aquatic pollution final exam
What does the acronym LIMB stand for, and how does it help to reduce emissions of SOx and NOx from electric power plants that use coal as a fuel?
LIMB stands for Low-Intensity Multi-stage Burner and involves the use of a series of burners in a staged combustion process. This helps reduce emissions of both Sox and NOx. In the first stage a low-intensity burner is used to partially combust the fuel, which produces a mixture of unburned fuel and combustion products. The mixture is then injected into a high-intensity burner where it is fully combusted to produce a lower emission flue gas. This process helps reduce the production of both Sox and NOx by promoting more complete combustion of the fuel.
An oil tanker breaks up in rough weather and loses its entire cargo of crude oil. The oil washes ashore onto a pebble beach. As the director of an international effort to clean up the mess and minimize the environmental damage, you are called in about a week after the spill. Which one of the following methods would you use to deal with the oil on the beaches?
Remove the oil by spraying the rocks with hot water
What is meant by the acronyms SBT and CBT and how have they been used to reduce oil pollution of the ocean?
Segregated Ballast Tank and Clean Ballast tanks. SBT tanks are used in oil tankers to carry ballast water, it is used to provide stability to the vessel during loading and unloading. The ballast water Is kept separate from the oil cargo in order to prevent contamination of cargo with ballast water. CBT are similar but they are used to hold ballast water that has been treated to remove any oil or other contaminants that may be present. Both are used to reduce oil pollution by minimizing the amount of oily ballast water that is discharged from tankers. By keeping it separate they can help prevent the discharge of oily ballast water into the ocean. Ballast water contains oil and pollutants that harms marine ecosystems.
What was the principal criticism of environmental groups to the New Source Performance Standards promulgated by the EPA in 1979?
Standards only applied to new power plants and did not require retrofitting of existing plants. Environmental groups argued that this would allow older plants to continue emitting pollutants at levels that were harmful to human health and the environment.
Why is wet stack gas scrubbing much more effective in removing SOx than NOx from stack gases?
Wet stack gas scrubbing involves passing the flue gases from power plants through a spray of water or other alkaline solution to neutralize acidic components like Sox and NOx. Sox can be more effectively removed than NOx because Sox has a high solubility in water. Sox compounds react readily with alkaline solutions to form stable salts or acids, which can be removed from the flue gases. On the other hand NOx compounds are less soluble in water and are more difficult to remove y wet scrubbing. Additionally the reaction of NOx compounds with alkaline solutions can produce N2O a potent greenhouse gas, making scrubbing less desirable for removing NOx
Which two of the following radionuclides are responsible for most of the heat emitted by spent nuclear power plant fuel elements?
90Sr and 137Cs
The radionuclides routinely released by nuclear power plants in the Unites States are primarily which one of the following?
Fission products
How does fluidized bed combustion reduce the production of NOx during the combustion of coal?
Fluidized bed combustion reduces the production of NOx during coal combustion by maintain a lower combustion temperature than traditional coal-fired power plants. The process involves suspending coal particles in a fluidized bed of air, which creates a turbulent mixing action that promotes complete combustion of the fuel. As a result the combustion temperature is lower which reduces the formation of nitrogen oxides. The limestone added to the bed reacts with sulfur dioxides to form calcium sulfate CaSO4 which can easily be removed through scrubbing. This reduces the emission of both Sox and NOx from the power plant.
How does fluidized bed combustion reduce the production of SOx during the combustion of coal?
Fluidized bed combustion reduces the production of Sox during coal combustion by introducing limestone or dolomite particles into the bed. The particles react with the sulfur dioxide produced during combustion to form calcium or magnesium sulfite which is then oxidized to calcium or magnesium sulfate, or gypsum. The resulting solid particles are then removed from the flue gas using a particulate control device. This process is called flue gas desulfurization (FGD) and it can remove up to 95% of the sulfur dioxide from the flue gas.
Two oil supertankers run headfirst into each other in the middle of the Atlantic Ocean because their crews are below deck playing cards and are intoxicated. Several cargo compartments rupture. Large numbers of aquatic birds are in the area. Sea conditions are very rough for 2 weeks after the spill. If you were in charge of trying to minimize environmental damage during the first 2 weeks after the spill, which one of the following steps would you take?
Use booms and skimmers to contain the oil and sop up the contained oil
Following accidents at nuclear power plants such as the 1957 incident at Windscale or the 1986 accident at Chernobyl, one of the major public health concerns was exposure to 131I. By what mechanism does this particular radionuclide find its way into humans, and why is it of such concern from a public health standpoint?
131I can be ingested or inhaled by humans and then concentrated in the thyroid gland, where it can cause damage to the gland or lead to the development of thyroid cancer. The thyroid is susceptible because it actively concentrates iodine for the purpose of producing thyroid hormones. In the event of a nuclear accident the release of large amounts of 131I can pose a significant public health risk if people were not able to evacuate quickly enough.
Which one of the following nuclides is primarily responsible for maintaining the chain reaction in conventional nuclear power plants in the United States? 238U 235U 239Pu 233U
235U
The flux of γ rays from a point source falls off as the square of the distance from the source of the radiation. Suppose that the flux of γ rays at a distance of 1 m from a source is 10,000 times the acceptable limit. How far would a person have to be from the source before the flux of γ rays was equal to the acceptable limit?
According to the inverse square law, the intensity of radiation from a point source decreases with the square of the distance from the source. The formular I1/I2=(D2/D1)^2 where I1 is the initial intensity, I2 is the final intensity or acceptable limit, D1 is the initial distance and D2 is the final distance. I1=10000 x acceptable limit I2=acceptable limit D1=1m so we are solving for D2. (10000 x acceptable limit)/acceptable limit=(D2/1)^2 10000=D2^2 so D2=100m Therefore a person would have to be 100 meters from the source before the flux of y rays was equal to the acceptable limit.
The Tóxica Basura Company operates a landfill for several decades and then goes bankrupt. Subsequently the aquifer under the landfill is found to be contaminated. Which one of the following pieces of federal legislation could be used to appropriate funds to clean up the contaminated aquifer? RCRA SDWA CWA CERCLA
CERCLA
The Grande Crevette Company plans to grow shrimp and intends to discharge wastewater from its shrimp ponds into the ocean. In order to discharge that wastewater, it must obtain a discharge permit under the authority of which one of the following pieces of federal legislation? RCRA SDWA CWA CERCLA
CWA
What is meant by the acronym COW and how has it been used to reduce oil pollution of the ocean?
Crude oil washing or COW is a method of cleaning the cargo tanks of oil tankers using the crude oil itself as the cleaning agent, the gets rid of using chemicals or detergents. This process involves using high-pressure water jets to break up and remove the residual oil in the tanks, which is then collected and processed along with the cargo. The cleaned tanks are then filled with crude oil, which is used to wash the remaining residue off the walls. COW reduces the amount of cleaning agents that need to be transported and disposed of, reducing the risk of pollution. It also reduces the amount of water needed for cleaning, reducing effluent oily wastewater.
Scientists believe that ghost fishing killed literally hundreds of thousands of aquatic birds every year in the 1980s. How is it that so many birds were killed by gear that was intended to catch fish, not birds?
Ghost fishing occurs when fishing gear like nets and lines are lost or abandoned in the ocean. This gear continues to fish and trap marine animals, including fish and birds for years or even decades. The trapped animals eventually die from exhaustion, starvation, or entanglement. The large number of aquatic birds killed by ghost fishing in the 1980s was due to the use of driftnets which are huge nets that can extend 50 miles long and are left in the ocean for days or weeks, these nets are not selective and can catch all types of marine animals, including birds. The birds are attracted to the fish caught in the nets and become entangled leading to death.
In commenting on certain aspects of the effort to clean up the oil spilled by the Exxon Valdez, one National Oceanic and Atmospheric administrator was quoted as saying, "Sometimes the best, and ironically the most difficult, thing to do in the face of an ecological disaster is to do nothing." What aspect of the cleanup effort prompted this statement and why?
High pressure hoses and hot water to wash the oil off rocks and beaches in the spill area. While this method was intended to remove the oil and minimize the environmental impact, it had unintended consequences. The hot water not only removed the oil, but also large amounts of intertidal zone. Intertidal habitats include clams, mussels, and other shellfish that play an essential role in the local ecosystem and economy. The cleanup efforts had more significant impact on the environment than the oil spill itself.
Why are underground salt deposits considered to be good candidates for the storage of radioactive wastes?
Impermeability, less likely to allow and escape of radioactive materials. Stability, geologic stability means they are less likely to experience significant changes over time that could lead to the released of radioactive materials. Self-sealing when salt is excavated it self-seals which helps prevent migration of fluids and radioactive materials. Availability there are several salt deposits around the world, making them a practical option. Easy to mine makes it less expensive to create storage facilities compared to other types of geologic formation.
The freshwater aquifer beneath the island of Oahu could become unfit for drinking purposes if rates of groundwater withdrawal exceed recharge rates. Evidence that this was happening would be which one of the following:
Increase in salinity of the water
According to Annex V of MARPOL, where is it legal to discharge plastic waste in the ocean?
It is legal to discharge plastic waste into the ocean if the ship is more than 12 nautical miles from the nearest land and the plastic waste meets the criteria such as being made of specific materials and not containing certain types of pollutants. Some countries and regions have stricter regulations and may prohibit plastic waste discharge entirely within their waters.
Why is liquid sodium rather than water pumped through the core of breeder nuclear reactors?
Liquid sodium is a better coolant than water for this type of reactor. Liquid sodium has a higher heat capacity and thermal conductivity, so it allows it to absorb and transport more heat away from the reactor core. Liquid sodium does not become radioactive when exposed to neuron radiation, unlike water, which can become contaminated with radioactive isotopes. It can help reduce the amount of radioactive waste generated by the reactor.
Briefly explain the technology involved in magnetic confinement fusion and explain why this technology is being explored as a possible means of operating nuclear power plants based on fusion
Magnetic confinement fusion involves heating a gas of hydrogen isotopes to temperatures exceeding 100 million degrees Celsius at which point the hydrogen nuclei becomes ionized forming a plasma. The plasma is then confined and compressed using magnetic fields to the point where the hydrogen nuclei fuse together releasing large amounts of energy. The technology explored means of operating nuclear power plants based on fusion because it offers several advantages over conventional nuclear power plants based on fission. Fission reactions release much more energy per unit mass of fuel than fission reactions making fusion a potentially more efficient source of power. Second fusion reactions do not produce large quantities of long-lived radioactive waste, unlike fission reactions, which produce significant quantities of radioactive isotopes that must be stored for thousands of years, the fuel for fusion reactions can be easily extracted from sea water.
What is the most likely explanation for the fact that sea turtles swallow plastic bags?
Plastic bags look like their main food source which is jellyfish. Jellyfish are mainly water and just flow with the currents so a plastic bag looks the same.
A person who owns a vacant lot is allowing people to dispose of items such as old refrigerators, broken-down cars, and discarded batteries in his lot. The person has no license to operate a solid waste disposal facility. He could be prosecuted under which one of the following pieces of federal legislation? RCRA SDWA CWA CERCLA
RCRA
The Peligrosos Desechos Company generates hazardous waste. In the United States, what happens to that hazardous waste is regulated/monitored under the authority of which one of the following pieces of federal legislation? RCRA SDWA CWA CERCLA
RCRA
The amount of radiation emitted by a radionuclide obeys the equation, where RT is the radioactivity at time T, R0 is the radioactivity at time 0, and T is the half-life of the radionuclide. Suppose that there has been an accident at a nuclear power plant resulting in the release of large amounts of radionuclide X. Public health authorities determine that the level of X in the area around the power plant is 8000 times the acceptable level and evacuate the area. How many half-lives will it take before the activity of X has declined to an acceptable level so that people can return to their homes?
RT=R0(0.5)^(T/t) where T is the half-life of the radionuclide and t is the time elapsed since the accident. Assuming the acceptable level of X is R0/8000, where R0 is the initial level of X before the accident. R0/8000=R0(0.5)^(T/t) after simplifying (0.5)^(n)=1/8000 after taking the log of both sides n=log(1/8000)/log(0.5) n=13.29 therefore it will take approximately 14 half-lives for the activity of X to decline to an acceptable level.
Water is considered to be neutral if the pH is 7.0, but acid rain is often defined as rainwater with a pH less than 5.6. Why?
Rainwater has a pH of 5.6 due to the presence of carbon dioxide in the atmosphere which dissolves in water to form carbonic acid. Acid rain describes rainwater that has a pH below 5.6, typically due to the presence of sulfur dioxide and nitrogen oxides from human activities like burning fossil fuels. These gases react with water and other atmospheric components to form strong acids such as sulfuric acid and nitric acid, which can lower the pH of rainwater significantly. Therefore a pH level of less than 5.6 is used as the threshold for defining acid rain.
What source of oil discharges to the marine environment did the load-on-top (LOT) procedure seek to minimize and by what means did LOT reduce that discharge?
The LOT procedure was developed to minimize the discharge of oil from tankers during loading and unloading operations. It sought to minimize the discharge of oil from venting of cargo tanks due to thermal expansion by loading oil in such a way that the tanks were not filled completely. Instead a space was left at the top of the tank to accommodate thermal expansion. Lot helped prevent discharge of oil due to thermal expansion by reducing the amount of oil I the tanks. This was a common source of oil pollution during loading and unloading. It also reduced the amount of oil that was spilled during the opening and closing of tank hatches
Why are some environmental groups opposed to the use of biodegradable plastics?
The biodegradable plastics may not degrade as quickly as claimed, some types of biodegrable plastics require specific conditions to degrade properly, like high temperatures and certain bacteria. This means that if biodegradable plastics are not disposed of properly this could persist into the environment and cause harm to wildlife. Some environmentalist argue that promoting the use of biodegrable could distract from efforts to reduce overall plastic consumption and shift the focus away from more sustainable alternatives like reusable products.
The Buzzards Bay oil spill near Cape Cod is generally agreed to have killed more marine organisms than the Ixtoc I oil well blowout in the Gulf of Mexico, even though the latter released about 840 times as much oil. How would you account for the greater impact of the Buzzards Bay spill?
The buzzards bay spill occurred in an area with a higher concentration of marine organisms, like clams, mussels, and oysters, these animals are particularly vulnerable to the effects of oil. The weather conditions at the time carried the oil to shore where it could impact intertidal and nearshore habitats. Response time was slow and not very effective compared to the Ixtoc I blowout. The oil had a longer time to affect the surrounding environment and the cleanup efforts were not as successful in mitigating the impact of the spill.
Why was there so much criticism of the use of chemical detergents to clean up the oil that washed ashore after the Torrey Canyon oil spill off the coast of England? If a similar accident occurred today and you were in charge of directing the response, what actions would you recommend?
The chemicals were not very effective at cleaning up the oil, it emulsified the oil, making it harder to remove from the shoreline. Detergents were toxic to many marine organisms and had long-term effects on the ecosystem. Chemical detergents created a significant amount of waste that has to be disposed of. A combination of methods needs to be used in directing the response to an oil spill, mechanical methods like booms and skimmers to collect and contain the oil before it reaches the shoreline. For the oil on the shore I would recommend using non-toxic biodegradable surfactants to clean it up. Prioritizing protecting sensitive habitats such as marshes and wetlands by using sorbent materials. Working closely with communities to ensure their concerns are heard would help build trust and ensure the response is tailored to the specific needs of the community.
Why is pretreatment and conversion of coal to a gas or liquid not a practical way to reduce emissions of NOx from electric power plants?
The conversion process does not remove nitrogen from coal. Therefore the NOx produced during combustion is not reduced but is instead transferred to the gas or liquid product. As a result pretreatment and conversion of coal to gas or liquid can actually increased NOx emissions when the gas or liquid product is burned.
In the 1970s rainfall in the northeastern United States was much more acidic during the summer than during the winter. During the same time period, the acidity of rainfall in the western United States showed little seasonal variability. How would you account for this fact?
The difference in seasonable variability between northern and western US can be attributed to the differences in the sources of acid-forming pollutants. In the northeastern US, the main source of acid-forming pollutants is emissions from coal-fired power plants and other industrial activities, these are more active during the summer months. In western US the main source is natural sources such as volcanic activity and wind-blown dust, these are relativity constant throughout the year.
Why are high-elevation lakes generally more susceptible to acidification than low-elevation lakes?
The soils and rocks in the surrounding watersheds have a lower buffering capacity due to their low calcium and magnesium content. Acid deposition can lower the pH of the lake water leading to harmful effects on aquatic organism. High elevation lakes are often more isolated an receive less buffering from adjacent soils and rocks which further contribute to their susceptibility to acidification.
Pumping water through the core of conventional nuclear power plants in the United States serves several purposes. What are those purposes?
To absorb heat produced by the nuclear reactions taking place in the core, to transfer heat to a steam generator where it is used to produce stream, to cool the fuel rods and prevent them from melting or being damaged, to provide a radiation shield that helps protect workers and the environment from high levels of radiation generated by the fuel rods.
The amount of radiation released to the environment as a result of the Chernobyl nuclear power plant accident was about 10 times greater than the corresponding quantity released by the Three Mile Island accident. The number of human lives lost as a result of the Chernobyl accident, however, will probably exceed the number of human lives lost as a result of the Three Mile Island accident by at least a factor of 10,000. Why are the radioisotopes released at Chernobyl expected to cause so much more harm to humans?
The radioisotopes released at Chernobyl, iodine-131 and cesium-137 were more biologically harmful because they were released in much larger quantity and were carried over a much wider area by wind and rain. The reactor at Chernobyl exploded and released a significant amount of radioactive material into the atmosphere, causing a widespread contamination of the environment. The accident at 3-mile island was contained within the reactor and only a small amount of radioactive material was released.
Why have some environmentalists objected to the decision to designate the Rocky Mountain Arsenal a national wildlife refuge following completion of the environmental cleanup at the site?
They believe that the cleanup was not thorough enough and that residual contamination may still pose a risk to human health and the environment. They argue that the site should have been remediated more thoroughly before it was opened to the public as a wildlife refuge.
Raw plastic is typically shipped in the form of small pellets a few millimeters in diameter. These pellets have been found in the stomachs of certain marine organisms. Why do we think that some marine organisms deliberately ingest these small pellets?
They look similar to the size and shape of their natural prey like fish eggs or small crustaceans. The pellets may become coated in a layer of organic material which can attract organisms and make then more likely to ingest the plastic.
Why has the EPA's policy of "pump and treat" been characterized as a waste of taxpayers' money by critics of the agency's approach to restoring contaminated aquifers?
This process is ineffective at fully restoring contaminated aquifers. The process involves pumping contaminated groundwater to the surface and treating it to remove pollutants. This approach does not address the source of the contamination and may take decades or even centuries to achieve the desired results. Additionally, the costs of long-term operation and maintenance of the treatment system can be prohibitive. Critics argue that resources would be better spent on preventing contamination I the first place through stricter regulations and enforcement.
What are the principal concerns associated with transuranic wastes? In other words, why does the US government put transuranic wastes in a separate category from other types of radioactive waste?
Transuranic wastes are those that contain elements with atomic numbers greater than uranium. These wastes have long half-lives and are extremely toxic. They are very difficult to handle and dispose of safety because they emit high levels of radiation and decay into other radioactive isotopes. The US government puts them in a different category from other radioactive wastes and requires that they be isolated and contained for very long periods of time.
The site presently contemplated for disposal of the Unites States' high-level radioactive wastes is:
Yucca Mountain, Nevada
Which one of the following sources of radiation is believed to account for more than half the natural radiation dose received by the average American at the present time?
daughter of 222Rn
The following radionuclides are of concern from the standpoint of human health? Which ones are produced primarily by neutron activation and which ones are fission products?
neutron activation= 90Sr and 137Cs fission products= 3H, 55Fe, 131I, 14C
