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pH and Alkalinity Analyser Description

The pH analysis system adds an acid-base indicator dye to a seawater sample. The indicator dye’s optical extinction coefficient changes with the acidity of the water sample which can be measured with a spectrometer. No drift occurs and no calibration in the field is needed if temperature and salinity are known accurately. The total alkalinity is determined with a tracer-monitored titration with a strong acid. The tracer bromocresol green allows to measure the concentration of the acid and therefore to calculate the alkalinity.


Process scheme of the alkalinity sensor.

pH and Alkalinity Analyser Typical Result

Seasonal Alkalinity of the North Sea Regular FerryBox transects between Cuxhaven and Immingham in 2017 show that the highest alkalinity occurs in the German Bight from June to October. This is probably due to alkalinity production in the summer months in the adjacent Wadden Sea and tidal transport into the North Sea. During this time, the oceanic bu¿er capacity and the uptake of atmospheric CO2 is increased


Time series of alkalinity, measured from a FerryBox (Immingham - Cuxhaven).

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