Oil Weathering Research Articles

Physical-chemical weathering of petroleum hydrocarbons from the IXTOC I blowout: chemical measurements and a weathering model

ABSTRACT Detailed chemical measurements on the saturated and aromatic hydrocarbon composition of surface oil/mousse, surface microlayer, and water column samples were coupled to attempts to model the chemical weathering of oil from the Ixtoc I blowout. Such a modeling effort, rooted firmly in analytical measurements on samples from an actual major spill, has been attempted here for the first time. The glass capillary gas chromatographic and GC/MS/computer analytical results were used to formulate evaporation, dissolution, and biodegradation weathering indicator parameters consisting of component groupings. The partitioning of these groupings into dissolved and evaporated fractions was then mathematically modeled along with the time-dependent change in the surface oil's composition. Biodegradation was of minimal relative importance in weathering oil from this spill. The model presented here is a product of fundamental physical-chemical principles, the parameters of which were refined through hindcast adjus...

Chemical and biological weathering of oil, from the Amoco Cadiz spillage, within the littoral zone

The spillage of oil from the wreck of the supertanker Amoco Cadiz resulted in massive oiling of the littoral zone along 320 km of shoreline of the Brittany Coast. This study examined the fate of Amoco Cadiz oil which entered the intertidal zone. Biodegradation by indigenous microbial populations was an extremely important process in the weathering of the oil. Alkanes were preferentially degraded but branched alkanes and polynuclear aromatic compounds also were subject to microbial attack. The chemical evolution of the residual ‘hydrocarbon mixture’ within the littoral zone led to a relative enrichment of isoprenoid alkanes, naphtheno-aromatic and napthenic compounds, alkylated phenanthrenes, aromatic organic sulfur compounds e.g. dibenzothiophenes, hopanes and C27−C31 alkanes. These classes of compounds appear to be most resistant to biological and chemical weathering. Continued inputs of relatively unweathered oil, which may be preserved in subsurface anaerobic sediments, and pooling of oil becomes increasingly important with time, producing a patchy distribution of oil, which has been weathered to varying degrees. The presence of hydrocarbons within the littoral zone, as a highly weathered residual oil, appears to be a long lived (multi-year) phenomenon.

PHYSICAL-CHEMICAL WEATHERING OF PETROLEUM HYDROCARBONS FROM THE IXTOC I BLOWOUT—CHEMICAL MEASUREMENTS AND A WEATHERING MODEL

ABSTRACT Detailed chemical measurements on the saturated and aromatic hydrocarbon composition of surface oil/mousse, surface microlayer, and water column samples were coupled to attempts to model the chemical weathering of oil from the Ixtoc I blowout. Such a modeling effort, rooted firmly in analytical measurements on samples from an actual major spill, has been attempted here for the first time. The glass capillary gas chromatographic and GC/MS/computer analytical results were used to formulate evaporation, dissolution, and biodegradation weathering indicator parameters consisting of component groupings. The partitioning of these groupings into dissolved and evaporated fractions was then mathematically modeled along with the time-dependent change in the surface oil's composition. Biodegradation was of minimal relative importance in weathering oil from this spill. The model presented here is a product of fundamental physical-chemical principles, the parameters of which were refined through hindcast adjustments and a combination of field observations and laboratory analyses. It has powerful predictive capabilities with regard to the oil's changing composition and its partitioning into the water column as a spill approaches an area of impact.

OHMSETT RESEARCH OVERVIEW, 1979–1980*

ABSTRACT This paper presents an overview of the 1979–1980 work performed at the OHMSETT spill research facility of the U.S. Environmental Protection Agency (EPA). The experiences of these 2 years are discussed in the light of the purpose and objectives of OHMSETT, as is the probable direction of research there during the coming years. Foremost among the objectives has been the evaluation and advancement of the state of the art for spill response. The bulk of the effort at OHMSETT, therefore, has been toward testing and investigating ways to improve equipment. This paper briefly summarizes the results of 12 equipment performance evaluations, 2 new equipment development programs, and an experimental oil weathering program. The equipment evaluated was the U.S. Coast Guard high speed “zero relative velocity” skimmer prototype; the Sapiens Sirene skimming system; the Hydrovac System sweeper arm; the Soviet harbor oil/debris skimmer; the Oil Mop remote skimmer prototype; the Versatile Bennett Arctic skimmer prototype; the Petro-Fiber, Oljesanering, AB Sorbent Distribution/Recovery System; the Global Oil Recovery (DiPerna) skimmer; the Clean Atlantic Associates Fast Response Open Sea Skimming System; the University of Lowell oil gelation system; the Peabody Meyers Corp. Vactor air conveyor; and a Coleman Environmental Pollution Control Equipment Co. vacuum truck. The equipment developed was the Johnson sampler for stratified liquids and the Johnson high speed skimmer. Several new areas of work are anticipated for the near future. These include evaluation of cleanup equipment in the presence of ice, increased emphasis on testing at spills-of-opportunity, a study of some of the problems associated with high viscosity water-in-oil emulsions, testing separators and pumps for spill response, increased emphasis on smaller skimmers, and further testing with hazardous materials.

The fate and weathering of surface oil from the bravo blowout

This paper presents a description of the drift spreading, dissipation and weathering of the oil on the surface following the Bravo blowout. Simulation of the drift, spread and dissipation of the oil on the surface is compared with field data. The dissipation computations are based upon a simple one-parameter budget model. Tidal currents are included in the drift (spreading) computations. The results of the computations show fair agreement with the observations. Drift card releases and statistical computations are also presented which illustrate the fortunate timing of the spill with regard to coastal pollution.

A computer simulation of oil spills

The discovery and development of oil resources in the Northern Florida Gulf Outer Continental Shelf will ultimately cause oil spills in this area. This study estimates the percentage of the spills that will reach the Florida coast. A computer simulation model incorporating data for seasonal winds, weathering of oil on the sea, and develop ment and transportation of crude oil is presented. Investigations show the effects of both the original location of the spill and the seasonal winds on the frequency with which oil spills reach the coast.

The weathering of tar on Bermuda

Abstract The indices to determine the weathering of crude oil, which were developed by Blumer, Ehrhardt and Jones (Deep-Sea Research, 20, 239–259, 1973), were applied with success to the tar that is being deposited on Bermuda. Relative to the fresh, floating incoming tar, sunken tar shows pronounced microbiological degradation while tar adhering to the rocky shore shows evaporative loss with less microbial degradation. Surprisingly, normal alkanes with an even number of carbon appear to be more prone to microbial degradation than the ones with an odd carbon number.

Who spilled the oil

Matching an oil spill with its source requires methods that take into account the weathering of oil in the spill.

Matching an oil spill with its source requires methods that take into account the weathering of oil in the spill

The analytical approach to the identification of the source of an oil spill is discussed. Since the identification of the source of an oil spill requires a forensic chemical analysis, several different types of analyses are used, namely, thin-layer chromatography, gas chromatography, liquid chromatography, low-temperature luminescence, infrared spectroscopy, and emission spectroscopy. The application of these methods to the process of proving or disproving the source of an oil spill is described with specific examples. Special sampling devices and special equipment for studying weathering effects on the validity of the methods are described.

Mechanical Dispersal of Oil Stranded in the Littoral Zone

The natural weathering and dispersion of oil stranded in the littoral zone depend on the type and volume of the oil and on the amount of available energy. Energy inputs can be biological, chemical, mechanical, or thermal; however, the single most important input appears to be from mechanical energy (winds, waves, tides, water levels, and ice). The residence time or persistence of stranded oils increases as mechanical energy levels at the shoreline decrease. The primary inputs of mechanical energy at the shoreline are due to wave action, and energy levels vary depending on the wind regime, fetch areas, and local exposure of a section of coast. In cold or polar climates, energy levels at the shoreline are reduced by the presence of ice on the sea or an ice foot on the beach. This review of the concepts associated with littoral processes, in terms of the mechanical dispersal of stranded oil, provides the basis for estimation of the persistence of oil on shorelines. Key words: petroleum (weathering, dispersal), coastal processes, wave energy, sea ice, ice foot, Canada

Analyses of Aromatic Hydrocarbons in Intertidal Sediments Resulting from Two Spills of No. 2 Fuel Oil in Buzzards Bay, Massachusetts

We have analyzed the two- and three-ring aromatic hydrocarbons from the Wild Harbor oil spill in September 1969 and the Winsor Cove oil spill in October 1974, in intertidal marsh sediments, using glass capillary gas-chromatographic and mass-fragmentographic analyses. Naphthalenes with 0–3 alkyl substitutions and phenanthrenes with 0–2 substitutions decreased in concentration with time in surface sediments. The more substituted aromatics decreased relatively less and in some cases actually increased in absolute concentration. The changes in composition of the aromatic fraction have potential consequences for the ecosystem and provide insight into geochemical processes of oil weathering. Key words: oil pollution, aromatic hydrocarbons; gas chromatography; gas chromatography–mass spectrometry; geochemistry; marsh; sediments; oil spills

EFFECTS OF MICROBIAL ACTIVITY ON AQUATIC POLLUTANTS*

Bacteria and fungi present in estuarine and marine water and sediment accomplish significant degradation of crude oil, refined oils, polychlorinated biphenyls, and organomercurials, with the rate and extent of degradation varying with species, geographic source, temperature, and other biologic and environmental parameters. Our biodegradation studies have been extended to determine if physical weathering and/or microbial degradation of oil by microorganisms present in Chesapeake Bay water and sediment produces potentially carcinogenic substances. Water and sediment from an area in Chesapeake Bay that receives heavy input of oil and from a relatively nonpolluted site have been assayed for mutagenic ability by use of the Ames method, which is a bacterial assay and is highly sensitive. Preliminary findings indicate the presence of mutagenic substances in samples collected from the polluted site. Extracts of oil subjected to microbial degradation under controlled laboratory conditions did not yield detectable mutagenic activity. In situ studies are in progress.

Modeling of oil evaporation in aqueous environment

A numerical model is developed to predict the changes of oil characteristics, specific gravity, percentage weight remain and percentage volume remain of oil on water through evaporation known to dominate the early stage of weathering. This model is based on the assumption that oil, though complex, can be considered as a chemical compound of individual fractions of distinguishable chemical and physical characteristics. The major driving forces for evaporation being considered here include air temperature, wind speed and size of slick. Laboratory experiments were conducted using No. 2 fuel oil, Nigerian Crude and Venezuelan Crude to calibrate the numerical model and to gain physical insight of the oil evaporation process. Based on the laboratory results, empirical relationships are proposed for determining the diffusion coefficient described in the first-order decay formula. Laboratory results revealed that the first-order decay law of a unique diffusion coefficient cannot adequately cover the total range of decay. Both numerical and laboratory results seemed to indicate that the effect of temperature on oil weathering is significant in the very early stage of weathering, but diminishes at a later time. The effect of wind speed is more uniform throughout the time duration being tested.

Comparative Identification of Oil Spills by Fluorescence Spectroscopy Fingerprinting

ABSTRACT A simple and rapid method for the comparative identification of oil spills with suspect source oils is described using fluorescence spectroscopy. The method involves the excitation of an oil, diluted in cyclohexane, at a distinct wavelength and obtaining a “fingerprint” in the form of an emission spectrum. Contamination and weathering of the environmental oil is considered. The method is applied to two different oil spills occurring near the same area at about the same time. Results are confirmed by gas chromatography.

Oil Spill-Source Correlation by Gas Chromatography: An Experimental Evaluation of System Performance

ABSTRACT A simple gas chromatographic method correlates unknown oils in natural waters with possible source oils. Under the operating procedures involved, unique matches are generally achieved without miscorrelations, even when up to 15 oils of the same type (#2, #4, #6 fuel; crudes, etc.) are possible sources. Oil samples are quantitatively characterized by ratios of intensities corresponding to their contents of several components of known geochemical variability and resistance to weathering. The effects of weathering, sample types, and added spill control chemicals were determined by “blind” correlation of 35 artificially weathered oils, each with one of 17 possible sources. Oil type and weathering did not seriously influence spill-source matching success. The presence of highly similar source oils was the major performance-limiting factor. We determined the extent of this limitation, and thereby the probability of successful performance, for collections of oils from Greater New York Harbor products, and from Portland, Maine (crudes: 450 tankers/yr.). The probability that a unique correlation can be reached decreased with increase in the number of oils of the same type which were a priori possible sources and therefore candidates for matching; for the New York Harbor and Portland collections examined success rates were: 1–8 candidate oils, 100 percent; 14 oils, 50 percent; 22 oils, 27 percent.

The use of ancrod to prevent thrombosis on prosthetic heart valves: An experimental study

<h3>Objectives</h3> After the Deepwater Horizon, response vessels were brought near the wellhead area to stop the leak, collect oil and drill the relief wells. The objective of this paper is to characterise inhalation exposure on these vessels for various exposure groups (EGs) to total hydrocarbons (THCs). <h3>Method</h3> Approximately 100 EGs based on job title group, tasks and time period during the response effort were standardised across these vessels. Descriptive statistics were calculated from the measurements for each EG on each vessel. Since many of the data were censored (i.e., below the limit of detection), a Bayesian method was used to obtain estimates for the arithmetic mean (AM), geometric mean, and geometric standard deviation. <h3>Results</h3> During the first time period (April 20–May 14), the range of the AMs on the vessels was 1.9–24.2 ppm THC. Exposures were lower during the second period (May 15–July 15) when dispersant was used to reduce air concentrations (0.1–14.6 ppm). After top-capping the well, a substantial reduction was observed on all seven ships (0.1–1.9 ppm). After bottom capping (&gt;August 10), exposures generally increased on the ships (0.1–3.8 ppm), most likely due to decontamination activities. The vessel capping the well and the vessel burning waste oil and gas had significant differences from the vessels drilling the relief wells. <h3>Conclusions</h3> Differences were found by vessel and time period that likely reflected oil weathering and differences in job and vessel activities.