Chapter 20 Reading Questions PDF

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CHAPTER 20 READING QUESTIONS EARTH...

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Chapter 20 Reading Questions 1. Describe the nature and causes of the annual dead (oxygen-depleted) zone in the Gulf of Mexico. The huge volume of oxygen-depleted water resulting from this seasonal event is called a dead zone because it contains little animals' marine life. Its low oxygen levels drive away faster swimming marine organisms and suffocate bottom-dwelling fish, crabs, oysters, and shrimp that cannot move to less polluted areas. Large amounts of sediment, mostly from soil eroded from the Mississippi River basin, can also kill bottom-dwelling forms of aquatic life. The dead zone appears each spring and grows until fall when storms churn the water and redistribute dissolved oxygen to the Gulf bottom. Oxygen-depleted zones represent a disruption of the nitrogen cycle caused primarily by human activities. This is because huge quantities of nitrogen from nitrate fertilizers are added to ecosystems such as the Mississippi River and Gulf of Mexico much faster than the nitrogen cycle can remove them. 2. Give two examples of both point source and non-point source pollution. Explain how certain efforts to clean up the air can contribute to water pollution. Explain how atmospheric warming will likely increase water pollution. Water pollution causes illness and death in humans and other species, and disrupts ecosystems. The chief sources of water pollution are agricultural activities, industrial facilities, and mining, but the growth of both the human population and our rate of resource use makes it increasingly worse. An example of point source pollution would be oil refineries and pump mills, an example of nonpoint source pollution would be excess fertilizers and herbicides/insecticides. Things like being more careful of a car owner can help reduce water pollution, always have good maintenance or it can lead to leaking oil, coolant, antifreeze and other nasty liquids that are carried by rainwater down driveways or through parking lots. Warmer temperatures increase the rate of evaporation of water into the atmosphere, In effect increasing the atmosphere's

capacity to "hold" water. Increased evaporation may dry out some areas and fall as excess precipitation in other areas. 3. List seven major types of water pollution and three diseases that can be transmitted to humans through polluted water. Describe some of the chemical and biological methods that scientists use to measure water quality. One of the major water pollution problems that we face is exposure to infectious disease organisms primarily through contaminated drinking water. Scientists use a variety of methods to measure water quality. For example, they test samples of water for the presence of various infectious agents such as certain strains of the coliform bacteria Escherichia coli, which live in the colons and intestines of humans and other animals and thus are present in their fecal wastes. Although most strains of coliform bacteria do not cause disease, their presence indicates that water has been exposed to human or animal wastes that are likely to contain disease-causing agents. To be considered safe for drinking, a 100-milliliter sample of water should contain no colonies of coliform bacteria. To be considered safe for swimming, such a water sample should contain no more than 200 colonies of coliform bacteria. By contrast, a similar sample of raw sewage may contain several million coliform bacterial colonies. Another indicator of water quality is its level of dissolved oxygen. Excessive inputs of oxygen-demanding wastes can deplete DO levels in water. Scientists can use chemical analysis to determine the presence and concentrations of specific organic chemicals in polluted water. They can also monitor water pollution by suing living organisms as indicator species. For example, they remove aquatic plants such as cattails from areas contaminated with fuels, solvents, and other organic chemicals, and analyze them to determine the exact pollutants contained in their tissues. Scientists also determine water quality by analyzing bottom-dwelling species such as mussels, which feed by filtering water through their bodies. Scientists measure the amount of sediment in polluted water by evaporating the water in a sample and weighing the resulting sediment. They also use instruments called colorimeters, which measure specific

wavelengths of light shined through a water sample to determine the concentrations of pollutants in the water 4. Explain how streams can cleanse themselves and how this cleansing process can be overwhelmed. Describe the varying states of steam pollution in more and less developed countries. Give two reasons why lakes cannot cleanse themselves as readily as streams. List ways to reduce or prevent cultural eutrophication. Describe the pollution of the great lakes and the progress being made in reducing this pollution. Streams and rivers around the world are extensively polluted, but they can cleanse themselves of many pollutants if we do not overload them or reduce their flows. Adding excessive nutrients to lakes from human activities can disrupt their ecosystems, and the prevention of such pollution is more effective and less costly than cleaning it up. Flowing rivers and streams can recover rapidly from moderate levels of degradable, oxygen-demanding wastes through a combination of dilution and bacterial bio-degradation of such wastes. But this natural recovery process does not work when streams become overloaded with such pollutants or when drought, damming, or water diversion reduces their flows. Also, while this process can remove biodegradable wastes, it does not eliminate slowly degradable and non-degradable pollutants. In a flowing stream, the breakdown of biodegradable wastes by bacteria depletes dissolved oxygen and creates an oxygen sag curve. Fish kills and drinking water contamination still occur occasionally in some of the rivers and lakes of more-developed countries such as the United States. Some of these problems are caused by the accidental or deliberate release of toxic inorganic and organic chemicals by industries and minding operations. Another cause is malfunctioning sewage treatment plants. A third cause is the non-point runoff of pesticides and excess plant nutrients from cropland and animal feedlots. Eutrophication is the name given to the natural nutrient enrichment of a body of water such as a lake, coastal areas at the mouth of a river, or a slow-moving stream. It is caused mostly by runoff of plant nutrients such as nitrates and phosphates from land bordering such bodies of water. An oligotrophic lake is low in nutrients and its water is clear. Over time, some lakes become more eutrophic as nutrients are added from natural and human sources in the surrounding watersheds. Near urban or agricultural areas human activities can greatly accelerate the input of plant nutrients to a lake--a process called cultural eutrophication. Such inputs involve mostly nitrate-and phosphate-

containing effluents from various sources, including farmland, feedlots, urban streets and parking lots, chemically fertilized suburban yards, mining sites, and municipal sewage treatment plants. Some nitrogen also reaches lakes by deposition from the atmosphere. There are several ways to prevent or reduce cultural eutrophication. We can use advanced waste treatment processes to remove nitrates and phosphates from wastewater before it enters a body of water. We can also use a preventive approach by banning or limiting the use of phosphates in household detergents and other cleaning agents, and by employing soil conservation and other controls to reduce nutrient runoff. There are several ways to clean up waters suffering from cultural eutrophication. They include mechanically removing excess weeds, controlling undesirable plant growth with herbicides and algaecides, and pumping air into lakes and reservoirs to prevent oxygen depletion, all of which are expensive and energy-intensive methods.

5. Explain why groundwater cannot cleanse itself very well. What are the major sources of groundwater contamination in the United States? List three harmful effects of groundwater pollution. List three ways to prevent groundwater contamination and three ways to clean up groundwater contamination. Describe the threat from arsenic in groundwater. Chemicals used in agriculture, industry, transportation, and homes can spill and leak into groundwater and make it undrinkable. There are both simple ways and complex ways to purify groundwater used as a source of drinking water, but protecting it though pollution prevention is the least expensive and most effective strategy. Scientists are now concerned about a new and growing potential threat to groundwater-the drilling of thousands of new natural gas wells in parts of the United States involving a process called hydraulic fracturing, or fracking. Groundwater contamination could result from leak well pipes and pipe fittings and from contaminated wastewater brought to the surface during fracking operations. Without strict monitoring and enforcement of pollution regulations, fracking could become a serious groundwater pollution threat. Groundwater that is used as a source of drinking water can also be contaminated with nitrate ion, especially in agricultural areas where nitrates in fertilizer can leach into groundwater. Nitrite ions in the stomach, colon, and bladder can convert some of the nitrate ions in drinking water to organic compounds that have been shown in tests to cause cancer in more than 40 animal species. The conversion of nitrates in tap water to nitrites in infants under 6 months old can cause a potentially fatal condition known as

"blue baby syndrome," in which blood lacks the ability to carry sufficient oxygen to body cells. It can take decades to thousands of years for contaminated groundwater to cleanse itself of slowly degradable wastes. On a human time scale, non-degradable wastes remain in the water permanently. Although there are ways to clean up contaminated groundwater, such methods are very expensive. Cleaning up a single contaminated aquifer can cast anywhere from $10 million to $10 billion. Thus, preventing groundwater contamination is the only effective and affordable way to deal with this serious water pollution problem. 6. Explain how drinking water is purified typically in more developed countries. List three ways to provide safe drinking water in poor countries. Describe the environmental problems caused by the widespread use of bottled water. Summarize the US laws for protecting drinking water quality. List three ways to strengthen the US Safe Drinking Water Act. In more-developed countries, wherever people depend on surface water sources, water is usually stored in a reservoir for several days. This improves its clarity and taste by increasing its dissolved oxygen content and allowing suspended matter to settle. The water is then pumped to a purification plant and treated to meet government drinking water standards. In areas with very pure groundwater or surface water sources, little treatment is necessary. Several major U.S. cities, including New York City, Boston, Seattle, and Portland, Oregon, have avoided building expensive water treatment facilities by investing in the protection of the forests and wetlands in the watersheds that provide their water supplies. We have the technology to convert sewer water into pure drinking water, which would help to reduce the depletion of some water supplies. However, recycling wastewater is expensive and it faces opposition from citizens and from some health officials who are unaware of the advances in this technology, much of it developed to recycle wastewater on the International Space Station. In a world where we will face deepening shortages of drinking water, wastewater purification is likely to become a major growth business and is much cheaper than using desalination to turn ocean water into drinking water. Wastewater is being recycled to provided freshwater in Israel, Singapore, Orange County and San Diego in California, and El Paso, Texas, among a growing number of places. In many areas of both more-developed and less-developed countries, people have turned to bottled water, hoping that it is a safe alternative to local drinking water sources. However, there are several simple ways to purify drinking water that are far less costly than using bottled water. For example, in tropical countries that lack centralized water treatment systems, the WHO urges people to purify drinking water by exposing a clear plastic bottle filled with contaminated water to intense sunlight. The sun's heat and ultraviolet rays can kill infectious microbes in as little as 3 hours. Painting one side of the bottle black improves heat absorption in this simple solar disinfection method, which applies the solar energy principle of sustainability. Combine

many of the drinking water treatment systems that serve fewer than 3300 people with nearby larger systems to make it easier for these smaller systems to meet federal standards. Strengthen and enforce requirements concerning public notification of violations of drinking water standards. Ban the use of any toxic lead in new plumbing pipes, faucets, and fixtures. Current law allows for fixtures with up to 10% lead content to be sold as lead-free. 7. How are coastal waters and deeper ocean waters often polluted? What causes algal blooms and what are their harmful effects? Describe an ocean garbage patch and how it can harm marine life. How serious is the oil pollution of the oceans? What are its effects and what can be done to reduce such pollution? Describe the 2010 BP Deepwater Horizon oil blowout and its causes and effects. Most ocean pollution originates on land and includes oil and other toxic chemicals, as well as solid waste, which threatens fish and wildlife and disrupt marine ecosystems. The key to protecting the oceans is to reduce the flow of pollution from land and air and from streams emptying into ocean waters. Runoff of sewage and agricultural wastes into coastal waters can carry large quantities of nitrate and phosphate plant nutrients, which can cause explosive growths of harmful algae and lead to dead zones during summer months. These harmful algal blooms are called red, brown, or green toxic tides. They can release waterborne and airborne toxins that poison seafood, kill fish and some fisheating birds, and discourage tourism in the affected coastal areas. Each year, harmful algal blooms lead to the poisoning of about 60000 Americans who eat shellfish contaminated by the algae. Harmful algal blooms occur annually in about 400 oxygendepleted zones around the world, mostly in temperate coastal waters and in large bodies of water with restricted outflows, such as the Baltic and Black seas. The largest of these zones in U.S. coastal waters forms each year in the Northerner Gulf of Mexico. A 2008 study by Luan Weixin, of China's Dalian Maritime University, founded that water pollutants such as nitrates and phosphates seriously contaminated about half of China's shallow coastal waters. Warmer ocean water temperatures, thought by most scientists to be due to climate change, are extending the size and duration of dead zones in the world's oceans. 8. List four ways to reduce water pollution from non-point sources. Describe the US successes and failures by using laws and regulations to reduce point source water pollution. Reducing water pollution requires that we prevent it, work with nature to treat sewage, and use natural resources far more efficiently. Reducing soil erosion and fertilizer runoff by keeping cropland covered with vegetation and using conservation tillage and other soil conservation methods. Using fertilizers that release plant nutrients slowly. Using no fertilizers on steeply sloped land. Relying more on organic farming and more sustainable food production to reduce the use and runoff of plant nutrients and

pesticides. 95% of all Americans are served by public drinking water systems that must meet federal health standards. 60% of all tested U.S. streams, lakes, and estuaries can be used safely for fishing and swimming, compared to 33% in 1972. 75% of the U.S. population is served by sewage treatment plants. Annual losses of U.S. wetlands that naturally absorb and purify water have been reduced by 80% since 1992. About 40% of the nations surveyed streams, lakes, and estuaries are still too polluted for swimming or fishing. Runoff of animal wastes from hog, poultry, and cattle feedlots and meat processing facilities pollutes seven of every ten U.S. rivers. Tens of thousands of gasoline storage tanks in 43 states are leaking. One in five US. water treatment systems violated t eh Safe Drinking Water Act between 2003 and 2008, releasing sewage and chemicals such as arsenic and radioactive uranium. There are currently no federal drinking water standards for hexavalent chromium, which studies indicate is a potent carcinogen/ In 2011, residents of Midland, Texas, sued Dow Chemical for allegedly putting dangerous levels of this chemical into their drinking water. About 45% of the country's largest water polluters have declared that the Clean Water Act no longer applies to waters that they are polluting. This results from a U.S. Supreme Court decision that created uncertainty over which waterways are projected by the law. About 117 million Americans get some or all of their drinking water from sources that are being polluted in this way. 9. What are the three ways to improve conventional sewage treatment? Summarize Ashley Murray’s plans for improving sanitation in less-developed countries. What is a waterless composting toilet system? Explain how we can use wetlands to treat sewage. Describe John Todd’s use of living machines to treat sewage. In urban areas in the United States and other more-developed countries, most waterborne wastes from homes, businesses, and storm runoff flow through a network of sewer pipes to wastewater or sewage treatment plants. Raw sewage reaching a treatment plant typically undergoes one or two levels of wastewater treatment. The first is primary sewage treatment--a physical process that uses screens and a grit tank to remove large floating objects and to allow solids such as sand and rock to settle out. Then the waste stream flows into a primary settling tank where suspended solids settle out as sludge. The second level is secondary sewage treatment--a biological process in which aerobic bacteria remove as much as 90% of dissolved and biodegradable, oxygen demanding organic wastes. A combination of primary and secondary treatment removes 95-97% of the suspended solid and oxygen-demanding organic wastes, 70% of most toxic metal compounds and non-persistent synthetic organic chemicals, 70% of the phosphorus, and 50% of the nitrogen. However, this process removes only a tiny fraction of the persistent and potentially toxic organic substances found in some pesticides and is discarded medicines that people put into sewage systems, and it does not kill pathogens. A third level of cleanup, advanced or tertiary sewage treatment, uses a series of specialized chemical

and physical processes to remove specific pollutants left in the water after primary and secondary treatment. In its most common form, advanced sewage treatment uses special filters to remove phosphates and nitrates from wastewater before it is discharged into surface waters. This third stage would help a great deal in reducing nutrient overload from nitrates and phosphates, but because of its high costs, it is not widely used. Before discharge, water from sewage treatment plants usually undergoes bleaching, to remove water coloration, and disinfection, to kill disease-carrying bacteria and some viruses. The usual method for accomplishing this is chlorination. But chlorination. But chlorine can react with organic materials in water to form small amounts of chlorinated hydrocarbons. Some of these chemicals cause cancers in test animals can increase the risk of miscarriages, and can damage the human nervous, immune, and endocrine systems. The use of other disinfectants, such as ozone and ultraviolet light, is increasing, but they cost more and their effects do not last as long as ...