Clean-Up after Territorial Oil Spills in the Arctic

Аннотация

… The nature of a spill will depend on the local weather conditions, including the presence or absence of snow, the absorptive capacity of the ground (which is influenced by the prevailing groundwater level), and local topography. … In clean-up operations after oil spills, the first requirement is to contain the spill in as small an area as possible, and to prevent it from reaching water courses and thus contaminating their environments. Devices and techniques can then be employed to remove oil from the contaminated region and convey it to temporary storage. Thirdly, the area can be treated to remove residual oil and promote its early restoration through the use of chemical and biological techniques. … In temperate regions, terrestrial spills are most readily contained by artificial dykes or dams constructed by means of earth-moving equipment, and it is also possible to dig trenches and ditches into which oil will flow and be retained. In areas of permafrost, however, suitable damming material may not be readily available, or may be obtained only if considerable areas of permafrost are exposed - that is, at the cost of additional environmental damage. The use of heavy vehicles, even if they are available, will compact the insulating active layer of permafrost and thereby cause eventual melting of the permafrost. Containment should involve a minimum of disturbance of the area, with no removal or compaction of the active layer and exposure of permafrost. A method of containment which may be feasible is to use damming material that can be quickly transported to the site and installed without the aid of machinery. For example, corrugated metal sheeting in sections about three feet high by ten feet long (1 m x 3 m approximately), with vertical corrugations, could be driven through the active layer down to the water table or frost level or thawed clay soil, all of which provide a basement to vertical oil penetration, and retained in position by T-bar stakes driven into the ground. … The presence of permafrost ironically brings the substantial benefit of there being little of the infiltration of oil into porous soils, with subsequent ground-water contamination, which constitutes such a severe problem in temperate regions; that is, clean-up operations can be facilitated by the presence of permafrost. Another approach to containment, which was tested briefly during the summer of 1974 on wet tundra on Richards Island in the Mackenzie Delta, is to cut a trench, 30 cm wide, to permafrost level across the path of the flowing oil. The trench successfully intercepts the flow of oil, both on and below the surface, and drains it to a low-level point from where it can be pumped to storage or for disposal. … A dam or trench of the type just described, which would necessarily have to be located on the downslope side of the area of spillage, would interfere with natural drainage, and so it would be necessary to control drainage from the area while oil and water were being separated. The present authors suggest that this control could be effected by the installation of an API (American Petroleum Institute) type of oil-water separator which can be constructed easily from prefabricated metal sheeting, usually about 5 feet deep by 10 feet wide by 30 feet long (1.5 m x 3 m x 9 m approximately). … Another possibility would be the use of a compact plate-type oil-water separator. … A significant further advantage of the general technique just explained is the possibility of controlling, and even accelerating, the flow from the area of spillage. … Small-scale laboratory tests have demonstrated that significant proportions of the absorbed oil can be floated out of detritus by gravity alone and without agitation. It is likely that, due to its slow rate of evaporation, the sub-surface oil would maintain a viscosity sufficiently low for it to be floated out by water. It is generally recognized, also, that the toxic constituents of oil are the most volatile and water-soluble. Thus, it is likely that the oil would exhibit toxicity only during the first few months after spillage, and then be permanently absorbed in the vegetation and soil and become immobilized. … As a final stage of restoration of an affected area, it may prove beneficial to fertilize it and promote the growth of oil-degrading microorganisms. Since the albedo of the area will be reduced, and so there will be greater absorption of radiation and increased depth of active layer, it may be desirable to increase the albedo artificially be sprinkling the area with reflective materials. In conclusion, the present authors contend that new techniques must be developed for the clean-up of terrestrial spills in the Arctic, since methods used in temperate regions are inappropriate. …