Evaluation of Storage and Filtration Protocols for Alpine/Subalpine Lake Water Quality Samples

Abstract

Many government agencies and other organizations sample natural alpine and subalpine surface waters using varying protocols for sample storage and filtration. Simplification of protocols would be beneficial if it could be shown that sample quality is unaffected. In this study, samples collected from low ionic strength waters in alpine and subalpine lake inlets and outlets in the western United States were used to evaluate (1) effects of refrigerated storage time on the chemistry of unfiltered samples, and (2) differences in sample filtration protocols. No analytes exhibited significant changes when stored less than 48 h. Six analytes (pH, sodium, ammonium, potassium, chloride, sulfate) exhibited statistically significant (but small) changes when storage time exceeded 48 h. Two analytes (calcium, nitrate) were significantly higher when samples were field filtered than when filtered in the laboratory, but the differences were also small. For waters similar to those in this test, unfiltered refrigerated samples may be stored up to 48 h without compromising sample quality. The small differences between field and lab filtration do not justify the expense, training, and contamination risk of field filtration.

Alkalinity of diverse water samples can be altered by mercury preservation and borosilicate vial storage

“…There was no effect of 0.45 µm filtration on A T of water samples from across a salinity spectrum. Other studies have also found no effects of filtration on the A T of alpine freshwater, pond water, and seawater 6 , 9 , 11 , 21 , 22 . Importantly there were no changes in the A T of filtered samples stored in polypropylene vials for at least 6 months, with the exception of groundwater in two of three experiments, demonstrating the enduring effectiveness of filtration.…”

“…The drawbacks of HgCl 2 have driven the search for low-cost, safer, and more environmentally benign alternatives 18 . Filtration does not affect the A T of alpine freshwater 9 , pond water 11 , or seawater 21 – 23 . Filtration is as or more effective than HgCl 2 in preserving stable isotope compositions ( δ 13 C) in dissolved inorganic carbon 24 , 25 .…”

“…There is, however, a paucity of studies comparing the effectiveness of preservation and storage methods for non-oceanic water samples, particularly for samples collected from groundwater or brackish ecosystems. Only three studies have examined aspects of preservation or storage methods for freshwater A T samples 9 – 11 . It is important that storage and preservation methods are investigated for non-marine water samples given there is growing interest in quantifying the role of estuarine, freshwater, and groundwater systems in the global carbon cycle 12 , 13 .…”

Concurrent measurement of nitrate and ammonium in water and soil samples using ion‐selective electrodes: Tackling sensitivity and precision issues

“…Immediately prior to use, all individual soil samples were sieved to 4 mm to remove plant materials, large stones, and earthworms followed by thorough mixing. Additionally, upstream and downstream water samples (n = 4) draining the BIFoR woodlands were sampled according to standard water sampling procedure 41,42 . Water analyzed for Nr included filtered and unfiltered samples since measurement using FIA required samples to be free of suspension.…”

“…Additionally, upstream and downstream water samples (n = 4) draining the BIFoR woodlands were sampled according to standard water sampling procedure. 41 , 42 Water analyzed for Nr included filtered and unfiltered samples since measurement using FIA required samples to be free of suspension. Pictures of sample location site are enclosed in Figure SI2.…”