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

October 1, 1993

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.

Publication Year 1993
Title Long-term frozen storage of stream water samples for dissolved orthophosphate, nitrate plus nitrite, and ammonia analysis
DOI 10.1029/93WR01684
Authors Ronald J. Avanzino, Vance C. Kennedy
Publication Type Article
Publication Subtype Journal Article
Series Title Water Resources Research
Index ID 70185433
Record Source USGS Publications Warehouse
USGS Organization Toxic Substances Hydrology Program