USGS: TWRI BK 5 CH1 (Susp Sed Sand): Suspended sediment particle size distribution in water by sieve and VA tube analysis
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Official Method Name
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Procedure for determining particle size distribution in suspended sediment samples |
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Current Revision
| 1969 |
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Media
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WATER |
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Instrumentation
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Not Applicable |
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Method Subcategory
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Inorganic |
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Method Source
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Citation
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Guy, H.P., 1977, Laboratory theory and methods for sediment analysis: U.S. Geological Survey Techniques of Water-Resources Investigations, book 5, chap. C1, 64 p. |
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Brief Method Summary
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This method describes the determination of sediment particle size distribution in water using sieve and visual-accumulation tube ("VA tube") procedures. The following is a summary of procedures used for the determination of particle sizes within the sand to coarse gravel range (particle sizes greater than 0.0625 mm). Sieve procedure: Separate sand from fines by washing the sample thru a 0.0625 mm sieve, saving material passing thru the sieve in a beaker; oven-dry the material retained in the sieve in an evaporation dish. Dry method: Weigh total dried sample; pass sample thru a coarse to fine nest of sieves defining the particle size breaks of interest by shaking on a mechanical shaker; weigh material retained in each individual sieve; material passing thru the 0.0625 sieve is added to the fine material separated out during the initial wash. Wet method: Start with the largest sieve, immerse into a dish so that the sieve mesh is beneath water; wash sample onto the wet sieve and vigorously agitate until all passable material has been moved thru. Wash material retained into an evaporation dish, dry, and weigh. Repeat this procedure for remaining material and wash water until all sieve sizes of interest have been used. Use the 0.0625 sieve last; material and wash water passed through this sieve is added to the fine material separated out during the initial wash. Calculation: Divide weights determined at each particle size break by the total dry sample weight and compute into a percentage. VA tube procedure: Separate sand from fines by washing the sample thru a 0.0625 mm sieve, saving material passing thru the sieve in a beaker; use sieves to remove particles larger than 2.0 mm, which are too large for measurement by this method. Note: refer to method report for details regarding choosing the appropriate sized VA tube for this analysis. Assemble the VA apparatus; fill the VA tube with water to just above the valve. Record the temperature of the water in the tube and close valve. Start the electrical tapping mechanism, which also closes the electrical circuit to a switch at the valve so that rotation of the recording cylinder will start when the valve is opened. Wash the sand sample into the funnel above the closed valve and fill to a mark; briskly stir the sample. Fully open the valve, starting the recording cylinder which records the simultaneous chart time and settling of the particles in the tube. Watch through the eyepiece and move the carriage vertically at a rate that keeps the horizontal hair level with the top of the accumulation of sediment. Continue until the pen has passed the 0.0625 mm size on the chart; rotation of the cylinder automatically stops. If material is still falling, continue this tracking operation intermittently until the maximum height of accumulation is determined. While the pen stands at the maximum height of accumulation, release the cylinder drive clutch and hand-rotate the cylinder to extend a horizontal line of maximum accumulation back across the chart to the time of zero accumulation. Close the valve and remove the tube plug. Extrude the sample into a beaker; slightly open the valve to drain out excess water and wash out the lower end of the tube more completely. Replace the plug and remove the recording chart. Calculation: Percent finer than a given size may be read directly from the chart by use of a scale dividing the total accumulation into 100 equal parts. Adjustments can be made to the scale to compensate for fine or coarse material removed prior to the VA analysis. |
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Scope and Application
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This method is applicable to the determination of the particle distribution of suspended sediment in water. Water samples may vary from containing minute quantities of sediment of very small particle sizes to samples containing large quantities of sediment in a wide range of particle sizes. It is important that the method used is appropriate for the concentration and character of the sediment being analyzed. |
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Applicable Concentration Range
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Sieve analysis: 0.0625 - 32.0 mm VA tube analysis: 0.0625 - 2.0 mm |
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Interferences
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The sieve procedure may be limited due to the period of time needed to pass all of the particles thru the sieves; the sieve-determined particle-size distribution may be in error due to irregularities in the size and shape of sieve openings; and possible adhesiveness of clay on the larger particles. The VA tube procedure is hindered by the presence of organic matter, which may be mistaken for sediment particles. For instance, a small number of root hairs, for example, although volumetrically small may have a considerable effect on the results of the analysis. Therefore, unless a sample is reasonably free of organic material, treatment for its removal is recommended. |
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Quality Control Requirements
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Sample analysis can be rerun as necessary to fit the quality control criteria outlined for the study being conducted. Laboratories analyzing sediment samples may also participate in the USGS' Sediment Laboratory Quality Assurance Project, which is further described at http://bqs.usgs.gov/slqa/frontpage_home.htm. |
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Sample Handling
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Store sample bottles on a rack or table so that the sediment settles from suspension. |
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Maximum Holding Time
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Not applicable |
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Relative Cost
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$51 to $200 |
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Sample Preparation Methods
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