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Marine Pollution |
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The Resource
Marine pollution is defined as pollution of any of the world's oceans, seas, or other saltwater systems. Focus on the oceans of the world is critical, because - not being owned by any individual nation - environmental protection of them is not easily regulated.
The first appearance of life on the earth is thought to have occurred in the oceans 2 or 3 billion years ago. Throughout history, people have been directly or indirectly influenced by the oceans. The waters that comprise our marine environment cover approximately two-thirds of the Earth's surface. They serve as a source of food, valuable minerals, means of transportation, provide a place for recreation, and have a profound effect upon the world's climate, rainfall, and water cycles generally. Unfortunately, they have also been used for waste disposal. Because of the rapid improvement in technologies to exploit marine resources, the twentieth century is witnessing a radical change in the oceans. The situation in which ocean resources exceeded our capabilities to utilize them has now changed, and a number of marine resources have become scarce. In the near-shore waters of some countries, the ocean's capacity to absorb pollutants from the land and from ships has been exceeded. The somewhat captive environment of estuaries and saltwater wetlands make these areas more susceptible to the impacts of pollutants, as the normal flushing process is significantly restricted.
Some of Alcoa's operations are located near to a marine environment. However, a majority of Alcoa's operations rely on access to marine waters for shipping, either from the import of raw or auxiliary materials and/or the export of produced goods. The dependence upon the marine environment at each site is related to their transportation requirements and the proximity to the sea. Inland waterways often flow to the coast, so that discharges to a freshwater tributary may impact in some way on marine ecosystems.
Movement of Marine Water
Marine waters are a globally shared resource, however, most effects of marine pollution are realized on a local scale. Tidal flows are the predominant form of water exchange on a local level, whereas well defined ocean currents are the principal driving forces for mixing ocean waters. Highly variable water flow patterns will be seen in different marine environments such as bays, inlets, coasts and open seas.
Contaminant Movement Water
Once a pollutant enters a marine environment, dilution occurs and the water movement may physically transport the substances away from the discharge point. From this point on, the inter-reaction between different pollutants with each other, or with organisms in the sea sediments, can lead to quite unpredictable and sometimes catastrophic results.
Aquatic Chemistry
Pollutants discharged to the marine environment may be converted to other forms, which may be more, or less toxic than the original substance. An example of this was the discharge of mercury compounds into Minamata Bay in Japan by a plastic manufacturer. At the time, mercury in this form was considered relatively harmless. Once in the sediments, micro-organisms converted the mercury into the highly toxic methyl mercury which was readily taken up and bioaccummulated in the food chain.
Another example involved the discovery of high levels of mercury in North Atlantic fish, demonstrating how localized pollution sources in coastal regions had reached water organisms in the depths of the ocean.
Possible Consequences of Contamination
When pollutants enter a marine environment, experience has shown that it is extremely difficult, if not impossible in most cases, to contain or control the spread of contamination. In this case, we are largely at the mercy of the assimilative capacity of the marine environment. Oil spills have been widely publicized as to their detrimental effects on marine ecosystems and their clean-up procedures are still reliant on natural dispersion to some degree. Special consideration needs to be taken of substances which are long persisting and exhibit toxic properties such as heavy metals and some pesticides. Excessive levels of some pollutants may lead to destruction or modification of aquatic ecosystems. As a consequence, marine species may become contaminated to a point where they are no longer fit for human or animal consumption. Mollusks and other water filtering organisms can act as indicator species for possible bioaccumulation in worst-case conditions.
Possible Sources
The main sources of pollutants entering marine ecosystems are discharging wastewater directly originating from industrial activities or residential areas, or by unplanned discharges. Ballast water from ships is one form of wastewater discharging directly to the marine environment, however, a more serious problem often overlooked is the introduction of pest or predator species foreign to the region. Toxic algal blooms have caused massive fish kills in many parts of the world, and many marine environments. Predator species include a wide array of organisms capable of altering the ecosystems in which they inhabit if allowed to spread uncontrolled. One such example is the worm infestation in the scallop beds of Port Philip Bay, Victoria. Another is the case of Zebra muscles transported from Europe to the USA. Other sources include migration of contaminants through groundwater, settling of particulates from stack plumes, scrubbing of stack gases by rain, and indiscriminate solid waste-dumping in marine waters. Dumping of garbage at sea is no longer an accepted practice.
Importance of Minimizing Pollutants
The high variability of individual ecosystems and their tolerances to pollutants mean any form of oceanic pollution should be avoided. Where it cannot be avoided, it should be minimized. Factors that determine the impact of pollutants include:
- water movement relative to the discharge point
- depth of water at the discharge point
- local ecology, sediments: particle size, type, etc., environmental significance of the marine waters, such as aquaculture, recreation, etc.
As discussed earlier, it is almost impossible to control pollutant migration once it has been discharged, therefore, treatment of wastewater to acceptable levels is required prior to discharge.
Specific Concerns for Alcoa
Potential concerns for Alcoa location where pollutants can enter the marine environment include:
- Heavy metals, such as mercury, chromium, lead, zinc, and copper
- Non-metal contaminants from smelting processes
- Spills of chemicals such as oil, caustic soda from shipping
- Ballast water discharges
- Acidic or alkaline process waters
- Silt from surface run-off during earth works
- Thermal pollution from cooling tower water
- Nutrients from landfill leachates and other sources
- Minerals from water-demineralisation plants.
- Stormwater run-off
Alcoa's Position
An investigation at each site should be undertaken to characterize all potential sources which may impact on a marine environment. Where possible, a quantitative assessment of potential pollutants should be done and help to ensure compliance where licence conditions, regulations, standards, or relevant water quality guidelines apply. This information can then be used to help quantify risks using sound ecological risk assessment procedures. To limit Alcoa's liability, any potential impacts on marine ecosystems need to be carefully monitored and quantified to establish an Operation's effect on the marine environment.
In summary, since ocean environments are really very fragile, ocean discharges in any form require careful study.
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