TABLE 2-4 Estimated PAH Contribution to North American Waters and Assumptions of Oil Type Composition by Source

Source

Description of Composition by Oil Type

Estimated PAH Contribution (thousands of tonnes per year)

Natural Seeps

Crude oil

2.5

Petroleum Extraction

 

Platforms

Crude oil, heavy distillates, light distillates, and gasoline

0.0016

Produced waters

Crude oil

0.052

Atmospheric deposition

See Chapter 3 and Appendix D

0.016

Subtotal

 

0.070

Petroleum Transportation

 

Vessel spills

Crude oil, heavy distillates, light distillates, and gasoline

0.12

Pipelines

Crude oil, heavy distillates, light distillates, and gasoline

0.030

Coastal facilities

Crude oil, heavy distillates, light distillates, gasoline

0.0040

Atmospheric deposition

See Chapter 3 and Appendix E

0.016

Subtotal

 

0.17

Petroleum Consumption

 

Land-based

See Chapter 3 and Appendix I

0.54

Aircraft dumping

Jet fuel

0.031

Recreational vessels

Lube oil

0.0015a

< 100 GT vessels

Light distillates

0.0040

> 100 GT vessels

Heavy distillates and light distillates

0.0084

Atmospheric deposition

See Chapter 3 and Appendix H

1.60

Subtotal

 

2.2

Total

 

4.9

aPyrogenic PAH produced during incomplete combustion is not included in this value, which must therefore be considered as a minimum estimate.

loads from various petroleum sources were derived for the major sources of petroleum (Table 2-4). Although these numbers may have value as first-order indicators of where loads of PAH may be important, it is important to note that the toxic effect of specific PAH compounds differ from that of the entire class. Furthermore, sensitivity to various specific PAH compounds can vary dramatically among species, even among closely related taxonomic groups (see Chapter 5). As with other effects from spills, the timing and nature of introduction of PAH, as well as the environmental processes (see Chapter 4) operating at the time, can play a significant role in determining the ultimate toxicological effect these compounds may have.

Many of the source types, including natural seeps, platforms, pipelines, produced waters, vessel spills, vessel operations, aircraft dumping, recreational marine vessels, vessels of less than 100 GT, and coastal facilities, PAH loadings were estimated as a fraction of the total petroleum hydrocarbon loadings, based on measured PAH content of crude oils and refined petroleum products (see Appendix J). Because coastal waters are undersaturated with dissolved PAH relative to the overlying atmosphere, there is a significant net transfer of atmospheric PAH to the oceans. PAH loadings from land-based sources were estimated by assuming that the PAH load from each river is proportional to the estimated petroleum hydrocarbon loading (see Chapter 3 and Appendix E for details). This refinement of the 1985 report Oil in the Sea is a step toward a more rigorous risk assessment of petroleum releases to the coastal oceans.

A significant effort was made to develop estimates of inputs by zone, both along shore regions and two zones offshore (a coastal zone that extended out to 3 miles and an offshore zone from 3-200 miles). This effort, to further delineate the geographic distribution of these inputs, is the second significant difference between the current study and the 1985 Oil in the Sea report, led to the subdivision of North American waters into 17 zones (Figure 2-3). These values were totaled to develop the first approximation of total inputs to the North American and world-wide marine environment listed in Table 2-2 (values reported in the “Regions” column). This regional approach allows the spatial distribution of the inputs to be used as a basis for evaluating the potential risks of the oil inputs to marine resources in each region (Fig. 2-4). It is clear that the ecological effects of oil inputs is a function of many factors, including oil type, release rates, fate processes, and distribution of biological resources. It is difficult to articulate in general terms how each of the input categories may affect marine resources because of the wide range of pathways of exposure, species sensitivity, and potential effects. Regional data may be of benefit to



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