Môi trường - Major marine pollutants

MAJOR MARINE POLLUTANTSGOOD MORNING CLASS!上午好学生们！Shang wu hao xue sheng men!The major marine pollutants are:OilSewagePesticides and other Persistent Organic ChemicalsMetalsRadioactivityOILOil is not a single homogeneous compound but consists of many different compounds.Some physical properties of oil include;ToxicitySolubilityViscosityOIL – cont’dFACTS:about 3 billion tonnes of crude oil is produced annually, and half of this is carried by sea. Averagely, 8.25 million tonnes of oil is floating on the sea daily.MOVEMENT OF OILMAJOR PRODUCERSArabian gulfGulf of MéxicoNorth seaMAJOR CONSUMERSAmericaWestern EuropeChinaThe risk of accidents by tankers is highest during maneuvers in portOIL SOURCES INTO THE OCEANOffshore oil productionRoutine ship operationShip accidents Ocean dumpingNatural sources Land-based sources Oil pollution SourcesContd..Source: UNEPEFFECTS OF OIL POLLUTIONEFFECTS OF OIL POLLUTIONGross fouling of beachesEffects on fish, birds, mammals & plantsEconomic effectsEFFECTS ON BIRDSBirds can drown in the oilThey loose their buoyancy and thermal insulationThey ingest the oil whilst trying to clean themselvesThey also pass some toxicity to their offspringEFFECTS ON FISHFish become tainted and unpalatableYoung fish can dieFish eggs may not be hatched as a result of pollutionBreeding patterns may be affected if the spawning grounds are polluted or if migratory routes are blocked.EFFECTS ON MAMMALSMammals which use their fur for insulation loose their thermal insulation (coated fur is a poor insulator). E.g. Northern SealThe oil affects their eyes and nostrilsMammals may die as a result of ingestion of oilEFFECTS ON PLANTSPlants like mangroves, Kelp, Marsh grass and sea grasses are destroyed by oil pollution.These plants serve as a habitat for other organisms within an ecosystem. As a result of pollution, there can be loss of cover and this may lead to serious environmental impacts.ECONOMIC EFFECTS OF OIL POLLUTIONHarbours, marinas, tourist beaches may be closed due to oil pollution. Hunting and fishing may be suspended and this may affect the traditional lifestyle of native people.Tourist guides, fishermen and outfitters may loose their sources of income.Some Major Oil Spill CatastrophiesCleaning-up oil spills:1. Dispersants: Oil can be broken down more quickly by spraying dispersants (chemicals) on the oil slick from boats or planes. This method only works on fresh, small oil spills.2. Booms: A boom has a floating skirt suspended down in the water and a sail holding it above the water line. The floating skirt stops the oil from passing. These are used to prevent oil from entering delicate and protected areas.3. Slick-lickers: This method uses a belt of oil absorbing material that sucks up the oil from the ocean water. The oil is then squeezed out of the absorbing material into a collecting bin.SEWAGE From an environmental point of view, the problem with sewage disposal has to do with: BIOLOGICAL OXYGEN DEMAND (BOD)Biological Oxygen Demand (BOD)It is the amount of oxygen required by bacteria to consume and degrade the waste.If the amount of oxygen present is equal to or less than the BOD, then anoxic conditions are created, which is very toxic to aquatic life.Most sewage treatment systems are designed to reduce the BOD. SEWAGE – cont’dSewage is usually separated into waste water and sewage sludge.The waste water is not always harmless; it sometimes contains nutrients like phosphates and nitrates which if discharged incorrectly, can stimulate excessive algae growth with very high oxygen demandThis is referred to as EUTROPHICATIONSEWAGE – cont’dAnother problem with sewage disposal has to do with contaminated sea food. Fish and shell fish can accumulate pathogens from sewage and when these are eaten by humans it can result in illnesses like simple stomach ache, typhoid, paratyphoid, diarrhea, salmonelisis, septicemia, gastroenteritis, infectious hepatitis, and skin infections.Pesticides & Other Persistent Organic ChemicalsThese are chemicals that cause great harm to the marine environment. They are usually in the form of Chlorinated Hydrocarbons (e.g. DDT) – dichlorodiphenyltrichloroethaneand Polychlorinated Biphenyls (PCB’s).General Properties Of These ChemicalsThey are generally fairly toxicPersistent in the marine environmentBioaccumulatedEffects of PesticidesDDT has been cited as the cause of the decline in the population of predatory birds like Peregrine Falcon, Osprey, Brown Pelican and the American Bald eagle in the 1960’s.DDT is said to interfere with the metabolism of calcium therefore causing the birds to lay eggs with abnormally thin shells. Therefore eggs were prone to breakages. Effects of Pesticides - cont’dPCB’s have been cited as the cause of infertility in Northern Seals. The PCB’s are thought to interfere with ovulation. akpe na mi!