Môi trường - Major marine pollutants - Metals

MAJOR MARINE POLLUTANTSMETALS Almost all natural metals can be found in seawater. Metals can be toxic if they are present in excess. Metals are needed in small quantities for the essential growth of organisms. Other metals have no known use. Incidentally, most of the metallic pollutants are the non essential ones.MERCURY (1) It is probably the most serious metallic pollutant. It occurs in two forms:Inorganic Organic The organic is more toxic than the inorganic mercuryMercury continuedMercury is mobile in the marine environment and can therefore get accumulated in fish and in other marine organisms.Eating seafood or any other food containing 0.3mg/day of mercury over an extended period can lead to the onset of: MINAMATA DISEASE (Mercury Poisoning)Symptoms of MINAMATAMental DisturbanceAtaxiaImpairment of gait, speech and hearingCADMIUM (2)This causes the disease called “itai – itai” This disease is characterized by brittle bones and considerable painTINTin can be found in anti-fouling paints (although banned).Tin has been found to be harmful to marine organismsFor instance, it causes IMPOSEX in marine snails and SHELL DEFORMATION in oysters.LEADLead basically affects the growth and development of children.In the past, at the Mersey River estuary, lead poisoning resulted in the death of a large number of seabirds.RadioactivityThe amount of radioactive material discharged into the sea as a result of human activity is LESS than the natural amounts contained in the sea.Therefore it does not seem to pose a problem to marine organisms or to the marine environment in generalThis implies There are two sources of radioactivity into the marine environment:Natural sources in the earth and the atmosphere2. Artificial inputs Artificial Inputs (General)Atomic weapon testingOther military uses (nuclear submarines, etc)Peaceful uses of nuclear energyImportant sources of radioactivityWaste discharges from nuclear fuel processing plantsWaste discharges from nuclear power generating plantsLow level radioactive waste dumped at seaDischarges from the unplanned return to earth of nuclear powered satellitesLoss of nuclear powered submarinesExplosion at reactor sites (E.g. Chernobyl)Concern Our main concern, as environmentalists, is with the potential routes by which artificial radioactivity added into the sea comes back to land, and results in excessive exposure to humansSuch routes include:Sea spray bloom inlandConsumption of certain sea grasses, fish and shell fishExposure to inter – tidal mudOTHER MARINE POLLUTANTSSOLID WASTEGARBAGEHEATSOLID WASTEUsually gets into the marine environment as Industrial waste. They include:China Clay/ “Kaolin” - causes a rapid drop in Ph levels and may result in heavy fish mortalityFly ash (coal fired boiler) – ash from boiler that contains heavy metals and is detrimental to human healthRed mud – extraction of alumina from bauxite – causes destruction to land masses (highly alkaline).Acid-iron waste: forms a white precipitate when discharged and can clog the respiratory and feeding systems of organisms.Dredge Spoil – smothering of benthic fauna. It is also heavily contaminated with oil and metallic pollutantsGARBAGEGarbage from a variety of sources gets into the marine environment. Plastic appears to be the worst nuisance because it is not biodegradableEFFECTS OF GARBAGECan affect the aesthetic value of tourist beachesSeabirds ingest plastics and this affects their ability to digest their proper foodsMammals get entangled in plastic ringsDiving birds and dolphins get entangled in plastic fishing nets and are drownedOccasionally, nets break away from fishing vessels and engage in “Ghost fishing”WASTE HEATThrough cooling water and effluences discharged at higher temperatures. Heat is a problem only when the ambient temperature is already highIn most tropical waters, marine organisms are already living close to the upper limit of the temperature clearance ranges. When the receiving environment is enclosed, energy cannot be dissipated by mixing with cooler watersvideo akpe na mi!