Environmental Problems, Their Causes, and Sustainability 1

ern India drink groundwater contaminated with highlevels of naturally occurring fluoride (F ). This cancause crippling backbone and neck damage and a varietyof dental problems.Groundwater used as a source of drinking watercan also be contaminated with nitrate ions (NO 3 ),especially in agricultural areas where nitrates in fertilizercan be leached into groundwater. Nitrite ions(NO 2 ) in the stomach, colon, and bladder can convertsome of the nitrate ions in drinking water to organiccompounds, which can cause cancer in various organsin more than 40 test animal species. The conversion ofnitrates in tap water to nitrites in infants under6 months old can cause a potentially fatal conditionknown as “blue baby syndrome,” in which blood lacksthe ability to carry sufficient oxygen to body cells.Toxic arsenic (As) contaminates drinking waterwhen a well is drilled into aquifers where soils androck are naturally rich in arsenic. According to theWHO, more than 112 million people are drinking waterwith arsenic levels 5–100 times the WHO standard of10 parts per billion (ppb). They include an estimated 30million people in Bangladesh, 6 million in India’s stateof West Bengal, and 6 million in China. According to estimatesby the WHO, long-term exposure to arsenic indrinking water is likely to cause 200,000–270,000 prematuredeaths from cancer of the skin, bladder, andlung in Bangladesh alone.Good news. The United Nations Children’s Fund(UNICEF) and several nongovernmental organizationsin Bangladesh have started a program to evaluate wellsserving several million people to identify those contaminatedwith arsenic and mark them with red paint.Arsenic can also be released into the air and waterby coal burning, copper and lead smelting, municipaltrash incinerators, landfills containing arsenic-ladenash produced by coal-burning power plants, and useof certain arsenic-containing pesticides.The international standard for arsenic in drinkingwater of 10 ppb was adopted in 1993 by the WHO andin 1998 by the European Union, and becomes the standardin the United States in 2006.But according to the WHO and other scientists,even the 10-ppb standard is not safe. A 2001 study bythe U.S. National Academy of Sciences found that routinelydrinking water with arsenic levels of even 3 ppbposes a 1 in 1,000 risk of developing bladder or lungcancer. Many scientists call for lowering the standardto 3–5 ppb, but this would be very expensive.Solutions: How Can We Protect Groundwater?Monitor and Say NoPrevention is the most effective and affordableway to protect groundwater from pollutants.Figure 22-10 lists ways to prevent and clean upgroundwater contamination. Treating a contaminatedaquifer involves eliminating the source of pollutionand drilling monitoring wells to determine how far, inwhat direction, and how fast the contaminated plumeis moving. Then a computer model is used to projectfuture dispersion of the contaminant in the aquifer.The final step is to develop and implement a strategyto clean up the contamination (Figure 22-10, right).This time-consuming and expensive process is somewhatlike a blind surgeon trying to find and remove acancer in your body before it grows too large.Because of the difficulty and expense of cleaningup a contaminated aquifer, preventing contamination isthe most effective and cheapest way to protect groundwaterresources (Figure 22-10, left).Underground tanks in the United States and anumber of other developed countries are now strictlyregulated. In the United States, thousands of old leakingtanks from gasoline stations and other facilitieshave been removed and the surrounding soil andgroundwater have been treated to remove gasoline.This is expensive but there is little choice because thegroundwater has already been contaminated.PreventionFind substitutes fortoxic chemicalsKeep toxicchemicals out ofthe environmentInstall monitoringwells near landfillsand undergroundtanksRequire leakdetectors onunderground tanksBan hazardouswaste disposal inlandfills andinjection wellsStore harmfulliquids inaboveground tankswith leak detectionand collectionsystemsSolutionsGroundwater PollutionCleanupPump to surface,clean, and returnto aquifer (veryexpensive)Injectmicroorganisms toclean upcontamination(less expensivebut still costly)Pumpnanoparticles ofinorganiccompounds toremove pollutants(may be thecheapest, easiest,and most effectivemethod but is stillbeing developed)Figure 22-10 Solutions: methods for preventing and cleaningup contamination of groundwater. Which two of these solutionsdo you believe are the most important?http://biology.brookscole.com/miller14503