Tuesday, 18 September 2012

Sewage and Eutrophication

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SEWAGE POLLUTION :

Coastal waters receive a variety of land-based water pollutants, ranging from petroleum wastes to pesticides to excess sediments. Marine waters also receive wastes directly from offshore activities, such as ocean-based dumping (e.g., from ships and offshore oil and gas operations).

One pollutant in the ocean is sewage. Human sewage largely consists of excrement from toilet-flushing; wastewater from bathing, laundry, and dishwashing; and animal and vegetable matter from food preparation that is disposed through an in-sink garbage disposal. Because coasts are densely populated, the amount of sewage reaching seas and oceans is of particular concern because some substances it contains can harm ecosystems and pose a significant public health threat. In addition to the nutrients which can cause overenrichment of receiving waterbodies, sewage carries an array of potentially disease-causing microbes known as pathogens.

 

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Animal wastes from feedlots and other agricultural operations (e.g., manure-spreading on cropland) pose concerns similar to those of human wastes by virtue of their microbial composition. Just as inland rivers, lakes, and groundwater can be contaminated by pathogenic microbes, so can coastal waters. Runoff from agricultural areas also contains nutrients such as phosphorus and nitrogen, which can cause overenrichment in coastal regions that ultimately receive the runoff.

The major types of ocean pollutants from industrial sources can be generally categorized as petroleum, hazardous, thermal, and radioactive. Petroleum products are oil and oil-derived chemicals used for fuel, manufacturing, plastics-making, and many other purposes. Hazardous wastes are chemicals that are toxic (poisonous at certain levels), reactive (capable of producing explosive gases), corrosive (able to corrode steel), or ignitable (flammable). Thermal wastes are heated wastewaters, typically from power plants and factories, where water is used for cooling purposes. Radioactive wastes contain chemical elements having an unstable nucleus that will spontaneously decay with the concurrent emission of ionizing radiation.

Sewage and Agricultural Wastes

Sewage originates primarily from domestic, commercial, and industrial sources. In many developed countries, these wastes typically are delivered either to on-site septic systems or to centralized sewage treatment facilities. In both methods, sewage is treated before being discharged, either underground (in the case of septic tanks) or to receiving surface-water bodies (in the case of sewage treatment plants), typically a stream, river, or coastal outlet.

Although sewage treatment facilities are designed to accommodate and treat sewage from their service area, partly treated or even untreated sewage sometimes is discharged. Causative factors include decayed infrastructure ; facility malfunctions; or heavy rainfall events which overwhelm systems using combined sewers and stormwater drains (known as combined sewer overflows). In unsewered areas, improperly designed or malfunctioning septic tanks can contaminate groundwater and surface water, including coastal waters. In some developed regions (e.g., Halifax Harbor in Nova Scotia, Canada), raw sewage continues to pour into harbors, bays, and coastal waters. In developing countries with no on-site or centralized sanitation facilities, no opportunity exists for any type of treatment, and human wastes go directly into surface waters, including the coastal ocean.

Sewage Sludge

Another source of ocean pollution by sewage-related waste is the disposal of bio solids, a semisolid byproduct of the sewage treatment process, often called sludge. Historically, sludge in developed nations was disposed in coastal waters: New York's twenty sewage treatment plants, for example, once disposed their sludge offshore in a region known as the New York Bight. Although today's environmental regulations in the United States prohibit this practice, sewage sludge is still disposed at sea in some countries.

 

Disease-causing microbes are the primary human health risk in sewage-contaminated waters, and the main cause of recreational beach closures. Here a sign warns San Diego beachgoers of sewage in the waters.

Agricultural Wastes

Animal wastes often reach water bodies via runoff across the land surface, or by seepage through the surface soil layers. Hence, agricultural runoff containing animal wastes does not receive any "treatment" except what is naturally afforded by microbial activity during its transit to a water body. In coastal watersheds, these wastes can flow through river networks that eventually empty into the sea.

Coastal Eutrophication

Nutrients and organic materials from plants, animals, and humans that enter coastal waters, either directly or indirectly, can stimulate a biological, chemical, and physical progression known as eutrophication. Coastal eutrophication is commonly observed in estuaries , bays, and marginal seas. In a broad sense, coastal eutrophication mirrors the eutrophication of lakes. For example, as increased nutrients stimulate algal and other plant growth, light transmission decreases. The eventual bacterial decay of algae and other plants lowers the dissolved oxygen level in the water. In extreme cases, all of the oxygen can be removed.

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Human-accelerated eutrophication (known as cultural eutrophication) can be triggered by inputs of sewage, sludge, fertilizers, or other wastes containing nutrients such as nitrogen and phosphorus. As recently as the 1980s, for example, the New York Bight was essentially lifeless due to oxygen depletion, caused largely by decades of sewage and sludge disposal. As of 2002, Halifax Harbor was still receiving a daily influx of raw sewage, creating serious ecological and public health concerns.

Nutrient-enriched runoff from agricultural land in the midwestern United States is the primary cause of the well-known Gulf of Mexico "Dead Zone." Half of the U.S. farms are located in the Mississippi River Basin, whose entire drainage basin empties into the gulf. Much of the nitrogen reaching the gulf is from agricultural fertilizers, with lesser amounts from residential fertilizers and other sources. The water of the 20,000-kilometer (7,728-square-mile) Dead Zone, extending from the mouth of the Mississippi River Basin to beyond the Texas border, has so little oxygen that essentially no marine life exists.

If human-accelerated eutrophication is not reversed, the entire coastal ecosystem ultimately may be changed. Sensitive species may be replaced by more tolerant and resilient species, and biologically diverse communities may be replaced by less diverse ones. Further, nutrient enrichment and the associated eutrophication in coastal waters is implicated in some harmful algal blooms, in which certain species of algae produce biotoxins (natural poisons) that can be transferred through the food web, potentially harming higher-order consumers such as marine mammals and humans.

Human Health

Sewage, particularly if partially treated or untreated, brings high microbe concentrations into the ocean. Human diseases can be caused by waterborne pathogens that contact the skin or eyes; waterborne pathogens that are accidentally ingested when water is swallowed; or foodborne pathogens found in the tissues of fish and shellfish consumed as seafood. *

Beach pollution consequently is a persistent public health problem. Annually, thousands of swimming advisories and beach closings are experienced because high levels of disease-causing microbes are found in the water. Sewage often is responsible for the harmful microbial levels.

Seafood contaminated by sewage-related pathogens sickens untold numbers of people worldwide. Regulatory agencies will close a fishery when contamination is detected. However, many countries lack regulatory oversight or the resources to adequately monitor their fisheries.

Industrial Wastes

Industrial wastes primarily enter coastal waters from terrestrial (land-based) activities. Industries, like municipalities and other entities that generate wastes, dispose of many liquid wastes through wastewater systems (and ultimately to waterbodies), whereas they dispose of their solid wastes in landfills.

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The quantity and characteristics of industrial wastewater depends on the type of industry, its water and wastewater management, and its type of waste pretreatment (if any) before delivery to a wastewater (sewage) treatment plant. Because industrial waste frequently goes down the same sewers as domestic and commercial nonindustrial waste, sewage often contains high levels of industrial chemicals and heavy metals (e.g., lead, mercury, cadmium, and arsenic).

Substances that are not removed by wastewater treatment processes are discharged via the treated effluent to a receiving stream, river, or coastal outlet. Inland waters ultimately reach the ocean, carrying with them some residual chemical that are not attenuated, stored, or degraded during their journey through the watershed. Other land-based sources of industrial pollutants in the ocean are pipeline discharges and transportation accidents, leaking underground storage tanks, and activities at ports and harbors. Intentional, illegal dumping in inland watersheds and in inland waterbodies also can deliver industrial wastes to drainageways, and ultimately to the ocean.

In coastal watersheds, some industries discharge their wastes directly to the ocean. Like industries located inland, these industries must first obtain a permit under the Clean Water Act. Industrial pollutants also can directly enter the ocean by accidental spills or intentional dumping at sea.

Wet and dry deposition of airborne pollutants is a sometimes overlooked, yet significant, source of chemical pollution of the oceans. For example, sulfur dioxide from a factory smokestack begins as air pollution. The polluted air mixes with atmospheric moisture to produce airborne sulfuric acid that falls on water and land as acid rain. This deposition can change the chemistry and ecology of an aquatic ecosystem. The major transport of PCBs to the ocean, for example, occurs through airborne deposition.

Industrial chemicals can adversely affect the growth, reproduction, and development of many marine animals. Pollutants are appearing not only in the Pacific, Atlantic, and Indian Oceans and their marginal seas, but also in the more remote and once-pristine polar oceans. An array of contaminants have been found in the flesh of fish and marine mammals in polar regions. In addition to the environmental and ecological issues, there is growing concern over the potential human health impacts in aboriginal communities whose residents depend on fish and marine mammals for daily sustenance.

A major public health concern is the safety of seafood as it relates to the chemical pollution of waters used for commercial and recreational fishing and mariculture . Heavy metals (e.g., copper, lead, mercury, and arsenic) can reach high levels inside marine animals, and then be passed along as seafood for humans. A well-known case of human poisoning occurred in Japan, where one industry dumped mercury compounds into Minimata Bay from 1932 to 1968. Methyl mercury that accumulated in fish and other animals was passed along to humans who consumed them. Over 3,000 human victims and an unknown number of animals succumbed to what became known as "Minimata Disease", a devastating illness that affects the central nervous system.

Monitoring by fisheries, environmental, and public health agencies can prevent or minimize cases of human illness caused by chemical contaminants in seafood. Some shellfish-producing areas off the U.S. coasts have been either permanently closed or declared indefinitely off-limits by health officials as a result of this type of pollution. A large percentage of U.S. fish and shellfish consumption advisories are due to abnormally high concentrations of chemical contaminants in seafood.

Regulatory Controls

The 1890 River and Harbors Act prohibited any obstruction to the navigation of U.S. Waters, and hence regulated the discharge of dredged material into inland and coastal waters. By weight, dredged material comprises 95 percent of all ocean disposal on a global basis. Its regulation (administered by the U.S. Army Corps of Engineers) increasingly is being accomplished in concert with broader concerns, including ecological integrity and other public interests.

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In 1972, the U.S. Congress passed the Marine Protection, Research, and Sanctuaries Act (Ocean Dumping Act) and the Federal Water Pollution Control Act Amendments (Clean Water Act) that, among other goals, prohibited the disposal of waste materials into the ocean, and regulated the discharge of wastes through pipelines into the ocean. The Ocean Dumping Act requires the federal review of all proposed operations involving the transportation of waste materials for the purpose of ocean dumping, and calls for an assessment of the potential environmental and human health impacts. The U.S. Army Corps of Engineers and U.S. Environmental Protection Agency implement the permit programs associated with these laws.

In the United States, ocean dumping of industrial wastes is prohibited. Yet the vastness of the open sea provides a haven for illegal dumping.

The Ocean Dumping Ban Act of 1988 significantly amended portions of the 1972 Ocean Dumping Act, and banned ocean dumping of municipal sewage sludge and industrial wastes (with limited exceptions) by phased target dates. The disposal of sewage sludge in waters off New York City was a major motivation for its enactment. Ocean disposal of sewage sludge and industrial waste was totally banned after 1991. Narrow exceptions were created for certain U.S. Army Corps of Engineers dredge materials that occasionally are deposited offshore. Dredging is necessary to maintain navigation routes for trade and national defense. Consequently, allowable ocean dumping in the United States since 1991 has essentially been limited to dredge material and fish wastes.

Two international conferences in 1972—the UN Conference on the Human Environment, and the Intergovernmental Conference on the Convention on the Dumping of Wastes at Sea—were the result of international recognition of the need to regulate ocean disposal from land-based sources on a global basis. These conferences resulted in an international treaty, the Convention on the Prevention of Marine Pollution by Dumping of Wastes and Other Matter (also known as the London Convention).

Another treaty addressing the issue of wastes disposed from vessels was adopted in 1973. The International Convention for the Prevention of Pollution from Ships (or MARPOL) calls for signatory nations to enforce bans on dumping oil and noxious liquids into the ocean from ships, but the disposal of hazardous substances, sewage, and plastics remains optional.

As per the U.S. regulations, the dumping of industrial wastes, radioactive wastes, warfare agents (chemical or biological), sewage, and incineration at sea are directly prohibited. Moreover, the ocean disposal of other waste materials containing greater than trace amounts of certain chemicals is strictly prohibited. Allowed under strictly regulated conditions are the ocean disposal of relatively uncontaminated dredged material (harbor sediments), geologic material, and some fish waste; burial at sea; and ship disposal.

In 2000, the U.S. Congress enacted the Beaches Environmental Assessment and Coastal Health Act (BEACH Act) to reduce the risk of disease to users of the nation's coastal and Great Lakes waters. Funds are being made available for states and tribes to establish monitoring programs for disease-causing microbes, and to notify the public when monitoring indicates and public health hazard.

EUTROPHICATION:

Introduction
Corals require the cleanest water quality of any coastal ecosystem, and suffer if it deteriorates. One crucial aspect of water quality is the concentration of nutrients in the water. Nutrients are essential elements needed for the growth of all forms of life, and when they are inadequate, organisms are unable to grow well, no matter how much other food is available. In coastal waters two nutrients, nitrogen and phosphorus, are typically present in such low concentrations that they prevent full growth. In the remote open ocean iron and other trace metals can also be scarce, but this is rarely the case in coastal waters due to abundance of these elements on suspended clays.

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Coral reefs have evolved in the lowest nutrient environment in the world, the tropical ocean, where plants often consume all available nitrogen and phosphorus, at which point new growth is limited to rates at which these elements are provided by decomposition of dead organisms. Although there is abundant nitrogen and phosphorus in the deep sea it cannot reach surface layers where bright light promotes the growth of plants and animals because a thick layer of warm waters floating on top of deep cold nutrient-rich water prevents its being mixed upward to the surface.

Tiny increases in nutrients above the near zero level are probably beneficial to corals, but it takes only very small increases for the net effect to turn negative. This is not because high nutrients harm corals directly, but because corals are quickly overgrown by much faster growing algae which need higher nutrient levels than corals. Only very little excess nutrients are needed to turn healthy coral reefs into waving fields of algae which smother and kill corals. This phenomenon is called eutrophication. Eutrophication takes place in all ecosystems and is responsible for green scummy layers of algae covering ponds into which sewage and manure flows. Coral reefs go eutrophic at the lowest level of nutrients of any aquatic ecosystem: nutrient levels which would be regarded as very low in any other marine or freshwater habitat will kill coral reefs. This web site has papers discussing these problems, and their solutions, in more detail.

Major sources of excessive nutrients include sewage, livestock manures, agricultural fertilizers, soils eroding away after deforestation, and upwelling of deep ocean waters. Where nutrient inputs are episodic, for example where there are strongly seasonal rivers, tourist sewage, or upwelling inputs reefs may be eutrophic part of the year only. Where nutrients continue to increase, coral will be killed. Due to the large increase of nutrients released into coastal waters from sewage discharged directly into the ocean or delivered via rivers and ground waters, the reefs off all coastal areas which are densely populated or developed for tourism are already eutrophic or quickly turning so. This can happen very rapidly, and in only a few years healthy reefs can be turned into coral graveyards. Probably no coral reef country is free of this problem, not even the smallest.


Only in recent years have we have learned just how low nutrients must be to maintain healthy coral reefs. The limits were found independently by two researchers working on opposite sides of the globe, who were not aware of each other's work. By looking at the relative amounts of corals and algae along nutrient gradients from intense land-based sources, namely agricultural fertilizers in Australia and bird droppings on a mangrove island in Belize, Peter Bell and Brian Lapointe independently determined exactly the same limit for acceptable nutrient concentrations. Biologically available nitrogen (nitrate plus ammonia) needs to be below 1.0 micromole per liter (less than 0.014 parts per million of nitrogen), and biologically available phosphorus (orthophosphate plus dissolved organic phosphorus) needs to be below 0.1 micromole per liter (less than 0.003 parts per million of phosphorus). In addition concentrations of chlorophyll (in the microscopic plants called phytoplankton) needs to be below 0.5 parts per billion.

These values are all regarded as extremely low levels, almost undetectable, in coastal waters of temperate and cold zones. For years researchers measured concentrations in this range but thought that values were too low to possibly cause problems to reefs. This was wrong because they used irrelevant standards for acceptable nutrient levels. It is essential that appropriate water quality standards be applied in coral reef ecosystems if they are to be protected against eutrophication. These standards must be below the levels given above. In general, where water quality standards have been applied for tropical waters, they are often based on uncritical adoption of nutrient standards from North America and Europe that are irrelevant to the tropics because cold ecosystems are normally exposed to much higher nutrient levels. Many nutrient water quality standards available are related to human health and are even more worthless for coral reefs because humans can drink water with nutrient levels hundreds of times higher than coral reefs can stand.

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Toxic/Hazardous materials

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Hazardous materials :

Hazardous substances, lead hazardous substances, stated dangerous goods and combustible liquids are examples of hazardous materials classified according to their relevance to workplace health and safety. Materials are classified as hazardous substances if they meet the National Occupational Health and Safety Commission’s Approved Criteria for Classifying Hazardous Substances. Materials are also classified as hazardous substances if their name appears in the NOHSC publication titled "List of Hazardous Substances" and are found above the stated cut-off concentrations in that publication. Hazardous materials, if not stored or handled correctly, can cause harm to workers, members of the public, property and the environment due to their physical, chemical, and biological properties. Hazardous materials include many commonly found industrial, commercial, pharmaceutical, agricultural and domestic chemicals.

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Examples of some hazardous materials include:

• paints

• drugs

• cosmetics

• cleaning chemicals • degreasers

• detergents

• gas cylinders

• refrigerant gases

• pesticides

• herbicides

• diesel fuel

• petrol

• liquefied petroleum gas

• welding fume.

Hazardous substances are chemicals and other substances including most dangerous goods for which a manufacturer or importer must prepare, amend, provide and review a Material Safety Data Sheet (MSDS). Hazardous materials can cause adverse health effects such as asthma, skin rashes, allergic reactions, allergic sensitisation, cancer, and other long term diseases from exposure to substances.

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Material Safety Data Sheets (MSDS)

An MSDS is a document containing important information about a hazardous substance and must state:

• a hazardous substance’s product name

• the chemical and generic name of certain ingredients

• the chemical and physical properties of the hazardous substance

• health hazard information

• precautions for safe use and handling

• the manufacturer’s or importer’s name, Australian address and telephone number.

The MSDS provides employers, self-employed persons, workers and other health and safety representatives with the necessary information to safely manage the risk from hazardous substance exposure. It is important that everyone in the workplace knows how to read and interpret a MSDS.

Access to MSDS

Access to a MSDS can be provided in several ways including:

• paper and microfiche copy collections of MSDS with microfiche readers open to use by all workers

• computerised and internet MSDS databases.

The register of MSDS should be used as an information tool to make sure everyone is involved in managing hazardous substances exposure at the workplace.

A MSDS should be reviewed whenever there is:

• a change in formulation which:

· affects the hazardous properties of the substance

· alters the form, appearance or mode of application of the substance

• a change to the hazardous substance which alters its health and/or safety hazard or risk

• new health and/or safety information on the hazardous substance such as exposure standard changes or a substance previously considered not harmful is now established to be harmful (e.g. carcinogenic)

• at least every five years. In respect of MSDS and labels, employers and self-employed personsmust:

• Obtain an MSDS of a hazardous substance from the supplier.

• Keep a register containing a list of all hazardous substances used at the workplace and put a copy of any MSDS obtained in the register.

• Take reasonable steps to ensure the MSDS is not changed other than by the manufacturer or importer.

• Keep the MSDS close to where the substance is being used.

• Ensure a label is fixed to a hazardous substance container.

• Ensure warnings are given about enclosed systems containing hazardous substances. Retailers are not required to distribute MSDSs. However, if a hazardous substance is purchased from a retailer, and the substance is for use at a workplace, an MSDS can be requested from another supplier of the hazardous substance such as the manufacturer or importer. In certain circumstances a supplier must provide copies of the MSDS to the workplace and fix a label to the containers of all classified hazardous substances because the substances:

• are on the National Occupational Health and Safety Commission (NOHSC) List of Designated Hazardous Substances

• on the designated list and are contained in a substance above a certain concentration

• meet the Approved Criteria (because of health effects). More information about MSDS is provided in Section 1 of the Hazardous Substances Advisory Standard 2003 (now known as a Code of Practice).

The format and content for a MSDS used in Australia is set out in the ‘National Code of Practice for the Labelling of Workplace Substances’. Employers can also ask the supplier of a hazardous substance for a 'National Industrial Chemicals Notification and Assessment Scheme (NICNAS) summary report' which provides more detailed advice about health hazards and control measures. Labelling and decanting Suppliers, employers and self-employed persons have specific labelling obligations for all hazardous substances containers in the workplace.

Label :

The label must be in English and contain the following:

• name of the product

• risk and safety phrases – as stated in NOHSC’s document entitled ‘National Code of Practice for the Labelling of Workplace Substances’ that gives information about the substance’s or lead’s hazards

• chemical names of particularly hazardous ingredients

• chemical or generic names of certain other ingredients.

If the manufacturer has amended a MSDS, the label should be changed to ensure that it is consistent with the information in the amended MSDS.

Containers of decanted hazardous substances at the workplace must be labelled with the product name and basic health and safety information (risk and safety phrases) from the supplier’s label. More information about labelling and decanting is available in Section 2 of the Hazardous Substances Advisory Standard 2003 (now known as a Code of Practice).

Health effects from hazardous substances in workplaces It is important when using hazardous materials in the workplace they are properly controlled if they are:

• toxic

• harmful

• corrosive

• irritant

• sensitising

• carcinogenic (causing cancer)

• mutagenic (causing genetic damage)

• teratogenic (causing abnormalities of the foetus).

Some of the health effects of exposure to hazardous materials include:

• skin irritation

• occupational asthma

• systemic chemical poisoning

• chemical burns from corrosives

• cancer.

Factors that determine whether illness or disease occurs include:

• amount and route of exposure

• simultaneous exposure to other hazardous substances

• sensitivity to the substance’s effects.

Some of the ways hazardous materials can enter the body include:

• breathing in (inhalation)

• skin contact (where skin is the target organ)

• absorbed through the skin and mucous membranes of the eye

• accidentally swallowed by eating or smoking with contaminated hands

• accidental injection through the skin.

These health effects can be acute, resulting from short-term (usually high) exposure, or chronic, resulting from long term (often low level) exposure over a period of time. Chronic effects may not occur for many years and the cause is often hard to identify.

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Oil pollution of marine habitats

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Oil pollution of marine habitats

Oil pollution is one of the most conspicuous forms of damage to the marine environment. Oil enters the seas not only as a result of spectacular oil tanker or oil rig disasters, but also – and primarily – from diffuse sources, such as leaks during oil extraction, illegal tank-cleaning operations at sea, or discharges into the rivers which are then carried into the sea. The designation of marine protected areas, increased controls and the use of double hull tankers are just some of the measures now being deployed in an effort to curb marine oil pollution.

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How oil enters the sea

The public generally takes notice of the problem of marine oil pollution when an oil tanker breaks up in heavy seas or a disaster occurs at an oil platform, one example being the Deepwater Horizon incident in the Gulf of Mexico in spring 2010. In such cases, oil slicks often drift towards the coasts and kill seabirds and marine mammals such as seals. Yet in reality, spectacular oil tanker disasters account for only around 10 per cent of global marine oil pollution.
Most of the oil enters the seas along less obvious pathways, making it correspondingly difficult to preci­sely estimate global oil inputs into the marine environ­ment. Around 5 per cent comes from natural sources, and approximately 35 per cent comes from tanker traffic and other shipping operations, including illegal discharges and tank cleaning. Oil inputs also include volatile oil constituents which are emitted into the atmosphere during various types of burning processes and then enter the water. This atmospheric share, together with inputs from municipal and industrial effluents and from oil rigs, ac­­counts for 45 per cent. A further 5 per cent comes from undefined sources.
Although vegetable oils such as palm oil are now being produced in increasing quantities and are therefore also entering the atmosphere, oil pollution still mainly consists of various types of oil from fossil sources, created over millions of years from deposits of microscopically small marine organisms, mainly diatoms

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Oil enters the sea along various pathways. Around one third comes from regular accident-free shipping operations.

This crude oil consists of around 10,000 individual substances, with hydrocarbons being the main component (more than 95 per cent). However, the precise composition can vary considerably according to the place of origin. Crude oil also contains heavy metals and nitrogen compounds.
The extent to which mineral oils and their components adversely affect the various marine habitats and their flora and fauna varies considerably from case to case. Major oil spills have the greatest and most disruptive impact, although their effects are in most cases regionally limited. Since the Torrey Canyon tanker disaster in 1967, when around 115,000 tonnes of crude oil were spilled on a reef off the southern English coast, resulting in the largest oil pollution incident ever recorded up to that time, numerous field studies have been carried out which now provide a very clear overview of the impacts of various types of oil on organisms and habitats. However, one oil disaster is quite never the same as another, and the precise effects of an accidental oil spill depend on a variety of conditions.
A crucial factor, for example, is how quickly the oil breaks down or sinks from the surface of the sea to the lower depths, where the damage it causes is likely to be relatively limited. This breakdown is influenced by various physical, chemical and biological processes. Depending on a variety of different environmental conditions such as temperature, nutrient content in the water, wave action etc., the breakdown of the petroleum hydrocarbons may take shorter or longer periods of time. During the first few hours or even during the first few weeks, the oil is modified by the following chemical and physical processes:

evaporation of volatile constituents;

spreading of the spilled oil in large oil slicks drifting on the surface waters;

formation of dispersions (small oil droplets in the water column) and emulsions (larger droplets of oil-in-water or water-in-oil);

photooxidation (molecular changes to the oil constituents caused by natural sunlight) and solution.

In the sea, oil is modified and broken down in a variety of ways. Generally, when an oil spill occurs, the oil immediately forms large slicks which float on the water’s surface. A proportion of the oil evaporates or sinks, but other oil constituents are broken down by bacteria or destroyed by solar radiation. Finally, the oil solidifies into clumps (tarballs), which are more resistant to bacterial breakdown.

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Processes such as sedimentation and breakdown by bacteria, on the other hand, may continue for months or even years, although in some cases, under favourable conditions, they may be completed within a matter of days.
The reason for this discrepancy is that, firstly, the various substance groups contained in the oil undergo biological breakdown at different rates. The speed of breakdown depends primarily on the molecular structure of the oil constituents. The more complex the hydrocarbon molecules, the longer it takes for the oil to be broken down by microorganisms. Secondly, the rate at which the various hydrocarbons are broken down is increased by the following factors:

high temperatures, promoting bacterial activity;

a large surface area (if necessary, the surface area of the slick can be increased through the use of dispersants, i.e. surface-active agents [surfactants] which promote the formation of dispersions);

good oxygen supply for the bacteria;

good nutrient supply for the bacteria;

lownumber of predator organisms which would
reduce the number of bacteria.

Some of the above-mentioned processes have a very considerable influence on the extent of oil damage. Water-in-oil emulsions, for example, are a contributory factor in the formation of “chocolate mousse”. This viscous emulsification can increase the original volume of the oil as much as fourfold, rendering the use of chemical dispersants impossible and making it far more difficult to pump the oil off the water surface.

How oil damages habitats

It is generally not possible to protect an entire coastline from the effects of a major oil spill, so the authorities have to set priorities for their oil spill response. It goes without saying that designated conservation areas, such as national parks, or sensitive marine areas are particularly worth protecting and are given high priority in clean-up efforts. As a rule, however, these areas are too large to be protected in their entirety. Here, sensitivity rankings can facilitate the oil spill response: these describe the general sensitivity of the various shoreline types to oil pollution. In exceptional cases, it may even be possible to define “sacrificial areas” which are less important from a nature conservation perspective and where no protective measures are taken.

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A specially equipped ship deploys a boom, consisting of inflatable floats, in an attempt to contain the crude oil spilled at sea by the oil tanker Sea Empress after it went aground off the coast of Wales in 1996. In rough seas, however, the use of these skimmers has little effect

When defining these sensitivity rankings, one factor which is taken into account is whether the section of coastline is a “high-energy” area, e.g. with rocky or sandy shores that are subjected to direct wave action, or whether they are relatively calm, “low-energy” areas such as the Wadden Sea, which are protected by sandbanks or offshore islands. Of course, within the major habitats described here, other more detailed sensitivity rankings can be defined for a targeted oil spill response.

EXPOSED ROCKY AND SANDY SHORES: Exposed rocky and sandy shores are classed as areas of relatively low sensitivity because the oil deposited by the sea is cleared very swiftly by wave action. Nonetheless, major oil spills can change the composition of biological communities in these habitats over the longer term. In such cases, populations of former dominant species such as crustaceans and molluscs may decline. In rocky crevices, rough gravel and on mussel beds, the oil pollution may persist for many years.

SANDY BEACHES: Here, a different situation applies. The extent to which the oil penetrates the ground and how long it remains there depend primarily on the structure of the beach. An extensive beach with little surf and with branching channels, for example, is far more vulnerable than a steep beach with a less diverse structure. Coarse-grained sediment facilitates oil penetration, makes the clean-up process more difficult, and increases the risk of follow-up damage from re-surfacing oil. Beach areas used as habitats or breeding sites by endangered species, such as turtles, are classed as particularly sensitive.

CORAL REEFS: Corals are also highly sensitive to oil pollution. Various studies show that damaged coral reefs are very slow to regenerate. Oil pollution can also affect entire communities. For example, less sensitive species of algae can colonize oil-contaminated areas which were previously coral habitats. Very little research has so far been undertaken to investigate how oil spills affect the relationship between corals and the many species asso-
ciated with them. The linkage between numerous specialized species and the great significance of symbioses within these ecosystems indicate that far-reaching and long-term impacts can be anticipated after major oil spills.

MANGROVES: Mangrove habitats react with particular sensitivity to oil pollution. Here, an oil spill can inflict severe damage on trees and the sensitive organisms living in them and in sediment. This damage is caused by toxic hydrocarbons, but can also occur as a result of oil cover, which shuts off the oxygen and freshwater supply. The regeneration of damaged populations of flora and fauna is a lengthy process. As the harmful hydrocarbons are removed from sediment very slowly in mangroves, habitat recovery is further delayed.

SOFT SUBSTRATES AND SANDBANKS: Sections of coastline with soft substrates and sandbanks, such as the Wadden Sea on the North Sea coast, are classed as particularly or highly sensitive. The organisms living at great density in and on the sediment provide the basic food supply for fish and birds. Although in most cases, very little oil penetrates the often water-saturated fine pores of muddy sediment, these areas are generally densely populated by burrowing organisms whose activities cause the oil to sink deeper into the ground. On the other hand, the stirring and mixing of sediment by these organisms – known as bioturbation – also help to break down the oil by churning up the sediment, exposing deeper layers to the air and bringing oily sediment to the surface. As this activity promotes a healthy oxygen supply, the oil is then broken down more quickly by bacteria. If the organisms in the sediment have been killed by the oil, however, bioturbation ceases and the oil remains in the ground for longer, causing long-term habitat damage.

SALT MARSHES: Very few studies have been carried out to investigate how oil affects invertebrate organisms found in salt marshes, such as insects and worms. The ve­­­getation, however, can suffer long-term damage from oil pollution, with major implications for breeding and resting birds in the salt marshes, whose plumage may be co­­­vered in oil or which could lose their basic food supply.
To sum up, the following regeneration periods can be assumed:

Exposed rocky and sandy shores: between a few months and 5 years;

Protected rocky shores and coral reefs: between 2 and more than 10 years;

Protected soft substrates, salt marshes, mangroves: between 2 and more than 20 years.

Responses to oil spills and pollution

In scenarios other than disasters that occur in deep waters, such as the explosion at the oil drilling rig in the Gulf of Mexico in spring 2010, an oil spill disaster response is most effective while the slick is still drifting on the water surface. From a technical perspective, some countries prefer to use exclusively mechanical methods to contain oil spills, such as oil skimmers or booms that form floating barriers on the water, while others opt for chemical methods, mainly involving the use of dispersants, which are usually dropped on the slick in large quantities from aircraft. The effectiveness of these chemicals is heavily dependent on the type and condition of the oil, however. A further limiting factor is that these dispersants can generally only be used for a short time after the spill has occurred, as the chemical and physical processes described above begin to impair their effectiveness after only a few hours. If the oil slicks are drifting towards sensitive sections of shoreline, using these agents may be a sensible option, however. The dispersants drive the oil from the surface down into deeper waters, reducing the risk that seabirds or sensitive flora will become coated with oil. Following the explosion at the Deepwater Horizon drilling rig in 2010, however, the oil flowed out of the borehole at great depth and entered the entire water column, partly as a massive cloud of oil. Very little experience has been gained in responding to disasters of this type and on this scale. As an initial response, massive quantities of dispersants were deployed, with currently unforeseeable ecological consequences. Bioremediation can also be successfully deployed in suitable – i.e. nutrient-poor – marine areas. This involves seeding the water with nutrients to promote the growth of bacteria that break down oil.

Although the quantities of oil being transported across the oceans have increased considerably since the 1970s, the amount of marine oil pollution caused by oil tanker disasters, technical defects or negligence has fallen dramatically. The sharp decrease in tanker traffic in the late 1970s was caused by the economic crisis which occurred during that period. The statistics cover oil spills above 7 tonnes; records of smaller spills are somewhat patchy.

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No matter which strategy is deployed, it can only be successful and effective as part of a broader national contingency plan in which well-trained emergency teams implement a coherent and well-thought-out response. In the US, Germany, other North Sea states and certain other countries, such contingency plans have been in place for a number of years. In these countries, the days when the authorities often failed to adopt a prompt, effective or appropriate response to oil spills due to a lack of clear responsibilities, equipment and personnel are over. On their own, however, technical management strategies are not enough. Global and regional agreements are required to protect the sea from oil pollution, and mechanisms need to be in place to monitor compliance with them. A positive example is the International Convention for the Prevention of Pollution from Ships, 1973, as modified by the Protocol of 1978 relating thereto (MARPOL 73/78), which from 1983 formed the basis for the designation of marine protected areas where tanker traffic is wholly or partly restricted. As a result of the Convention, there was a reduction in the number of oil tanker disasters during the 1980s. In addition to other provisions on operational discharges of oil, MARPOL 73/78 also paved the way for the introduction of double hull tankers. The United States’ 1990 Oil Pollution Act and the International Management Code for the Safe Operation of Ships and for Pollution Prevention (ISM Code) adopted by the International Maritime Organization (IMO) in 1998 also contributed to the further decrease in oil pollution over subsequent decades.

Workers on a beach at the popular Gulf Shores resort in the US remove sacks of oil-covered algae. The resort, along the coast of Alabama, is one of the communities in the Gulf of Mexico which have been polluted by oil from the Deepwater Horizon disaster in June 2010.

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The outlook for the future – cautious optimism

Marine oil pollution has undoubtedly decreased in recent decades. International conventions, the designation of protected areas and the mandatory introduction of double hull tankers have all made a contribution here. At the same time, as the Deepwater Horizon disaster clearly demonstrates, the situation for the marine environment continues to give cause for concern. Furthermore, the illegal discharge of oil during tank-cleaning operations, which still accounts for one third of oil pollution, cannot be tackled effectively without more stringent controls and tough penalties. Combating oil pollution in shallow waters such as the Wadden Sea will also continue to be a problem in future as response vessels generally cannot operate in waters of less than 2 metres depth.

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Thursday, 13 September 2012

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Monday, 10 September 2012

Types of Marine pollution

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Below mentioned types of ocean pollution are referred by various researchers till date.

  1. Oil pollution.
  2. Toxic materials.
  3. Sewage and Eutrophication.
  4. Garbage.
  5. Radio active waste.
  6. Ship pollution.
  7. Plastic debris.
  8. Under water noise.
  9. Agricultural land runoff.
  10. Atmospheric.
  11. Deep sea mining.
  12. Agricultural run-off.
  13. Air pollution.
  14. Sun screen.
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