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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