ABSTRACT:
U.S. Environmental Protection Agency (EPA) and U.S. Geological Survey (USGS) guidelines for collection and analysis of water quality samples require that samples be field- or lab-analyzed within 24 hours if they are not filtered (USGS standard) or acidified below a pH of 2 (EPA standard) in the field to allow for longer sample holding times. These collection and analysis standards are not always met for a number of reasons. This experiment tests alternate storage methods and holding times to determine whether these factors affect water analysis results. Unfiltered water samples were collected from nine creeks at Sierra Foothill Research and Extension Center. One set of samples was analyzed within 24 hours. Replicate samples were treated with six different combinations of refrigeration and storage times. Most combinations simulated common field-to-lab times or automatic water sampler holding times. Measurements taken after each experimental period were compared to each other and to the field measurements. Despite the federal standards, researchers found no significant statistical difference in chemical composition between the samples measured immediately and those left unrefrigerated for a week.
Footnotes
Authors are associate professor and graduate students, respectively, Dept. Environmental Science, Policy and Management, Ecosystem Sciences Division, University of California, Berkeley, CA.
- Copyright 1998 by the Soil and Water Conservation Society
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