USGS: SIR-2005-5077 (Susp Sed Coll): Introduction to Suspended-Sediment Sampling
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Official Method Name
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Introduction to Suspended-Sediment Sampling |
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Current Revision
| 2005 |
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Media
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WATER |
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Instrumentation
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Isokinetic Sampler (see Method Summary for more information) |
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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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Nolan, K.M, Gray, J.R., and Glysson, G.D., 2005, Introduction to suspended-sediment sampling: U.S. Geological Survey Scientific Investigations Report 2005-5077 (CD-ROM) [available on-line at http://pubs.usgs.gov/sir/2005/5077/] |
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Brief Method Summary
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The purpose of sediment sampling is to determine the instantaneous mean discharge-weighted suspended-sediment concentration at a river cross section. Sediment-sampling methods and frequency of collection are dictated by the hydrologic and sediment characteristics of the stream, the required accuracy of the data, the funds available, and the proposed use of those data collected. This method describes the collection of suspended samples using isokinetic and non-isokinetic methods. Isokinetic methods: The samplers used in this method must allow water to enter the nozzle isokinetically (the velocity of the river water being sampled is maintained as it enters into the sampler); permit the sample nozzle to reach its maximum depth at all vertical sections; and be deployed using the equal-discharge interval method (EDI) or equal width interval method (EWI). Refer to the USGS National Field Manual TWRI Book 9, Ch. A4, section 4.1.3 for specific details regarding EDI and EWI methodology. Depth integrating samplers using standard pint-sized glass bottles should not be used in depths exceeding 15 ft; instead, 3-L bag samplers should be used. Non-isokinetic methods: The sample is collected directly into a sample bottle and without the use of a nozzle or a sampler. This is applicable in rivers where the river is too shallow or the velocity is too low. For both sampling methods: raise and lower the sampler or sample bottle at a steady pace in each vertical section being sampled. As a guide, transit rate ratios are provided in USGS Office of Surface Water Memo 99.01 and in USGS Office of Water Quality Memo 99.02. Generally, the sampler transit rate should not exceed 0.4 times the mean river velocity. Samples should be collected in duplicate at each vertical section. Compare each pair of bottles to ensure that they are representative of the vertical section. Bottles that are under- or over-filled, or demonstrate an inordinate amount of sediment when compared the companion bottle should not be submitted for analysis. |
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Scope and Application
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This method is applicable to the collection of suspended sediment samples in a range of water depths and conditions. Emphasis is placed on the collection of a sample which represents the mean sediment concentration over a discrete time interval. |
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Applicable Concentration Range
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Depends on the analytical method and equipment capabilities, generally within tenths of ug/L to thousands of mg/L. |
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Interferences
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Use of an incorrect transit rate will cause the internal bottle pressure to not equilibrate with external pressures and can cause air to not be expunged from within the sampler or the sample enters the bottle too quickly through the nozzle or air exhaust. This will result in either too much sample collected or in not enough sample being collected. The sample bottle and sample bag cannot be overfilled. |
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Quality Control Requirements
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Collect duplicate samples at each vertical. Inspect each bottle for differences (such as volume differences indicate the use of differing transit rates; visible sand settled at the bottom of the bottle indicate that the bed has possibly been dug into while lowering the sampler). |
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Sample Handling
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Collect sample in bottles or bags (which are emptied into sample containers). Mark bottles and other sample containers with the site name, date, time, vertical station, bottle number (if in a series), gage height, temperature, and initials. |
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Maximum Holding Time
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Not applicable |
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Relative Cost
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3 - 6 hrs. per site/sample |
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Sample Preparation Methods
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