aliphatic hydrocarbons are more easily degraded than short-chain compounds, 

 though it may sometimes be difficult to provide adequate dispersion of long- 

 chain paraffins to allow for the maximum rate of degradation. Also, branched 

 chain hydrocarbons are utilized preferentially over their straight-chain 

 isomers. Unsaturation in a hydrocarbon offers a site for immediate hydro- 

 lysis, and as such encourages microbial oxidation. Multiply unsaturated 

 compounds such as butadiene are rapidly oxidized, but they do not occur in 

 crude oil. Aromatic compounds are attacked quite readily, possibly because 

 there are much more water-soluble than aliphatic compounds of comparable 

 molecular weight. The addition of side-chains to an aromatic compound facil- 

 itates microbial oxidation, as does increasing molecular weight. 



The mechanisms by which spilled oil is transported away from the surface 

 of the ocean are complex and poorly understood. A major facet of the contin- 

 uous study of accidental oil spills must of necessity be the sampling and 

 analysis of the oil itself, the water column beneath the oil slick, and the 

 sediment /water interface, which is often the ultimate sink of "weathered" 

 oil. Such investigations were undertaken by the several groups involved in 

 the short- and medium-term assessment of the fate of the Argo Merchant oil. 



There are numerous mathematical models in existence that attempt to de- 

 scribe the transport of oil in the marine environment. Most of these models 

 are limited to two-dimensional spreading and advection at the sea-air inter- 

 face. Understanding the physical and chemical transformations that oil 

 undergoes when spilled in the marine environment is an important facet in 

 developing three-dimensional oil spill models that will accurately predict 

 the transportation and concentrations of oil in the water column, and ulti- 

 mately to the sediments and littoral regions. For this reason, samples of 

 oil were collected from the Argo Merchant, from the slick, the water column, 

 and the sediments beneath the slick. All the samples were initially screened 

 at the USCG Research and Development Center by ultraviolet fluorescence and 

 thin-layer chromatography to determine the amount of oil present. Selected 

 samples have been sent to the NOAA's National Analytical Facility in Seattle, 

 Washington, for gas-chromatographic-mass spectrometric (GC-MS) analysis. It 

 is the goal of this research effort to determine the extent to which the 

 Argo Merchant oil entered the water column as well as the sediments during 

 and immediately after the spill. 



3.2 Oil Sampling 



One of the technical problems associated with the Argo Merchant oil 

 spill was the initial lack of reference samples of the cargo oil and bunker 

 fuel carried by the vessel. There are still no reference samples of the 

 latter. Two different No. 6 fuels were carried as cargo: 50,000 barrels of 

 one, and 139,000 barrels of other. The only oil sample withdrawn directly 

 from one of the cargo tanks was a 16-ounce sample taken from the No. 4 port 

 tank by J. H. Milgram of the Massachusetts Institute of Technology (MIT) on 

 December 19, 1976. Other samples of oil were taken from the slick on several 

 different occasions, as described below, but no samples were taken from the 

 Argo Merchant other than the one obtained by Milgram. Since the viscosities 



69 



