MARINE POLLUTION

GENESIS 0F MARINE POLLUTION - ITS PREVENTION AND MITIGATION

1. What is pollution

Pollution occurs when concentrations of various chemical or biological constituents exceed a level at which a negative impact on ecosystem or human health can occur. Pollution results primarily from human activities. More specifically, in the marine context "Pollution of marine environment means the introduction by man, directly or indirectly, of substances or energy into the marine environment, including estuaries, which results or is likely to result in such a deleterious effect as to harm living resources and marine life, hazardous to human health, hindrance to marine activities, including fishing and other legitimate uses of the sea, impairment of quality for use of seawater and reduction of amenities". The sources of pollution include sewage, urban run-off, industrial wastes, coastal development, and shipping activities. The chemical or biological constituents creating pollution are known as contaminants. More specifically, they can be divided into inorganic contaminants, such as metals; organic contaminants such as pesticides, PCB or petroleum hydrocarbons; Biological contaminants such as coliform bacteria and other pathogens.

The list of potential contaminants is quite exhaustive; our understanding of the potential impacts of trace metals, bacteria, or hydrocarbons is well established. However, the long-term effects of man made organic compounds such as pesticides, PCB and other plastics, etc are not yet fully understood.

Pollution is not a recent phenomenon. It occurred since the man concentrated around a port area.

2. Effects of Marine Pollution

The major effects of marine pollution are :

*	Disturbance in the balance of the ecosystem
*	Loss of flora and fauna
*	Migration of fisheries
*	Bio-magnification of undesirable material
*	Aesthetic Degradation
*	Accelerated Corrosion

3. Sources of Marine Pollution

The oceans have long been considered to have limitless capacity to receive and absorb all types of wastes. Since the 1950's many scientists began to warn that this limitless capacity is running out and the very survival of the marine environment was in danger. Therefore, it is imperative the control the sources of pollution.

The origin of various sources of pollution are listed below :

Source	Percentage
Land	45
Air	33
Transportation	12
Dumping	9
Offshore	1

As observed from the above table marine transportation routinely contributes to only 12% of the total marine pollution out of which major oil spills contribute to only 2%. Therefore routine ship movements cause more than 10% of the pollution. However, land based activities are the major sources and have to be significantly controlled to save the marine ecosystem.

4. Dredging

Among all land based activities that cause marine pollution, dredging of ports and harbours is probably the most significant in terms of propagation of pollutants. The process of dredging causes the disruption of bottom sediments. More often than not, bottom sediments of ports & harbours, are contaminated by chemicals, minerals, hydrocarbons and domestic wastes. Toxic materials released from the disturbed soils may go into solution and cause severe mortality to marine estuarine life. Re-deposition of suspended materials could possibly eliminate bottom flora & fauna. Organic material in the suspended material may deplete available oxygen in the surrounding waters and can create temporary stress conditions for aquatic animals. If suspended sediments are sufficiently concentrated, penetration of light in the water column is significantly reduced, thereby causing damage to light depending photosynthetic algae, corals and other aquatic organisms. Explosives used to break rock formations destroy bottom habitants. Pressure radiation due to blasting, often injure or disable marine life at considerable distances.

The problems associated with disposal of dredged materials are a matter of serious concern in both in industrial and developing countries. Traditionally, dredged materials, have been disposed in open water, without any kind of restrictions. Increased concern with the environmental impact on the marine environment, restrictions have been placed on such disposals, especially if they are contaminated. Areas of sediment depositions, typically contain fine grained sand which act as "sinks" for many compounds. Many organic contaminants have a low solubility in water and therefore are associated with suspended solids and are transported along with the sediments. Since these sediment zones are areas often require maintenance dredging, in most cases dredged material contain hazardous contaminants. Usually the contaminants are due to land based activities such as industrial effluents, fertilisers, and pesticides, urban sewage, etc.

As the contaminants originate from land based activities, the disposal of contaminated dredged materials does not address the source of the problem, it is only a symptom. The problem of dredged material disposal can be considerably reduced, if effluents from land based sources are controlled. Further to control limit the propagation of contaminants can be achieved by proper selection of dredging process, equipment and disposal sites. Another mitigative measure that could be taken into consideration is to avoid or minimise dredging during fish migration, breeding and spawning seasons.

In areas where, chemical contaminants of the bottom sediments exceed threshold values, selection of appropriate dredging equipment is to be considered. These include:

*	Oozer pump suction dredger to avoid the release of material at the point of excavation
*	Closed clamshell bucket dredger or trailing cutter suction dredger with no overflow
*	Proper offloading equipment on a disposal barge to pump to disposal sites without leakage

Unconfined open water disposal has been traditional method of dredged spoils disposal because it is the most economical option. Even, if a "safe" disposal site has been identified, strong upper water column or low bottom currants can carry significant quantities of low-density materials away to distant locations. This off-site transportation can lead to re-filling of the dredged areas, silting fish spawning areas and the redistribution of contaminated areas.

For the contaminated dredged material the following disposal options must be considered :

*	Thin Layer Disposal: In this method, dredged spoils are spread very thinly over a wide area of a pre-identified disposal site. The thickness of the layer is calculated so that leachates of contaminants does not exceed threshold values that could be dangerous to marine flora and fauna.
*	Confined Land Disposal: In case, the contaminants are high, suitable land based clay/polymer lined disposal sites may be considered. This is an expensive method and a rough estimate is that it costs five times more than unconfined open water disposal. This process is suitable for small quantities of highly contaminated dredge spoils.
*	Open Water Disposal with Capping: In this process, dredged spoils are disposed in the open sea followed by "capping" with inert material. Typically contaminated sediments are buried under one meter of "clean sediment". In this process, the contaminants are immobilised by the capping material.
*	Specialised Treatment: When the materials are small and the contaminants are highly toxic, for example radio-active wastes, the spoils must be brought to shore based facilities for specialised treatment before disposal.

5. Ship Discharges

Discharges and spills from ships and shore based facilities result in the environmental degradation of marine life. In ports, the situation is even more critical due to the fact that most ports have relatively poor exchanges with the open sea. This results in the pollutants having long residence times in the port area. Untreated sewage discharges stagnating in port areas can cause serious epidemics to humans. It may also result in serious degradation of port waters. Discharge of garbage in port waters results in un-aesthetic conditions due accumulation of plastics, glass and metal containers. Frequently, plastic bags & sheets block intakes of cooling water pipelines of industrial units and floating crafts.

Ship discharges include :

*	Ballast water from cargo tanks oil tankers
*	Tank washings from oil tankers
*	Bilge waste from machinery spaces
*	Residues from fuel & lubricating oil purification units, spent lubricating oils, and sludge from tankers
*	Sanitary wastes
*	Garbage

Although many large ships have sewage treatment, and oil/water separation facilities, smaller ships and other port crafts lack these facilities. To mitigate this problem all ports must have connections from ship to shore-based facilities to receive and treat sanitary wastes, oily waste & garbage. For vessels anchored outside port, a floating reception facility such as towed or self propelled barge may be considered.

6. Ballast Water Discharges

Discharge of ballast water in ports may result in coliform & pathogens from the port of origin to propagate to the port of destination. Increases in ship speeds, especially those of container vessels, have resulted in increase of survival rates of these pathogens. A proposed annexe to the MARPOL regulations makes it mandatory for ships to exchange their ballast water several times in course of their voyage.

7. Spills - Detection and Cleanup

Although major oil spills constitute an estimated two-percent of the total marine pollution, they cause in addition to environmental damage, a serious aesthetic degradation of the shoreline. The major causes of the spill are :

*	Marine causalities such as collisions, grounding, fires, etc.
*	Hull failure
*	Failure of equipment such as pipelines, flanges, hoses, etc.
*	Incorrect operating procedures

The avoidance of spill is a key requirement. Many ports in developing countries are particularly lax in enforcing regulations both from calling ships and their own port craft. To alleviate this problem, strict discipline must be observed. All ports must have an emergency contingency plan clearly outlining authority and responsibility for dealing with such situations. A mechanism for alerting and reporting must be established. Oil spill clean up equipment must be available with all ports to deal with minor to medium spills. These equipments must include containment booms, recovery equipment and suitable dispersants. All operators should be trained to handle the equipment. These equipments should be routinely checked and regular exercises must take place to test the efficiency reporting, alerting and operating mechanisms.

8. Anti-fouling Paints

By their very nature anti-fouling paints inhibit the growth and/or destroy a wide variety of marine organisms. Severe damage to the aquatic life is caused by the application of paints containing tri-butyl-tin. Careless application of this paint causes more damage than necessary. Removal of old paint from vessels and floating craft in the waterfront also causes similar damage. New ship building/repair facilities should be located where marine life is minimal.

9. Runoff from Raw Material Storage

Raw materials such as coal, mineral ores, sulphur, salt, etc, are usually stored in the open in port areas prior to loading or after unloading from ships. Due to their large volumes, it is uneconomical to store them otherwise. Due to prevalent weather conditions such as rain and wind, frequently, significant amounts of these materials find themselves in harbour waters. Over a period of time, enormous quantities are built up to such levels that cause acute toxicity and fatalities to aquatic life.

To alleviate this problem, bunds are to be built along the periphery of the storage areas along with suitable drains. These drains may flow to a centralised location, where water can be treated before disposal to harbour waters.

10. Waterfront Drainage

Most port jetties are designed so that they have slight slope towards the harbour waters. Ostensibly, this is to avoid flooding and/or water stagnation due to heavy rainfall. Inadvertently, this type of jetty design allows unimpeded flow of contaminants into harbour waters. The principal constituents of these contaminants are oils, diesel, hydraulic oils, and spillages of cargo on the wharf.

As far as possible, direct drainage from the wharves and piers must be avoided. These areas are to be paved and sloped so that they direct flows to catch basins, where the water collected is treated before disposal.

11. Hazardous Cargoes

A hazardous material can generally be defined as a substance which has a inherent instability, which under certain conditions can lead to fire, explosions or highly corrosive, toxic, or are radio-active. Some examples of hazardous chemicals are liquefied natural gas (LNG), acids, explosive chemicals, radio-active materials, Ammonia, etc. During transportation and storage of these materials, it is quite possible that serious accidents can occur which not only endanger marine life but also human lives, directly.

Some of the techniques that are to be adopted to reduce the risk of accidents during transportation of such materials are listed below

*	Precise information must be obtained regarding the type, quantity, nature and condition of material.
*	Proper segregation of these materials must be maintained
*	These materials are to be appropriately packed and the integrity of the packing must be maintained during transportation
*	Ships carrying hazardous cargoes must be constructed and operated at higher levels of safety
*	Entry and departure to and from ports are to be carefully monitored to avoid risks due collisions

 The above is the paper presented by Dr. Aditya Mukerjee, Adviser, NSDRC at the technical meeting on 3rd Febraury 2001

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