TAILIEUCHUNG - BIOMES OF THE EARTH - OCEANS Phần 9

Tham khảo tài liệu 'biomes of the earth - oceans phần 9', ngoại ngữ, anh ngữ phổ thông phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 204 OCEANS Crude oil from the Exxon Valdez floating on the sea surface in Prince William Sound Alaska Courtesy of Flip Nicklin Minden Pictures Bahamas-registered Prestige sank off the coast of Spain in November 2002 releasing fuel oil onto Spanish fish and shellfish grounds and polluting more than 185 miles 300 km of coastline. The wreck has the potential to release twice as much oil as the Exxon Valdez spill of 1989. Heavy metals Domestic and industrial wastewater and runoff from polluted land may contain trace amounts of heavy metals such as mercury lead and cadmium that are poisonous to many forms of life. The most dramatic case of heavy-metal pollution happened in Minamata Bay Japan in the mid-1950s. A local plastics factory began discharging mercury-contaminated THE HEALTH OF THE OCEANS 205 Exxon Valdez oil spill On March 24 1989 the supertanker Exxon Valdez struck a reef in Prince William Sound Alaska. About 38 500 . tons 35 000 tonnes of oil spilled into the sea. The oil spill eventually covered more than 1 200 miles 1 950 km of shore in an unsightly sludge that smothered or poisoned wildlife. Experts estimated that up to 300 000 seabirds 5 000 sea otters and 300 harbor seals died in the incident. The local herring- and salmon-fishing industry was devastated. However the affected shores and coastal waters are slowly recovering. By 2000 the salmon were back and so were many seabirds although harbor seals and herring had yet to return. Today safety vessels escort all tankers that enter Prince William Sound. wastewater into the sea. The wastewater contained a particularly harmful mercury-based substance methyl mercury. This substance enters the cells of organisms more readily than mercury itself. An unusually large number of local people began experiencing a range of symptoms headaches shaking paralysis and even blindness. It took about 10 years for the authorities to be convinced that the contaminated wastewater was the cause of the outbreak. By that time .

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