UVM Theses and Dissertations
Format:
Print
Author:
Snyder, Lisle
Dept./Program:
Natural Resources
Year:
2012
Degree:
MS
Abstract:
An in situ wet chemistry autoanalyzer was used to simultaneously monitor nitrate, phosphate and ammonium concentrations in arctic tundra streams. The objectives of this work were to assess whether the specific instrument, an Autonomous Profiling Nutrient Analyzer (APNA) can be reliably used for stream ecosystem research in remote field environments and to evaluate whether this type of instrument will be useful for long-term stream monitoring programs.
Field work was conducted over two summers (2010 and 2011) near Toolik Field Station, Alaska. Two sampling regimes were used with the instrument: first, time-interval sampling was conducted where hourly measurements ofnitrate, phosphate, and ammonium were made over deployments of up to two weeks. Second, continuous monitoring (one second data return for all analytes) of slug nutrient additions was performed to test the instrument utility in stream nutrient uptake experiments.
Inverse diurnal oscillations of nitrate and ammonium were observed during a time-interval deployment during baseflow conditions. Nitrification during ammonium slug injections was also seen. Based on these results it is clear that in stream processing ofnutrients on a short time-scale is of major importance in these systems. Validation of nitrate and phosphate concentrations based on comparisons between in situ measurements and laboratory analyzed grab samples showed a close relationship. In situ ammonium measurements were imprecise, likely due to the deterioration of photo-sensitive reagents.
For future use in stream research it is recommended that the OPA analytical method for ammonium be substituted for the nitroprusside method, which will be less sensitive and less likely to degrade over a deployment of several weeks. Despite this, the APNA proved to be robust with several uses in stream ecological research. This instrument has proven to be reliable in a challenging field environment, useful for long term monitoring programs, and has shown potential to advance our general knowledge of fine time-scale stream nutrient cycling.
Field work was conducted over two summers (2010 and 2011) near Toolik Field Station, Alaska. Two sampling regimes were used with the instrument: first, time-interval sampling was conducted where hourly measurements ofnitrate, phosphate, and ammonium were made over deployments of up to two weeks. Second, continuous monitoring (one second data return for all analytes) of slug nutrient additions was performed to test the instrument utility in stream nutrient uptake experiments.
Inverse diurnal oscillations of nitrate and ammonium were observed during a time-interval deployment during baseflow conditions. Nitrification during ammonium slug injections was also seen. Based on these results it is clear that in stream processing ofnutrients on a short time-scale is of major importance in these systems. Validation of nitrate and phosphate concentrations based on comparisons between in situ measurements and laboratory analyzed grab samples showed a close relationship. In situ ammonium measurements were imprecise, likely due to the deterioration of photo-sensitive reagents.
For future use in stream research it is recommended that the OPA analytical method for ammonium be substituted for the nitroprusside method, which will be less sensitive and less likely to degrade over a deployment of several weeks. Despite this, the APNA proved to be robust with several uses in stream ecological research. This instrument has proven to be reliable in a challenging field environment, useful for long term monitoring programs, and has shown potential to advance our general knowledge of fine time-scale stream nutrient cycling.