Oct 04, 2024

Public workspaceUSDA LTAR Common Experiment measurement: Dissolved ammonia (NH3) concentration

DOI
dx.doi.org/10.17504/protocols.io.j8nlk8b61l5r/v1
  • Oliva Pisani1,
  • John L. Kovar2,
  • Robert W. Malone2,
  • Amy J. Morrow3,
  • Kevin J. Cole2
  • 1USDA Agricultural Research Service, Southeast Watershed Research Laboratory, Tifton, GA;
  • 2USDA Agricultural Research Service, National Laboratory for Agriculture and the Environment, Ames, IA;
  • 3USDA Agricultural Research Service, National Laboratory for Agriculture and The Environment, Ames, IA
Lori J. Abendroth
Icon indicating open access to content
QR code linking to this content
DOI: dx.doi.org/10.17504/protocols.io.j8nlk8b61l5r/v1
External link: https://ltar.ars.usda.gov
Protocol Citation: Oliva Pisani, John L. Kovar, Robert W. Malone, Amy J. Morrow, Kevin J. Cole 2024. USDA LTAR Common Experiment measurement: Dissolved ammonia (NH3) concentration. protocols.io https://dx.doi.org/10.17504/protocols.io.j8nlk8b61l5r/v1
License: This is an open access protocol distributed under the terms of the Creative Commons Attribution License,  which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited
Protocol status: Working
We use this protocol and it's working
Created: February 27, 2024
Last Modified: October 04, 2024
Protocol Integer ID: 97097
Keywords: Long-Term Agroecosystem Research, LTAR, USDA LTAR, Common Experiment, crops, ammonia, mineralization, aquatic environment, agricultural runoff, eutrophication, hypoxia, surface water, total ammonia N, colorimetry,
Funders Acknowledgement:
United States Department of Agriculture
Grant ID: -
Disclaimer
This research is a contribution from the Long-Term Agroecosystem Research (LTAR) network. LTAR is supported by the United States Department of Agriculture. The use of trade, firm, or corporation names in this publication is for the information and convenience of the reader. Such use does not constitute an official endorsement or approval by the United States Department of Agriculture or the Agricultural Research Service of any product or service to the exclusion of others that may be suitable. USDA is an equal opportunity provider and employer.
Abstract
Ammonia can form naturally from organic matter mineralization or can enter the aquatic environment via anthropogenic sources such as municipal effluent discharge and agricultural runoff. The presence of ammonia (NH3) vs. ammonium (NH4+) in water depends on water pH and temperature. The un-ionized NH3 form is toxic to aquatic organisms, and both forms (NH4+ and NH3) can contribute to eutrophication and hypoxia of surface waters. The reported measurement of ammonia in water is typically the total ammonia N (TAN = NH3 + NH4+). The recommended techniques for measuring NH3 in water are the colorimetric salicylate and phenate methods, whereby an indophenol color complex is proportional to the NH3 concentration of the sample.
Safety warnings
Follow appropriate safety, health, and environmental precautions based on the selected methods, instrumentation, and workflow. Laboratory supervisors are responsible for knowledge of these precautions and their implementation.
Sample collection and filtration
Sample collection and filtration
Return samples to the laboratory TemperatureOn ice and filter them on collection day if possible.

Filter samples through a 0.45 micrometer (µm) pore-size filter to minimize interference from particulates before chemical analysis.

Note
  • Filters can be either membrane or glass fiber.
  • Occasional checks of filter blanks by filtering deionized water with the same equipment are always prudent.
  • Ammonia is particularly prone to air contamination outdoors or in a lab.

As samples collected and stored in an autosampler are vulnerable to ammonia loss by volatilization and nitrification, ideally, pre-acidify the samples to pH < 2 (H2SO4) and retrieve from the field within seven days of autosampler collection.

Note
Ammonia concentrations can change if samples are left in ambient conditions too long, regardless of autosampler refrigeration (Burke et al. 2002).

If pre-acidification is not possible, retrieve the samples as soon as possible and transport them back to the laboratory TemperatureOn ice .

Sample storage and preservation
Sample storage and preservation
1d
1d
As soon as possible after sample collection, filter the water samples through a 0.45 µm pore-size filter to minimize interference from particulates.
Analyze samples within 24 hours after collection.

Analyze
To store samples not pre-acidified in the field, preserve the samples with sulfuric acid to pH < 2, cool them at Temperature4 °C , and hold them for up to 28 days (US EPA, 1993).

Preserve the samples that are not acidified by freezing to minimize ammonia loss by volatilization.
Archiving
Archiving
Store the water samples for NH3 analysis until data certification (QA/QC verification).

Note
The storage of preserved water samples should not exceed 28 days.

Sample analysis
Sample analysis
Direct determination of NH3-N without distillation is possible for water samples with low NH3-N concentrations.


Samples with high NH3-N concentrations (> 5 mg-N/L) may need to be distilled before analysis to minimize interferences and improve precision (APHA, 2005).


The colorimetric determination of ammonia in water is carried out using the salicylate or phenate method.

Note
Several automated colorimetric procedures are available from the US EPA and USGS National Water Quality Laboratory (NWQL).

Salicylate method : Heat the sample with salicylate and hypochlorite in an alkaline phosphate buffer in the presence of sodium nitroprusside (catalyst). The reaction produces an emerald-green indophenol dye proportional to the NH3 concentration of the sample.

Note
The salicylate method has become popular primarily because it is much less toxic and less sensitive to changes in pH.

Phenate method : In this method NH3 reacts with alkaline phenol and sodium hypochlorite in the presence of sodium nitroprusside to enhance sensitivity. The indophenol blue dye is proportional to the NH3 concentration of the sample.

Note
The EPA accepts the phenate method for regulatory monitoring (USEPA, 1993).

Covariate metrics to be sampled concurrently
Covariate metrics to be sampled concurrently
Dissolved NO3- concentration, total dissolved N (TDN), total dissolved P (TDP), and total suspended solids (TSS). These metrics are described in the following protocols:

  • USDA LTAR Common Experiment measurement: Dissolved nitrate (NO3-) concentration
  • USDA LTAR Common Experiment measurement: Total nitrogen (TN) and total dissolved nitrogen (TDN) concentration
  • USDA LTAR Common Experiment measurement: Total phosphorus (TP) and total dissolved phosphorus (TDP) concentration
  • USDA LTAR Common Experiment measurement: Total suspended solids (TSS)
Calculations
Calculations
Prepare a calibration curve by plotting the blank-corrected area of each standard peak against its respective NH3-N concentration.
Compute the NH3-N concentration in the sample by comparing the sample peak area to the calibration curve. Report the concentration as mg NH3-N/L.
Recommendations for data collection
Recommendations for data collection
Table 1. Summary of recommendations for the collection and measurement of dissolved NH3-N concentration.

ABCD
AttributePreferredMinimumComments
Spatial scaleFieldPlot
FrequencyEvent-drivenEvent-drivenMore frequent (weekly) measurements can be preferential when the flow regime can increase seasonally or after precipitation events. Sampling in this protocol should be event-driven to enable cross-site comparisons.
Covariate metricsNO3-N, TDN, TDP, TSSNO3-N, TDN, TDP
Sample preservation and storageFilter with a 0.45 μm pore-size filter (membrane or glass fiber), refrigerate and analyze within 24 hoursFilter with a 0.45 μm pore-size filter (membrane or glass fiber), refrigerate, acidify to pH < 2 as soon as possible, store at 4°C, and analyze within 28 daysOmit sample acidification if dissolved organic matter (DOM) analyses are performed. Alternatively, use a 0.7 μm GF/F. Use a 0.2 μm pore-size filter to exclude bacteria from samples but at much slower flow rates.
Sample analysisColorimetric salicylate methodColorimetric phenate method
Water quantityDischarge or flow rate Discharge or flow rateCalculate NH3-N loads by linking this metric to the water quantity metric “flow”
Covariate metrics = other metrics to sample concurrently. NO3--N = nitrate-N; TDN = total dissolved N; TDP = total dissolved phosphorus; TSS = total suspended solids

Protocol references
American Public Health Association (APHA), (2005). Standard Methods for the Examination of Water and Wastewater, 21st ed. Washington, DC: American Public Health Association, American Water Works Association, and Water Environment Federation.

Burke PM, Hill S, Iricanin N, Douglas C, Essex P, Tharin D, (2002). Evaluation of preservation methods for nutrient species collected by automatic samplers. Environmental Monitoring and Assessment 80: 149-173.

Dalzell, B. & Pisani, O. (2024). USDA LTAR Common Experiment measurement: Total suspended solids (TSS). protocols.io dx.doi.org/10.17504/protocols.io.261ge5pjog47/v2
Hamilton, S. K., Pisani, O., Kovar, J. L., Malone, R. W., Morrow, A. J., & Cole, K. J. (2024). USDA LTAR Common Experiment measurement: Total phosphorus (TP) and total dissolved phosphorus (TDP) concentration. protocols.io dx.doi.org/10.17504/protocols.io.8epv5r7m6g1b/v1

Lizotte, R., Pisani, O., Veum, K. S., Kovar, J. L., Malone, R. W., & Cole, K. J. (2024). USDA LTAR Common Experiment measurement: Dissolved nitrate (NO3-) concentration. protocols.io
Malone, R. W., Morrow, A. J., Pisani, O., Kovar, J. L., Hamilton, S. K., & Cole, K. J. (2024). USDA LTAR Common Experiment measurement: Total nitrogen (TN) and total dissolved nitrogen (TDN) concentration. protocols.io dx.doi.org/10.17504/protocols.io.5jyl82rkrl2w/v1

US Environmental Protection Agency (US EPA), (1993). Method 350.1, Revision 2.0: Determination of Ammonia Nitrogen by Semi-Automated Colorimetry.