production discharges, or a land-based facility. In these cases, there may be a strong gradient from high to low oil concentration as a function of distance from the source. In other cases, such as land-based runoff and atmospheric inputs, the origin of the oil is a non-point source, and environmental concentration gradients of oil compounds may be weak. Chronic exposures may also result from the incorporation of oil into sediments in which weathering of oil is slow and from which nearly fresh oil may be released to the water column over extended periods. In recent years, it is the long-term effects of acute and chronic oil contamination that have received increasing attention (Boesch et al., 1987)

Petroleum Hydrocarbon Pollution and Its Possible Effects

Petroleum hydrocarbon inputs into North American and worldwide marine waters were computed, based on various databases, for several major categories. Three activities— extraction, transportation, and consumption—are the main sources of anthropogenic petroleum hydrocarbon pollution in the sea. Each of these activities poses some risk of oil release, and as greater amounts of petroleum hydrocarbons are imported into North American waters, the risk increases. The categories are listed in Table 2-2. Details of the methods used, discussion of databases, and computation and distribution of sources are discussed in Appendixes C, D, E, F, G, H, and I. Table 2-2 and Figures 2-2A and 2-2B summarize the sources and inputs for North American and worldwide waters (see Chapter 3 for greater details). Table 2-3 summarizes conclusions about the intercomparability of the data, methods, and assumptions used develop these estimates with those reported by the NRC in 1985 and what significance if any, can be attached to changes in those estimates.

The acute toxicity of petroleum hydrocarbons to marine organisms is dependent on the persistence and bioavailability of specific hydrocarbons. The ability of organisms to accumulate and metabolize various hydrocarbons, the fate of metabolized products, the interference of specific hydrocarbons (or metabolites) with normal metabolic processes that may alter an organism’s chances for survival and repro

TABLE 2-2 Average, Annual Releases (1990-1999) of Petroleum by Source (in thousands of tonnes)

 

North Americaa

Worldwide

 

Best Est.

Regionsb

Min.

Max.

Best Est.

Min.

Max.

Natural Seeps

160

160

80

240

600

200

2000

Extraction of Petroleum

3.0

3.0

2.3

4.3

38

20

62

Platforms

0.16

0.15

0.15

0.18

0.86

0.29

1.4

Atmospheric deposition

0.12

0.12

0.07

0.45

1.3

0.38

2.6

Produced waters

2.7

2.7

2.1

3.7

36

19

58

Transportation of Petroleum

9.1

7.4

7.4

11

150

120

260

Pipeline spills

1.9

1.7

1.7

2.1

12

6.1

37

Tank vessel spills

5.3

4.0

4.0

6.4

100

93

130

Operational discharges (cargo washings)

nac

na

na

na

36

18

72

Coastal facility spills

1.9

1.7

1.7

2.2

4.9

2.4

15

Atmospheric deposition

0.01

0.01

traced

0.02

0.4

0.2

1

Consumption of Petroleum

84

83

19

2000

480

130

6000

Land-based (river and runoff)

54

54

2.6

1900

140

6.8

5000

Recreational marine vessel

5.6

5.6

2.2

9

nde

nd

nd

Spills (non-tank vessels)

1.2

0.91

1.1

1.4

7.1

6.5

8.8

Operational discharges (vessels ≥100 GT)

0.10

0.10

0.03

0.30

270

90

810

Operational discharges (vessels<100 GT)

0.12

0.12

0.03

0.30

ndf

nd

nd

Atmospheric deposition

21

21

9.1

81

52

23

200

Jettisoned aircraft fuel

1.5

1.5

1.0

4.4

7.5

5.0

22

Total

260

250

110

2300

1300

470

8300

aNumbers are reported to no more than two significant figures.

b“Regions” refers to 17 zones or regions of North American waters for which estimates were prepared. These are discussed later in this chapter.

cCargo washing is not allowed in U.S. waters, but is not restricted in international waters. Thus, it was assumed that this practice does not occur frequently in U.S. waters (see Chapter 3 and Appendix E).

dEstimated loads of less than 10 tonnes per year reported as “trace.”

eWorldwide populations of recreational vessels were not available (see Chapter 3 and Appendix F).

fInsufficient data were available to develop estimates for this class of vessels (see Chapter 3 and Appendix E).



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