Methods Used To Estimate PAH Loadings to the Marine Environment
To understand the toxic effects of petroleum hydrocarbon releases to the coastal ocean, one has to examine the loading of the more toxic components of the hydrocarbon mixture. Since PAH are thought to be responsible for many of the biological effects of petroleum, the committee estimated PAH loads from various petroleum sources. This refinement of the 1985 National Research Council (NRC) report is a step toward a more rigorous risk assessment of petroleum releases to the coastal oceans. For many of the source types, including natural seeps, platforms (offshore andcoastal), pipelines (offshore and coastal), produced waters, vessel spills, vessel operations, aircraft dumping, two-stroke engines, 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. Environment Canada has measured the amount of a standard suite of PAH listed in Table J-1 in a variety of oils. These data were used to estimate the average total PAH amounts in five types of oils: crude oil, heavy distillates, light distillates, jet fuel, and lube oil (Table J-2). Additionally, the PAH content of gasoline was assumed to be negligible. The best estimates of petroleum hydrocarbon inputs to the sea by the sources discussed above were broken down into the six oil types (crude oil, heavy distillates, light distillates, jet fuel, lube oil, and gasoline), which were then multiplied by the appropriate fractions of PAH in the six types of oil to estimate the PAH contributions to the sea by source.
PAH loadings to North American coastal waters from the atmosphere were calculated for 21 individual PAH based on estimated PAH levels in the coastal atmosphere (Table 2-; see Chapter 3 and Appendix B for details). 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 I for details).
TABLE J-1 PAH Compounds Measured by Environment Canada
TABLE J-2 Oils or Refined Products Used to Calculate Amount of PAH in Different Petroleum Hydrocarbons Discussed in This Report