 2000; National Energy Policy Group, 2001). mb/d (17 mt/d) in 2020. The annual rate of growth is projected at 2.3 percent, as compared to a growth rate of 1.6 percent per year from 1970 to 1999. Historically, the industrialized nations have been the major consumers of oil (see Figure 1-6). However, by the year 2020, consumption in the developing countries is expected to be nearly equal to that of the industrialized countries. The largest growth in oil demand over the next two decades is projected for the developing countries of Asia. In particular, from 1999 to 2020 the oil demands of China and India are projected to increase by 6.1 mb/d (0.9 mt/d) and 3.9 mb/d (0.6 mt/d), respectively. The majority of this expected in
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Oil in the Sea III: Inputs, Fates, and Effects FIGURE 1-4 Comparison of historical trends (millions of barrels per day) in U.S. consumption and importation of oil (National Energy Policy Group, 2001). crease is related to the transportation sector and more specifically, to motor vehicles. Significant increases in land-based runoff of petroleum hydrocarbons can be expected as a by-product of this increased consumption. To meet the increased demand, an increase in world oil supply of roughly 45 mb/d (6.4 mt/d) is projected for the next two decades. It is expected that Organization of the Petroleum Exporting Countries (OPEC) producers will be responsible for more than two-thirds of this increase. Imports into industrialized countries are therefore expected to increase from 34.0 to 43.7 mb/d (4.9 to 6.2 mt/d), and imports into developing countries from 19.3 mb/d to 42.8 mb/d (2.8 to 6 mt/d). Much of these imports will move by sea. Major importers and exporters are shown in Figure 1-7. Increased imports into China and Pacific Rim countries will come largely from the Persian Gulf. North American imports are projected to increase from 11.0 mb/d (1.57 mt/d) in 1998 to about 18.0 mb/d (2.6 mt/d) in 2020. More than half PHOTO 1 The Genesis Spar, located in the Green Canyon 205 Field about 150 miles south of New Orleans, is typical of the new technology allowing oil and gas development in deep waters of the Gulf of Mexico. (The original discovery well was drilled in 1988 in 2600 feet of water.) The Genesis Development Project is a joint venture development between ChevronTexaco Production Company, Exxon Company USA, and PetroFina Delaware, Inc. (Photo courtesy of Environmental Research Consulting.) of the North American imports are expected to come from the Atlantic Basin, principally Latin American and West African producers. Imports into North America from the Persian Gulf are expected to double, from 2.2 to 4.2 mb/d (0.3 to 0.6 mt/d). It is apparent that greater and greater amounts of oil will be transported by vessel, refineries will have to increase capacity, and more coastal petroleum handling facilities will be needed. These have the potential to increase the input of hydrocarbons into the oceans. However, the operational and accidental discharge of oil from vessels and platforms has declined substantially over the past three decades, and it is reasonable to expect continued improvements in these areas in future years as the benefits from recently enacted regulations and improved operational practices are fully realized. The expected growth in worldwide consumption, with much of the increase concentrated in the transportation sector, is of concern. Land-based runoff of petroleum hydrocarbons can
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Oil in the Sea III: Inputs, Fates, and Effects FIGURE 1-5 Worldwide energy consumption by fuel type, 1970-2020 (Energy Information Administration, 1999). FIGURE 1-6 Worldwide consumption by region, 1970-2020 (Energy Information Administration, 1999). be expected to increase with consumption unless steps are taken to reduce the release of petroleum from consumption-related activities. EXXON VALDEZ AS SEMINAL MOMENT On March 24, 1989, the tanker Exxon Valdez, en route from Valdez, Alaska, to Los Angeles, California, ran aground on Bligh Reef in Prince William Sound, Alaska. The vessel was traveling outside normal shipping lanes in an attempt to avoid ice. Within six hours of the grounding, the Exxon Valdez spilled approximately 10.9 million gallons (37 kilotonnes) of its 53 million gallon cargo (156 kilotonnes) of North Slope Crude oil. The oil would eventually impact more than 1,100 miles (2400 km) of noncontinuous coastline in Alaska, making it the largest oil spill to date in U.S. waters. The biological consequences of the Exxon Valdez oil spill (EVOS) have been well studied, resulting in significant insights and raising important questions about lethal and sublethal impacts of oil exposure (Box 1-1). The scientific controversies arising from work carried out in and around Prince William Sound have important implications for understanding effects from the release of oil at a variety of scales. Thus, while resolving specific controversies centered around EVOS is clearly beyond the scope of the study, they are discussed in terms of their broader implications throughout this report, but especially in Chapters 2 and 5. The response to the Exxon Valdez involved more personnel and equipment over a longer period of time than any other accidental spill in U.S. history. At the height of the response, more than 11,000 personnel, 1,400 vessels, and 85 aircraft were involved in the cleanup. Shoreline cleanup began in April of 1989 and continued until September of 1989 for the first year of the response. The effort continued in 1990 and 1991 with cleanup in the summer months and limited shoreline monitoring in the winter. Monitoring of fate and effects by state and federal agencies continues. Beyond the ecological damage, the Exxon Valdez disaster caused fundamental changes in the way the U.S. public thought about oil, the oil industry, and the transport of petroleum products by tankers. Despite continued heavy use of fossil fuels in nearly every facet of our society, “big oil” was suddenly seen as a necessary evil, something to be feared and mistrusted. The reaction was swift and significant. PREVIOUS STUDIES The extraction, transportation, and consumption of petroleum hydrocarbons increased significantly with the expansion of modern ground and air transportation systems and the need for industrial and public power generation. Early in the twentieth century, greater attention was paid simply to the demand for more oil than to the environmental consequences of the potential pollution problems associated with its extraction, transportation, and consumption. Because little was known about petroleum hydrocarbon inputs to the marine environment, a workshop was convened in 1973 to evaluate this aspect of marine pollution. It led to the publication in 1975 of a National Research Council (NRC) report entitled Petroleum in the Marine Environment. That report, using the best data available at the time, discussed petroleum hydrocarbon inputs, analytical methods, fates, and effects of oil discharged to the marine environment. The report gener
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Oil in the Sea III: Inputs, Fates, and Effects FIGURE 1-7 Worldwide sea borne flow of oil in 2000 (modified from Newton, 2002; other information sources include U.S. Geological Survey, U.S. Coast Guard, Minerals Management Service). Solid black dots indicate spills included in the average, annual (1990-1999) estimates discussed in this report.
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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 BOX 1-1 T/V Exxon Valdez, Alaska The T/V Exxon Valdez grounded on Bligh Reef in Prince William Sound, Alaska on March, 24 1989, releasing an estimated 36,000 tonnes (10.9 million gallons) of Alaska North Slope crude oil (API [American Petroleum Institute] gravity = 29.8). Wolfe et al. (1994) estimated that, as of 1991, 41 percent of the oil stranded on intertidal habitats in Prince William Sound. About 25 percent was transported out of the sound, stranding mostly along the Kenai Peninsula, lower Cook Inlet, and the Kodiak Archipelago. More than 2,000 km of shoreline were oiled, reflecting the persistence of the spilled oil and the influence of a spring gale and a major coastal current on the transport of a large volume of oil. The extent and degree of shoreline oiling resulted in the most intensive shoreline cleanup effort ever attempted. Large volumes of water heated to 140ºF were used to flush oil from almost 30 percent of the rocky shores and gravel beaches in Prince William Sound. Despite the aggressive cleanup, oil residues persisted for more than 13 years in more sheltered habitats and porous gravel beaches. Monitoring studies have shown that intensive treatment resulted in delayed recovery of rocky shore intertidal communities (NOAA, 1997). These studies demonstrate how too-aggressive cleanup, in some instances, can slow recovery of these affected communities. No doubt, the Exxon Valdez was a large spill that affected many valuable resources. Large numbers of animals were estimated to have been killed directly, including 900 bald eagles (Bowman, 1993), about 250,000 seabirds (Piatt and Ford, 1996), 2,800 sea otters (Garrott et al., 1993; Bodkin et al., 2001), and 300 harbor seals (Frost et al., 1994a). Both the Exxon Valdez Oil Spill Trustee Council and Exxon conducted numerous studies to assess the impacts of the spill, and Exxon paid the state and local governments $900 million for natural resource damages. Never before have so much effort and money been spent on trying to determine the extent of negative effects and the course of recovery. Yet the interpretations of the studies conducted by the trustees and Exxon varied significantly, particularly concerning sublethal and long-term impacts. There were issues with the scale and power of the studies, interpretations of uncertainty, the role of natural changes in gauging recovery, and even the source of the background hydrocarbons in Prince William Sound. The trustees’ results showed enhanced mortality to pink salmon larvae hatching in oiled gravel beds that affected their productivity and survival (Heintz et al., 1999, 2000). Exxon studies showed equal survival of eggs collected from oiled and unoiled streams (Brannon et al., 1995). Carls et al. (1999) concluded that oil exposure contributed to disease induction that caused a collapse in Pacific herring five years after the spill, although other factors could have played a role. Black oystercatchers and harlequin ducks from oiled areas of western PWS were thought to have significant declines in abundance and productivity for at least four years post-spill for oystercatchers (Klosiewski and Laing, 1994; Andres, 1997) and eight years for harlequin ducks (Esler et al., 2000c) when compared to populations from unoiled eastern PWS, although the number of breeding pairs studied was very small. However, laboratory analyses reported by Boehm et al. (1996) concluded that the body burden for individuals in the PWS duck populations were 1-3 orders of magnitude lower than that shown to cause demonstrable effects in mallards. The Exxon Valdez oil spill changed much about what is now done to prevent such spills, to be better prepared for response, and to select shoreline cleanup methods, as well as to understand the acute and long-term impacts of oil on a wide range of species, communities, and habitats. ated considerable interest and was used as a primary source of information by industry, government agencies, scientists, and the general public. By the mid-1980s, it was realized that an update to this important document was needed, and the U.S. Coast Guard requested that the Ocean Sciences Board of the National Research Council (later the Board on Ocean Science and Policy [BOSP] and now the Ocean Studies Board [OSB]) undertake a new examination of this subject. The BOSP appointed a steering committee consisting of six members from academia, government service, and industry to be responsible for updating the 1975 NRC report. A public meeting was held in 1980, at which representatives from the oil industry, universities, government, and environmental groups were invited to make presentations on topics important to the committee. In early 1981, 46 expert contributors were invited to prepare summary papers on all aspects of petroleum in the world’s oceans, and later in 1981, an international workshop was held to discuss the main issues of petroleum hydrocarbon inputs into the marine environment. In early 1982, the steering committee began preparing the new report, which was published in 1985. The report Oil in the Sea: Inputs, Fates, and Effects (NRC, 1985) generally followed the same format as the 1975 report but was much more detailed and contained significant new data and information that had been acquired since the earlier report. The 1985 report has served as a seminal publication that documented petroleum hydrocarbon discharge into the marine environment and the fates and effects of this discharge. Prior to and since the 1985 NRC report Oil in the Sea, there have been a series of studies undertaken to examine the load of petroleum hydrocarbons to the marine environment. The majority of studies has focused on quantifying the volume from tanker spills, and many have been conducted under the auspices of the International Maritime Organization (IMO) or its Joint Group of Experts on the Scientific Aspects of Marine Pollution (GESAMP). One of the most recent GESAMP reports, Impact of Oil and Related Chemicals
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Oil in the Sea III: Inputs, Fates, and Effects PHOTO 2 MODIS (or Moderate Resolution Imaging Spectroradiometer) satellite imagery (250 m resolution) of southern Alaska, including Cook Inlet (on the left), Prince William Sound (center) and the Copper River delta (on the right). The Exxon Valdez ran aground on Bligh Reef in northeastern Prince William Sound on March 24, 1989, eventually releasing 10.9 million gallons of crude oil. (Image courtesy of NASA.) and Wastes on the Marine Environment (GESAMP, 1993), summarizes studies completed prior to 1993.2Table 1-2 was compiled from that report and summarizes estimates of the release of crude oil and refined petroleum products through 1985. Limitations to Examining Historical Estimates In addition to the NRC studies discussed above, the 1993 GESAMP report specifically discusses an 1990 update of volumes from maritime operations reported in the 1985 NRC report. The numbers given in the 1993 GESAMP report and listed in Table 1-3 are not official or reviewed estimates, but are based on discussions held at an NRC planning workshop in 1990. Despite the absense of any analysis to determine how changes in data and methods might bring about changes in overall estimates, GESAMP (1993) attributed the reduction from 1.47 million tonnes in 1981 to 0.54 million tonnes to the entry into force of the International Convention for the Prevention of Pollution from Ships (MARPOL 73/78). This analysis points out a significant obstacle that one encounters when trying to draw long-term conclusions about relative changes in estimates from various sources of petroleum to the sea. Lack of rigorous review or thorough documentation of the methods used in each analysis makes comparisons among various studies almost meaningless. SCOPE OF CURRENT STUDY In the fall of 1997, representatives of the U.S. Minerals Management Service approached the Ocean Studies Board of the National Research Council (NRC) about officially updating the 1985 NRC report Oil in the Sea. After numerous discussions, it was agreed that the primary function of the new study would be not only to develop new estimates for the load of petroleum hydrocarbons to the sea, but also to develop and widely disseminate the methods and sources of data used to derive those estimates. Furthermore, because of the greater availability of data for North American waters, the NRC was asked to evaluate spatial and temporal trends in the release of petroleum hydrocarbons to those waters. Finally, the NRC was asked to review the tremendous number of studies on the fate and effect of petroleum in the marine environment that had been published since the release of Oil in the Sea (NRC, 1985) in an effort to drawn some conclusions about the relative threats to the marine environment posed by various sources. (It was agreed early on that inclusion of an examination of potential effects on human 2 GESAMP is currently attempting to examine the impact of entry into force of MARPOL 73/78 (The International Convention for the Prevention of Pollution from Ships) on tanker spills worldwide. That report is expected to be released in 2002.
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Oil in the Sea III: Inputs, Fates, and Effects TABLE 1-2 Worldwide Estimates of Total Petroleum Input to the Sea Summary of Inputs (thousand tonnes × 1000) NRC, 1975 Kornberg, 1981 Baker, 1983 NRC, 1985 Natural seeps 600 600 300 (50-500) 200 (20-2,000) Extraction of petroleum 80 60 50 (40-70) 50 (40-60) Transportation of petroleum 1,580 1,110 1,150 1,250 Pipeline spillsa Spills (tank vessels) 300 300 390 (160-640) 400 (300-400) Operational discharges (cargo washings) 1,080 600 710 (440-14,500) 700 (400-1,500) Coastal facility spills 200 60 100 (60-6,000) Other coastal effluents 150 50 (30-80) 50 (50-200) Consumption of petroleum 3,850 2,900 1,770 1,700 Urban runoff and discharges 2,500 2,100 1,430 (700-2,800) 1,080 (500-2,500) Losses from non-tanker shipping 750 200 340 (160-6,400) 320 (200-6,000) Atmospheric deposition 600 600 300 (50-500) 300 (50-500) Total 6,110 4,670 3,270 3,200 Percentage of totals Natural seeps 10 13 9 6 Extraction of petroleum 1 1 2 2 Transportation of petroleum 26 24 35 39 Consumption of petroleum 63 62 54 53 aSpills from pipelines were not specifically broken out, but appear to be included under coastal facility spills. SOURCE: Compiled from GESAMP, 1993. populations, while undoubtedly of interest, would overly complicate an already daunting task.) Based on these discussions, the NRC formally committed to undertake the study in the spring of 1998, and the Committee on Oil in the Sea was formed that summer (Appendix A; Box 1-2). SOURCES, LOADS, FATES, AND EFFECTS A comprehensive examination of the input, fates, and effects of petroleum hydrocarbons on the marine environment is a major undertaking. As is discussed in the subsequent chapters, the release of petroleum to the marine environment can take place in a wide variety of ways, and the size and TABLE 1-3 Estimated Inputs from Shipping and Related Activities Source 1981 (million tonnes) 1989 (million tonnes) Tanker operations Tanker accidents 0.7 0.159 Bilge and fuel oil discharges 0.4 0.114 Dry-docking 0.3 0.253 Marine terminals (including bunkering operations) 0.03 0.004 0.022 0.030 Non-tanker accidents 0.02 0.007 Scrapping of ships − 0.003 Total 1.47 0.57 SOURCE: GESAMP, 1993. impact of releases varies dramatically as each release involves a unique combination of physical, chemical, and biological parameters. An estimate of the total load of petroleum entering the marine environment worldwide, in and of itself, is not particularly meaningful, given the huge volume of water that comprises the global ocean. Petroleum entering the marine environment through spills or chronic releases, such as urban runoff, is eventually broken down or removed from the environment by natural processes or is diluted to levels well below even conservative concentrations of concern. However, from the time the material enters the environment until it is removed or sufficiently diluted, it does pose some threat to the environment. The magnitude of that threat varies dramatically depending of the size, composition, location, and timing of the release, the interactions of the introduced petroleum with various processes that affect the material after its introduction, and the sensitivity of the organisms exposed. Regional or worldwide estimates of petroleum entering the environment are, therefore, useful only as a first order approximation of need for concern. Sources of frequent, large releases have been recognized as an area where greater effort to reduce petroleum pollution should be concentrated, despite the fact that not every spill of equal size leads to the same environmental impact. In addition, by attempting to repeat the development of estimates of petroleum pollution, a metric of performance for prevention efforts becomes available. This study, as did the 1975 and 1985 NRC reports, attempts to develop a sense of what the major sources of petroleum entering the marine environment are, and whether
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Oil in the Sea III: Inputs, Fates, and Effects BOX 1-2 Statement of Task The Committee on Oil in the Sea will attempt to identify, categorize, and quantify, to the extent possible, all sources of hydrocarbon input to the marine environment with an emphasis on North American waters. The committee will examine worldwide data in an effort to place numbers derived for North American waters into a global context. The committee will also assess knowledge, both quantitative and qualitative, about the fate and effects of fossil fuel hydrocarbons input to the marine environment. Specifically the committee will— identify natural and anthropogenic sources of hydrocarbons entering the marine environment; identify and evaluate, to the extent possible, sources of quantitative information regarding the volume of hydrocarbon input to the marine environment worldwide from all sources; develop a methodology for evaluating the accuracy of estimates for hydrocarbon inputs from various sources; develop and summarize quantitative estimates of hydrocarbon inputs to the marine environment with an emphasis on North American waters; develop and summarize quantitative estimates of hydrocarbon inputs to the marine environment worldwide or for specific non-North American regions (as data and time permit); assess and discuss the physical and chemical characteristics and behavior of these hydrocarbons; assess and discuss the transport and fate of various hydrocarbon mixtures in the marine environment; assess and discuss the effects of these mixtures on marine organisms from subcellular to ecosystem level; evaluate, to the degree possible, the relative risk posed to the marine environment by each fossil fuel hydrocarbon mixture or type of input, given its source, abundance, and behavior, and the range of organisms or ecosystems affected. these sources or the volume they introduce, have changed through time. To accomplish this goal, the committee considered the approaches used in earlier efforts and rapidly decided to develop new techniques based on more complete data or expanded knowledge. The values reported in the study, unless specifically attributed to other work, are therefore original estimates using the techniques discussed in the appendixes. In addition, considerable effort has gone toward making general conclusions about what kind of information is available, or needs to be made available, to move beyond the estimates themselves to a discussion of their significance of the release of petroleum in terms of impact to the environment. The fundamental nature of the problem has not changed significantly since 1985, but some progress has been made, especially in terms of our understanding of the pattern of petroleum release in North American waters and in the understanding of how petroleum can impact the environment. However, extrapolating from general estimates of volumes released to specific magnitude of effect at a given location is still largely beyond the ability of the science. This report is an effort to strike a balance between providing a cogent analysis of the problem in a format accessible by a nontechnical reader and providing the technical under-pinning for review and argument by a diverse, technically sophisticated audience. The remainder of the report is organized as follows. Chapter 2 provides an overview of the problem; presents the input estimates on a coarse, but understandable scale; and discusses recommendations for addressing the problem and expanding understanding. Some readers will necessarily want greater detail; thus, Chapter 3 discusses the input of petroleum to the sea in greater depth, Chapter 4 discusses the fate and transport of petroleum released to the environment in more detail, and Chapter 5 explores and synthesizes much of what has been learned about the effects of such releases on the environment since the early 1980s. Finally, the appendixes contain as much of the primary information used to derive the input estimates as practical. Appendixes C though J discuss the data, assumptions, and calculations used to develop the input estimates for readers who desire the greatest possible insight into their derivation. PHOTO 3 Lightering oil from a supertanker at the Louisiana Offshore Oil Port in the Gulf of Mexico south of New Orleans. Tankers have historically been seen as a major source of oil pollution. Recent changes in tanker design (e.g., introduction of partitioned tanks and double hulls) and in oil handling procedures (e.g., offshore lightering) have significantly reduced the size and frequency of spills (Photo courtesy of Nancy Rabalias.)
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