Hydrocarbon biodegradation in soil can be limited by many factors, including nutrients, pH, temperature, moisture, oxygen,soil properties and contaminant presence (Atagana 2008, Al Sulaimani 2010; Bundy et al., 2002). Biostimulation involves the modification of the environment to stimulate existing bacteria capable of bioremediation. This can be done by addition of various forms of limiting nutrients and electron acceptors, such as phosphorus, nitrogen, oxygen, or carbon (. in the form of molasses), which are otherwise available in quantities low enough to constrain microbial activity (Elektorowicz, 1994; Piehler et al., 1999; Rhykerd et al., 1999).
Figure 5. Subaqueous dunes and pockmarks on the upper continental slope in the northwestern Gulf of Mexico. Longitudinal megadunes measure –1 kilometer crest to crest, 1–10 kilometers long, and 3–10 meters tall. Pockmarks occur atop Nueces Dome (top center) and, Gulf-wide, pockmarks occur within a general water depth range of 300–600 meters. Pockmarks in this region have been attributed to explosive dissociation of natural methane hydrate following basinward migration of the hydrate stability zone during the Wisconsin Glacial sea level lowstand [ Hovland and Judd, 1988; Roberts and Carney, 1997]. BOEM has identified more than 4000 pockmarks in federal waters of the northern Gulf of Mexico. Credit: BOEM Figure 6. Gas expulsion mounds with adjacent thrust folding and faulting caused by lateral salt migration in the southern Terrebonne Basin in the central Gulf of Mexico. The image illustrates some of the features formed by the dynamic processes shaping the Gulf, specifically salt tectonics and natural hydrocarbon seepage. Thrust faulting and folding are due to southeast verging lateral movement of salt. Movement of salt is what gives the Gulf of Mexico seafloor its wrinkled nature, also creating faults and fracture networks that provide pathways for oil and gas seeps. These particular expulsion mounds were formed as a result of basin compaction and compression, resulting in upward gas migration [ McConnell and Kendall, 2002]. Credit: BOEM Figure 7. Spectacular new detail of Alaminos and Perdido canyons and their associated fans, western Gulf of Mexico. The canyons funnel sediments to create an intermingling basin-floor fan system hundreds of meters thick. Core sampling determined that drainage from the Rio Grande River provides coarse, sandy sediments to the Perdido system [ Damuth et al., 2006], whereas cores and well logs in Alaminos Canyon reveal primarily fine-grained deepwater sediment [ Bouma et al., 1968; Meyer et al., 2005]. Credit: BOEM
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