Ocean dumping

Ocean dumping is internationally defined as "any deliberate disposal at sea of wastes or other matter from vessels, aircraft, platforms, or other man-made structures at sea, and any deliberate disposal at sea of vessels, aircraft, platforms, or other man-made structures at sea." The discharge of sewage and other effluents from a pipeline and the discharge of waste incidental to, or derived from the normal operations of, ships are not considered ocean dumping. Wastes have been dumped into the ocean for thousands of years. Fish and fish processing wastes, rubbish, industrial wastes, sewage sludge , dredged material, radioactive waste , pharmaceutical wastes, drilling fluids, munitions, coal wastes, cryolite, ocean incineration wastes, and wastes from ocean mining have all been dumped at sea. Ocean dumping has historically been more economically attractive, when compared with other land-based waste management options.

The 1972 Convention on the Prevention of Marine Pollution by Dumping of Wastes and Other Matter , commonly called the London Convention, came into force in 1975 to control ocean dumping activities. The framework of the London Convention includes a black list of materials that may not be dumped at sea under any circumstances (including radioactive and industrial wastes), a grey list of materials considered less harmful that may be dumped after a special permit is obtained, and criteria that countries must consider before issuing an ocean dumping permit. These criteria require the consideration of the effects dumping activities can have on marine life, amenities, and other uses of the ocean, and encompass factors related to disposal operations, waste characteristics, attributes of the site, and availability of land-based alternatives. Most ocean dumping permits (90–85%) reported by parties to the London Convention are for dredged material. Currently only three parties to the London Convention dump sewage sludge at sea. Other categories of wastes that are permitted for ocean dumping include inert, geological materials, vessels, and fish wastes. The International Maritime Organization is responsible for administrative activities related to the London Convention, and it facilitates cooperation among the countries party to the Convention. As of 2001, 78 countries had ratified the Convention.

In the early 1990s, the parties to the London Convention began a comprehensive review of the treaty. This resulted in the adoption of the 1996 Protocol to the London Convention. The purpose of the Protocol is similar to that of the Convention, but the Protocol is more restrictive: application of a "precautionary approach" is included as a general obligation; a "reverse list" approach is adopted; incineration of wastes at sea is prohibited; and export of wastes for the purpose of dumping or incineration at sea is prohibited. Under the reverse list approach, dumping is prohibited unless explicitly permitted, and only seven categories of materials may be considered for dumping: dredge material; sewage sludge; fish waste; vessels and platforms; inert, inorganic geological material; organic material of natural origin; and bulky items of unharmful materials when produced at locations with no other disposal options. The Protocol will enter into force after 26 states ratify it (15 of which are party to the London Convention). So far, 16 countries have ratified it (13 of which are party to the London Convention).

Ocean dumping has been used as a method for municipal waste disposal in the United States for about 80 years, and even longer for dredged material. The law to regulate ocean dumping in the United States is the Marine Protection, Research, and Sanctuaries Act of 1972. This Act, also known as the Ocean Dumping Act, banned the disposal of radiological, chemical, and biological warfare agents, high-level radioactive waste, and medial waste. It requires a permit for the ocean dumping of any other materials. Such a permit can only be issued where it is determined that the dumping will not unreasonably degrade or endanger human health, welfare, or amenities, or the marine environment, ecological systems, or economic potentialities. Furthermore, all permits require notice and opportunity for public comment. EPA was directed to establish criteria for reviewing and evaluating ocean dumping permit applications that consider the effect of, and need for, the dumping. The Ocean Dumping Act has been revised by the United States Congress in the years since its enactment. In 1974, Congress amended this Act to conform with the London Convention. In 1977, the Act was amended to incorporate a ban by 1982 on ocean dumping of wastes that may unreasonably degrade the marine environment . As a result of this ban, approximately 150 permittees dumping sewage sludge and industrial waste stopped ocean dumping of these materials. In 1983, the law was amended to make any dumping of low-level radioactive waste require specific approval by Congress. In 1988, the

Ocean Dumping Ban Act was passed to prohibit ocean dumping of all sewage sludge and industrial waste by 1992. Virtually all material ocean dumped in the United States today is dredged material. Other materials include fish wastes, human remains, and vessels.

Physical properties of wastes, such as density, and its chemical composition affect the dispersal, and settling of the wastes dumped at sea. Many contaminants such as metals found in trace amounts in natural materials are enriched in wastes. After material is dumped at sea, there is usually initial, rapid dispersion of the waste. For example, some wastes are dumped from a moving vessel, with dilution rates of 1,000 to 100,000 from the ship's wake. As the wake subsides, naturally occurring turbulence and currents further disperse wastes eventually to nondetectable background levels in water in a matter of hours to days, depending on the type of wastes and physical oceanic processes. Dilution is greater if the material is released slower and in smaller amounts, with dispersal rates decreasing over time. Wastes, such as dredged material, that are much denser than the surrounding seawater sink rapidly. Less dense waste sinks more slowly, depending on the type of waste and physical processes of the dumpsite. As sinking waste particles reach seawater of equal density, they begin to spread horizontally, with individual particles slowly settling to the sea bottom. The accumulation of the waste on the sea floor varies with the location and characteristics of the dumpsite. Quiescent waters with little tidal and wave action in enclosed shallow environments have more waste accumulate on the bottom in the general vicinity of the dumpsite. Wastes dumped in more open, well-mixed ocean waters are transported away from the dumpsite by currents and can disperse over a very large area, as much as several hundred square kilometers.

The physical and chemical properties of wastes change after the material has been dumped into the ocean. As wastes mix with seawater, acid-base neutralization, dissolution or precipitation of waste solids, particle adsorption and desorption, volatilization at the sea surface, and changes in the oxidation state may occur. For example, when acid-iron waste is dumped at sea, the buffering capacity of seawater rapidly neutralizes the waste. Hydrous iron oxide precipitates are formed as the iron reacts with seawater and changes from a dissolved to a solid form.

The fraction of the waste that settles to the bottom is further changed as it undergoes geochemical and biological processes. Some of the elements of the waste may be mobilized in organic-rich sediment ; however, if sulfide ions are present, metals in waste may be immobilized by precipitation of metal sulfides. Organisms living on the sea floor may ingest waste particles, or mix waste deeper in the sediment by burrowing activities. Microorganisms decompose organic waste , potentially recycling elements from the waste before it becomes part of the sea floor sediments. Generally sediment-related processes will act on waste particles over a longer time scale than hydrologic processes in the water column.

The effects of dumping on the ocean are difficult to measure and depend on complex interactions of factors including type, quantity, and physical and chemical properties of the wastes; method and rate of dumping; toxicity to the biotic community ; and numerous site-specific characteristics, such as water depth, currents (turbulence), water column density structure, and sediment type. Many studies have found that the effects of ocean dumping on the water column are usually temporary and that the ocean floor receives the most impact. Impacts from dumping dredged material are usually limited to the dumpsite. Burial of some benthic organisms (organisms living at or near the sea floor) may occur; however, burrowing organisms may be able to move vertically through the deposited material and fishes typically leave the area. Seagrasses, coral reefs, and oyster beds may never recover after dredged material is dumped on them. There also can be topographic changes to the sea floor.

See also Dredging

[Marci L. Bortman Ph.D. ]

RESOURCES

OTHER

ArmyCorps of Engineers Ocean Disposal Database. [cited July 2002]. <http://ered1.wes.army.mil/ODD>.

"EPA's Ocean Dumping and Dredged Material Management." EPA Web Site. July 16, 2002 [cited July 2002]. <http://www.epa.gov/owow/oceans/regulatory/dumpdredged/dumpdredged.html>.

London Convention. [cited July 2002]. <http://www.londonconvention.org>.