Long-term frozen storage of stream water samples for dissolved orthophosphate, nitrate plus nitrite, and ammonia analysis

Water Resources Research
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Abstract

Many researchers have used freezing as an effective, short-term, water sample preservation method for subsequent nutrient analysis. In this study, filtered samples held at −16±2°C for 4–8 years were reanalyzed for orthophosphate, nitrate plus nitrite, and ammonia. Orthophosphate and ammonia concentrations decreased by 0.2 μg P/L and 5 μg N/L, respectively, at mean concentrations of 69.4 μg P/L and 246 μg N/L. Nitrate plus nitrite increased by 1.1 μg N/L at a mean concentration of 139.1 μg N/L. An anaerobic well sample proved to be unsuitable for freezing because it lost significant amounts of orthophosphate during the freezing process. None of the differences observed over long periods of frozen storage were more than twice the estimated standard deviation of the analytical methods used in the study. The small changes observed demonstrate the effectiveness of frozen storage as a means of nutrient preservation in water samples that are unaffected by the freezing process itself.

Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Long-term frozen storage of stream water samples for dissolved orthophosphate, nitrate plus nitrite, and ammonia analysis
Series title Water Resources Research
DOI 10.1029/93WR01684
Volume 29
Issue 10
Year Published 1993
Language English
Publisher American Geophysical Union
Contributing office(s) Toxic Substances Hydrology Program
Description 6 p.
First page 3357
Last page 3362