Dr. Casey Name: ______________________Exam 2Spring 2006 Signature: ______________________Chem. 104Honor Statement: By signing this exam, you indicate that you have neither given nor receivedaid 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 aquiferarrow indicating recharge arrow indicating site and direction of discharge2. Drinking water wells often withdraw water from confined aquifers. Irrigation wells often withdraw water from either unconfined or confined aquifers. Explain why this is reasonable in terms of potential for aquifer contamination and desired uses for different water resources.Impermeable RockStreamLand SurfaceWater Table3. Explain in detail how overuse of groundwater relates to 2 of the 3 situations below. i. Drinking water availabilityii. Subsidence of the groundiii. Saltwater intrusion4. In the Rio Grande River calcium (a major element) is present at 2.72 mg/L and chromium (a trace element) is present at 0.012 mg/L. Agricultural land adjacent to the river is amended with an organic mixture that contains calcium at 625 mg/kg and chromium at 92 mg/kg. Explain whether state regulators might be concerned with calcium contamination, chromium contamination or both.5. A wetland is situated adjacent to an agricultural field. The wetland soils are saturated most of theyear and the agricultural soils are usually unsaturated.a. Identify each soil as aerobic or anaerobicb. For the anaerobic soil, explain how it becomes anaerobicc. Determine the oxidation state of As in each of the ions in the reaction below.AsO4-  AsO3-d. Which form of As would you expect to find in the wetland? Why?6. An organic N fertilizer is applied to the agricultural field described in question 5.a. Describe the transformations of the organic N fertilizer that will take place in the agricultural soils.b. Describe the interaction of plants with the different forms of N in the agricultural soils.c. Which forms of N are most likely to be transported away from the agricultural soils in a rainstorm?d. If rainwater carries N from the agricultural soils into the wetland, describe the transformations of N that will occur in the wetland.e. Describe the significance of denitrification in dealing with the problem of excess N in the environment.7. What is meant by the statement that “there are no safe forms of phosphorus”? Are there ways in which phosphorus can be made “relatively safe” in the