API JITF Subsea
Dispersant Injection Newsletter here>>
Dispersant Use meeting report (May
26 & 27, 2010) here>>
Deepwater Horizon Dispersant Use meeting press
release (May 27, 2010) here>>
Dispersant Research Information here>>
Dispersed Oil Research Forum Presentations -
February 1-2, 2007 here>>
& Development Needs For Making Decisions Regarding Dispersing
Oil workshop report here>>
|Please click to view the video (Joseph Katz, JHU)
Chemical dispersants are applied on the surface of oil slicks to break up the oil into droplets and disperse these droplets into the water column. The dispersant molecules interact at the oil-water interface, reducing the oil-water interfacial tension, and allow oil droplets to break apart from slicks or sheens. In order for dispersants to be effective, the water must be turbulent. The mixing energy provided by wind and waves allows the oil to break down to smaller size droplets. Katz (2009) used holographic imagery to capture how this process occurs view project here>>. The stretching of the droplet into a curved "dumbbell" shape is caused by turbulence and the lowered interfacial tension of the oil as a result of the dispersant. This process produces a range of droplet sizes, referred to as a droplet size distribution. The size distribution is a function of the magnitude of turbulence and the type and amount of dispersant applied. Droplet size is one of the key factors dictating the fate and behavior of the oil. The ultimate goal of dispersants is to dilute the oil to an extent that it represents a low risk to the environment. This is accomplished through dispersing oil droplets into the water column, where they enter the mixed layer (ML) and disperse via currents and natural diffusion in three dimensions. Dispersants do not decrease the quantity of oil, they force dilution of the oil droplets into a large volume of water. Once dispersed, these oil droplets can have various potential fates including: sedimentation; dissolution; biodegradation; re-coalescence; and uptake by biota, either through ingestion or absorption (i.e., via direct contact on membranes or body surfaces).
Coastal Response Research Center Hosts Dispersants Working Group and Workshop
|Please click to enlarge.
The 2005 National Research Council report entitled Understanding Oil Spill Dispersants: Efficacy and Effects notes that there are "significant gaps in the knowledge needed to make sound decisions regarding the use of dispersant in areas that [are] nearshore, shallow, or with restricted flushing rates." It also recommends that "National Oceanic and Atmospheric Administration (NOAA), the Environmental Protection Agency (EPA), Minerals Management Service (MMS), U.S. Geological Survey (USGS), U.S. Coast Guard (USCG), relevant state agencies, industry, and appropriate international partners should work together to establish an integrated research plan which focuses on collecting and disseminating peer-reviewed information about key aspects of dispersant use in a scientifically robust, but environmentally meaningful context." The Coastal Response Research Center (CRRC), a partnership between NOAA's Office of Response and Restoration and the University of New Hampshire (UNH), convened a meeting of many of these entities in July 2005 to discuss the possibility of forming an integrated approach to dispersants research. The participants decided to form a Dispersants Working Group (DWG) and agreed to participate in a coordinated research plan in which:
- Each participating entity will maintain its autonomy;
- Requests for proposals (RFPs), Broad Agency Announcements (BAAs), other funding announcements and all research results will be shared among the DWG and made public, where possible.
The CRRC agreed to coordinate DWG activities and to provide the mechanism by which reports, RFPs and other elements of interest are distributed and shared among the entities and the oil spill community. Hence, the development of this collaborative website.
As the inaugural DWG event, the CRRC hosted a workshop entitled Research & Development Needs for Making Decisions Regarding Dispersing Oil at UNH on September 20-21, 2005. The goal of the workshop was to develop a list of priority topics that can serve as a basis for a coordinated research plan. The workshop brought together more than 30 representatives from federal and state agencies, industry, academia, and the private sector for small group and plenary discussions of the effectiveness and effects of dispersant use. The dedication and hard work of the participants resulted in an impressive list of research topics for future funding announcements. View the resulting workshop report here>>
For more about the 2005 Dispersants Workshop, see the following: