Dispersants Bibliography

Abstract
Three medium-scale field experiments on the effects of oil, a dispersant and an oil/dispersant mixture were carried out in an intertidal mud flat ecosystem of the Wadden Sea (German Bight). For six successive tides each contaminant was added to the water enclosed in a mesocosm during submersion of the flat. The fate of the oil in the sediment and effects on phytobenthos, bacteria and macrozoobenthos were studied. Penetration of the oil into the sediment was mainly observed at the surface layer. were present when oil was chemically dispersed. Sublethal effects were found in some macrofauna species (reduced feeding activity) and in phytobenthic organisms (increased activity); oil degrading bacteria increased. No major effects were observed when the dispersant alone was added

Abstract
Experiments with chemically and ultrasonically dispersed Arabian light crude oil and a dispersant (Finasol OSR 5) were carried out on an intertidal sand flat in the Wadden Sea (German Bight). “Bremerhaven Caissons,” flow through mescocosms for intertidal field experiments, allowed pollutant addition to the enclosed water during submersion time. Reiterated contaminations over a period of 12 successive tides of low concentrations of oil (10 ppm) and dispersant made it possible to study penetration and alteration processes of the dispersed oil in the sediment. Sublethal and lethal effects upon microphytobenthos, meiofauna, and macrofauna were observed. Oil reduced the activity of microbenthic algae and the food uptake of filter feeding bivalves and a polychaete. Nematodes showed a lower diversity and decreasing abundance in some groups. No major differences between the effects of chemically and ultrasonically dispersed oil on the benthos were observed. Application of dispersant alone had no clear effects when compared to controls

Abstract
Gas chromatography with flame ionization detection was employed to determine the effectiveness of Corexit 9500 on various crude oils. Effectiveness was found to decrease with increasing weathering, but did not correlate with simple oil properties, such as density, viscosity, or maximum weathering percentages

Abstract
A reevaluation of the analytical procedure used for the Swirling Flask Test found that the integration method could be improved. It is believed that integrating the entire chromatogram, rather than its peaks, would lead to a decrease in the maximum variation from 5% to 2%. Authors also recommended a consideration of using a vessel with a septum port instead of a spout. Results of tests using a septum flask found effectiveness results were approximately 8% lower, and showed lower standard deviations than the standard flask

Abstract
Among the topics covered in this review are testing methodologies and procedures, environmental and physical variables, and analytical measurements and standards

Abstract
This review compiles the findings of studies related to testing methodologies in effectiveness studies of dispersants done in large tanks. Critical factors warranting consideration included in methodology include mass balance, analytical method, measurements related to physical properties of the oil, and properties of the water in the tank, among other things

Abstract
The authors review field monitoring protocols related to dispersant effectiveness. Current protocols, including NOAA’s Special Monitoring Applied Response Technology (SMART), are subject to false positives and false negative associated with the techniques. Twenty-eight considerations related to dispersant monitoring are listed, and recommendations are given for screening tests of dispersants to be undertaken before application of the dispersant in field tests

Abstract
A review of published literature on oil spill countermeasures was initiated to find any data related to performance of countermeasure techniques in varying weather conditions. Results found that wind and wave height were the most important factors influencing countermeasures. The application and effectiveness of dispersants were found to be affected by weather because of the amount of dispersant that is applied directly to a spill is wind-dependent, and because the dispersal of oil and the amount of oil suspended in the water column are both dependent on turbulence of the ocean

Abstract
Recent results of dispersant testing are reviewed, including slight revision in the dispersant analytical procedures, testing of new products, testing of long-term stored dispersants, and a comparison of Corexit 9527 and 9500 dispersant formulations. The procedure for the Swirling Flask Test has not altered appreciably since its inception, however the analysis of the quantity of oil dispersed has undergone significant changes. The originally-developed procedure made use of colorimetric analysis, but has since advanced to gas chromatographic analysis. With the change in analysis method, however, a host of subtle changes have been required that were not considered when first changing from colorimetry to gas chromatography. A number of minor improvements have been made to the procedure to correct and upgrade facets of the analysis. Several new dispersant products have been tested, results of this testing will be summarized. A test series was conducted on the dispersant Corexit 9527 that had been stored for more than 20 years in a tank truck. The tests show that the effectiveness, toxicity and colour of the product did vary somewhat between the three levels, however this might not be significant in terms of field effectiveness. A comparison of the laboratory effectiveness of Corexit 9527 and 9500 was completed. Results show that the effectiveness of 9500 is generally greater than that of 9527, however, this is not related to the amount of effectiveness. Generally, the higher the effectiveness, the greater the effectiveness of 9500 and vice versa. Statistically, about ¼ of the time, 9527 is more effective than 9500

Abstract
Data are provided on 106 separate offshore experimental spills to determine dispersant field effectiveness. Effectiveness ratings for 25 of these spills were assigned by the experimenters; they vary from 0 to 100% and have an average of 33%. Measurement techniques used for these experiments are reviewed and describe. The techniques include: subsurface measurements to determine oil in the water column, surface sampling to determine oil remaining, dispersant application amount or distribution, and the use of remote sensing to observe visually the results or to quantify the area of surface oil. Existing means of detection and quantification appear to be effective. Most experimenters have used subsurface oil data in an attempt to establish a mass balance and thereby an effectiveness value. This technique is critically examined using values from historical trials, and it is shown that the subsurface oil does not have a regular distribution in relation to the surface slick. Correlation cannot be established between concentrations at depth or with time and distance. This lack of correlation implies that mass balance values based on subsurface oil concentrations in relation to the surface slick are not reliable. Effectiveness results claimed in the literature are also suspect because they do not correlate well with the maximum oil concentration seen at a given depth. The mathematical relationships used to provide the integrated amount of oil in the water column are also examined. It is shown by simulation that effectiveness claimed is highly sensitive to both assumptions and mathematical treatment. Historical data are used to show that effectiveness values can vary over an order of magnitude depending on the algorithm used. Values in the literature are generally the highest one would obtain using reasonable algorithms. A number of phenomena have been observed at spill sites. Herding of oil occurs immediately after dispersant application and has sometimes been misinterpreted as dispersion. Examinations of spills where slicks were monitored for longer than 3 h show that extensive resurfacing of oil occurred. Resurfacing is particularly problematic because, depending on current and wind, resurfacing may occur outside slick boundaries. When this occurs, resurfaced oil is not included in subsequent calculations, and consequently, effectiveness is overestimated. Field effectiveness cannot be reliably determined by using only measurements of oil in the water column. The distribution of oil in the water column is not known nor does it necessarily bear a relationship to surface slick boundaries. Furthermore, in the initial hours--perhaps as many as 7--the oil concentration in the water column may be transitory as significant amounts of oil resurface. Remote sensing over a long-term such as two or three days is suggested as the primary technique for monitoring experimental spills and for attempting to establish a mass balance

Abstract
We have reviewed the laboratory testing of the chemical and natural dispersion of oil, noting the weaknesses of the Mackay test and comparing it to other methods. Results of both chemical and natural dispersion tests show that anomalous test results are produced in the Mackay apparatus at 0° C. This is attributed to preferential viscous shearing when the oil viscosity is 30 to 200 centistokes (cs). A new test uses a small swirling flask. Dispersant effectiveness results for ten oils from the Mackay, Labofina, and swirling flask tests were compared and the correlation found to be low. Results from the new swirling flask test correlate well with physical property data, especially viscosity. Each laboratory test produces somewhat unique results, and no way has yet been found to determine which test most accurately represents reality

Abstract
Laboratory tests and apparatus for oil spill dispersant effectiveness were the subject of the present study. A review of previous work shows that test results from different apparatus are not highly correlated, and often the rank of effectiveness is also not correlated. The effect of two experimental parameters--settling time and oil-to water ratio--are examined in this study and found to be very important in determining final effectiveness value. Four apparatus--the swirling flask, the flowing column, the Labofina, and the Mackay--are used with 3 dispersants and 16 oils to examine effectiveness values when the oil-to-water ratio is the same (1: 1,200) and when the settling time is maintained at the same value (10 minutes) in all apparatus. The effectiveness values resulting from the four devices are nearly identical after values from the more energetic devices are corrected for natural dispersion. Our conclusions are that the most important parameters of laboratory dispersant testing are settling time and oil-to-water ratio. Energy is less important than previously thought and is important only to the extent that when high energy is applied to an oil-dispersant system, dispersion is increased by an amount related to the oil's natural dispersibility

Abstract
Laboratory tests of oil spill dispersant effectiveness are used around the world to select dispersants for application to specific oils. These tests are presumed, by some, to represent real sea conditions and to provide the user with a result that is representative if not identical to a real dispersant application at sea. A number of tests have been developed over the years. At this time, the two most widely used tests are the Mackay test, otherwise known as the Mackay-Nadeau-Steelman (MNS) test, and the Labofina test, otherwise known as the Warren Springs or rotating flask test. The Mackay test employs a high velocity air stream to energize 6 L of water, whereas the Labofina test uses rotation of a separatory funnel with 250 mL of water. Both tests apply a large amount of energy to the oil/water system. This paper compares test results from these apparatus with those from two lesser known devices, the oscillating hoop and the swirling flask. Both devices are relatively new, and protocols for their use have not been finalized. The oscillating hoop apparatus uses a hoop which is moved up and down at the water surface. The concentric waves serve both to energize the oil in the hoop and to contain it. Thirty-five litres of water are used in this test. The swirling flask test makes use of a 125-mL Erlenmeyer flask. The flask is rotated using a standard chemical/biological shaker to produce a swirling motion in the contents. The results obtained using all 4 apparatus with a number of oils and dispersants are presented. A total of 121 oil/dispersant combinations were tested in the 4 apparatus. The correlation of numeric values between the Mackay, Labofina, oscillating hoop, and swirling flask is low. The correlation of effectiveness ranking is also poor. An oil that disperses more readily than another, according to one test, is less readily dispersable according to one or more of the other tests. Similarly, a dispersant that is more effective by one test is less effective by another. The results from the oscillating hoop correlate poorly with all other test results. Specific tests were also conducted to ascertain the effect of settling or rising time (the time the oil-in-water mixture is allowed to sit unagitated before a sample is taken). Longer settling times alter the oscillating hoop test results dramatically, improve the correlation for results with different apparatus and enhance correlation with physical data such as viscosity.differences in the effectiveness results are still present. Results show that all the high energy tests (the Mackay, the Labofina and the oscillating hoop) produce unique dispersant effectiveness results and those correlate poorly with the physical properties of the oil

Abstract
This paper is a review of five types of chemical treatments for oil spills. Gelling agents change oil to a solid or semi-solid form, but are not widely used because of the large amount of agent required. Elastol, a recovery improvement agent, has been tested and proven to function well under a variety of conditions. A number of oil-in-water emulsion preventers and breakers have been proposed, but none is commercially available. A demoussifier developed by Environment Canada has been recently tested and found to be effective. Surface washing agents contain surfactants and quantitative results on a number of these agents are presented. Dispersants contain surfactants which are intended to break up oil into small droplets in the water column. No undisputed documentation exists to show that dispersants have been very effective in field situations, but analytical means to measure field effectiveness are poor. Laboratory effectiveness results are presented for a number of oils and dispersants. The main concern with treating agents is their effectiveness, and this is often dependent on molecular size and type. Oil has many molecular types and sizes, thus rendering treatment much les than totally effective