The Rates of Transport and Fates of Petroleum Hydrocarbons in a Controlled Marine Ecosystem, and a Note on Analytical Variability

Abstract

In order to predict the chemical behavior of oil spilled in a marine environment, it is necessary to quantify the rates of the different transport mechanisms operating on the oil. At the Marine Ecosystems Research Laboratory (MERL), University of Rhode Island, the fluxes of water and sediment are controlled, making possible accurate budgeting of petroleum hydrocarbons in an environment approximating a temperate estuary. Four separate laboratories have cooperated in a study on the MERL tanks to which known amounts of water-accommodated No. 2 fuel oil have been added. A preliminary budget has been completed, indicating that the primary loss was to the atmosphere via evaporation. Biodegradation was important for some classes of hydrocarbons and increased with temperature and duration of oil exposure. Particulate material adsorbed hydrocarbons amounting to approximately 15 percent of the oil added to the tanks, and carried them to the sediment where 7–16 percent of the added oil was eventually found. The sedimentary hydrocarbons were depleted in low molecular weight aromatic compounds (up to three rings) relative to the original oil. An unexpected but valuable result of these studies has been a better understanding of the levels of variability to be expected when naturally inhomogeneous systems are studied by different methods in different laboratories. Variability has been determined for measuring lipids in uncontaminated water (x = 8.2 µg/1; σn–1 = 6.5; one laboratory; 43 samples taken over a period of 8 weeks) and in tank sediments (x = 146 µg/g dry weight; σn–1 = 33.6; two laboratories; 37 samples taken over a period of six months). Comparisons have also been conducted on rates of biodegradation obtained by two different methods (gas chromatographic analyses of water column hydrocarbons with emphasis on the changing ratios of n-alkanes to isopre-noids, and laboratory studies of individual radio-labelled hydrocarbons converted to 14CO2).

Low Chronic Additions of No. 2 Fuel Oil: Chemical Behavior, Biological Impact and Recovery in a Simulated Estuarine Environment

“…The F, hydrocarbon fraction (25 % of the total) included substituted benzenes, naphthalene and its C,-through C,-substituted isomers, dibenzothiophene and C,-dibenzothiophenes, and phenanthrene with its C,-to C,-substituted isomers. The OWD used for dosing was slightly richer than the original oil in its content of the more soluble aromatic (F,) compounds (Gearing et al, 1979), in agreement with the measured solubilities of exposed to a range of oil concentrations. During the first experiment (1977), the total hydrocarbon level varied from 300 to 500 @g l-I just after a dosing to 30 to 70 pg 1-I immediately before the next dosing, with an overall average concentration of 190 pg 1-' (Fig.…”

“…The concentrations of petroleum-derived hydrocarsamples (Gearing et al, 1979) and 25 % for sediment bons decreased exponentially with time following samples (Gearing et al, 1978).…”

“…Work-up and analysis of hydrocarbons have been performed in 3 laboratories. Detailed descriptions of individual analytical methods are given in Farrington and Tripp (1977), Gearing et al (1978Gearing et al ( , 1979Gearing et al ( , 1980, and Wade and Quinn (1980).…”

“…S), especially in relation to the total amount of oil added (cf. Gearing et al, 1979;Gearing et al, 1980;Wade and Quinn, 1980). The primary cause of the discrepancy is probably a difference in sampling efficiency of the 2 coring devices usually employed, with the flow-through corer of 1978/79 being much more efficient than the ball-valve corer of 1977 (Gearing et al, 1980).…”

Impact of man on the coastal environment / technical editor, Thomas W. Duke.

“…2 fuel oil as the pollutant. It was found that added oil was 40 to 60 percent removed by evaporation, but significant quantities of both saturated and aromatic hydrocarbons were transported to the bottom by adsorption on sinking particles (Gearing et al, 1979). At water column concentrations of 93 ppb total hydrocarbon, most species of benthic animals declined relative to a control tank.…”