SO461 Lab, Fall 2014

Wet Sieve and Pipette Sediment Analysis

 

  1. One member of the group should label and weigh 6 small beakers.  You must use the sensitive balances with the weighing enclosures accurate to 0.0001 g, because we will have very small quantities of sediment. Use this data sheet.
  2. Sediment prep

        Select a sample of about 25 g of sediment.  Obvious shells should be removed.  This need be accurate only the nearest gram, and insures an adequate sample size without inducing flocculation

        Use the #230 sieve, with a pan below it

        Use the fine brush and a squirt bottle of distilled water, and wash the sediment through the sieve.  You should have a small number of sand grains on the sieve, and all the fines in a watery mixture in the pan.

        Place the sand in a small beaker.  You can wash the sieve, and drain off any excess water from the beaker.  This is sample #1

        Transfer the fines/water mix into a 1000 ml graduated cylinder.  Wash the pan clean.

        Add 20 ml of 0.5% calgon solution to the graduated cylinder.  This prevents flocculation.

        Fill the cylinder to the 1000 ml level

  1. Check the water temperature to determine the correct time table to use.
  2. Use the stirrer to thoroughly mix the fines in the water.
  3. Start timing.
  4. At the indicated time (http://pubs.usgs.gov/of/of00-358/graphics/chapter1/c1tab2.htm), and withdrawal depth, remove 20 ml of solution with a pipette.  Place the solution in one of the beakers.
  5. If the next time comes too soon, you can restir the mixture and restart the clock.  This should only be a problem for the 5F sample.
  6. You should be able to take samples for 4,5,6,7 F samples.  These will be samples #2 to #5.
  7. Take a sample of 20 ml of the Calgon solution and place it in a beaker.  This is sample #6.  This amount of Calgon will be in each of the pipette samples.
  8. Dry the samples in the drying oven overnight.  Verify that you have 6 beakers, and they are labeled so that you can identify them as belonging to your group and the sample.
  9. Reweigh the samples and compute the weight in each class.  Use this data sheet.

 Equipment per group:

 Equipment for class:

 The removal of organic matter may be necessary to achieve complete dispersion of the clay and, in sediments with an elevated organic content (>3%), to prevent the organics from being counted as part of the sample, which would bias the grain-size distribution. The sample is placed in a 600-ml beaker and a small volume (~10 ml) of 30% hydrogen peroxide is added. The sample is stirred and, if necessary, water is added to slow the reaction down and prevent bubbling over. More hydrogen peroxide is added until the dark color of the organic matter has largely disappeared; then the sample is washed three times with a NaOAc buffer of pH 5 and once with methanol to remove the remaining released cations (Jackson, 1956).

 

References:


PLG  9/22/2014