Difference between revisions of "Nutrient analysers"
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| + | This article discusses two types of analysers to measure nutrients: a wet chemical analyser and an optical nitrate analyser. A nutrient analyser is an example of an [[oceanographic instrument]] to measure the concentration of certain nutrients (e.g. nitrate, nitrite, ammonia, phosphate and silicate) [[in situ]]. | ||
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==Introduction== | ==Introduction== | ||
Nutrient analysers are [[oceanographic instruments]] to measure the concentration of certain nutrients [[in situ]]. While most measurements of nutrients are still made by taking water samples for later analysis in the lab a variety of [[in situ]] instruments has become available that automatically measure nutrient concentrations at pre-programmed intervals. These instruments allow a much higher temporal resolution of measurements than what can be achieved by taking samples. | Nutrient analysers are [[oceanographic instruments]] to measure the concentration of certain nutrients [[in situ]]. While most measurements of nutrients are still made by taking water samples for later analysis in the lab a variety of [[in situ]] instruments has become available that automatically measure nutrient concentrations at pre-programmed intervals. These instruments allow a much higher temporal resolution of measurements than what can be achieved by taking samples. | ||
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Parameters limiting the deployment time of wet-chemical analysers are reagent consumption, reagent degradation time, available electrical energy (batteries) and [[biofouling]]. | Parameters limiting the deployment time of wet-chemical analysers are reagent consumption, reagent degradation time, available electrical energy (batteries) and [[biofouling]]. | ||
| − | A distinct advantage of wet-chemical analysers is the capability of conducting in situ calibrations by piping a blank or standard solution of known concentration into the analyser instead of the sample. Any instrument drift can be detected and the measurements corrected for the drift. | + | A distinct advantage of wet-chemical analysers is the capability of conducting [[in situ]] calibrations by piping a blank or standard solution of known concentration into the analyser instead of the sample. Any instrument drift can be detected and the measurements corrected for the drift. |
| − | Nutrients that can be measured in situ include dissolved nitrate, nitrite, ammonia, phosphate and silicate (see links to companies below for details). | + | Nutrients that can be measured [[in situ]] include dissolved nitrate, nitrite, ammonia, phosphate and silicate (see "external links" to companies below for details). |
==Optical nitrate analysers== | ==Optical nitrate analysers== | ||
| − | Optical nitrate analysers use the property of dissolved nitrate that it absorbs ultraviolet light. The instrument consists of a light source (deuterium lamp of flash lamp), collimating optics, a light path through the sample water and a spectrometer with photodetector. The resulting absorption spectra have to be analysed (either by an on-board computer or after data recovery) as other constituents in the seawater also absorb ultraviolet light. (For details see Johnson & Colleti (2002)) | + | Optical nitrate analysers use the property of dissolved nitrate that it absorbs ultraviolet light. The instrument consists of a light source (deuterium lamp of flash lamp), collimating optics, a light path through the sample water and a spectrometer with photodetector. The resulting absorption spectra have to be analysed (either by an on-board computer or after data recovery) as other constituents in the seawater also absorb ultraviolet light. (For details see Johnson & Colleti (2002<ref>Johnson, K.S., Coletti, L.J., 2002. In situ ultraviolet spectrophotometry for high resolution and long-term monitoring of nitrate, bromide and bisulfide in the ocean. Deep-Sea Research I 49, 1291-1305.</ref>)) |
Optical nitrate analysers do not require any chemical reagents and have a very fast response (on the order of 1 s) and therefore are also suitable for measurements during profiling work, on towed vehicles and AUV's. The detection limits depend on the length of the optical absorption path, generally these instruments are not well suited for low nitrate concentrations (< 1 umol). | Optical nitrate analysers do not require any chemical reagents and have a very fast response (on the order of 1 s) and therefore are also suitable for measurements during profiling work, on towed vehicles and AUV's. The detection limits depend on the length of the optical absorption path, generally these instruments are not well suited for low nitrate concentrations (< 1 umol). | ||
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The deployment time of the optical instruments is limited by available electrical energy (batteries) and [[biofouling]] (though for some instruments anti-biofouling measures can be added). | The deployment time of the optical instruments is limited by available electrical energy (batteries) and [[biofouling]] (though for some instruments anti-biofouling measures can be added). | ||
| − | == | + | ==See also== |
| − | * | + | ===Internal links=== |
| − | * | + | * [[Instruments and sensors to measure environmental parameters]] |
| − | + | * [[Light fields and optics in coastal waters]] | |
| − | + | ||
| − | ==External | + | ===External links=== |
*[http://www.satlantic.com/default.asp?mn=1.15.25.34 Satlantic] Optical nitrate analysers, water quality monitor. Accessed 14.5.2007 | *[http://www.satlantic.com/default.asp?mn=1.15.25.34 Satlantic] Optical nitrate analysers, water quality monitor. Accessed 14.5.2007 | ||
*[http://www.trios.de/__science/uk/index.html TriOS Optical Sensors] Optical nitrate analysers. Accessed 14.5.2007 | *[http://www.trios.de/__science/uk/index.html TriOS Optical Sensors] Optical nitrate analysers. Accessed 14.5.2007 | ||
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*[http://www.act-us.info/ Alliance for Coastal Technologies], database of instruments for studying and monitoring of the coastal environment, technology evaluations, needs & use assessments. Accessed 14.5.2007 | *[http://www.act-us.info/ Alliance for Coastal Technologies], database of instruments for studying and monitoring of the coastal environment, technology evaluations, needs & use assessments. Accessed 14.5.2007 | ||
| + | ===Further reading=== | ||
| + | * Grasshoff, K., Kremling, K., Erhardt, M. (eds.) (1999), Methods of Seawater Analysis, Wiley-VCH, 600 pp., ISBN: 978-3527295890 | ||
| + | * Hanson, A.K., Donaghay, P.L., 1998. Micro- to fine-scale chemical gradients and layers in stratified coastal waters. Oceanography, 11(1), 10-17. | ||
| + | * Johnson, K.S., J.A. Needoba, S.C. Riser, W.J. Showers, 2007. Chemical Sensor Networks for the Aquatic Environment, Chem. Rev., 107, 623-640. | ||
| + | |||
| + | ==References== | ||
| + | <references/> | ||
| + | |||
| + | {{author | ||
| + | |AuthorID=5068 | ||
| + | |AuthorName=Schroeder, Friedhelm | ||
| + | |AuthorFullName=Schroeder, Friedhelm}} | ||
| + | |||
| + | {{author | ||
| + | |AuthorID=12968 | ||
| + | |AuthorName= Prien, Ralf | ||
| + | |AuthorFullName=Prien, Ralf}} | ||
| + | |||
| + | [[Category:Theme 9]] | ||
[[Category:Evaluation and assesment in coastal management]] | [[Category:Evaluation and assesment in coastal management]] | ||
[[Category:Techniques and methods in coastal management]] | [[Category:Techniques and methods in coastal management]] | ||
| − | [[Category: | + | [[Category:Hydrological processes and water]] |
Revision as of 15:54, 28 November 2007
This article discusses two types of analysers to measure nutrients: a wet chemical analyser and an optical nitrate analyser. A nutrient analyser is an example of an oceanographic instrument to measure the concentration of certain nutrients (e.g. nitrate, nitrite, ammonia, phosphate and silicate) in situ.
Contents
Introduction
Nutrient analysers are oceanographic instruments to measure the concentration of certain nutrients in situ. While most measurements of nutrients are still made by taking water samples for later analysis in the lab a variety of in situ instruments has become available that automatically measure nutrient concentrations at pre-programmed intervals. These instruments allow a much higher temporal resolution of measurements than what can be achieved by taking samples.
Most of the nutrient analysers are based on proven wet-chemical laboratory analysis methods. In recent years nitrate analysers based on the absorbance of ultraviolet light by nitrate in water have been introduced.
Wet chemical analysers
A variety of wet chemical nutrient analysers exist on the market. These analysers draw in sample water and mix it with a reagent (or reagents). The resulting solution develops a characteristic property (e.g. colour complex or fluorescence) depending on the concentration of the target analyte, that is then measured in an absorption cell (colour complex) or by a light source and photodetector (fluorescence). In some cases heating of the solution is required to speed up development.
Depending on the chemical protocols followed (i.e. if heating and/or preconcentration steps are needed), the time response (time between independent measurements) is on the order of a few seconds to minutes.
Parameters limiting the deployment time of wet-chemical analysers are reagent consumption, reagent degradation time, available electrical energy (batteries) and biofouling.
A distinct advantage of wet-chemical analysers is the capability of conducting in situ calibrations by piping a blank or standard solution of known concentration into the analyser instead of the sample. Any instrument drift can be detected and the measurements corrected for the drift.
Nutrients that can be measured in situ include dissolved nitrate, nitrite, ammonia, phosphate and silicate (see "external links" to companies below for details).
Optical nitrate analysers
Optical nitrate analysers use the property of dissolved nitrate that it absorbs ultraviolet light. The instrument consists of a light source (deuterium lamp of flash lamp), collimating optics, a light path through the sample water and a spectrometer with photodetector. The resulting absorption spectra have to be analysed (either by an on-board computer or after data recovery) as other constituents in the seawater also absorb ultraviolet light. (For details see Johnson & Colleti (2002[1]))
Optical nitrate analysers do not require any chemical reagents and have a very fast response (on the order of 1 s) and therefore are also suitable for measurements during profiling work, on towed vehicles and AUV's. The detection limits depend on the length of the optical absorption path, generally these instruments are not well suited for low nitrate concentrations (< 1 umol).
The deployment time of the optical instruments is limited by available electrical energy (batteries) and biofouling (though for some instruments anti-biofouling measures can be added).
See also
Internal links
- Instruments and sensors to measure environmental parameters
- Light fields and optics in coastal waters
External links
- Satlantic Optical nitrate analysers, water quality monitor. Accessed 14.5.2007
- TriOS Optical Sensors Optical nitrate analysers. Accessed 14.5.2007
- Systea S.p.a., wet chemical nutrient analysers. Accessed 14.5.2007
- SubChem Systems Inc., submersible chemical analysers for nutrients, trace metals. Accessed 14.5.2007
- YSI Inc., nutrient analysers. Accessed 14.5.2007
- EnviroTech LLC, nutrient analysers. Accessed 14.5.2007
- Alliance for Coastal Technologies, database of instruments for studying and monitoring of the coastal environment, technology evaluations, needs & use assessments. Accessed 14.5.2007
Further reading
- Grasshoff, K., Kremling, K., Erhardt, M. (eds.) (1999), Methods of Seawater Analysis, Wiley-VCH, 600 pp., ISBN: 978-3527295890
- Hanson, A.K., Donaghay, P.L., 1998. Micro- to fine-scale chemical gradients and layers in stratified coastal waters. Oceanography, 11(1), 10-17.
- Johnson, K.S., J.A. Needoba, S.C. Riser, W.J. Showers, 2007. Chemical Sensor Networks for the Aquatic Environment, Chem. Rev., 107, 623-640.
References
- ↑ Johnson, K.S., Coletti, L.J., 2002. In situ ultraviolet spectrophotometry for high resolution and long-term monitoring of nitrate, bromide and bisulfide in the ocean. Deep-Sea Research I 49, 1291-1305.
Please note that others may also have edited the contents of this article.
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Please note that others may also have edited the contents of this article.
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