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Abstract

Automatic samplers are a common method of data collection for numerous monitoring projects in the South Florida region and elsewhere. Although total phosphorus (TP) is the primary parameter of interest within this region, nitrogen species such as ammonia nitrogen (NH4-N), nitrate+nitrite nitrogen (NOx-N), and total kjeldahl nitrogen (TKN) are also collected and analyzed. Federal and state quality assurance guidelines require nutrient samples to be preserved by acidification with H2SO4 to a pH < 2 and stored immediately at 4 degrees C. However, the remoteness of many sampling locations in South Florida makes it difficult to supply electricity for the refrigeration of samples collected by autosamplers. In addition, the use of propane-powered refrigerated autosamplers is a costly and ineffective solution in the South Florida climate. Consequently, while samples collected at these remote locations are routinely pre-preserved with acid, they are not cooled to 4 degrees C for a period from one to seven days. This study evaluated if a statistically significant difference (approximately = 0.05) existed between concentrations of nitrogen species from a common source sample that was either: processed immediately; refrigerated to 4 degrees C for seven days; or not refrigerated for seven days. In all cases, the collected sample was pre-preserved by adding 1 mL of 50% H2SO4 to each 1 L discrete sample container before each 7 day testing period. Differences in concentrations of the calculated parameter total nitrogen (TN) were also investigated. Analyses using the Wilcoxon Signed-Rank Test showed no significant differences among the three treatment groups for NOx-N, TKN, TN and TP. Significant differences were observed when the NH4-N samples that were processed immediately were paired with NH4-N samples that were left unrefrigerated or refrigerated for seven days. Information from this study can be used by researchers and managers in evaluating the usefulness of nutrient water quality data that is collected when sample refrigeration is not available.

Evaluation of Sodium Omadine for Short-Term Preservation of Nitrate-N and Orthophosphate in Water Samples

“…The concentrations for both pond and stream water were variable, increasing by as much as 9.92% on Day 1 for stream water and decreasing by as much as 6.25% on Day 7 for stream water. Overall, the findings in this study are in agreement with other studies that found sulfuric acid to be a sufficient preservative for nitrate-N for up to seven days [10]. However, this study indicates suitability of sulfuric acid to preserve samples for up to 14 days.…”

“…In contrast, a study found that while refrigeration and filtration were necessary, acidification was the most effective preservation method for nitrate-N [9]. Sulfuric acid can serve as a sufficient preservative for maintaining nitrate-N and total N concentrations for up to seven days [10], but may be unsuitable for samples containing high concentrations of nitrite because sulfuric acid can cause the chemical conversion to nitrate [11]. Furthermore, a study in California, USA, found that long-term freezing can serve as a viable method, as it did not have a significant effect on concentration [12].…”

“…Some studies have tested current preservation methods, like freezing, acidification by sulfuric acid, refrigeration, and regular storage-affected nitrogen and phosphorus levels, and then compared the abilities of these methods to maintain concentrations [8][9][10][11][12][13][14][15]. A study using tile drainage water, river water, and surface runoff water in Indiana found that freezing at subzero temperatures was the best overall method for preserving water samples for orthophosphate and nitrogen (nitrate-N and ammonium) [8].…”

Effects of amino acid composition in pig diet on odorous compounds and microbial characteristics of swine excreta

“…Reduced N excretion in pig slurry is closely associated with decrease in the odour emission from pig facilities [ 39 ]. Total Kjeldahl nitrogen (TKN) is the sum of organic nitrogen, ammonia (NH3), ammonium (NH4) and therefore to calculate total nitrogen, concentration of nitrate-N and nitrite-N needs to be determined and added to TKN [ 40 ]. Total N and TKN levels, interestingly, tended to be lower but ammonium nitrogen (NH 4 -N) was higher in 2012 group than in 2007 group in our study.…”

Using high-frequency phosphorus monitoring for water quality management: a case study of the upper River Itchen, UK

“…Alternatively, automatic water samplers can be used for time series acquisition (e.g. hourly or daily) (Burke et al 2002). This approach has provided insights into temporal nutrient dynamics on the time-scales of hydrological responses in agriculturally dominated catchments (Bieroza et al 2014;Bieroza and Heathwaite 2015).…”