Effects of cold storage on anion, ammonium, and total nitrogen concentrations in soil water

Yorks, T.E.; McHale, P.J.

Effects of cold storage on anion, ammonium, and total nitrogen concentrations in soil water

2000

Yorks, T.E. | McHale, P.J.

Researchers frequently must store water samples >24 h after collection until chemical analyses can be accomplished. Samples are commonly stored in darkness at near-freezing temperatures until analysis, but effects of this storage method on soil water chemistry are not well-documented. Soil water samples were collected from eastern hemlock [Tsuga canadensis (L.) Carriere] stands and analyzed initially and over time to determine if nitrate (NO3(-), chloride (Cl(-)), sulfate (SO4(2-)), ammonium (NH4(+)), and/or total nitrogen (TN) concentrations changed when samples were stored in darkness at 2-4 degrees C. Subsamples were analyzed <24 h after collection and reanalyzed five times in a 12 to 24 wk period following sample collection. Nitrate concentrations remained stable for at least one wk and were only slightly lower than initial concentrations after 3-16 wk of storage. Chloride and SO4(2-) remained stable for 16 wk, while TN remained stable for 8 wk and decreased slightly after 24 wk. Most NH4(+) concentrations were below the limit of quantification, but concentrations of samples with quantifiable NH4(+) decreased in the first week of storage. Overall, cold storage in darkness was effective for preserving NO3(-), Cl(-), SO4(2-), and TN concentrations in soil water, but NH4(+) analyses should probably be performed as soon as possible after sample collection.

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