A Multi-Pumping Flow System for In Situ Measurements of Dissolved Manganese in Aquatic Systems

• Main Authors: David Meyer, Ralf D. Prien, Olaf Dellwig, Joanna J. Waniek, Ingo Schuffenhauer, Jan Donath, Siegfried Krüger, Malte Pallentin, Detlef E. Schulz-Bull
• Format: Article
• Language: English
• Published: MDPI AG 2016-11-01
• Series: Sensors
• Subjects: manganese; in situ; multi-pumping flow system; sea water; redoxcline; Baltic Sea
• Online Access: http://www.mdpi.com/1424-8220/16/12/2027

A METals In Situ analyzer (METIS) has been used to determine dissolved manganese (II) concentrations in the subhalocline waters of the Gotland Deep (central Baltic Sea). High-resolution in situ measurements of total dissolved Mn were obtained in near real-time by spectrophotometry using 1-(2-pyridylazo)-2-naphthol (PAN). PAN is a complexing agent of dissolved Mn and forms a wine-red complex with a maximum absorbance at a wavelength of 562 nm. Results are presented together with ancillary temperature, salinity, and dissolved O 2 data. Lab calibration of the analyzer was performed in a pressure testing tank. A detection limit of 77 nM was obtained. For validation purposes, discrete water samples were taken by using a pump-CTD system. Dissolved Mn in these samples was determined by an independent laboratory based method (inductively coupled plasma–optical emission spectrometry, ICP-OES). Mn measurements from both METIS and ICP-OES analysis were in good agreement. The results showed that the in situ analysis of dissolved Mn is a powerful technique reducing dependencies on heavy and expensive equipment (pump-CTD system, ICP-OES) and is also cost and time effective.