USGS-OWQ: TM1-D5 Sensor Selection:  Optical nitrate sensor selection

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Official Method Name
 Optical Techniques for the Determination of Nitrate in Environmental Waters: Guidelines for Instrument Selection, Operation, Deployment, Maintenance, Quality Assurance, and Data Reporting
Current Revision
2013
Media
 WATER
Instrumentation
 UV-Fluorescence
Method Subcategory
 Sampling/Preparation
Method Source
  USGS-OWQ
Citation
  Optical Techniques for the Determination of Nitrate in Environmental Waters: Guidelines for Instrument Selection, Operation, Deployment, Maintenance, Quality Assurance, and Data Reporting
Brief Method Summary
 A number of factors come into play when selecting the appropriate UV nitrate sensor for use in field settings. Individual sensor selection can be determined by the expected range of environmental conditions, data-quality specifications, and logistical constraints. Differences in sensor design, such as path lengths and the wavelengths measured, are critical features that affect data quality and, consequently, are important to be considered along with the depth rating, temperature rating, and maintenance requirements.
Scope and Application
 Key questions to consider when selecting a UV nitrate sensor for field deployment include the following:
1. What is the expected range of environmental conditions at the site?
  • What are the expected ranges in concentration of interfering constituents, including suspended sediment, dissolved organic matter, and bromide?
  • What are the expected ranges of temperature and maximum depth where the instrument will be deployed?
  • What is the expected level of biological or mineral fouling?

2. What are the data specifications for nitrate concentrations at the site?
  • What is the expected range in nitrate concentrations?
  • What accuracy, precision, and detection limit are needed, given the study goals?
  • What is the optimal sampling interval, and how many measurements are needed, per interval, to achieve study goals?

3. What are the site requirements and logistical considerations?
  • Will instruments be accessible by land or by boat?
  • Will the instruments be accessible across the range of hydrologic and weather conditions expected for the site (including ice cover)?
  • Does the site have existing infrastructure, power, and communication systems?
  • What is the anticipated frequency of site visits?
  • What level of technical expertise is available to manage the instruments?
Applicable Concentration Range
Interferences
Quality Control Requirements
Sample Handling
Maximum Holding Time
Relative Cost
 Unknown
Sample Preparation Methods
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