Environ. Sci. Technol. 2010, 44, 5685–5686
After the oil is no longer leaking.. . DANNY REIBLE The University of Texas, Austin, Texas
RHONDA SAUNDERS
Authors’ Viewpoint
We have all watched with fascination and horror at the developing environmental tragedy in the Gulf of Mexico. Our concern is aggravated by the fact that even now we do not know the potential extent of the tragedy because the oil is continuing to be released. Whiletheoilflowswemustbeappropriatelycircumspectingiving opinions about the potential gravity of the oil leak but it seems clear that we have been unable to predict the scope of the disaster or how we can effectively mitigate its long-term effects. Much of this uncertainty is associated with the size of the oil release and its location in deep water, far offshore. We do not seem to possess the ability to predict the chronic behavior and effects when a large volumeofoilcontaminantsmaybedispersedthroughoutthewater column or may penetrate deep into sensitive coastal marshes. Certainly our experiences with large oil spills, which have largely occurred near relatively high energy, rocky coastlines, do not providemuchguidanceonthebehaviorofoil,itstoxicconstituents, and dispersants in a relatively quiescent environment with shorelines of marsh grasses and soft sediments. Perhaps our best source of information on the effects of a large leak in the Gulf is the 1979 release of 140 million gallons over nine months from the Ixtoc leaking wellhead off the coast of Mexico. The wellhead was located in shallow waters (50 m), however, and the scientific investigation was relatively limited (1). Unfortunately, our uncertainty has only heightened concern in the general public and left many with an understanding of the environmental consequences of the 10.1021/es1020372
2010 American Chemical Society
Published on Web 06/28/2010
spill driven only by media reports. I am reminded of the initial stages of the flooding of New Orleans after Hurricane Katrina. The flooding of New Orleans was a disaster to many and a reflection of failures at the local, state, and federal level, but despite initial reports to the contrary, widespread regional environmental contamination was not a consequence (2, 3). Only time will tell if the developing environmental problems of the current spill represent a disaster for the entire Gulf or, like Katrina, an environmental concern with serious but more localized consequences. Each day that the spill continues enhances concerns that the Gulf will be influenced more broadly. Regardless of the ultimate consequences of the spill, however, it has demonstrated that their remain significant gaps in our knowledge of the behavior of such a spill. Additional research is needed to be better able to recover from the current situation and to respond if or when the next large scale leak or spill occurs in the Gulf. Why did the preventer fail? How can it be redesigned to avoid future failures? What backup systems can be put in place to avoid problems in the future? These are perhaps the first obvious questions but ones that are probably best addressed by industry, perhaps with the encouragement of new regulations and the assistance of selected academic researchers. A number of questions that require answers, however, are not as easily addressed by industry and instead should be taken up by the academic and nonprofit research community. First among these is the behavior of oil and dispersed oil in the deep ocean currents. A better understanding is needed of those deep currents and their ability to transport and disperse contaminants and of the fate of these contaminants. Especially vexing is the problem of immiscible or emulsified contaminants that exhibit substantially different physical and chemical properties. In addition, the toxicity of oil and dispersants have been studied separately but the toxicity of the emulsified oil is apparently not well understood. The large scale use of dispersants, particularly at the source of the leak at depth, has elevated concerns about the toxicity of the emulsified oil. Additional research is also needed on how to respond to the acute effects of the oil. The fraction of the oil that has reached the coastline is a small fraction of the volume released but it seems to have overwhelmed the existing technologies. Improving these dated, physical-separation-based technologies is sorely needed. The introduction of active agents to either absorb or degrade oil constituents in place would be highly desirable. Amendments such as activated carbon, for dissolved contaminants, and organophilic clays, for both separate and dissolved phase contaminants, could be introduced at the coastline to reduce the chemical availability of hydrophobic contaminants. Other amendments have been proposed to aid degradation of oil spill contaminants. Although these or other amendments could not be easily applied to the entire spill volume, they could hold promise at eliminating or reducing the effects of the oil and its constituents in particularly sensitive or strongly impacted VOL. 44, NO. 15, 2010 / ENVIRONMENTAL SCIENCE & TECHNOLOGY
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coastal areas. Research is needed to define the most effective amendments and how to most appropriately apply them. In considering the effects of oil, we often focus on organisms at the top of the food chain which make compelling photographs. Potentially more important, however, are the plants whose destruction may speed loss of vital coastal wetlands or the small insects and animals that are at the base of the food chain. Understanding the effects of the oil spill on these organisms is at least as important as the direct effects on the larger animals. We also typically focus on simple measures of risk such as bulk solid concentration. Many of the constituents of weathered oil, for example long chain alkanes, exhibit relatively low toxicity. Other constituents present more serious consequences. Aromatic and polyaromatic hydrocarbons are toxic and may disrupt the local ecology. The mere presence of these or other toxic compounds, however, may not effectively indicate risk due to sorption onto low availability, strongly sorbing phases. The typically low dissolved phase concentrations in the interstitial water concentrations may be a better indicator of the risk of these constituents than bulk solid concentrations. Passive samplers using polymer sorbents that can measure the dissolved phase concentration may be more effective indicators of risk (4). Moreover they could indicate both the presence of these compounds at low concentrations in the water column and as a function of depth into the sediments. Demonstrating the effectiveness of these tools could aid assessment of the long-term risks and recovery from oil spills. Ultimately, the recovery of the sensitive Gulf coast ecosystem will be the result of natural sedimentation processes and degradation processes driven by the microbial community, benthic animals, and plants. Any invasive remedial efforts are likely to result in even more damage to
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the ecosystem. Understanding these natural processes and identifying means of appropriately enhancing their effectiveness represents the best means to address the longterm risks posed by the oil. Research is needed to understand these processes for the constituents of concern on the scale of the present spill. There is a lot of existing research on smaller scales and typically more weathered and aged contaminants that can help guide these efforts. The goal of all of the research identified above is to more effectively understand and respond to oil spills and to allow the scientific community to provide more definitive answers to questions being asked by the public. In an area as important to U.S. oil reserves as the Gulf of Mexico, there is little justification for our being unable to assess and predict the behavior of an oil spill of any size. I hope that many researchers will take up this call and find opportunities to assist in both the assessment and recovery of the current release and, in so doing, provide a better understanding and tools to respond to any future oil spill.
Literature Cited (1) Boehm, P. D.; Fiest, D. L. Subsurface distributions of petroleum from an offshore well blowout. The Ixtoc I blowout, Bay of Campeche. Environ. Sci. Technol. 1982, 16 (2), 67–74. (2) Reible, D. D.; Haas, C. N.; Pardue, J. H.; Walsh, W. J. Toxics and contaminant concerns generated by Hurricane Katrina. The Bridge (National Academy Press) 2006, 36 (1), 5–13. (3) Schwab, K. J.; Gibson, K. E.; Williams, D. L.; Kulbicki, K. M.; Paullo, C.; Mihalic, J.; Breysse, P. N.; Curriero, F. C.; Geyh, A. S. Microbial and Chemical Assessment of Regions within New Orleans, LA Impacted by Hurricane Katrina. Environ. Sci. Technol. 2007, 41, 2401–2406. (4) Mayer, P.; Tolls, J.; Hermens, J. L. M.; Mackay, D. Equilibrium sampling devices. Environ. Sci. Technol. 2003, 37 (9), 184A–191A.
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