USGS-NWQL: I-3860: Turbidity, nephelometric
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Official Method Name
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Turbidity, nephelometric |
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Current Revision
| 1985 |
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Media
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WATER |
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Instrumentation
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Turbidity |
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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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Methods for the Determination of Inorganic Substances in Water and Fluvial Sediments, Techniques of Water-Resources Investigations of the United States Geological Survey, Book 5, Chapter A1 Edited by Marvin J. Fishman and Linda C. Friedman |
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Brief Method Summary
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The method presented below is based upon a comparison of the intensity of light scattered by the sample under defined conditions with the intensity of light scattered by a standard reference suspension under the same conditions. The greater the intensity of scattered light, the greater the turbidity. Formazin polymer, which has gained acceptance as the turbidity standard reference suspension in the brewing industry, is also used as the turbidity standard reference suspension for water. It is easy to prepare and is more reproducible in its light-scattering properties than is clay or turbid, natural-water standards. The turbidity of a particular concentration of Formazin suspension is defined as 40 NTU. This same suspension of Formazin has a turbidity of approximately 40 units when measured on the Jackson candle turbidimeter; therefore, turbidity units based on the Formazin preparation will closely approximate those derived from the Jackson candle turbidimeter but may not always be identical to them. For additional information on the turbidity measurement and its significance, see American Public Health Association and others (1980), California State Water Quality Control Board (1963), and U.S. Public Health Service (1962). |
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Scope and Application
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This method is generally applicable to any water that does not contain coarse material that settles rapidly. Samples having greater than 100 nephelometric turbidity units (NTU) must be diluted prior to analysis. |
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Applicable Concentration Range
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0.1 to 100 NTU. |
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Interferences
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The presence of colored solutes causes measured turbidity values to be low. Precipitation of dissolved constituents (for example, Fe) causes measured turbidity values to be high. |
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Quality Control Requirements
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Calibrate instrument using calibration standards (CAL); quality control samples (QCS); and laboratory blanks (LB) analyzed at a minimum of 1 for every 10 samples. |
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Sample Handling
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Container Description: 125 mL polyethylene bottle. Treatment and Handling: Use unfiltered sample to rinse bottle. |
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Maximum Holding Time
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NA |
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Relative Cost
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Less than $50 |
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Sample Preparation Methods
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