Biology I
– Soil Analysis Laboratory
Lab Procedures
1. Visual Examination -
Macroscopic
Texture: Use the flow chart in
your handout or the sample field guide to make a visual and manual determination
of whether the sediment is silt, sand, clay, loam, or a mixture. This will help
you describe the type of sediment and the environment in which it was
deposited.
Density: Use the Fractionation Testing
Method for sorting the sediment in a column of water and describe its various
component levels. This will help confirm the texture and particle size determination
you did above. This involves placing a fixed amount of sediment (the same for
each sample you analyze) into a graduated cylinder filled with water, shake it
up, watch it settle, and record the approximate percentage of each group of particle
sizes separated by the water.
Permeability: Use a filter paper to measure
the rate at which water seeps through the sediment sample, which is the permeability of the sample. This is
useful in characterizing the sediments ability to absorb water (for the
usefulness of the soil in farming). Place the filter paper over a beaker,
include a fixed amount of sediment (same amount for each sample), pour a fixed
amount of water through the paper and sediment, and record how long it takes
for the water to seep through the sediment.
2. Visual Examination –
Microscopic
Examine your sample under the microscope, draw and
describe your observations, especially focusing on the types of inclusions (such
as quartz, caliche) and the evidence of biotics (such as seeds, plant
materials, and insects). If you can’t identify anything, just draw what you
see.
3. Color Examination
Use the Munsell color book to describe the
4. Chemical Essay
Carbonate Testing: Add drops of hydrochloric
acid (HCl) to your sample. If you detect
bubbles, that indicates carbonates. Carbonates form from the decomposition of shellfish,
and suggest the sediment was from a water environment (lakes, oceans, rivers).
Sulfide Testing:
At the same time as you test the samples for carbonates (above), smell the
sample (carefully!!!). If you detect a “rotten egg” smell, this indicates the presence of
sulfides. Sulfides are the result of recent organic decomposition, meaning dead
animal flesh in the sediment.
pH Testing: Make sure your sediment
sample is wet with purified water. Put a strip of pH paper in the water and
watch for a color change, then compare it to the guide to tell the pH of the
water. The pH describes acidity or alkalinity, and is used to determine the
usefulness of the sediment for agriculture.
Organic Reduction: [I’ll do this test, just
record the results I get] Using the triple balance, measure the weight (mass)
of a sample of sediment, then apply heat to the sample, “cooking it,” and measure
the sample again, noting the difference in weight before and after. This
difference is due to the oxidation of organics, which will cook at low heats.
This is called organic mass fractionization.
Soil Analysis – Report Procedures
1. Choose a group of approximately three to four people. Pick your group
carefully! You will not be allowed to change groups after you start, and your
grade will depend on the success of the whole group, so maybe think twice about
which people you pick to be in your group.
2. Observe and take notes on the lab demonstration run-through I will
perform. This will be your guide for completing your turn at the soils testing
lab. Take careful notes on what I do so you can duplicate it when you do the
lab yourself.
3. During the lab investigations, distribute tasks within the members of
the group, including assigning at least one person to perform the experiments,
and one person to make observations of the results and record them in your lab
notebook. You will need detailed observations on the results to complete your
report.
4. Each of you will be responsible for turning in a report for this lab.
You can work together as a group to produce the report and include all your
names on it.
5. This report will be worth at least a gazillion points (actually 200)
so if you ace it, it will serve as your exam for this unit, and you won’t have
a test this Friday, maybe. It really depends on how the entire class performs
during the lab exercise.
6. I will also be taking notes on your behavior and participation during
this lab, which will be worth another 50 points. No late assignments will be
accepted! Don’t even think about thinking about being late with this, seriously
dudes.