Grab versus composite sampling: A primer for the manager and engineer |
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Authors: | David J. Schaeffer Harold W. Kerster Konanur G. Janardan |
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Affiliation: | (1) Illinois Environmental Protection Agency, 62706 Springfield, Illinois;(2) Environmental Studies Center, California State University, 95819 Sacramento, California;(3) Math Systems, Sangamon State University, 62708 Springfield, Illinois |
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Abstract: | Effluent subsamples are usually aggregated into flow or time proportional samples before analysis. Although this provides information on average process conditions, that on process variability is lost by compositing. Fisher's information is defined and used to estimate the loss due to compositing. The results of simulations based on parameters derived from actual waste streams support the fact that random grabs serve as well as composite samples for monitoring purposes. These findings favor changes in regulatory practice to allow compliance to be demonstrated by grab sample averages. Reporting requirements based on moving averages are shown to be inferior to those based on averages taken over nonoverlapping time periods. |
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Keywords: | Grab and composite sampling sample mean and variance economics regulations pollution |
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