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Oil in the Sea III: Inputs, Fates and Effects

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Executive Summary

There is little argument that liquid petroleum (crude oil and the products refined from it) plays a pervasive role in modern society. As recently as the late 1990s, the average price of a barrel of crude oil was less than that of a take-out dinner. Yet a fluctuation of 20 or 30 percent in that price can influence automotive sales, holiday travel decisions, interest rates, stock market trends, and the gross national product of industrialized nations, whether they are net exporters or importers of crude oil. A quick examination of world history over the last century would reveal the fundamental impact access to crude oil has had on the geopolitical landscape. Fortunes are made and lost over it; wars have been fought over it. Yet its sheer magnitude makes understanding the true extent of the role of petroleum in society difficult to grasp. Furthermore, widespread use of any substance will inevitably result in intentional and accidental releases to the environment. The frequency, size, and environmental consequences of such releases play a key role in determining the extent of steps taken to limit their occurrence or the extent and nature of mitigation efforts taken to minimize the damage they cause.

Consequently, the United States and other nations engaged in strategic decisionmaking regarding energy use spend a significant amount of time examining policies affecting the extraction, transportation, and consumption of petroleum. In addition to the geopolitical aspects of energy policymaking, the economic growth spurred by inexpensive fuel costs must be balanced against the environmental consequences associated with widespread use of petroleum. Petroleum poses a range of environmental risks when released into the environment (whether as catastrophic spills or chronic discharges). In addition to physical impacts of large spills, the toxicity of many of the individual compounds contained in petroleum is significant, and even small releases can kill or damage organisms from the cellular- to the population-level. Compounds such as polycyclic aromatic hydrocarbons (PAH) are known human carcinogens and occur in varying proportions in crude oil and refined products. Making informed decisions about ways to minimize risks to the environment requires an understanding of how releases of petroleum associated with different components of petroleum extraction, transportation, and consumption vary in size, frequency, and environmental impact.

In recognition of the need for periodic examinations of the nature and effect of petroleum releases to the environment, various governments have commissioned a variety of studies of the problem over the last few decades. Within the United States, federal agencies have turned to the National Research Council on several instances to look at the issue. One of the most widely quoted studies of this type was completed in 1985 and entitled Oil in the Sea: Inputs, Fates, and Effects. The report that follows was initially requested by the Minerals Management Service (U.S.) in 1998. Financial support was obtained from the Minerals Management Service, the U.S. Geological Survey, the Department of Energy, the Environmental Protection Agency, National Oceanic and Atmospheric Administration, the U.S. Coast Guard, the U.S. Navy, the American Petroleum Institute, and the National Ocean Industries Association. Although originally envisioned as an update of the 1985 report, this study goes well beyond that effort in terms of proposing a clear methodology for determining estimates of petroleum inputs to the marine environment. In addition, the geographic and temporal variability in those inputs and the significance of those inputs in terms of their effect on the marine environment are more fully explored. Like the 1985 report, this report covers theoretical aspects of the fate and effect of petroleum in the marine environment. This current effort, however, benefited tremendously by the existence of more systematic databases and the voluminous field and laboratory work completed since the early 1980s, work largely stimulated by the Exxon Valdez oil spill in Prince William Sound, Alaska.

PETROLEUM INPUTS TO THE SEA

An examination of reports from a variety of sources, including industry, government, and academic sources, indicate that although the sources of petroleum input to the sea are diverse, they can be categorized effectively into four major groups, natural seeps, petroleum extraction, petroleum transportation, and petroleum consumption. Natural seeps are purely natural phenomena that occur when crude oil seeps from the geologic strata beneath the seafloor to the overlying water column. Recognized by geologists for decades as indicating the existence of potentially economic reserves of petroleum, these seeps release vast amounts of crude oil annually. Yet these large volumes are released at a rate low enough that the surrounding ecosystem can adapt and even thrive in their presence. Petroleum extraction can result in releases of both crude oil and refined products as a result of human activities associated with efforts to explore for and produce petroleum. The nature and size of these releases is highly variable, but is restricted to areas where active oil and gas exploration and development are under way. Petroleum transportation can result in releases of dramatically varying sizes, from major spills associated with tanker accidents such as the Exxon Valdez, to relatively small operational releases that occur regularly. Petroleum consumption can result in releases as variable as the activities that consume petroleum. Yet, these typically small but frequent and widespread releases contribute the overwhelming majority of the petroleum that enters the sea due to human activity.

Based on analysis of data from a wide variety of sources, it appears that collectively these four categories of sources add, each year on average, about 260,000 metric tonnes (about 76,000,000 gallons) of petroleum to the waters off North America. Annual worldwide estimates of petroleum input to the sea exceed 1,300,000 metric tonnes (about 380,000,000 gallons). Although these are imposing figures, they are difficult to interpret in terms of their ecological significance, as they represent thousands or tens of thousands of individual releases whose combined effect on the environment is difficult to clearly establish. Regional or worldwide estimates of petroleum entering the environment are useful only as a first order approximation of need for concern. Sources of frequent, large releases are rightfully recognized as areas 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. 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 these sources or the volume they introduce, have changed through time. Thus, this report not only attempts to quantify the amount released each year, but makes an effort to examine the geographic distribution and nature of releases of petroleum to the marine environment, as well as the processes that can mitigate or exacerbate the effect of these releases on the environment. Where appropriate, comparisons of estimates of petroleum pollution among studies over the last 25 years provide the basis needed to explore the performance for prevention efforts implemented during that time.

Natural Seeps

Natural seepage of crude oil from geologic formations below the seafloor to the marine environment off North America is estimated to exceed 160,000 tonnes (47,000,000 gallons), and 600,000 tonnes (180,000,000 gallons) globally, each year. Natural processes are therefore, responsible for over 60 percent of the petroleum entering North American waters, and over 45 percent of the petroleum entering the marine environment worldwide. Oil and gas extraction activities are often concentrated in regions where seeps form. Historically, slicks of oil from seeps have been attributed to releases from oil and gas platforms, and vice versa. In North America, the largest and best known natural seeps appear to be restricted to the Gulf of Mexico and the waters off of southern California, regions that also have extensive oil and gas production. As mentioned earlier, the seepage of crude oil to the environment tends to occur sporadically and at low rates. Federal agencies, especially USGS, MMS, and NOAA, should work to develop more accurate techniques for estimating inputs from natural seeps, especially those adjacent to sensitive habitats. This effort will aid in distinguishing the effects of petroleum released by natural processes versus anthropogenic activities. Furthermore, areas surrounding natural seeps are extremely important natural laboratories for understanding crude oil behavior in the marine environment, as well as how marine life responds to the introduction of petroleum. Federal agencies, especially USGS, MMS, NSF, and NOAA, should work with industry and the academic community to develop and implement a program to understand the fate of petroleum released from natural seeps and the ecological response to these natural releases.

Petroleum Extraction

Activities associated with oil and gas exploration or production introduce, on average, an estimated 3,000 tonnes (880,000 gallons) of petroleum to North American waters, and 38,000 tonnes (11,000,000 gallons) worldwide, each year. Releases due to these activities, therefore, make up roughly 3 percent of the total petroleum input by anthropogenic activities to North American waters and 5 percent of the total worldwide. Although dwarfed by some other sources of petroleum to the marine environment, these inputs are not trivial, as they can occur as large spills or as slow, chronic releases concentrated in production fields. Furthermore, those releases from petroleum extraction activities that take place near shore or even on shore can pose significant risks to sensitive coastal environments. Again, these releases are concentrated in areas of petroleum production in the Gulf of Mexico and the waters off of southern California, northern Alaska, and eastern Canada. Releases from oil and gas extraction can include accidental spills of crude oil from blow outs, surface spills of crude from platforms, or slow chronic releases associated with the disposal of water produced from oil or gas-bearing formations during extraction (referred to as produced water) or oil-bearing cuttings created during the drilling process. Volatile organic compounds (VOC) commonly associated with, or dissolved in, petroleum are released during extraction activities and also contribute to the total load of hydrocarbon input to the sea. These compounds, however, rapidly volatilize into the atmosphere and thus appear to have a short residence time in marine waters. Despite recent and significant decreases in the amount of petroleum released during extraction activities, the potential for a significant spill, especially in older production fields with aging infrastructures, cannot be ignored. The threat posed by even a minor spill in a sensitive area remains significant. Federal agencies, especially MMS, should continue to work with state environmental agencies and industry to enhance efforts to promote extraction techniques that minimize accidental or intentional releases of petroleum to the environment. Furthermore, like areas surrounding natural seeps, production fields represent unique opportunities to study the ecological response to slow, but chronic releases of small amounts of petroleum over time. Federal agencies, especially USGS, MMS, NSF, and NOAA, should work with industry and the academic community to develop and implement a program to understand the ecological response to such extraction-related releases as part of a larger effort to understand the impact of chronic releases from all sources of petroleum to the marine environment.

Petroleum Transportation

The transportation (including refining and distribution activities) of crude oil or refined products results in the release, on average, of an estimated 9,100 tonnes (2,700,000 gallons) of petroleum to North American waters, and 150,000 tonnes (44,000,000 gallons) worldwide, each year. Releases due to the transportation of petroleum, therefore, make up roughly 9 percent of the total petroleum input through anthropogenic activities to North American waters and less than 22 percent worldwide. Similar to releases from petroleum extraction, these volumes are dwarfed by those from other sources of petroleum to the marine environment. And like releases from extraction activities, these inputs are not trivial, as they can occur as large spills. Unlike releases associated with extraction, which tend to be concentrated in production fields in the Gulf of Mexico or coastal areas off California and Alaska, these spills can occur anywhere tanker vessels may travel or where pipelines are located statistically. Areas near major petroleum handling facilities face the greatest threat. Spills from transportation activities may release a wide variety of petroleum products (not just crude oil) each of which behaves differently in the environment (for example light distillates tend to evaporate rapidly), or contain different concentrations of toxic compounds like PAH. VOC are also released from tankers underway or involved in loading and offloading activities, and they contribute to the total load of hydrocarbons input to the sea. Again, these compounds rapidly volatilize into the atmosphere and thus appear to have a short residence time in marine waters. Despite recent and substantive decreases in the size and frequency of petroleum spills from tankers, the potential for a large spill is significant, especially in regions without stringent safety procedures and maritime inspection practices. Furthermore, tanker traffic is expected to grow over the coming decades as the centers of oil production continue to migrate towards the Middle East and Russia. Federal agencies, such as the U.S. Coast Guard and the Maritime Administration, should expand efforts to work with ship owners domestically and internationally through the International Maritime Organization, to develop and enforce effective international regulatory standards that have contributed to the decline in oil spills and operational discharges. In addition, the potential for large spills from aging pipelines and other coastal facilities is especially disconcerting, as these facilities often lie near sensitive coastal areas. Federal agencies, especially the U.S. Coast Guard, the Office of Pipeline Safety, and EPA, should continue to work with state environmental agencies and industry to evaluate the threat posed by aging pipelines and to take steps to minimize the potential for a significant spill.

Petroleum Consumption

Releases that occur during the consumption of petroleum, whether by individual car and boat owners, non-tank vessels, or runoff from increasingly paved urban areas, contribute the vast majority of petroleum introduced to the environment through human activity. On average, an estimated 84,000 tonnes (25,000,000 gallons) of petroleum are input to North American waters, and 480,000 tonnes (140,000,000 gallons) are input worldwide, each year from these diffuse sources. Therefore, releases associated with the consumption of petroleum make up nearly 70 percent of the petroleum introduced to the world's oceans from anthropogenic sources and nearly 85 percent of the total petroleum input from anthropogenic sources to North American waters. Unlike other sources, inputs from consumption occur almost exclusively as slow, chronic releases. Furthermore, because the vast majority of the consumption of petroleum occurs on land, rivers and waste- and stormwater streams represent the most significant source of petroleum to the marine environment. Another smaller, but still significant source, are two-stroke engines. Collectively, land runoff and two-stroke engines account for nearly three quarters of the petroleum introduced to North American waters from activities associated with petroleum consumption. This is particularly significant because, by their very nature, these activities are almost exclusively restricted to coastal waters. In fact, the estuaries and bays that receive the bulk of the load are often some of the most sensitive ecological areas along the coast. Federal agencies, especially EPA, should continue efforts to regulate and encourage the phase-out of older, inefficient two-stroke engines, and a coordinated enforcement policy should be established. Unfortunately, the estimates for land-based sources of petroleum are the most poorly documented, and the uncertainty associated with the estimates range over several orders of magnitude. Federal agencies, especially EPA, USGS, and NOAA, should work with state and local environmental agencies to develop and implement a system for monitoring the input of petroleum to the marine environment from land-based sources via rivers and storm- and waste-water facilities. Again, VOC are released during consumption activities and contribute to the total load of hydrocarbon input to the sea. Like VOC released by other sources, these compounds rapidly volatilize into the atmosphere and thus appear to have a short residence time in marine waters.

Significant Cross-cutting Issues

As discussed briefly above, the effect of a release of petroleum is not directly related to the volume. It is instead a complex function of the rate of release, the nature of the released petroleum (and the proportions of toxic compounds it may contain), and the local physical and biological ecosystem exposed. Progress has been made in understanding some basic processes affecting the fate of released petroleum. Much more needs to be learned about how petroleum interacts with marine sediment and how it is transported or dispersed by ocean and coastal processes such as waves and currents. Federal agencies, especially NOAA, MMS, 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 in the marine environment.

Although the VOC released during the extraction, transportation, and consumption of petroleum appear to have short residence times in the marine environment, their impact on air quality may be significant. Federal agencies, especially the U.S. Coast Guard, MMS, and EPA, should work with the International Maritime Organization to assess the overall impact of VOC on air quality from tank vessels and other sources, and establish design and/or operational standards on VOC emissions where appropriate.

Studies completed in the last 20 years again bear out the significant environmental damage that can be caused by spills of petroleum into the marine environment. No spill is entirely benign. Even a small spill at the wrong place, at the wrong time, can result in significant damage to individual organisms or entire populations. With a few notable exceptions (e.g., the Exxon Valdez, North Cape, and Panama spills), there have been a lack of resources to support studies of the fates and effects of spilled oil. Much of what is known about the fate and effect of spilled oil has been derived from a very few, well-studied spills. Federal agencies, especially the U.S. Coast Guard, NOAA, and EPA, should work with industry to develop and implement a rapid response system to collect in situ information about spill behavior and impacts.

Despite the significant progress made in understanding the behavior and effect of petroleum spills on the marine environment and on preventing their occurrence in the first place, relatively little work has progressed on understanding the threat posed by small, chronic releases of petroleum from all sources. Insights have been made from long-term studies of sites of major spills or polluted harbors, but to a large degree the significance (in terms of environmental damage) of the large inputs from land-based sources or other chronic releases is not known. Recent studies, however, suggest that PAH, even in low concentrations, can have a deleterious effect on marine biota. Furthermore, 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 EPA, NOAA, NSF, USGS, and MMS, should work with academia and industry to develop and implement a major research effort to more fully understand and evaluate the risk posed to the marine environment by the chronic release of petroleum (especially the cumulative effects of multiple types of hydrocarbons present in these kinds of releases).

Finally, although there is now good evidence for 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. Such information is imperative if the impacts of individual spills or chronic releases in local areas are to be evaluated against the health of entire populations, species, or ecosystems. The U.S. Departments of Interior and Commerce should identify an agency, or combination of agencies, to prioritize and support continued research on the effects of releases (chronic and catastrophic) of petroleum on wild populations.