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| Titel |
An autonomous spectrophotometric system for high resolution measurement of seawater pH |
| VerfasserIn |
E. R. Reggiani, R. G. J. Bellerby |
| Konferenz |
EGU General Assembly 2012
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 14 (2012) |
| Datensatznummer |
250060328
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| Zusammenfassung |
| The increase in carbon dioxide (CO2) concentration in the ocean is a growing concern and is
undergoing considerable research. A comprehensive monitoring of the carbonate system in
seawater is essential to understand ocean acidification and modification to oceanic carbon
transport and the ocean’s atmospheric CO2 uptake. Providing calibration and drift-free
measurements, spectrophotometric detection of pH, with the monitoring of one of the other
“major” carbonate variables (pCO2, total alkalnity, dissolved inorganic carbon) allows the
determination of the entire carbonate system speciation with the uncertainty required to
detect long-term oceanic acidification. Stability, reliability and robustness are the critical
features when in-situ long-term deployment is required. We have developed a method that
makes use of a high-resolution low noise miniature spectrophotometer and a combined low
power LED source, an optimal absorbance detection is achieved in a custom designed
bubble-free cuvette with a sample volume of 6 ml, limiting indicator perturbations within the
on-line precision of the instrument, currently evaluated at 0,0005 pH units and
achieving the adequate uncertainty for systematic shifts evaluation. The system operates
unattended with a sampling frequency up to 2 samples per minute and the actual
temperature of the sample is monitored, not controlled, thus reducing power consumption.
With its portability, the system is ideally suitable for both underway operation on
ships of opportunity and for discrete sample analysis in remote research campaigns. |
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