Spills of Emulsified Fuels Risks and Response (2002) / Chapter Skim
Currently Skimming:
2 Behavior and Fates: Summary and Evaluation of Available Information
2 Behavior and Fates: Summary and Evaluation of Available Information
Pages 14-43
The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
Select key terms on the right to highlight them within pages of the chapter.
From page 14... ...
It is comparable in pour point) and viscosity to an industrial fuel oil.
|
From page 15... ...
, but they would be expected to float in more saline water. The average bitumen droplet size in fresh Orimulsion is around 20 ,um (Ostazeski et al., 1998a, 1998b)
|
From page 16... ...
For the most part, predicting Orimulsion spill behavior becomes a matter of predicting the behavior of the dispersed bitumen cloud. Chemical Characterization The Cerro Negro bitumen used to produce Orimulsion comes from the Orinoco Belt in the Eastern Venezuelan Basin (Bitumenes Orinoco)
|
From page 17... ...
Figure 2.4 presents flame ionization detector gas chromatographic profiles. These profiles show neat Orimulsion (sample 3)
|
From page 18... ...
. I ' 0 10 20 30 40 8 l ~ ~,hL~~L~ 50 60 0 10 20 30 40 50 60 FIGURE 2.4 Flame ionization detector gas chromatographic profiles for neat Orimulsion (sample 3)
|
From page 19... ...
6 fuel oil Density (g/ml at 15°C) 1.01-1.02 0.94-1.02 Pour point (°C)
|
From page 22... ...
This rate of biodegradation is at variance however with oxygen consumption studies on the specific AE mixture used for Orimulsion-400 that have shown a biodegradability (compared to complete chemical oxygen demand with potassium dichromate) of 79 percent in seawater over a 28-day period (VKI, 1997a)
|
From page 23... ...
6 fuel oil spilled in water of varying salinities. These studies concluded that the majority of the surfactants are contained in the aqueous phase and that they would be diluted by the receiving water during an Orimulsion spill.
|
From page 24... ...
, which were the predominant dissolvedphase components in the near-equilibrium 30 percent aqueous phase in the original Orimulsion fuel mixture (e.g., see Table 2.4~. As discussed further in the section titled "Water Column Processes - Dissolution," the high-molecular-weight
|
From page 25... ...
In fact, for spill response purposes, fresh Orimulsion can almost be considered predispersed oil. The near-equilibrium dissolved-phase PAH in the aqueous phase of the product would behave as a neutrally buoyant, or near neutrally buoyant, contaminant.
|
From page 27... ...
Dissolution An Orimulsion spill into a water body results in input of dispersed bitumen droplets and the dissolved constituents in the aqueous phase (BTEX, dissolved PAH at near-equilibrium levels, and surfactants)
|
From page 28... ...
1 1 1 1 1 0 500 1,000 1,500 2,000 2,500 3,000 3,500 4,000 4,500 5,000 5,500 6,000 Reaction time (min.) FIGURE 2.6 Mean values of total dissolved aromatic hydrocarbons from Orimulsion as a function of salinity and batch-mode equilibrium exposure time.
|
From page 29... ...
concluded that significant PAH dissolution weathering from the bitumen droplets can occur over time, particularly given the high surface-area-to-volume ratios of the 1- to 80-,um-diameter dispersed bitumen droplets (Stout, 1999~. French, using equilibrium partitioning theory, and the initial PAH concentrations in neat Orimulsion from two different sources determined that the effective initial concentration of dissolved PAH in the neat fuel would be in the range of 15,uglL (calculated as shown in Table 2.4 based on the 2,286 ppm of PAH in neat Orimulsion reported by Stout (1999)
|
From page 30... ...
As shown by the data in the table, PAH are predicted to continue to dissolve from the dispersed bitumen droplets as they are diluted into the receiving water body, but the dissolved PAH will never exceed the initial
|
From page 31... ...
. TABLE 2.6 Percentage of MAH and PAH Dissolved from Orimulsion Diluted by the Indicated Factors, as Computed from an Equilibrium Partitioning Model Dilution MAH + PAH MAH PAH 1 0.00 0.07 0.0010 10 0.02 0.66 0.010 70 0.1 1 4.24 0.07 100 0.16 5.86 0.10 1,000 1.16 33.75 0.91 10,000 6.22 81.39 7.17 100,000 26.46 97.70 34.62 1,000,000 67.76 99.76 80.00 SOURCE: Data provided by D
|
From page 32... ...
For purposes of this report, an assumption has been made that coalescence and surfacing of the bitumen in salt water and brackish water will be significant. Interactions with Suspended Particulate Material Numerous batch-mode and flume studies have been undertaken to evaluate the interaction of dispersed bitumen droplets and suspended sedimentary material
|
From page 33... ...
Similar experiments conducted in fresh water showed no transport of bitumen-kaolinite agglomerates to the bottom, with the majority of the dispersed bitumen remaining suspended in the water column, presumably because of the effectiveness of the surfactant in fresh water. Long-Term Fate and Microbial Degradation of Sedimented Bitumen Droplets It appears that Orimulsion is capable of being biodegraded although the rates are believed to be extremely slow.
|
From page 34... ...
Stranding of Weathered Bitumen As long as bitumen that is dispersed in the water remains wet within the sediments, it will penetrate freely into pebble beaches but will remain on or near the surface of sand beaches (Harper and Kory, 1997~. Unlike weathered bitumen patties, such dispersed bitumen is more mobile within the coarse-grained beach substrate than a typical heavy fuel oil.
|
From page 35... ...
USE OF MODELING AND SCENARIOS TO UNDERSTAND THE BEHAVIOR OF ORIMULSION SPILLS A widely used oil spill model has been modified to simulate possible Orimulsion behavior (French and Mendelsohn,1995~. This model has been used to evaluate the effects of hypothetical Orimulsion spills in Tampa Bay and Delaware Bay and River (French McCay and Galagan, 2001)
|
From page 36... ...
The surface tarballs or patties will be transported by winds and surface currents, in a fashion similar to tarballs from any weathered fuel oil slick. Being only slightly buoyant, they will be subject to overwash, making their observation by spill response personnel difficult.
|
From page 37... ...
Marine Nearshore Figure 2.9 presents the schematic fate diagram for nearshore coastal marine spills of Orimulsion, which are expected to behave differently than open-water spills. Because of the land and bottom boundary conditions, vertical diffusive mixing could be reduced and pockets of higher near-surface concentrations of bitumen and dissolved components could persist longer than would occur in open water.
|
From page 38... ...
Estuarine (Brackish Water) Figure 2.10 presents the schematic fate diagram for an Orimulsion spill in estuarine or brackish water environments.
|
From page 39... ...
A river spill of Onmulsion would typically result in rapid mixing of the bitumen and dissolved components throughout the water column with subsequent rapid dilution. The surfactant would usually remain effective for a sufficient period of time to allow the bitumen droplets to Suffactant Attachecl to Bitumen :~ Too Ligh to Settle T Current ~ I Scour Pa ~ Minor Sedimentation Spi// Survei//ance / Water intake Closures Debris Pi/es FIGURE 2.11 Schematic representation of the distribution and fate of Orimulsion-400 spilled into an idealized nontidal river environment.
|
From page 40... ...
However, the low mixing energy would delay this process. The PAH fraction in the carrier aqueous phase would be subject to limited dilution if the volume Suspension Innovative Recovery of Suspended Bitumen Cleanup Options are Viable elChant~ - Settles in Days - Not Stickier as Long as Wet FIGURE 2.12 Schematic representation of the distribution and fate of Orimulsion-400 spilled into a quiescent fresh water environment.
|
From page 41... ...
On Land Near Water Figure 2.13 presents the schematic fate diagram for an Orimulsion spill on land with subsequent migration through a wetland into a riverine environment. If Orimulsion is released on land, it would be expected to behave initially like a fuel oil with a similar viscosity.
|
From page 42... ...
The bitumen droplets chemically resemble the residue that would be found in a heavy fuel oil spill at the end of short-term weathering processes. The concentrations of dispersed bitumen droplets and water-soluble constituents decrease significantly due to dispersion into the surrounding water column.
|
From page 43... ...
However, given the high surface-area-to-volume ratio of the very fine bitumen droplets, the potential for PAH uptake exists and thus should be evaluated. For Orimulsion spills on land, the water phase can separate from the bitumen and infiltrate the underlying substrate.
|
Key Terms
This material may be derived from roughly machine-read images, and so is provided only to facilitate research.
More
information on Chapter Skim is available.