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Oil in the Sea III: Inputs, Fates, and Effects
obtain detailed information describing how specific determinations were made, including initial data and intermediate calculated values for individual compounds of interest). Globally, wet deposition and dry aerosol deposition supply 43,000 and 13,600 metric tonnes of C10 to C33n-alkanes to the ocean, respectively. This estimate of 56,600 metric tonnes is within the range of 40,000 to 400,000 metric tonnes reported earlier by Duce and Gagosian, (1982). Most importantly, this loading is overwhelmed by the volatilization of 3,000,000 metric tonnes of these compounds. Clearly these results indicate that the world’s oceans are a net source of hydrocarbons to the atmosphere, where they are transported globally and degraded. In North American coastal waters, 16,000 and 5,030 metric tonnes of C10 to C33n-alkanes are delivered from the atmosphere to the water’s surface, and 1.76 million metric tonnes volatilize (See Table H-1). It is apparent that terrestrial hydrocarbon loadings and near shore sources support dissolved hydrocarbon loadings in coastal waters that far exceed that in equilibrium with the atmosphere. Hydrocarbon degassing from coastal waters is a major geochemical process.
TABLE H-1 Summary of Alkanes and PAH Included in Net Annual Atmospheric Deposition Calculations