Ecological Impact Analysis of Dispersants and Dispersed Oil: An Overview (original) (raw)
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Oil Spill Dispersants: Boon or Bane?
Environmental Science & Technology, 2015
Dispersants provide a reliable large-scale response to catastrophic oil spills that can be used when the preferable option of recapturing the oil cannot be achieved. By allowing even mild wave action to disperse floating oil into tiny droplets (<70 μm) in the water column, seabirds, reptiles, and mammals are protected from lethal oiling at the surface, and microbial biodegradation is dramatically increased. Recent work has clarified how dramatic this increase is likely to be: beached oil has an environmental residence of years, whereas dispersed oil has a half-life of weeks. Oil spill response operations endorse the concept of net environmental benefit, that any environmental costs imposed by a response technique must be outweighed by the likely benefits. This critical review discusses the potential environmental debits and credits from dispersant use and concludes that, in most cases, the potential environmental costs of adding these chemicals to a polluted area are likely outweighed by the much shorter residence time, and hence integrated environmental impact, of the spilled oil in the environment.
Proceedings, 2001
The Marine Spill Response Corporation (MSRC) and the American Petroleum Institute (API) recently completed a multiyear research program on dispersants and dispersed oil consisting of four elements: information synthesis and dissemination, improved laboratory methods for toxicity evaluation, mesocosm testing, and field experiments. These research efforts contributed to the recent changes in the way dispersants are viewed in the United States. When combined with other research findings from the last 10 years, this information, now available to response planners, greatly improved and contributed to a growing interest in the use of dispersants, including the potential for the extension of preauthorization areas. The primary objectives of this paper are to summarize the objectives of the program, highlight major findings, and identify the sources where the results can be examined in detail.
Chemical dispersants: Oil biodegradation friend or foe?
Marine pollution bulletin, 2016
Chemical dispersants were used in response to the Deepwater Horizon oil spill in the Gulf of Mexico, both at the sea surface and the wellhead. Their effect on oil biodegradation is unclear, as studies showed both inhibition and enhancement. This study addresses the effect of Corexit on oil biodegradation by alkane and/or aromatic degrading bacterial culture in artificial seawater at different dispersant to oil ratios (DORs). Our results show that dispersant addition did not enhance oil biodegradation. At DOR 1:20, biodegradation was inhibited, especially when only the alkane degrading culture was present. With a combination of cultures, this inhibition was overcome after 10days. This indicates that initial inhibition of oil biodegradation can be overcome when different bacteria are present in the environment. We conclude that the observed inhibition is related to the enhanced dissolution of aromatic compounds into the water, inhibiting the alkane degrading bacteria.
Environmental Science and Pollution Research, 2013
Dispersants are important tools in oil spill response. Taking advantage of the energy in even small waves, they disperse floating oil slicks into tiny droplets (<70 μm) that entrain in the water column and drift apart so that they do not re-agglomerate to reform a floating slick. The dramatically increased surface area allows microbial access to much more of the oil, and diffusion and dilution lead to oil concentrations where natural background levels of biologically available oxygen, nitrogen, and phosphorus are sufficient for microbial growth and oil consumption. Dispersants are only used on substantial spills in relatively deep water (usually >10 m), conditions that are impossible to replicate in the laboratory. To date, laboratory experiments aimed at following the biodegradation of dispersed oil usually show only minimal stimulation of the rate of biodegradation, but principally because the oil in these experiments disperses fairly effectively without dispersant. What is needed is a test protocol that allows comparison between an untreated slick that remains on the water surface during the entire biodegradation study and dispersant-treated oil that remains in the water column as small dispersed oil droplets. We show here that when this is accomplished, the rate of biodegradation is dramatically stimulated by an effective dispersant, Corexit 9500®. Further development of this approach might result in a useful tool for comparing the full benefits of different dispersants.
Removal of crude oil from highly contaminated natural surfaces with corexit dispersants
Journal of Environmental Management, 2019
Dispersants are used to reduce the impact of oil spills in marine environment. Experiments were conducted with natural materials which were contaminated by direct application of fresh Louisiana crude oil. The natural materials evaluated included sea sand (South Beach in Miami, Florida), red mangrove leaves (Rhizophora mangle), and sea shells (Donax variabili). Salt water at two different salinities (17 and 34 ppt) was used with two types of Corexit dispersant solutions (9500A and 9527A) in concentrations ranging from 100 to 3500 mg/L. Washing of the contaminated samples was conducted by a three-step mixing procedure (salt water only, then with the addition of the dispersant solution to the salt water, and salt water) to simulate oil-saltwater-dispersant interactions. In general, increasing dispersant concentration increased the percentage of oil dispersed into the aqueous phase up to dispersant solutions containing 400 mg/L for Corexit 9500A and 300 mg/L Corexit 9527A. Increasing the dispersant concentration above these levels also decreased the dispersion of oil from the surfaces. At very high concentrations of dispersant solutions (above 1500 mg/L), the percentage of oil dispersed into the solution from the contaminated surfaces was about one half what was observed at 400 mg/L with Corexit 9500A and 300 mg/L Corexit 9527A. Although dispersants were most effective for removing the fresh Louisiana crude oil from sand particles and dispersing into the solution due to large surface area of the particles per unit weight; the residual oil remaining on the sand particles was relatively high in comparison to mangrove leaves and sea shells due to clustering of sand particle with oil. There was some oil penetration into the porous structure of the sea shells (at the microscopic level) which could not be removed.
International Oil Spill Conference Proceedings, 2003
This paper describes two comprehensive technical assessments of potential dispersant use in the Gulf of Mexico Region (GOMR) and Pacific Outer Continental Shelf Region (POCSR). The assessments considered both operational and environmental issues. Spill scenarios currently used for spill response planning or environmental impact assessments were analyzed. Dispersibility of oils and “time-windows” (TWs) for dispersant operations were assessed for GOMR- and POSCR-produced crude oils, as well as for oils imported into California. The TWs were estimated by oil fate modeling. It was found that most of the GOMR-produced oils for which data were available are light and dispersible when fresh. By contrast, only a few of the POCSR produced oils appear to be dispersible. The situation for oils imported into California is more favorable, as over 50% of crude oil volume imported annually is comprised of oils with adequate TWs. Logistic capacities of various dispersant application platforms were ...
The Use of Dispersants in Marine Oil Spill Response
2020
Committee on the Evaluation of the Use of Chemical Dispersants in Oil Spill Response Ocean Studies Board Board on Environmental Studies and Toxicology Division on Earth and Life Studies This prepublication version of The Use of Dispersants in Marine Oil Spill Response has been provided to the public to facilitate timely access to the report. Although the substance of the report is final, editorial changes may be made throughout the text and citations will be checked prior to publication. The final report will be available through the National Academies Press in the summer 2019.
Journal of Marine Science: Research & Development, 2015
Dispersants are essential tools for responding to large marine oil spills, both at the surface and in deep water at uncontrolled well-heads. By reducing the interfacial tension between oil and water, they allow turbulence from surface wavelets or well-head ejection to disperse oil as tiny droplets (<70m). Although the intrinsic density of the oil is unaffected, droplets are too small to rise rapidly, and minor turbulence and diffusive dilution impede droplet encounter and coalescence. Oil droplets disperse to very dilute concentrations, and provide substantial surface area for indigenous microbes to rapidly degrade the oil hydrocarbons. While the literature on this latter point is confused because few experiments have assessed biodegradation at environmentally relevant concentrations in natural seawater, we show here that three dispersants widely-available in international stockpiles effectively stimulate biodegradation when compared to oil in floating slicks, decreasing the residence time of the oil in the environment from many months (and potentially years if tarballs form or the oil reaches a shoreline) to a few weeks.