(完整版)环境科学交叉关系学科课后题答案第十七、十八章

CHAPTER 171. As illustrated in figure 17.2, the waste generation rates of people are directly related to their economic condition.Nation with high standards of living and productivity tend to have more municipal solid waste per person than less-developed countries.3.1)The remaining numbers of landfills in US are declining as some small, poorly run landfills areclosed as they fail to meet regulations. Others are closed due to full capacity. Therefore, new, modern landfills are in urgent need, especially in metropolitan cities(LA, NY, Toronto).However, it is difficult to find a geologically suitable site and building new ones often receive local opposition.2)What’s more, a modern landfill is becoming increasingly more complex and expensive, and itis sometimes no more cost effective compared to incineration. Experts also suggest that unless further steps are taken to detoxify landfilled materials, they will place burden on upcoming generations to address future impacts.3)Landfills may present long-term threats to groundwater and surface water that arehydrologically connected. Leachate is of particular concern, if the landfill system is not properly sealed, the rain or connected water source may leak through buried trash, dissolving and carrying hazardous materials with it, and pose the major threat to the current and future quality of groundwater.4)There is a problem about the air pollution too. Methane produced by decomposing wasteshould be collected and treated, and they can be used to produce heat or to generate electricity, or they might enter atmosphere and become a kind of greenhouse gas.5.1)Design changes to soft drink bottles and milk jugs can keep out more than one hundredmillion kg of plastic out of the waste stream per year.2)Manufacturing processes have been changed in many industries to reduce the amount ofwaste produced. This kind of change could be done by paying more attention to incidence like leaks, spills and accidents.3)Purchasing decisions can significantly reduce the amount of waste produced. Choosing topurchase things that have reduced packaging waste, not only could this reduce the amount of waste , but also might it encourage the producer to use less in packaging.4)Using materials in such a way that waste is not generated is an important means of curbingwaste. Using less-hazardous alternatives and sharing products that contains hazardous chemicals, following the label directions and using the smallest amount necessary are way to reduce waste or its toxicity5)Reusing items is a way to reduce waste at the source because it delays or prevents the entryof reused items into the waste collection and disposal system.7.Several kinds of program have contributed to the increase in recycling rate.Container laws and mandatory recycling laws in many states provide an incentive to recycle andcurbside recycling make it convenient to recycle. A prominent RecycleBank is a recent program of success.9.1)Electronic waste is a growing problem worldwide as obselete or broken computers andother electronic equipments are discarded. A major problem is the toxic heavy metals used as components, as estimations of 70 percent of heavy metals in US landfills come from discarded electronics, while e-waste account for 2 percent of total trash by volume.2)The amount of e-waste is expected to grow rapidly as people in developing countriespurchase a large number of cellphones and other electronics.3)Much of e-waste is exported to developing countries and laborers use crude techniquesincluding smashing, melting and adding acid or burning plastic coating, which often occur in open space where they release toxins into environment and endanger the health of workers.ndfill gas contain sufficient amount of methane, and can be utilized to generate electricity through the following steps:1)Anaerobic decomposition, as the bacteria feed on organic waste and produce methane andcarbon dioxide.2)Accessing the gas. Drill well into the landfill and insert perforated pipes filled with gravel andsealed on top, which allow gas to be collected from deep down the waste. After vacuumed out the gas, it will be piped to a nearby compression facility where it is dehydrated, filtered and pressurized.3)Becoming electricity. Processed methane gas is piped to an electricity-generating facility andworks as fuel to spin turbine/engine to produce current.4)Back to source. Landfill gas in utility transmission lines will be delivered to businesses orhomes where garbage collection starts or piped directly to where it may be needed as fuel.CHAPTER 181.There are several kinds by classifications of DOT:1)Explosives,which cause a rapid release of gas and heat;2)Gases that may be flammable, nonflammable or toxic;3)Oxidizing substances and organic peroxides;4)Poisonous materials and infectious materials;5)Radioactive materials;6)Corrosives.3.The EPA defines hazardous waste as those with four characteristics:Ignitability, corrosiveness, reactivity and toxicity.It has also compiled a list of hazardous wastes.5.The uranium miners are exposed to radioactive gases, while those who smoke tobacco and thusexposed to toxins in tobacco smoke have unusually high incidences of lung cancer. It is apparent that the radioactive gases in uranium mines interact synergistically with carcinogens found in tobacco smoke.7.It is hard to determine appropriate exposure limits as nearly all substances are toxic in sufficiently high doses.Typically the regulatory agency will determine the level of exposure at which none of the test animals is affected( threshold level) and then set the human exposure level lower to allow for a safety margin. The safety margin is important because threshold levels vary significantly among species and even members of the same species.9.Hazardous wastes enter the environment in several ways:1)Many molecules that evaporate readily are vented directly into the atmosphere. Many kindsof solvents used in paints and other industrial processes fall into such category.2)Other materials escape from faulty piping and valves, but they are often called fugitiveemissions.3)Uncontrolled or improper incineration of hazardous wastes whether on land or at sea, cancontaminate the atmosphere and the surrounding environment.11.CERCLA was enacted in 1980 to deal with financing the cleanup of large uncontrolled hazardous-waste sites. It has several key objectives:1)To develop a comprehensive program to set priorities for cleaning up the worst existinghazardous-waste sites.2)To make responsible parties pay for those cleanups whenever possible.3)To set up a 1.6 billion dollars Hazardous Waste Trust Fund to support the identification andcleanup of abandoned hazardous-waste sites.4)To advance scientific and technological capabilities in all aspects of hazardous-wastemanagement, treatment and disposal.13.The National Priorities List are those hazardous-waste sites which require urgent attention by Superfund. It included 11000 in the initial evaluation of 40000 sites, while the number fluctuated as new sites are added and sites removed when they are cleaned up or deleted from the list.15.Metal Mining accounted for 31 percent of all toxic waste, which are deposited primarily on surface of land. Electric utilities (power generation) are responsible for 24 percent of releases, most of which into the atmosphere. chemical and metal processing industries are also significant sources.17.Prevent accidental spills, leaks from pipes and valves and loss from broken containers,etc. Other measures include:1)Changing a process so that a hazardous solvent is replaced with water.2)Using a waste produced in a process in another aspect of the process to reduce the amountof waste produced.3)Using a still to clean solvents so that they can used repeatedly4)Allowing water to evaporate from waste can reduce the total amount of waste produced,thus concentrating the hazardous material.19.1)Neutralization of dangerous acids and bases by reacting them with one another can convertthem to non-hazardous materials.2)Biodegradation of organic materials by microorganisms can convert hazardous chemicals toinnocuous substances, Such as in sewage treatment plants3)Air stripping is used to remove volatile chemical from water. Steam stripping works on thesame principle while the high temperature can force out chemicals that ordinary air can not.The volatile compounds can be captured or reused or disposed of.4)Carbon absorption tanks contain specifically activated particles of carbon to treat hazardouschemicals in gaseous and liquid waste. Carbon combines chemically with waste or catch hazardous particles like a fine wire mesh catches grains of sand.Contaminated carbon must then be disposed of or cleaned and reused.5)Precipitation involves adding special materials to a liquid waste. These bind to hazardouschemicals and cause them to precipitate out of the liquid and form large particles called floc.Floc that settles can be seperated as sludge; floc that remain suspended can be filtered and the concentrated waste can be sent to a hazardous-waste landfill.21.The Basel Convention was established in response to the debate over controlling hazardous-waste movements between countries in 1989. There is particular concern about rich, industrialized countries exporting such wastes to developing countries lacking administrative and technological resources to safely dispose of or recycle the waste.Its main objective is to minimize the generation of hazardous wastes and to control and reduce their transboundary movements to protect human health and the environment.23.Transuranic nuclear waste is highly radioactive waste that contains large numbers of atoms larger than uranium with half-lives greater than 20 years. Most of these come from processes involved in the production of nuclear weapons. As the clean-up of former nuclear weapons sites in US take place, transuranic waste is transported to the Waste Isolation Pilot Plant near Calsbad, New Mexico, for storage. （WIIP)25. Low-level radioactive waste can come from a variety of sources, in nuclear power facilities, hospitals and research institutions. Examples include radioactive materials used in medical field. Protective clothing worn by persons who work with radioactive materials, contaminated cleaning materials and other uses of radioactive isotopes.。