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Lab Report on Physical Properties of Soils and Surficial Materials
Geomorphology and Soils (GG282)
Part 2 of GG282 Lab
Soil and Surficial Material Physical Properties
Follow-up to Atterberg Limits; Hydrometer Methods for Soil Texture, Soil pH, and Conductivity
By midnight tonight, this lab must be finished and submitted.
Dropbox YOUR lab section’s submissions!
This week, we’ll look at a method for determining the percentages of sand, silt, and clay in a soil, as well as soil pH and conductivity.
Data from Samples in Summary
You’ll use the data and knowledge from last week’s lab to help you with this one.
Hydrometer Method for Soil Texture
We would have been able to finish this section in the lab if we had been there in person. The TA will demonstrate a technique for determining the percentages of sand, silt, and clay in a soil or sediment sample by showing a video. The method described here is a quick and easy way to determine the percentages of sand, silt, and clay in soil or sediment. A more sophisticated wet settling process can be utilized to obtain more detailed information on particle size distribution. However, because the clays settle slowly, this procedure takes several days to complete.
A far faster method is to take a small sample of dirt and disperse it in an aqueous solution. Laser light is used to illuminate the sample. The laser light is diffracted by the particles in the solution, with the amount of diffraction affected by the particle sizes present in the sample. Laser diffraction has evolved as a dependable quick technique for determining the detailed distribution of particle sizes in samples containing sand, silt, and clay in the last 20 years. A laser particle size diffraction equipment in the GES department is used to help research projects that require detailed information on particle sizes.
We would suspend the components in the cylinder for each sample, let the cylinder to settle, and take a hydrometer measurement after 40 seconds. Repeat three times, averaging your 40-second reading each time. The data in the table below was provided by the TA.
Q1. The percentages of sand, silt, and clay were calculated using hydrometer methods. Refer to the soil textural triangle in the Lab 1 Part 1 Handout for more information. Determine the proper textural word for each sample based on the percentages of sand, silt, and clay.
Sample ID (percentage of sand, silt, and clay) Textural Class (percentage of sand, si
a sample of 1 54 33 13
2nd Sample 32.6 34.4 33
87.6 8.4 4 87.6 8.4 4 87.6 8.4 4 87.6
64.6 20.4 15 64.6 20.4 15 64.6 20.4 15 64.6 20.4 15 6
84 10 6 84 10 6 84 10 6 84 10 6 84 10
pH and Conductivity of the Soil
There is a document in the Lab 2 folder that provides a process for determining soil pH and conductivity. A sample mass of soil (10 g) is poured in 50 ml of de-ionized water and stirred for at least 20 minutes to perform a pH test. After allowing the dirt to settle, the pH of the resulting soil solution is measured using a pH meter. Base cation-rich soils will be closer to neutral or slightly alkaline. The pH of soils with a lot of hydrogen ions will be lower.
As a result of the following factors, soils tend to become acidic:
Basic ions are being washed away by rainwater (calcium, magnesium, potassium, and sodium)
carbon dioxide released by decomposing organic matter and root respiration dissolves in soil water, forming a mild organic acid;
Decomposition of organic materials and oxidation of ammonium and sulfur fertilizers result in the creation of powerful organic and inorganic acids.
The ease with which a fluid may conduct an electrical charge is measured by conductivity. A fluid with a high concentration of dissolved ions can easily pass an electrical current; a fluid with a low concentration of dissolved ions will pass a current with difficulty. The same process as for determining pH is used to assess conductivity: 10 g of soil is mixed with 50 ml of deionized water and stirred. A portable meter is used to determine the conductivity of the produced fluid. Higher conductivities are seen in soils with higher concentrations of easily dissolved mineral and organic elements.
The pH and conductivity were estimated using the five samples we calculated for organic content last week. The information is shown in the table below.
Q2. Create a table with the pH and conductivity values for Samples 1, 2, 3, 4, and 5, as well as the average Organic Matter Content from last week. Examine the five samples and describe their color for each one, then enter the information into the table. Add the appropriate textural descriptor to the table at the end.
The table should be laid out as follows:
Identification of the sample pH Electrical
Color Textural Class (percentage)
Redish-orange Sample 1 5.5 178 1.4
7.1 466 2.4 Tan or Tan-Grey Sample 2
6.9 536 5.8 Browny-Tan Sample 3
4 6.4 636 4.9 Light Brown Sample
5 5.1 768 8.6 Dark Brown Sample
Comment on the findings; are there any patterns or connections in the data?
variables? Take into account all of the samples’ characteristics. (3 points)
Q3. We looked at some new aspects of five soil samples this week, and the Loss on Ignition data from last week was based on the same five samples. You’ll find descriptions of five unknown materials below. Each of these descriptions corresponds to one of the five samples utilized in the organic matter determinations, as well as the other data shown above. The five elements were: I a Podzol’s B horizon, (ii) a Glacial Till’s A-C horizon, (iii) a sandy river bed deposit with organic material, (iv) a Luvisol’s B horizon, and (v) a Podzol’s A horizon. For the aforementioned studies, we used samples 1 to 5 in the lab (organic sample 1 to organic sample 5).
Determine the material description each of the Organic Samples corresponds to (1 to 5). Organic Sample 1 for example, meets the podzol’s description of the A horizon because….. For each sample, write a concise statement. (5 points)
1 Unknown Material Description (A Horizon from a Podzol)
One of the samples was taken from the upper portion of an A horizon in a mixed forest with coniferous species such as eastern white cedar and red and white pine dominating. A limited percentage of deciduous trees, such as sugar maple and American beech, are also present. The forest canopy is closed, and 3-5 cm of needles, twigs, and leaf litter blanket the A horizon’s surface. In this case, the soil evolved from a sandy substrate (the parent material had a fine sand texture). This sample was taken in central Bruce County, at the Bruce Peninsula’s base.
Unknown Material 2 Description (B Horizon from a Luvisol)
Another sample was taken from the B horizon of a soil sample from a Waterloo Region agricultural field. The parent material of the soil is glacial till. The texture of glacial till is clayey silty, with a low percentage of stones (gravels). The B horizon was extracted from a Luvisol soil, which has a rather high clay content in the B horizon as one of its diagnostic properties.
Unknown Material 3 (Description) (Sandy stream bed deposit)
Another sample was obtained from a sand-bedded little stream channel. The sample was taken from the streambed itself, in a segment with a gradual gradient (low gradient), low velocity, and a depth and width that was relatively deep and wide. There was a lot of aquatic vegetation in that portion of the canal, as well as woody debris from the neighboring floodplain. Erosion activities brought debris from historic dunes and beach features into the stream.
4 Unknown Material Description (B Horizon from a Podzol)
One of the samples came from a B horizon of soil that grew under a cedar and pine canopy (see Description 1). This soil’s parent ingredient is fine sand. The B horizon was taken from a Podzol type of soil. A reddish, reddish-orange, or reddish yellow color due to a high iron content is one of the distinguishing properties of B horizons in various podzols.
5 C Horizon composed of Glacial Till) Description of Unknown Material
One of the samples came from a soil sample taken from an agricultural area east of Pickering’s C horizon. This sample is from a glacial till deposit and is the parent material C horizon). This parent material isn’t sorted in any way. Between the fine elements is a clayey silt matrix with sands and pebbles. Soil formation and weathering processes haven’t had much of an impact on it.
Lab Report on Physical Properties of Soils and Surficial Materials