Zielinski, Oliver and Rüssmeier, Nick and Ferdinand, Oliver D. and Miranda, Mario L. and Wollschläger, Jochen
(2018)
Assessing fluorescent organic matter in natural waters: towards in situ excitation–emission matrix spectroscopy.
Applied Sciences, 8 (12).
p. 2685.
ISSN 2076-3417
Abstract
Natural organic matter (NOM) is a key parameter in aquatic biogeochemical processes.
Part of the NOM pool exhibits optical properties, namely absorption and fluorescence. The latter is
frequently utilized in laboratory measurements of its dissolved fraction (fluorescent dissolved organic
matter, FDOM) through excitation–emission matrix spectroscopy (EEMS). We present the design and
field application of a novel EEMS sensor system applicable in situ, the ‘Kallemeter’. Observations
are based on a field campaign, starting in Norwegian coastal waters entering the Trondheimsfjord.
Comparison against the bulk fluorescence of two commercial FDOM sensors exhibited a good
correspondence of the different methods and the ability to resolve gradients and dynamics along the
transect. Complementary laboratory EEM spectra measurements of surface water samples and their
subsequent PARAFAC analysis revealed three dominant components while the ‘Kallemeter’ EEMS
sensor system was able to produce reasonable EEM spectra in high DOM concentrated water bodies,
yet high noise levels must be addressed in order to provide comparable PARAFAC components.
Achievements and limitations of this proof-of-concept are discussed providing guidance towards full
in situ EEMS measurements to resolve rapid changes and processes in natural waters based on the
assessment of spectral properties. Their combination with multiwavelength FDOM sensors onboard
autonomous platforms will enhance our capacities in observing biogeochemical processes in the
marine environment in spatiotemporal and spectral dimensions.
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