Environmental Problems, Their Causes, and Sustainability 1

Oil slicks that wash onto beaches can have a seriouseconomic impact on coastal residents, who lose incomenormally gained from fishing and tourist activities. Oilpollutedbeaches washed by strong waves or currentsbecome clean after about a year, but beaches in shelteredareas remain contaminated for several years. Despitethe localized harmful effects, EPA experts rate oilspills as a low-risk ecological problem.How Well Can We Clean Up Oil Spills? NotVery WellCurrent methods can recover no more than about 15%of the oil from a major spill, explaining why preventionis the best strategy.If they are not too large, oil spills can be partiallycleaned up by mechanical, chemical, fire, and naturalmethods. Mechanical methods include using floatingbooms to contain the oil spill or keep it from reachingsensitive areas, skimmer boats to vacuum up some ofthe oil into collection barges, and absorbent devices suchas large mesh pillows filled with feathers or hair tosoak up oil on beaches or in waters too shallow forskimmer boats.Chemical methods include using coagulating agentsto cause floating oil to clump together for easierpickup or to sink to the bottom (where it usually doesless harm) and dispersing agents to break up oil slicks.But these agents can damage some types of organisms.Fire can burn off floating oil, but crude oil is hard to igniteand burning it produces air pollution.In time, the natural action of wind and wavesmixes or emulsifies oil with water (like emulsifiedsalad dressing), and bacteria biodegrade some of theoil. Scientists are developing biological methods inwhich “cocktails” of bacteria are sprayed on the oil tobreak it down into chemicals that the bacteria consumeor that disperse harmlessly into the sea. Addingspecial nutrients required by the bacteria usuallyspeeds up the decomposition process. This bioremediationcleanup by naturally occurring bacteria ischeaper and may be much more effective than othercleanup methods.Scientists estimate that current methods can recoverno more than 15% of the oil from a major spill.This explains why preventing oil pollution is the mosteffective and in the long run the least costly approach.Good news. Because of concern over the 1989 ExxonValdez oil spill, the Oil Pollution Act of 1990 set up atrust fund to provide up to $1 million per spill forcleanup. It also required that by 2015 all oil tankers operatingin U.S. waters must be constructed with twohulls—one inside the other—to help protect againstspills. Similar international laws have been established,and in 2002 the European Union voted to ban singlehulloil tankers from their waters by 2010 and by 2005for the largest tankers. Some members of Congresshave unsuccessfully proposed legislation to requiredouble hulls for tankers in U.S. waters by 2007.Bad news. In 2004, about half of the world’s 10,000oil tankers still had the older and more vulnerable singlehulls. Cruise ships can also pollute coastal waterswith oil and other waste—most of which is dumped atsea or in fragile coastal areas when the ships visit variousports. Scuba diving, anyone?Solutions: How Can We Protect CoastalWaters? Think PreventionPreventing or reducing the flow of pollutionfrom the land and from streams emptying into theocean is the key to protecting the oceans.Figure 22-14 list ways analysts have suggested to preventand reduce excessive pollution of coastal waters.Study this figure carefully.PreventionReduce input of toxicpollutantsSeparate sewageand storm linesBan dumping ofwastes and sewageby maritime andcruise ships incoastal watersBan ocean dumpingof sludge andhazardous dredgedmaterialProtect sensitiveareas fromdevelopment, oildrilling, and oilshippingRegulate coastaldevelopmentRecycle used oilRequire double hullsfor oil tankersSolutionsCoastal Water PollutionCleanupImprove oil-spillcleanupcapabilitiesSprinklenanoparticlesover an oil orsewage spill todissolve the oil orsewage withoutcreating harmfulbyproducts(still underdevelopment)Require at leastsecondarytreatment ofcoastal sewageUse wetlands,solar-aquatic, orother methods totreat sewageFigure 22-14 Solutions: methods for preventing and cleaningup excessive pollution of coastal waters. Which two of these solutionsdo you believe are the most important?508 CHAPTER 22 Water Pollution