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The Nitrogen CycleDr. Casey Name: ______________________Exam 3Fall 2002 Signature: ______________________Chem. 104Honor Statement: By signing this exam, you indicate that you have neither given nor received aid from any unauthorized source.Answer each question in the space provided. If you need more space, use the back of the sheet. All work must be shown to receive partial credit. You have until the regularly scheduled end of class to complete the exam. Good luck!1. Identify or draw the following features on the diagram below:aerated (unsaturated) zone confining layerconfined aquifer unconfined aquiferwater tableImpermeable RockStreamLand Surface2. In areas where there are water shortages, three options are available to increase the amount of usable water:a. Clean currently available water to meet desired usesb. Move clean water from another areac. Use less waterWhich of these strategies are employed in major metropolitan areas such as Los Angeles and New York City? Which of these strategies are usually not employed? Why?3. Water has several important properties that are relatively unusual for its small size. Explain the following circumstances based on the water property given.a. Water is an unusually good solvent. What are the implications for surface and groundwater contamination?b. Solid water (ice) floats on top of liquid water. How does this affect the survival of aquatic species in cold climates?4. Which type of aquifer is more susceptible to contamination, confined or unconfined? Why?5. Match the form of N with its given properties. More than one form of N may fit a given property.N2 N2O NO2-NO3- NH3NH4+Organic Na. N combined with carbon and hydrogen in biological molecules __________________b. N with an oxidation state of –3 __________________c. N that is toxic to estuarine plants __________________d. N that is toxic to fish __________________e. N in the form of a gas __________________f. N that is unavailable as a nutrient __________________6. A nitrogen fertilizer in the form of NH3 is applied to an aerobic soil with crops. What other forms of nitrogen could occur in the soil as a result of chemical transformations? Which forms do you expect to be major components, and which will be present in only small levels? 7. Nitrogen fixation occurs through bacterial processes. Since the 1940’s, humans have also been capable of nitrogen fixation. What is nitrogen fixation? What are the implications of large-scale human nitrogen fixation on the global nitrogen problem?8. a. What is a riparian zone?b. What role do riparian zones play in the transformation of nitrogen that is transported through nonpoint source processes?9. a. How do wetlands serve to keep phosphorus from contaminating lakes and rivers?b. Explain the difference in mechanisms by which wetlands retain N and P. Which nutrient is removed permanently from contaminated water, N or P? Why?The Nitrogen CycleN2NH3Org NNO3-NO2-N2O


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TOWSON CHEM 104 - Exam 3

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