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J Inputs Petroleum hydrocarbons (PHC) sources. Estimates of these sources are interrelated and INTRODUCTION enter the marine environment from many PHC inputs remain uncertain because the ~ available data are minimal. Figure 2-1 shows the international flow of petroleum. The width of that flow is representative of the amount of petroleum being transported along these routes. This pattern of flow may change significantly in future years, particularly in arctic areas where petroleum production is increasing. A major fraction of the world's petroleum continues to be produced and transported from countries different from those in which the petrol- eum is refined and consumed. During the past decade the quantity of petroleum transported by sea, as well as the number and tonnage of ships in operation, has increased significantly (British Petroleum Company, Ltd., 1980; Lloyd's Register of Shipping, 1980~. This increase is shown in Table 2-1. Sources of PHC into the marine environment considered in this report include natural sources; offshore oil production; marine transportion (operational discharges, drydocking, marine terminals, bunker operations, bilge and fuel oil transfer, and accidental spillages); the atmosphere; coastal, municipal, and industrial wastes and runoff; and ocean dumping. Each source type will be addressed in the following sections. NATURAL SOURCES The direct input of PHC from natural sources is estimated to be 0.025-2.5 million metric tons per annum (mta), the best estimate being 0.25 mta. Natural seeps contribute the major fraction of this total. A minor contribution is estimated to come from erosional processes. These consensus estimates, developed at the 1981 workshop, are based on geological and geochemical principles, many of which were described by Wilson et al. (1973~. In this report on natural sources, hydrocarbons of a petroleum origin are the only ones considered. Biogenically produced hydrocar 43

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45 TABLE 2-1 Petroleum Tr anspor t at Sea 1971 1980 Ratio. 1980/197 1 O it movement at sea (mta) Crude oil Product oil Total World' s merchant fleet Number of sh ips Gross tonnage Wor Id ' s tanker f feet Number of sh ips Total deadwe igh t tons Average deadweight tons 1,100 255 1,355 55, 041 247,200,000 6, 292 169, 355, 000 26,900 1,319 269 1,588 73,832 419,911,000 7,112 339 ,802,000 47,800 1.19 1.05 1.16 1.34 1.70 1.13 2.01 1.78 loons, some of which have the same chemical structure as some PHC (e.g., n-alkanes and isoprenoid alkanes), are synthesized by marine organisms (see Chapter 3, Chemical Methods section). Petroleum hydrocarbons, considered here as liquid petroleum and tar ~ ,~ ~ _ , _ or more carbon atoms), enter the marine environment naturally by means of two main processes--submar ine seepage and erosion of sedimentary rocks. Estimating the contribution of each of these is a formidable problem for the following reasons: (hydrocarbons and other organic compounds with five 1. Direct observation of submarine seeps is limited because the seeps are not normally visible. This invisibility leads to inaccurate estimates of seepage rates. 2. Submarine seeps flow intermittently, thus complicating both detection and estimation of seepage rates. The estimate is an average over geologic time, and in any particular year seepage events can exceed this estimate by orders of magnitude. 3. The potential area of continental margins where submarine seeps can occur is vast, whereas the areas of individual seepages are usually small, making an adequate inventory impossible with current technology and available monetary resources. In addition, the products of seepage cannot always be distinguished from petroleum pollution. 4. There are no direct measurements of the amount of petroleum entering the oceans by means of erosional processes, thus limiting the accuracy of any estimate. Natural Seeps Wilson et al. (1973) combined seepage rates on land with information on reported marine seeps, then extrapolated the data to the continental

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46 margins, which they classified into areas of potentially high, medium, and low seepage. They incorporated tectonic history, earthquake activity, and sediment thickness in their appraisal. Five basic assumptions were used in their estimates: 1. More seeps exist in offshore basins than have been observed. 2. Factors that determine the total seepage in an area {number of seeps per unit area and the daily rate for each seep) are related to the general geologic structure of the area and to the stage of sedimentary basin evolution. 3. Within each structural type, the number of seeps and, to a lesser extent, rate per seep are thought to depend primarily on the area of exposed rock and not on rock volume. This assumption presumes that there is suff icient sediment volume and organic matter for matur at ion and gener at ion of petroleum. 4. Most mar ine seeps are clustered within the continental margins where the thickness of sedimentary rocks, which provides the needed source rocks for the seepage, exceeds a certain minimum. 5. Seepage rates are lognormally distributed. Although the geologic relationships developed by Wilson et al. (1973) that affect seepage rates are reasonable and seem to agree with observations, the statistical arguments of the last assumption may be questionable. On purely abstract grounds, an exponential distribution of seepage rates is more likely than a lognormal distr ibution. While oil field volumes are generally lognormally distributed, the actual volumes of all oil accumulations (most of which are perhaps too small to be produced and thereby cannot be classified as fields) are likely to have an exponential distribution (Harbaugh and Ducastaing, 1981~. The volumes of natural seepages are probably statistically distr ibuted in a manner similar to the volumes of oil accumulations in general, because seeps do not necessarily need sources as large as oil f ields . Consider ing the cliff iculties encompassed in the other assumptions, however, the form of the frequency distr ibution may be a minor matter. Since Wilson et al. (1973, 1974) made their estimate, little new information has become available that would alter their worldwide estimates of marine seepage rates. Their compilations of 190 reported submarine seeps were derived mostly from Johnson (1971) and Landes (1973) and can be augmented by four newly identif fed seep areas (Scott Inlet, Canada; Buchan Gulf, Canada; Australian North Coast; and Laguna de Tamiahua, Mexico) . All identif fed submar ine seep areas are shown in F igure 2-2; 54 individual submar ine seeps are represented by one dot of f the Cal if ornia coast, and another 28 are so represented in the Gulf of Alaska. Of the four recent reports (Levy, 1978; Levy and Ehrhardt, 1981; McKirdy and Horvath, 1976; and Geyer and Giammona, 1980), none estimates rates of seepage. The estimates available to Wilson et al. `1973) for Coal Oil Point (Santa Barbara Channel) and Santa Monica Bay ranged from 0.0007 to 0.05 mta. The more recent estimate of Fischer (1978) for the entire Santa Barbara Channel ranges from 0.002 to 0.03 mta, a span of values not greatly different from earlier estimates.

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48 TABLE 2-2 Petroleum Resource Estimates Source Amount Mill ions of Metr ic Tons Billions of Barrels Reference Offshore oil "tar" sands Total offshore petroleum resources Total petroleum resources 1,000,000 in place Proven oil reserves and potential resources offshore Total proven reserves and potential resources onshore and offshore World exploitable oil (discovered 163,000 mt; undiscovered 141,000 mt) Large ~ tar n depos its 30,000 350, 000 14, 000 200 2,500 7, 200 100 86, 000630 304,0002,200 320, 0002, 100 Weeks (1965) Weeks ~ 1965) Hunt (1972) Albers et al. (1973} Albers et al. (1973) Halbouty and Moody ( 1980 Dema ison (1977 ~ Geolog ical Impl icat ions of Seepage Rates A compar ison of estimated seepage rates with the amount available for seepage can be used to assess the maximum geologic time during which seepages could be sustained. Table 2-2 lists petroleum resource estimates for several categories of petroleum and illustrates the wide range of resource estimates that have been calculated. Table 2-3 illustrates the compar ison. The wide range of assumed seepage rates includes the estimates of Wilson et al. ( 1973, 1974 ~ but extends downward to 0 .02 mta and upward to 10 mta. At the low end, 10 ,000 mt is near the value of 14 ,000 mt of total proven reserves and potential resources offshore as estimated by Albers et al. (1973) . At the other end of the scale, Wilson et al. (1973, 1974) accepted an estimate of 300,000 mt in place. Because this amount may represent only l% of the petroleum mobilized from source beds, they assumed that the amount available for seepage may be as much as 30 ,000 ,000 mt. This scale available for seepage has been augmented to 100,000,000 mt to attempt to include unknowns with regard to the amount of petroleum that would have been available for seepage during geologic time and will become available in the future dur ing the 1 if etimes of the seepage. Table 2-3 shows that to maintain petroleum seepage for a span of geologic time of at least 50 million years (most of the Tertiary period) requires that seepage rates be equal to or less than 2 mta, and

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49 TABLE 2-3 Maximum Lifetimes (Million Years) of World Oil Deposits O il Available Assumed Seepage Rates (mta) forSeepage (mt) 0.02 0.040.20 0.60 1.0 2.0 6.0 10 10,000 0.5 0.25.05 0.02 0.02 0.005 0.002 0.001 30,000 1.5 0.75.15 0.05 0.03 0.015 0.005 0.003 100,000 5 2.S0.5 0.2 O.1 0.05 0.02 0.01 300,000 15 7.51.5 0.5 0.3 0.15 0.05 0.03 1,000,000 50 25 5 2 1 0.5 0.2 0.1 3,000,000 150 75 15 5 3 1.5 0.5 0.3 10,000,000 500 250 50 20 10 5 2 1 30,000,000 1,500 750 150 50 30 15 5 3 100,000,000 5,000 2,500 500 200 100 50 20 10 at the same time the amount available for seepage must be equal to or greater than 1,000,000 mt. If seepage is maintained for 500 million years (most of the Phanerozoic), then seepage rates must be equal to or less than 0.02 mta and the amount available for seepage must be equal to or greater than 10,000,000 mt. The petroleum seepage rate that best seems to accommodate the requirements of reasonable geologic time and reasonable assumptions concerning availability for seepage is 0.2 mta with an uncertainty both upward and downward of an order of magnitude. Thus, the conclusion is reached that the average rate of petroleum seepage over time ranges from 0.02 to 2.0 mta, with a best estimate of 0.2 mta. This value is lower by a factor of 3 than the best estimate of Wilson et al. (1973, 1974) of 0.6 mta. Erosional Inputs of Petroleum The amount of petroleum that enters the marine environment by erosional processes has not been estimated before. Previous work by Wilson et al. (1973, 1974) considered only the marine input from natural seeps. Any estimation of erosional input of petroleum into the oceans can only be approximate. There are at least three places where the erosional input of petroleum into the oceans could be studied in detail. Weaver (1969) showed examples of petroleum seeps at the beach and in the sea cliffs facing the Santa Barbara Channel, where erosion presently is taking place. Giammona (1980) described the Laguna de Tamiahua area where there are onshore and offshore seeps. The Marine Pollution Subcom- mittee of the Br itish National Committee on Oceanic Research (1980) identif fed the Dorset coast of southern England as another place where petroleum source rocks as well as petroleum-containing reservoir rocks are exposed. They suggested this area for the study of natural seeps and erosional processes affecting the distribution of petroleum in the marine environment. Because no direct information is available on erosional inputs of petroleum into the oceans, an indirect approach must be taken. This

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so approach assumes that a portion of the organic carbon transported by all r ivers is petroleum. Estimates of the organic carbon input into the oceans by r ivers vary by nearly 2 orders of magnitude, from 30 to 1,000 mba, as summarized by Schlesinger and Clack (1981~. They concluded , however, on the teas is of two approaches , that the amount o f organic carbon transported by r ivers is 370-410 mta. Independently, Meybeck (1981) reached a similar estimate of 400 mta. In estimations of the organic carbon content of r ivers, no distinc- tion has been made between carbon from modern biological sources, carbon from pollution, and ancient carbon indigenous to the eroded sediment being car r fed by the r ivers . This latter class of carbon is of interest in estimating the eras tonal input of petroleum into the oceans . The total organic matter content of rivers is divided about equally between dissolved organic carbon and particulate organic carbon (Ileybeck, 1981) . Meybeck further estimated that of the approximately 179 mta of particulate organic carbon that is transported by r ivers, about 88 mta is ancient organic carbon. This ancient organic carbon is f inely dispersed in Plastic and carbonate rock particles, eroded from sedimentary rock formations on the continents (Ronov, 19761. In ancient sedimentary rocks the amount of extractable organic matter constitutes, on the average, about 6% of the total organic matter tHunt, 19791. If the extractable fraction in sediment par ticles in rivers is the same as that of source rocks, the amount in particu- lates in r ivers would be 10.6 mta. Most of the extractable organic mater Hal is d isper sed in sedimentary rocks, but O. .596 of this mater ial is petroleum tHunt, 1972) . I f this factor is applied to the extractable organic matter of sediment par- ticles in r ivers, then the amount of petroleum transported from eroding outcrops by r ivers to oceans is about O. .05 mta. This estimate may be high, because loss of organic carbon by oxidation during river transport and by sedimentation in estuar ies leading to the oceans was not con- sidered because of lack of data on these processes. Because of the numerous assumptions used to obtain this estimate, the uncertainty is at least an order of magnitude. In estimating rates of seepage of petroleum into the marine environment, these rates have been compared with the amount assumed to be available for seepage over geologic time (Table 2-3 ~ . Th is same petroleum would be available for erosional processes over geologic tune. The amount available is suff icient to sustain the estimated rates of natural seepage as well as rates of erosion of petroleum for an amount of time equivalent to the Tertiary per lad and probably longer . OFFSHORE PRODUCTI ON The amount of petroleum enter ing the mar ine environment from offshore petroleum production is estimated to be from 0.04 to 0.07 mta. Of these totals, ma jor spills (>7 metr ic tons) from platforms contr ibute 0.03-0.05 mta, minor spills (<7 metric tons) 0.003-0.004 mta, and operational discharges O. . 007-0 .011 mta.

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51 TABLE 2-4 Offshore Petroleum Production, 1979 Country Pr oduct ion Rate . x 109 bbl/year x 106 mta Saudi Arabia 1.03 147 United Kingdom 0 .57 81 United States 0.39 56 Venezuela 0.38 54 Other countries 2.24 320 TOTAL 4.61 658 These estimates for the release of petroleum into the marine environment are lower, by about 30-50%, than the estimates generated earlier (NRC, 1975~. Better data are available for operations, and major spill incidents in the United States have been more comprehen- sively documented since the earlier estimates were made. The available international data suggest that reductions have also been experienced outside the United States. As reported by Burnet (1980), worldwide offshore petroleum produc- tion totaled approximately 658 mta in 1979. Over 50% of the production came from four countries: Saudi Arabia, the United Kingdom, the United States, and Venezuela. These data, which are the latest available published information, are summarized in Table 2-4. They are the basis for all subsequent calculations of the current petroleum input to the oceans from offshore petroleum production operations. Operational (Produced Water) Discharges In the United States, offshore produced water is normally discharged into the ocean after being processed to minimize the entrained petroleum content. Actual rates of discharge for produced water are not currently available. However, until 1976, the U.S Geological Survey (USGS) maintained records on these discharges from outer continental shelf operations in the Gulf of Mexico. At that tine, 0.8 barrels of water were produced with every barrel of crude oil. This ratio is assumed to be still valid, and the same ratio is assumed to apply to all U.S. offshore production. This estimate is believed to be conservative, because recent Bureau of Land Management (BLM) environmen- tal impact statements for outer continental shelf (OCS) lease sales assume a 0.6 water-to-crude-oil production ratio. The Department of Environment, U.K. (1976} report concerning discharges from offshore operations in U.K. waters stated: "The proportion of production water in crude oil will initially be less than 1 percent but will increase to

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52 some 30 percent as the reservoir becomes depleted, particularly when water in jection is used on an increasing scale. n This study assumed a proportion of 10% averaged over the life of the U.K. fields. For other countries an assumption of 30% was used. It should be noted that no water is produced off the Saudi Arabian shore. Produced water regulations in the United States require that the daily maximum petroleum content not exceed 72 mg/L and that the monthly average be less than 48 mg/L. The Environmental Protection Agency (EPA, 1976) Development Document on which these guidelines are based also includes the results of an in-depth statistical analysis of all available data, which indicates that facilities meeting the above limitations will achieve a long term average petroleum content of 25 mg/L or less. These figures, however, do not include the C6-C14 "volatile liquid" hydrocarbons, which are not determined by the solvent extraction technique used for "oil and grease" analysis. Therefore, a somewhat higher estimate of 35 mg/L hydrocarbons entering the oceans from U.S. produced water discharges was used. Because this regime does not include (1) upset and bypass situations in which higher discharge 1 evels are probably experienced and (2) the fact that state-of-the-art equipment is not installed at all locations, a high estimated average Is believed to be twice this level, 70 mg/L. A reasonable best estimate is 50:20 mg/L volatile liquid" hydrocarbons and 30 mg/L higher-molecular-weight hydrocarbons (>C14~. Similar arguments for the U.K. offshore operations and those in other countries (Table 2-5) lead to a range of 50-70 mg/L for the estimated hydrocarbon content of produced waters. Based on these assumptions, the volume of petroleum enter ing the world's oceans from offshore produced water discharges is calculated to be between 0.0075 and 0.0115 mta, with a best estimate of 0.0095 mba (Table 2-6 ) . Specific estimates were not made for deck drainage, drilling fluid discharges , and other minor sources of petroleum (Schreiner, 1980 ~ . These sources are probably accounted for within the 1 imits of conf idence of the above number s . Minor Spills S ince 1971 the USGS has maintained a computer ized OCS events f ile for Gulf of Mexico oil and gas operations (Danenberger, 19761. Included are data on all crude oil spills . The USGS classif ies spills as minor (7 metric tons or 50 barrels) . Table 2-7 summer izes the minor spi Its in the Gulf of Mexico OCS for the 8-year per lad 1971-1978 . The average spillage rate for this period was 0.000249 of total crude oil produced. The record for minor spills in offshore Alaska is better. The Lower Cook Inlet spillage rate for all spills from 1971 to 1980 is 0.0001% of total crude oil produced (Wondzell, 19811. Similar data for operations in other U.S. areas and outside the United States are not readily available. Offshore operations are moving into more severe environments, such as the arctic regions.

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53 TABLE 2-5 Offshore Produced Water Effluent Limitations Country Oil and Grease Content Limit (mu/L) Average Maximum Abu Dhabi - 15 Australia 30 50 Denmark 40 Egypt - 60 (Mediterranean) 15 (Red Sea) France - 20 Indonesia 30 _ Malaysia 100 (offshore) - 10 (coastal) - Netherlands Nigeria Norway Spain - 75 25-30 40 (Atlantic) 60 (Mediterranean) 100 40 100 - Trinidad 50 _ United Kingdom 40 {large facilities) no more than 4% 50 (small facilities) greater than 100 mg/L United States 48 (monthly) 72 25 (long term) Venezuela 35 _ NOTE: Limitations shown here are from various sources. They are either existing government regulations, proposed government regulations (which could change), or limitations imposed by authorities for installations in operation in countries without regulations. However, to balance this effect, there have been significant techno- logical advances (such as warning systems and improved blowout preventers) that are reducing the occurrence of spills of all sizes. Average experience for all U.S. offshore operations probably is comparable to the Gulf of Mexico average, so a range of 0.00021-0.00030% is used for the United States. Another assumption is made that the worldwide percentage is about twice that of the United States, or 0.00042-0.00060 (Table 2-8~. Clearly, there is uncertainty associated with this assumption. With these data a range of 0.0027-0.0038 mta has been calculated as the estimate of petroleum entering the marine environment from minor spillage from offshore drilling and production activities worldwide. The best estimate is 0.003 mta, which is lower than the earlier NRC (1975) estimate of 0.01 mta.

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78 TABLE 2-20 Selected Urban Runoff Studies Location Drainage Area (ha) Number of Storms Studied Reference Seattle-- Wakeham (1917) North Philadelphia616 Hunter et al. (1979) North Philadelphia6165 Hunter et al. (1979) North Philadelphia616 Whipple and Hunter ( 19 7 9 Trenton A82 Wh ipple and Hunter (1979) Trenton B823 Tipple and Hunter ( 1979 Los Angeles210,0001 Eganhouse and Kaplan (1981, 1982) Leon County, Fla. 357 1 Byrne et al . (1980 Narragansett Bay, R.T . 167,000 21 Hoffman et al. (1982) River Discharges Reexamination of the global input of hydrocarbons to the oceans indi- cates that the inclusion of a separate category for river discharges may be improper because of double accounting of hydrocarbon input. The ma jor sources of hydrocarbons in rivers are the untreated and treated wastewater discharges, runoff {both urban and rural) , and spills. All these sources are quantified and reported separately for coastal areas. If an additional 110 million people discharge PHC into the interior r ivers of the United States (at a rate of 6 .8 g/cap/d) and if 5% of these PHCs eventually reach the oceans, then this yields an annual flux of PHC from rivers to U.S. coastal waters of 0.013 mta. Assuming this amount is one-third of the world total, the river discharge of PHC to the ocean would be 0.04 mta. OCEAN DUMPING Some hydrocarbons are discharged into U.S. and world coastal regions in association with municipal wastewater treatment plant sludge/underflow. The sludge is generally discharged from dumping by barge or by dis- charges through pipelines. In the United States, this sludge is discharged by dumping in the New York Bight and by Pipeline on the West Coast. In the New York Bight ~ approximately 7 x 10 wet tons of sludge are discharged per year. This material contains approximately 2,000 ppm of oil and grease, of which about 4096 are hydrocarbons. This

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79 TABLE 2-21 Per Capita Estimates of PHC Contr ibutions in Urban Runof f On it PHC Contr ibution Location (g/cap/d) Reference Ph iladelph ia 0 . 0 3 ~ ipple and and Trenton Hunter (1979 Narragansett Bay 2.7 Hoffman et al. (1982 ~ Los Angelesa 1.9 Eganhouse and Kaplan (1981) Seattle 0.3 Wakeham (1977) Swede ~0.3 NRC (1975) BSingle storm extrapolated to annual runoff by author. bTypical urban area (0.2 parking, 0.3 multifamily, and 0.6 single family). amounts to 0.006 mta of THC. In addition, the Los Angeles pipeline discharges about 2,4SO tons of oil and grease annually through the 7 mile sludge outfall (Eganhouse and Kaplan, 1981~. This is estimated to be 0.001 mta of TIC. The annual worldwide discharge of wastewater sludge into the oceans is approximately 16 million tons. Thus, applying a similar ratio to that used for the United States, the total amount of hydrocarbons discharged worldwide by ocean dumping is about O .02 mta. Hydrocarbons are also released to the oceans from the dumping of dredge spoils. Dredge spoils are river and channel sediments that have been relocated by dredging and dumping operations. The hydrocarbons that accompany these spoils are accounted for in other sections of this report and are not included in the ocean dumping category. GEOGRAPHICAL DISTRIBUI ION OF INPUTS The input of petroleum hydrocarbons into the ocean is certainly not distr ibuted evenly. The geographical distr ibution of the inputs from each source is discussed below. Mar ine transportation (1.5 mta) . The input of PHC from this source is concentrated along the pr incipal transportation routes and in harbors and ports where oil tankers or other vessels are loaded or unloaded. About half the transportation total is der ived from tanker operations (0.7 mta). Most of this loss is probably at sea along the prominent tanker routes from the Middle East to Europe, the American

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80 continents, or the Far East. Another major source in this category is tanker accidents (0.4 mta). These also tend to occur along the tanker routes, but in more congested areas near ports or in narrow straits. The third major source, that of bilge and fuel oils (0.3 mta), probably follows a similar distribution pattern to that of the tanker operations. Offshore oil production (0.05 mta). This relatively minor input occurs at offshore oil production facilities, and these tend to be near coastlines. The largest offshore producing areas are the Arabian Gulf, the North Sea, the Gulf of Mexico, offshore California, offshore Malaysia and Indonesia, and the west coast of Africa. Refineries (0.1 mta). This input of PHC into the sea is con- centrated near the coasts of countries that do most of the refining of petroleum (e.g., the United States, Great Britain, Germany, France, Japan, Canada, Mexico, Kuwait, and Saudi Arabia). Nonrefinery wastes (0.2 mta). This input into the sea is concentrated near the coasts of the more industrialized nations in the world, such as the United States. the northern EuroDean countries and Japan. , _ , _ _ , Municipal wastes (0.75 mta). This input of PHC is distributed in much the same way as the nonrefinery industrial wastes. It would be concentrated near the coasts of the more highly industrialized and heavily populated nations. Best examples would again be the united States, the northern European countries, and Japan. Urban runoff (0.12 mta). This input of PHC closely follows the input from municipal wastes. The input would be primarily into coastal areas of counts ies with high industrialization and large populations. River runoff (0. 04 mta). This input is in coastal areas near the mouths of large rivers, such as the MiSSiSSippi, the Rhine, the Danube, the Saint Lawrence, and the Elbe. Natural sources (0.3 mta). Submarine seeps, at least those identified thus far, seem to be associated with tectonically active regions of the world and are usually near the coasts of continents. Such areas are offshore California and Alaska, the Arabian Gulf and the Red Sea, the northeast coast of South America, and the South China Sea. Atmosphere (0.05-0.5 mta). This input of PHC into the seas would be primarily downwind of heavily industr ialized areas. Again, the inputs are greatest near the coastlines, with concentrations decreasing away from the coasts. The northwest Atlantic, the North Sea, and the northwest Pacific (near Japan) would probably have typically large atmospheric inputs of PHC. Data are not available to estimate total PHC input by region except in an extremely qualitative manner. If one looks at information on the geographical distribution of each input, then one can say, qualitatively, that coastal areas off the United States, Europe, and Japan and the Arabian Gulf would probably have greater inputs.

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81 SUMMARY AND RECOMMENDATIONS The estimated range for total input of petroleum from all sources is 1.7-8.8 million mta. The best single-number estimate of total input is 3.2 mta. We believe that the range is a more accurate summary of the state of knowledge than a single-number best estimate. Uncertainties are particularly evident with certain sources, i.e., natural inputs (seeps and erosion), transportation, municipal/industrial runoff, and atmospheric inputs. There are also wide geographical gaps in informa- tion on sources, especially in the southern hemisphere. Table 2-22 presents sources, probable ranges, and best estimates for sources. The spread in probable range about the best estimate is a qualitative measure of the faith in the best estimate. For example, the tanker accident probable range is narrow (0.3-0.4 mta), so the best estimate is probably good . On the other hand, the mar ine seep probable r ange is wide (0.02-2.0 mta), indicating small reliability in the best estimate. The 1975 NRC report gave only a single-number estimate of total input of petroleum, namely, 6.1 mta. No range was given. This number falls within the current estimated range of 1.7-8.8 mta. The difference in the two single-number estimates, 6.1 mta in 1975 and the current 3.2 mta, does not necessarily reflect a significant decline in input but indicates better estimation of individual inputs. Although the amount of petroleum and petroleum products transported by sea, as well as crude oil produced offshore, has increased during the past 8 years, PHC input into the marine environment estimated at the 1981 NRC workshop does not appear to have followed this trend. This may be for the following reasons: (1) the individual input estimates are more accurate due to improved analytical data on PHC concentrations in effluent streams, (2) positive steps have been taken to reduce operational and accidental release of petroleum into the sea, and (3) double accounting of PHC inputs from sources has been reduced. Double accounting arises when it becomes difficult to distinguish PHC inputs from closely related sources (e.g., urban runoff, river runoff, industrial and municipal wastes). Thus, there may be the tendency to count the same PHC inputs twice or more times under different sources. One source of PHC into the marine environment that was not estimated was PHC released from pleasure craft, primarily in near-coastal marine waters. Pleasure craft are primarily small inboard or outboard motor- boats. While inputs from pleasure craft may be locally significant, we believe that the total amount of this input would not be on the same scale with the other inputs considered. Major problems still remain in the estimation of PHC inputs into the marine environment. Certainly, significant improvements have been made in recent years in obtaining better analytical data on concentra- tions of PHC entering the marine environment from varied sources. However, additional work is still needed, particularly in the acqui- sition of improved data on PHC inputs from the atmosphere, from municipal and industrial waste sources, and from natural sources such as marine seeps and erosion of terrestrial sediments. Following is a list of recommended research programs or projects that would address these problems:

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82 TABLE 2-22 Input of Petroleum Hydrocarbons Into the Mar ine Environment (mta ~ Sour ce Probable Range Best Estimatea Natur al sources Plar ine seeps 0 . 02-2 . O O .2 Sediment erosion 0 . 005-0 .5 0 .0 5 (Total natural sources) (0.025) - (2.5) (0.25) Offshore production 0.04-0-.06 0.05 Tr anspor tat ion Tanker operations 0.4-1.5 0.7 Dry-docking 0.02-0.05 0.03 Mar ine terminals 0 . 01-0 .03 0 .02 Bilge and fuel oils 0 . 2-0 .6 0 .3 Tanker acc idents 0 . 3-0 . 4 0 . 4 Nontanker accidents 0.02-0.04 0.02 (Total transportation) (0.95) - (2.62) (1.47) Atmospher e 0 . 0 5-0 . 5 0 . 3 Municipal and industr ial wastes and runoff Municipal wastes 0 . 4-1 .5 0 .7 Refineries 0.06-0.6 0.1 Nonr ef ining industr ial wastes 0 .1-0 .3 0 .2 Urban runoff 0.01-0.2 0.12 - River runoff 0.01-0.5 0.04 Ocean dumping 0 . 005-0 . 02 0 .0 2 (Total wastes and runoff) (0 .585) - (3.12) (1.18) TOTAL 1. 7-8 . 8 3 . 2 Ache total best estimate, 3.2 mta, is a sum of the individual best estimates. A value of 0.3 was used for the atmospheric inputs to obtain the total, although we well realize that this best estimate is only a center point between the range limits and cannot be supported r igorously by the data and calculations used for estimation of this input. 1. Improved methods should be developed for large scale, areal documentation of the continental margins to determine the extent of submarine seepages of petroleum. A program should be undertaken to gauge accurately flow rates for seeps of significantly different sizes, including probable microseeps. 2. There should be continued monitor ing of all facilities dis- charg~ng low levels of petroleum hydrocarbons dispersed or dispersed in

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83 aqueous effluents (e.g., offshore platforms, refineries, and other industrial plants and transportation units such as tankers and terminals). 3. Rain samples collected from several locations on the ocean and near sea coasts should be analyzed for PHC content. This work is important since rain scavenging of atmospheric particles is believed to be the major pathway for petroleum into the ocean from the atmosphere. It is also necessary to determine reactions of, and changes occurring in, various petroleum components as they are transported from sources through the atmosphere across and into the oceans. 4. More applied investigations, including accurate measurements of PHC, are needed to better define municipal, industrial, and runoff inputs to the oceans. This is particularly needed in southern hemis- phere countries. These investigations may lead to quantitative methods for distinguishing petroleum hydrocarbons from oil and grease and natural hydrocarbons found in municipal and industrial waste as well as samples of runoff. 5. Data should be collected on the C2-C1O aliphatic hydrocarbons in vapor, particulate, and rain samples from over the oceans, to relate these to the distributions of other classes of organic compounds present in petroleum. 6. Better solubility data are needed for n-alkanes and polynuclear aromatic hydrocarbons to better ascertain the importance of rain scavenging of gases and air-sea gas exchange processes to the contribu- tion of the flux of atmospheric petroleum hydrocarbons to the ocean. 7. There is a need to determine the reactions and organic compound class distributional changes that occur for the various organic com- pounds in petroleum, as this material is transported from its source through the atmosphere across the oceans. 8. Better solubility data are needed for n-alkanes, polynuclear aromatic hydrocarbons, etc., to better ascertain the importance of rain scavenging of gases and a~r-sea gas exchange processes to the contribu- tion of the flux of atmospheric petroleum hydrocarbons to the ocean. REFERENCES Albers, J.P., M.D. Carter, A.L. Clark, O.B. Coury, and S.P. Schweinfurth. 1973. Summary of petroleum and selected mineral statistics for 120 countries, including offshore areas. Professional Paper 817. U.S. Geological Survey, Washington, D.C. 149 pp. Atlas, E., and C.S. Giam. 1981. n-Alkane atmospheric input into the tropic North Pacific Ocean. Unpublished manuscript. Texas A&M university. Bertrand, A.R.V. 1979. Les principaux accidents de diversements patrollers en mer et la banque de donnees de l' Institute Francais du Petrole sur les accidents de navires (1955-1979~. Rev. Inst. Francais Petrole 34:3-7. Bjorseth, A., G. Lunde, and A. Lindskog. 1979. Long range transport of polycyclic aromatic hydrocarbons. Atmos. Environ. 13:34-53.

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