No abstract

A new shoreline cleaner, which was specially developed during the cleanup of the Valdez spill in Alaska, was tested to determine its effectiveness in removing oil from Louisiana Gulf Coast marsh grass thus minimizing the oil impact. Intact plugs of Spartina alterniflora containing living plants, roots, and soil microbial communities were collected from salt marshes and transferred to a greenhouse. Plant photosynthesis, respiration, and stomatal conductance were monitored following various oiling and cleaning scenarios. The treatments included: oiled, oiled and cleaned after one day, oiled and cleaned after two days, cleaner only, and control. Plant recovery depended upon the degree of oiling and the type of oil used. Fouling with bunker C oil caused almost total plant mortality unless the plants were cleaned with the shoreline cleaner. South Louisiana crude oil was less toxic but cleaning accelerated recovery as was evident by photosynthetic activity and other plant functions such as regeneration of new shoots. Collectively, these studies demonstrate the potential for saving an oiled Spartina alterniflora marsh by use of this shoreline cleaner in a real oil spill.

Modern oil spill dispersant formulations are concentrated blends of surface active agents (surfactants) in a solvent carrier system. The surfactants are effective for lowering the interfacial tension of the oil slick and promoting and stabilizing oil-in-water dispersions. The solvent system has 2 key functions: 1) reduce viscosity of the surfactant blend to allow efficient dispersant application, and 2) promote mixing and diffusion of the surfactant blend into the oil film. A more detailed description than previously given in the literature is proposed to explain the mechanism of chemical dispersion and illustrate how the surfactant is delivered by the solvent to the oil-water interface. Laboratory data are presented which demonstrate the variability in dispersing effectiveness due to different solvent composition, particularly for viscous and emulsified test oils with viscosities up to 20,500 mPa∙s. Other advantages of improved solvent components can include reduced evaporative losses during spraying, lower marine toxicity and reduced protective equipment requirements. Through this improved understanding of the role of the solvent, dispersants which are more effective over a wider range of oil types are being developed.

Partial removal of dissolved or absorbed solvent from polymers can be accomplished during the process of screw extrusion. This paper shows how two simple transport models based either on an effective diffusivity or on a n empirical mass transfer coefficient can be combined with the fluid mechanical equations which describe polymer flow during screw extrusion. I n this way, the drying of solvent from a polymer during extrusion can be correlated in terms of the design and operating parameters of the extruder screw and a mass-transfer coefficient or a n effective diffusivity. This approach is illustrated employing data obtained by using two extruders of different size and two different solvent-polymer systems. Furthermore, it is pointed out how the results can be used t o predict the extent of drying during screw extrusion a s well as how modifications in extruder-screw design can permit more extensive drying of polymers during the extrusion process.

An overview of the mechanism of chemical dispersion is presented in order to put the subject in the proper perspective. The methodology and role of the surface active agent in the generation of finely dispersed oil droplets are reviewed. This discussion of the dispersing mechanism will help resolve some of the misconceptions that have persisted for the past 10 years, such as the dispersant acting to either sink or solubilize the oil droplets into the water column, or both. The incentives, concerns, and resultant present status of chemical dispersion are developed.