Unformatted text preview: Lab: Soil Quality This assignment has several subparts. Soil has many different characteristics; this lab will allow you to investigate several of these characteristics. After you have completed this assignment, please submit your work to the appropriate dropbox. Materials: Soil Sample Funnel Beaker or jar Water Bottle Clean clear jar non-‐sudsing detergent coffee filters or filter paper Part I: Soil Texture Soil texture refers to proportions of sand, silt, and clay sized particles. This proportions determine, water infiltration rates, permeability rates and water holding rates. There are several different ways to determine type of soil texture. One way to determine soil texture is to use a soil texture triangle. If the percentages of the soil components are known, the soil texture can be found on the soil texture triangle. Example: 65% Sand, 20% Silt and 15% Clay = Sandy Loam You will determine the soil texture of a soil sample using fractionation. To conduct this investigation you will mix a soil sample with water and use how the particles settle to determine percentages of sand, silt, and clay. Sand is larger and so will settle out faster in a suspension, silt is the next in size so it then settles out next. Clay is the smallest size particle so they will settle on top. Complete the following to test your soil sample. 1.
8. Prepare a soil sample by crushing by hand to breakdown aggregates as fine as possible. Place 1 cup of your soil sample in a clean clear jar (at least 24 oz). Add 3 tablespoons of non-‐sudsing detergent (dish washer detergent or Calgon) to jar. This sodium-‐containing chemical acts as a dispersing agent to break down the soil aggregates into separate sand, silt and clay particles. Add 3 cups of water, cover jar and shake vigorously, at intervals for 5-‐10 minutes. Let stand for 24 hours Measure the total height of the sediment from the bottom of the jar to the bottom of the effluent (water). Measure the height of each of the sediment layers (sand will be on the bottom, silt in the middle, and clay on top). Calculate the percentages for each of the soil components and use these percentages and the chart provided to determine soil type for your sample. ℎ × 100 = % ℎ ℎ × 100 = % ℎ ℎ × 100 = % ℎ Part II: Water Holding Capacity of Soil The groundwater that we use is found in Aquifers. Aquifers are made up of rock or loose soils that can hold and easily release their waters. To do this, these units must be composed of porous and permeable materials. Porosity refers to the amount and size of the spaces between soil or rock particles. This is determined by the amount of water it can hold. Materials like sands and gravels have a lot of spaces between particles in which they can hold water. Because of this, sands and gravels have a high porosity. Clays are also very porous; some can hold up to 60 percent of their total volume. Permeability refers to the rate at which water moves through the rocks or soil. Materials like sand, gravel, and some limestone is both porous and permeable. The spaces are connected, allowing water to move easily through them. While clay is very porous, it is not very permeable. Its fine particles fit together and do not allow water to move easily through it. Because of this, clays are said to be impermeable. Review more information on soil permeability using the links provided in the sidebar. 1.
4. Use two coffee filters or filter paper and fit them to a funnel. Add approximately 20 grams of your soil sample into the funnel. Hold funnel of soil over the beaker and pour 10 ml of water into the funnel. Time how long it takes for the water to start coming out of the bottom and the time it takes water to stop coming out of the bottom. The time interval indicates the permeability or hydraulic conductivity of the soil. Complete out the chart below and compare the data to your sample. Calculations of water holding capacity can be quite complex, so for this lab you will simply calculate the rate of water flow through each of the samples. In the field, permeability is often measured in terms of the flow of water through soil in a given period of time. This is typically expressed in centimeters per hour or meters per second. Use the data provided to calculate the rate of water through each of the samples; one has been completed for you. Sample Time to Start (s) Time to Stop (s) Distance traveled (cm) Sand 97 12.7 Clay 19.8 2760 12.5 Silt 4.1 1060 12.3 Your sample 7.8 Rate of water flow through a sample of sand: ! = ∆!; ∆ = ! − ! ∆ = 97 − 7.8 = 89.2 12.7
0.01 = × = 0.00142377 = . × ! 89.2
3600 = × = 512.556 = . × 89.2
1ℎ Part IV: Soil Salinity This section of your soil quality lab includes a virtual lab. Complete the Virtual Soil Lab and take notes on the procedures necessary for testing the salinity of the soil. Be prepared to answer the questions listed in the analysis section. Analysis and Discussion When you tested your soil sample for texture, what was the soil texture identified? Why might the soil texture be an important test of soil quality? Describe the significance of the comparison of porosity and permeability of silt, clay, and sand. How does the capacity to hold water influence the viability of terrestrial biomes? Compare and contrast porosity and permeability. How do these characteristics influence the ability of soil to hold water? Using the data collected when testing the water holding capacity of your soil samples, calculate the rate of permeability in meters per second for each sample. Be sure to show all your work. How do these values compare with the standard permeability classes? What is soil salinity? Describe how scientists test soil salinity. Be sure to include descriptions of how the test is prepared, the equipment required, and the units of measurement. Familiarize yourself with the lab report rubric on the next page. This is the rubric that will be used to grade this assignment and throughout the course, so be sure to review it carefully. AP Environmental Science Lab Report Rubric When you complete your lab reports for this course, you will need to follow the guidelines included in the rubric below. Be sure to label each section of your lab report accordingly. Points Possible Title Prepare a specific and appropriate title that briefly describes the scope and purpose of your investigation. Introduction Develop 1-‐2 informative paragraphs that describe the initial observations; problem statement; background information including important terms and key points related to the investigation; the purpose of the investigation and how it relates to the topic of study; and a testable hypothesis written in an if/then/because or null/alternative format. Materials & Procedures Compile a complete listing of the materials and supplies used with the exact steps followed to conduct the investigation. The narrative should include enough detail in the experimental design so that others can duplicate the investigation. Be sure to identify the control, variables, and the measurement techniques used. Data Collection Record all qualitative and quantitative data collected during the investigation. Data should include raw data, field notes, pictures, or drawings presented in appropriately labeled data tables or diagrams. Analysis & Discussion Summarize results as an explanation of the data as presented in the appropriate graphs and charts. Graphs must include descriptive titles, axes labels, and a legend if necessary. All mathematical determinations should be figured with complete formulas and error analysis as necessary. Required questions and answers must be included. Show all calculations, including equations and computation. Conclusion Describe what your findings mean and relate them to conclusions you can draw from the data. Give valid explanation based on correct interpretation of results in relation to hypothesis. Where appropriate, compare results with accepted values. Evaluate procedure and results to discuss limitations, weaknesses, or sources of error. State realistic suggestions to improve the investigation and questions for further investigation. 5 15 10 20 25 15 Formatting Paper is properly formatted following class guidelines for font, margin and page settings. All lab reports should include in-‐text citations and references to acknowledge the sources used to support findings and explanations. 10 Total Points Points Earned 100 ...
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- Spring '16
- Environmental Science