EFFECTIVENESS, BEHAVIOR, AND TOXICITY OF DISPERSANTS

1983 ◽  
Vol 1983 (1) ◽  
pp. 65-71 ◽  
Author(s):  
Donald Mackay ◽  
Peter G. Wells
Keyword(s):  
Water Column ◽  
Oil Spills ◽  
Current Status ◽  
Dispersed Oil ◽  
Chemical Studies ◽  
Key Issues ◽  
Oil Emulsions ◽  
Dispersant Effectiveness ◽  
Individual Hydrocarbons ◽  
Physical And Chemical

ABSTRACT Three key issues must be addressed when deciding on the desirability of using chemical dispersants for mitigating the adverse effects of oil spills: (1) how effective a given dosage of dispersant will be on a given oil slick; (2) how the dispersed oil and dispersant diffuse into the water column, dissolve, volatilize, degrade, and interact with suspended and bottom sediments; and (3) what effects the dissolved and particulate oil and dispersant will have on water column and benthic biota. It is essential that the first two areas (physical and chemical studies) relate closely to the third (biological aspects) in order that bioassay exposure (in terms of concentration of dispersant, classes of and individual hydrocarbons, and duration) addressing the toxicity issue be realistic. Here, we review the current status of a research program which addresses these issues. Under the program, attempts are being made to quantify dispersant effectiveness (including consideration of effectiveness testing using the Mackay-Nadeau-Steelman system for oils which have evaporated and/or formed water-in-oil emulsions to various extents), water column diffusion, and partitioning of specific hydrocarbons among water, oil, and suspended sediment as well as into the atmosphere. A procedure is described which has been used to quantify the acute toxicity of dispersants to copepods and which is being extended to apply also to the toxic contributions of dissolved and particulate oil. Hopefully, by assembling quantitative expressions for effectiveness, behavior, and toxicity, those situations in which dispersion is desirable can be better identified.

DISPERSANT PERFORMANCE: FINDING NEW RESULTS IN EXISTING DATA

2017 ◽  
Vol 2017 (1) ◽  
pp. 704-724
Author(s):  
Kimberly Bittler
Keyword(s):  
Water Column ◽  
Large Scale ◽  
Oil Spills ◽  
Meta Analysis ◽  
Federal Agencies ◽  
Aquatic Environments ◽  
Risks And Benefits ◽  
Dispersed Oil ◽  
History Of ◽  
Dispersant Effectiveness

Abstract No. 092 Abstract: Chemical dispersants are used to mitigate oil spills in aquatic environments. Dispersants promote the breakdown of oil into smaller droplets that more readily diffuse into the water column. Federal agencies, industry, and academia have a long history of investigating dispersant performance at diverse scales and environmental conditions, including several recent publications. Several studies estimate dispersant performance as dispersion effectiveness (DE, measured as the percent of oil retained in the water column for a period of time after treatment), the concentration of oil in the dispersed in the water column, or the size of dispersed oil droplets. While many organizations have drawn qualitative conclusions from this body of work, a quantitative meta-analysis drawing together historic and recent research on the topic of dispersant effectiveness has not been conducted. This paper analyzed controlled studies measuring performance of dispersants across lab, tank, and large-scale studies. Although this paper examined only a subset of commonly tested oils, the findings strongly support that treatment with dispersants is correlated with increased effectiveness across several metrics, studies, and test methodologies. The conclusions provided by this analysis could be a critical tool for weighing the risks and benefits of using dispersants to respond to oil spills in aquatic environments.

scholarly journals 3-D Oil spill modelling. Natural dispersion and the spreading of oil-water emulsions in the water column

2013 ◽  
Vol 13 (4) ◽  
pp. 325-338 ◽  
Keyword(s):  
Surface Wave ◽  
Water Column ◽  
Oil Spills ◽  
Stokes Equations ◽  
Probability Model ◽  
Breaking Waves ◽  
Navier Stokes ◽  
Two Phase ◽  
Dispersed Oil ◽  
Oil Emulsions

A 3-D hybrid turbulence model, simulating the transport and fate of oil spills in various waters, is used to evaluate the influence of natural dispersion on the spreading of water-in-oil emulsions formed in the water column. The model combines the Navier-Stokes equations for two-phase flows, the RNG k-ε submodel, and parameterized expressions of the basic processes affecting the fate of oil spills. The model also considers the presence of waves, the wind- and wave- induced surface drifts, and the influence of surface wave breaking on the oil spills. Using a stochastic probability model of breaking waves, the loss of surface wave energy into turbulence, due to breaking, is derived and the rate of natural dispersion of oil mass and that of oilwater emulsions formed in the water column is evaluated, under a variety of sea state conditions. Results in the form of oil concentration profiles with depth, graphs showing the variation of the fraction of water (mass) absorbed by the dispersed oil, at various depths and times, as well as graphs showing the oil mass balance, at the sea surface, at various times are compared with counterpart profiles, and graphs obtained from the literature, and useful conclusions are drawn.

scholarly journals Development of an Algorithm for Chemically Dispersed Oil Spills

2020 ◽  
Vol 7 ◽  
Author(s):  
Merv F. Fingas ◽  
Kaan Yetilmezsoy ◽  
Majid Bahramian
Keyword(s):  
Wind Speed ◽  
Water Column ◽  
Oil Spills ◽  
Regression Equations ◽  
Oil Viscosity ◽  
Mixing Depth ◽  
Chemical Dispersion ◽  
Closed Form Solutions ◽  
Dispersed Oil ◽  
Chemically Dispersed Oil

An algorithm utilizing four basic processes was described for chemical oil spill dispersion. Initial dispersion was calculated using a modified Delvigne equation adjusted to chemical dispersion, then the dispersion was distributed over the mixing depth, as predicted by the wave height. Then the droplets rise to the surface according to Stokes’ law. Oil on the surface, from the rising oil and that undispersed, is re-dispersed. The droplets in the water column are subject to coalescence as governed by the Smoluchowski equation. A loss is invoked to account for the production of small droplets that rise slowly and are not re-integrated with the main surface slick. The droplets become less dispersible as time proceeds because of increased viscosity through weathering, and by increased droplet size by coalescence. These droplets rise faster as time progresses because of the increased size. Closed form solutions were provided to allow practical limits of dispersibility given inputs of oil viscosity and wind speed. Discrete solutions were given to calculate the amount of oil in the water column at specified points of time. Regression equations were provided to estimate oil in the water column at a given time with the wind speed and oil viscosity. The models indicated that the most important factor related to the amount of dispersion, was the mixing depth of the sea as predicted from wind speed. The second most important factor was the viscosity of the starting oil. The algorithm predicted the maximum viscosity that would be dispersed given wind conditions. Simplified prediction equations were created using regression.

OIL SPILL CLEANUP WITH DISPERSANTS: A BOOMED OIL SPILL EXPERIMENT

1981 ◽  
Vol 1981 (1) ◽  
pp. 263-268
Author(s):  
Joseph Buckley ◽  
David Green ◽  
Blair Humphrey
Keyword(s):  
Water Column ◽  
Oil Spill ◽  
Oil Spills ◽  
Sea Water ◽  
Visual Observation ◽  
Oil Droplets ◽  
Oil Boom ◽  
Dispersed Oil ◽  
Vertical Density ◽  
Oil Spill Cleanup

ABSTRACT Three experimental oil spills of 200, 400, and 200 litres (l) were conducted in October, 1978, in a semiprotected coastal area on Canada's west coast. The surface slicks were restrained with a Bennett inshore oil boom. The spilled oil was chemically dispersed using Corexit 9527, applied as a 10-percent solution in sea water and sprayed from a boat. The dispersed oil was monitored fluorometrically for some hours. Surface and dispersed oil were sampled for chemical analysis. The highest recorded concentration of dispersed oil was 1 part per million (ppm). After a short time (30 minutes), concentrations around 0.05 ppm were normal, decreasing to background within 5 hours. The concentrations were low compared to those expected for complete dispersion which, as visual observation confirmed, was not achieved. The dispersed oil did not mix deeper into the water column with the passage of time, in contrast to predicted behaviour and in spite of the lack of a significant vertical density gradient in the sea water. This was attributed to the buoyancy of the dispersed oil droplets and the limited vertical turbulence in the coastal locale of the experiment. The integrated quantity of oil in the water column decreased more rapidly than either the mean oil concentration of the cloud or the maximum concentration indicating that some of the dispersed oil was rising back to the surface. The surfacing of dispersed oil was confirmed visually during the experiment. The mixing action of the spray boat and breaker boards apparently created large oil droplets that did not form a stable dispersion. Horizontal diffusion of the dispersed oil was initially more rapid than expected, but the rate of spreading did not increase with time as predicted. The results imply that the scale of diffusion was larger than the scale of turbulence which again can be attributed to the locale of the experiment.

scholarly journals WHERE HAS ALL THE OIL GONE? DISPERSED OIL DETECTION IN A WAVE BASIN AND AT SEA

1987 ◽  
Vol 1987 (1) ◽  
pp. 307-312 ◽  
Author(s):  
H. M. Brown ◽  
R. H. Goodman ◽  
Gerard P. Canevari
Keyword(s):  
Water Column ◽  
Large Scale ◽  
The Past ◽  
Controlled Conditions ◽  
Dispersed Oil ◽  
Wave Basin ◽  
Effective Wave ◽  
Dispersant Effectiveness ◽  
Canada Limited

ABSTRACT During the past 10 years, there have been many sea trials of dispersant chemicals for the purpose of demonstrating the effectiveness of specific products or elucidating the processes of oil dispersion into the water column. Unfortunately, most of these tests have proved inconclusive, leading many to believe that dispersant chemicals are only marginally effective. Wave basin tests have been carried out at the Esso Resources Canada Limited laboratory in Calgary, Canada, to measure dispersant effectiveness under closely controlled conditions. These tests show that dispersed oil plumes may be irregular and concentrated over small volumes, so that extensive plume sampling was required to obtain accurate dispersant effectiveness measurements. In large-scale sea trials, dispersants have been shown effective, but only where sufficient sampling of the water column was done to detect small concentrated dispersed oil plumes and where it was known that the dispersant was applied primarily to the thick floating oil.

Development of the “Next Generation” Chemical Dispersants

1973 ◽  
Vol 1973 (1) ◽  
pp. 231-240 ◽  
Author(s):  
Gerard P. Canevari
Keyword(s):  
Oil Spill ◽  
Oil Spills ◽  
Development Trend ◽  
Current Status ◽  
Next Generation ◽  
Spontaneous Emulsification ◽  
Mixing Energy ◽  
Dispersed Oil ◽  
The Many ◽  
Spill Control

ABSTRACT In order to fully appreciate the development trend for the “next generation” chemical dispersants for oil spills, the current status of this field is briefly reviewed. Recent applications illustrate the specific beneficial potential role of chemical dispersants in the oil spill control, as well as their limitation. The present mechanism of dispersing oil spills by the application of chemical dispersants is well understood and is the subject of many technical papers. While there is some variation in the relative performance and toxicity of the many commercially available products, they all require mixing after application. In instances wherein the dispersant has been marginally effective, inadequate mixing was usually the reason. Thus, mixing is the limiting step rather than application. The mixing of an oil spill by boat propellers, fire hoses, etc., is laborious and time consuming. However, dispersant may be readily applied to large areas by aerial application similar to “crop dusting.” In some instances, the oil spill may even become inaccessible for convenient mixing (e.g., under piers, shallow water). Hence, the elimination (or minimizing) of the mixing step would be a major improvement in the dispersion process. The “next generation” oil spill dispersants will require little or no mixing energy and will approach spontaneous emulsification. The mechanism of “self-mixing” will be outlined in this presentation. Performance data comparing this generic type of chemical dispersant with the more conventional systems commonly used will illustrate the major differences. Another important aspect of this system is the resultant dispersed oil droplet size. The remaining concerns and other considerations requiring further study will be discussed.

Ultrasonic Scattering Measurements of Dispersed Oil Droplets in the Presence of Gas

2014 ◽  
Vol 2014 (1) ◽  
pp. 266-282 ◽  
Author(s):  
Paul D. Panetta ◽  
Dale McElhone ◽  
Kyle Winfield ◽  
Grace Cartwright
Keyword(s):  
Natural Gas ◽  
Water Column ◽  
Droplet Size ◽  
Oil Spills ◽  
Acoustic Scattering ◽  
Gas Bubbles ◽  
Deepwater Horizon ◽  
Oil Droplets ◽  
Large Wave ◽  
Dispersed Oil

ABSTRACT To help minimize the effects of oil spills on marine environments, chemical dispersants are used to disperse the oil in the water column so the oil can be consumed by naturally occurring bacteria. During the Deepwater Horizon incident, 1.1 million gallons of dispersant were injected directly into the flowing plume of oil and natural gas over 1500 meters deep. Dispersant's main effect is to decrease the surface tension at the oil-water interface causing the oil to form droplets smaller than ~70 microns so they can remain in the water column. Currently the efficacy of aerial applied dispersants on surface slicks is determined by measuring the droplet size decrease using a Laser In-Situ Scattering Transmissometer (LISST) or by detecting the oil in the water column using fluorometers. LISST instruments are limited to dilute mixtures, below ~500 ppm, because the LISST signal saturates for concentrated mixtures, and their windows can become occluded by oil and biofilms. Fluorometers only measure oil concentration; thus they cannot distinguish between naturally dispersed oil droplets, which can float back to the surface, from chemically dispersed oil droplets, which will remain in the water column to be naturally biodegraded. When gas is present as was the case in the Deepwater Horizon incident where it was estimated that the plume consisted of ~22% natural gas, the LISST cannot distinguish between oil droplets and gas bubbles and thus is not able to track the effectiveness of dispersants in the presence of gas. Acoustic measurements overcome the problems associated with the LISST and fluorometers and are ideal for applications subsurface near a blowout and for low ppm levels expected for surface slicks. One of the key features of the sound wave propagating through the water is the scattering at the interface between the water and object. In previous work we showed the proof of concept to measure the average oil droplet size using acoustic. We used the resonance behavior of the gas bubbles to identify them and separate their contribution to the measured acoustic scattering for various oil and dispersant combinations . We developed acoustic scattering and resonance measurements to track the size of oil droplets in the presence of gas during subsurface releases at SINTEF and in Ohmsett's large wave tank.

Dispersant Effectiveness and Toxicity—An Integrated Approach

2003 ◽  
Vol 2003 (1) ◽  
pp. 335-339
Author(s):  
M.C. Sterling ◽  
R.L. Autenrieth ◽  
J.S. Bonner ◽  
C.B. Fuller ◽  
C.A. Page ◽  
...  
Keyword(s):  
Water Column ◽  
Toxicity Testing ◽  
Integrated Approach ◽  
Droplet Coalescence ◽  
Oil Droplets ◽  
Oil Droplet ◽  
Shear Rates ◽  
Dispersed Oil ◽  
Dispersant Effectiveness ◽  
Experimental Dispersion

ABSTRACT An integrated approach to study chemical dispersant effectiveness and dispersed oil toxicity is presented. Conventional lab scale effectiveness tests generally provide a measure of overall dispersant effectiveness. However, chemical dispersion can be viewed as two processes: (1) dispersant-oil slick mixing and (2) oil droplet transport into the water column. Inefficiencies in either process limit the overall dispersant effectiveness. This laboratory study centered on the latter process and was conducted to focus on the impacts of water column hydrodynamics on the resurfacing of dispersed oil droplets. Using a droplet coalescence model (Sterling et al., 2002), the droplet coalescence rates of dispersed crude oil was determined within a range of shear rates. A controlled shear batch reactor was created in which coalescence of dispersed oil droplets were monitored in-situ. Experimental dispersion efficiencies (C/C0) and droplet size distributions were compared to those predicted by Stokes resurfacing. Experimental C/C0 values were lower than that predicted from Stokes resurfacing. Experimental dispersion efficiency values (C/C0) decreased linearly with increasing mean shear rates due to increased coalescence rates. These results suggested that dispersed oil droplet coalescence in the water column can adversely impact overall dispersant efficiency. To avoid high control mortality in toxicity testing, the toxicity exposure chamber was designed with separate compartments for scaled mixing and organism exposure, respectively. Chamber design includes continuous re-circulation between mixing and exposure chamber. A 1-minute exposure compartment residence time was determined from tracer studies indicating virtually identical oil concentrations in the mixing and exposure compartments. In addition, the 96-hour mortality of 14-day oil Menidia beryllina varied from 2% in the no-oil control tests to 87% in the dispersed oil (200 mg/L) tests. These results show the effectiveness of the integrated vessel for the characterization and toxicity testing of oil dispersions.

USING OIL SPILL DISPERSANTS ON THE SEA

1989 ◽  
Vol 1989 (1) ◽  
pp. 343-353 ◽  
Author(s):  
James N. Butler
Keyword(s):  
Water Column ◽  
Oil Spills ◽  
Field Tests ◽  
Long Term Effects ◽  
Oil Slick ◽  
Dispersed Oil ◽  
Oil Spill Dispersants ◽  
The Times ◽  
Aerial Sprays

ABSTRACT Primary consideration in this critical review was given to treating oil spills at sea with the intent of reducing the environmental impact of that oil if it should reach the shore. The general conclusions reached were:In carefully planned and monitored laboratory and sea tests, oil has been effectively dispersed; but at many field tests and at accidental spills, reported effectiveness has been low—perhaps because of poor targeting and distribution of aerial sprays, because the oils were too viscous to be dispersable, or the observations of effectiveness were inconclusive.The acute lethal toxicities of dispersant formulations currently in use are usually lower than those of the more volatile and soluble fractions of crude oils and their refined products; hence the toxicity of dispersed oil is due primarily to the oil and not to the dispersant.Sublethal effects of dispersed oil observed in the laboratory occur in most cases at concentrations comparable to or higher than those expected in the water column during treatment of an oil slick at sea (1 to 10 ppm) but seldom at concentrations less than are found several hours after treatment (less than 1 ppm). Since the times of exposure in the laboratory are much longer than predicted exposures during slick dispersal at sea (one to three hours), the effects would be correspondingly less.In open waters, organisms on the surface will be less affected by dispersed oil than by an oil slick, but organisms in the upper water column will experience greater exposure to oil components if the oil is dispersed. In shallow habitats with poor water circulation, benthic organisms will be more immediately affected by dispersed than untreated oil. Long-term effects of dispersed oil on some habitats, such as mangroves, are less, and the habitat recovers faster if the oil is dispersed before it reaches that area.Because the principal benefit of dispersant use is to prevent oil stranding on sensitive shorelines, and because dispersability of oil decreases rapidly with weathering, prompt response is essential.

EFFECTS OF CHEMICAL DISPERSANTS AND MINERAL FINES ON PARTITIONING OF PETROLEUM HYDROCARBONS IN NATURAL SEAWATER

2008 ◽  
Vol 2008 (1) ◽  
pp. 633-638 ◽  
Author(s):  
Kenneth Lee ◽  
Zhengkai Li ◽  
Thomas King ◽  
Paul Kepkay ◽  
Michel C Boufadel ◽  
...  
Keyword(s):  
Crude Oil ◽  
Water Column ◽  
Petroleum Hydrocarbons ◽  
Oil Spills ◽  
Suspended Sediments ◽  
Bulk Water ◽  
Natural Seawater ◽  
Dispersed Oil ◽  
Aliphatic And Aromatic Hydrocarbons ◽  
Mineral Aggregates

ABSTRACT The interaction of chemical dispersants and suspended sediments with crude oil influences the fate and transport of oil spills in coastal waters. Recent wave tank studies have shown that dispersants facilitate the dissipation of oil droplets into the water column and reduces the particle size distribution of oil-mineral aggregates (OMAs). In this work, baffled flasks were used to carry out a controlled laboratory experimental study to define the effects of chemical dispersants and mineral fines on the partitioning of crude oil, major fractions of oil, and petroleum hydrocarbons from the surface to the bulk water column and the sediment phases. The dissolved and dispersed oil in the aqueous phase and OMA was characterized using an Ultraviolet Fluorescence Spectroscopy (UVFS). The distribution of major fractions of crude oil (the alkanes, aromatics, resins, and asphaltenes) was analyzed by thin layer chromatography coupled to flame ionized detection (TLC/FID); aliphatic and aromatic hydrocarbons were analyzed by gas chromatography and mass spectrometry (GC/MS). The results suggest that chemical dispersants enhanced the transfer of oil from the surface to the water column as dispersed oil, and promoted the formation of oil-mineral aggregates in the water column. Interaction of chemically dispersed oil with suspended particular materials needs to be considered in order to accurately assess the environmental risk associated with chemical oil dispersant use in particle-rich nearshore and esturine waters. The results from this study indicate that there is not necessarily an increase in sedimentation of oil in particle rich water when dispersants are applied.

Sign in / Sign up

Export Citation Format

Share Document