Nebraska Pedology

Materials

• Link to Soil Lab Data spreadsheet

• Butcher paper

• Containers for sample storage

• Mortar and pestle

• 2-mm sieve and sieve pan

• Labeling tape

• 50 mL centrifuge tubes

• Sample rack

• Top loading balance

• Analytical balance

• Scoop spatula

• 20% bleach solution with 25 mL bottletop dispenser

• 5 mL dispenser pipette

• Centrifuge

• Vacuum/aspirator

• 10% HCl with 2 mL bottletop dispenser

• 50 g/L Sodium Hexametaphosphate with 10mL bottletop dispenser

• Shaker

• Malvern instrument

• 1000 mL beaker

• 1000 µm mesh sieve

• 250 mL beaker

• Aluminum tins

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Methods

1. Enter sample information, including Site, Profile ID, and Horizon Depth Range, into Soil Lab Data spreadsheet and create a unique Lab ID (e.g., 2019_1)

2. Spread the sample out on a sheet of butcher paper to dry overnight

3. For sample containing gravels

   • Tare a container that will fit the sample on the top loading balance, then transfer sample into the container and weigh and record mass in Soil Lab Data spreadsheet

   • Working in batches if necessary, use mortar and pestle to gently break up soil aggregates

   • Transfer the sample form the mortar and pestle to a 2-mm sieve with pan and gently shake for 1 minute

   • If any aggregates (not gravels) remain in the 2-mm sieve, transfer them back to the mortar and pestle and repeat gentle crushing and sieving until all aggregate greater than 2 mm are broken up (you may remove any gravels from the sample during this procedure to make it easier to crush the sample, collecting them in an appropriate sized container for weighing later)

   • Once all batches are sieved, weigh any gravels that were collected, record their mass in the Soil Lab Data spreadsheet, and dispose of them in the spent soil container

   • Transfer the sieved soil back to the sample container and label this container with Lab ID, Site, Profile ID, and Horizon Depth Range (or discard if no further analysis will be required).

4. For samples without gravels: gently crush with a mortar an pestle until the sample passes through at 2-mm sieve

5. Label a 50 mL centrifuge tube with the Lab ID

6. Place centrifuge on the analytical balance and tare.  Mix the sample in the container and randomly pull out the sample with the spatula. Weigh out appropriate amount of sample (see chart) and record the sample mass in the "VCO Sand" spreadsheet.

7. Take a second sample from each container to determine the moisture content: 

   • Label an empty aluminum tin with the Lab ID of the sample

   • Record the mass of the empty aluminum tin​ in the "VCO Sand" spreadsheet 

   • Transfer 5-10 g of sample to the tin

   • Record the mass of the tin + air-dry sample in the "VCO Sand" spreadsheet

   • Place the tin in the drying oven overnight (105 dec C)

   • Record the mass of the tin + oven-dry sample in the "VCO Sand" spreadsheet

   • Discard the oven-dry sample, but keep the tin to use again later

8. For samples with organic matter*

   • Working under the hood, add 25 mL 20% bleach solution

   • Allow to sit overnight in hood

   • Place in centrifuge in a balanced arrangement

   • Centrifuge 6 minutes at 3000 min/g

   • Use vacuum/aspirator to draw off water

   • Fill centrifuge tubes with water, centrifuge and draw off water again

9. For samples with carbonates

   • Under the hood, add 2ml of 10% HCl to the sample

   • Allow sample to sit under the hood at least 20 minutes or longer if it is still effervescing

   • Once the sample has stopped effervescing, add equal amounts of water to each centrifuge tube

   • Place in a balanced pattern in centrifuge and run for 5 minutes at 3000min/g

   • Use vacuum/aspirator to draw off water from sample

   • Fill centrifuge tubes with water again and place on shaker for 5 minutes

   • Centrifuge again and draw off water

10. Add 10 mL of 50 g/L Sodium Hexametaphosphate solution.

11. Cap and place on shaker overnight or until ready to run on Malvern

12. Turn on the Malvern pump (top set of buttons on the pump keypad)

13. Open the Malvern software using the Mastersizer 2000 desktop icon

14. Use File > New to create a new measurement data file

    1. Label the file with your name and project (e.g., Danielle Jones – Senior Thesis)

15. Use Measure > Start SOP to open the SNR_SOP_2 measurement window

16. Enter the Lab ID into the sample name box when prompted

17. Place a 1000 µm mesh sieve over a 250 mL beaker and pour the sample through the sieve into the beaker. Rinse the sieve with DI water to make sure all fines are washed through. Place the sieve in the drying oven until it is needed again for the next sample. When the sieve is needed again, transfer the sands into the tin used previously for moisture content and return them to the oven to dry overnight. 

18. Fill the 1000-mL beaker with 600 mL of water from the carboy next to the sink, then click the green Start button in the SOP window.

19. Follow the instruction in the yellow box of the SOP window to measure sample

    • When prompted to, pour the sample from the 250-mL beaker into the 1000 mL beaker, rinsing with DI water bottle to flush ALL grains of sample into the beaker

    • Apply 1 minute of ultrasound: press the start button on the pump keypad next to the Ultrasonic Timer

    • When ultrasound stops, the obscuration should be in the green zone, between 5% and 20%.  If the obscuration is above 20%, add DI water to the beaker to dilute the mixture.  If obscuration is still too high, or too low, the sample will have to be re-run (making adjustment to amount of sample used), but run that sample as is for now

    • When the obscuration is correct, press the green Start button to run the sample

    • Do you want to run this SOP again? Select YES if you want to run another sample or NO is you are finished

    • Rinse the beaker and Malvern tank until clean. Remove beaker, dump sample into sink, rinse beaker and fill with DI water and replace beaker under pump.  Allow pump to run for about 10-15 second to flush out any sediment in the Malvern tank. Repeat at least 3 times to adequately clean out the tank and tubes

    • If running another sample, fill beaker to about 600 mL with DI water to prevent diluting sample. If done for the day, fill beaker to 800-900 mL with DI water to prevent air form getting into tubes.

20. When run is complete, export the data to excel.  Open the particle-size analysis spreadsheet (excel file on desktop) and copy-and-paste the data into the template.  Save the template, renaming it with your name, project, and date.

21. The next day, weigh the tins containing the over-dry sands and add their mass to the "VCO Sand" spreadsheet.  Enter the percentage >1000 um calculated by the "VCO Sand" spreadsheet to the spreadsheet created yesterday using the particle size analysis template.  Email the file to jturk3@unl.edu.

22. Enter the final % sand, silt, clay, and particle size class into the Soil Lab Data spreadsheet.  Make note of any issues with the run (e.g., obscuration too high or two low)

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*Alternate method for organic matter removal (use Nalgene centrifuge tubes)

• Add 5 mL of distilled water to the soil and stir

• Place the centrifuge tube in water bath preheated to 80 deg C, and cover loosely with cap.  When suspension is hot, add 30% hydrogen peroxide in 5 1-mL increments at about 20 min intervals.  If a foam approaches top of centrifuge tube, squirt sparingly with acetone.  Stir occasionally with a glass rod. 

• Leave sample on water bath for at least 2 hr to completely decompose the hydrogen peroxide

• Add 10 mL of 100 g/L Sodium Hexametaphosphate solution (note: concentration is different from what is used in the other method)

• Continue from step 11