Environmental Engineering Reference
In-Depth Information
at peak A- and T
UV
-regions. The latter fluorescent compounds are occasionally una-
ble to undergo photoinduced decomposition, particularly the fluorophores at the T
UV
-
region (Mostofa et al.
2010
).
A review by Leenheer and Croué (
2003
) includes the comparison between
the fluorescence properties of various fluorophores within natural organic matter
(NOM). Another review by Hudson et al. (
2007
) focuses on the effect of metal
ions on DOM fluorescence and photodegradation, and on the application of DOM
fluorescence in natural waters. A recent review by Coble (
2007
) covers the topic
of marine optical biogeochemistry and discusses the chemical properties and the
sinks of chromophoric or colored dissolved organic matter (CDOM), as well as
its fluorescence characteristics. Another review covers the application of fluores-
cence to the identification and monitoring of sewerage-derived DOM and to the
impact of treatment processes on fluorescence. It provides useful information on
how fluorescence could be a potential tool for recycled water systems (Henderson
et al.
2009
). Finally, another review summarizes the fluorescence properties of
various organic components. From field observations in natural waters and the
use of standards, it can be derived that all the fluorescent components in DOM
can be grouped in four regions: peak C-region (280-400/380-550 nm), peak
A-region (220-280/380-550 nm), peak T-region (260-285/290-380 nm), and peak
T
UV
-region (215-260/280-380 nm) (Mostofa et al.
2009a
).
This chapter will provide a general overview on the fluorophores, on the fluo-
rescence properties of key organic substances in combination with their molecular
characteristics, and on PARAFAC modeling to identify the fluorescent compo-
nents. This paper will deal with the identification of autochthonous DOM, and in
particular of autochthonous fulvic acids of algal or phytoplankton origin. It will be
discussed how these autochthonous fluorescent components differ from allochtho-
nous fulvic and humic acids. This review will extensively discuss the key factors
that significantly affect the fluorescence properties of FDOM. It will also address
the photoinduced and microbial FDOM degradation as well as the mechanisms,
the controlling factors and their significance to understand the biogeochemical
FDOM activity in freshwater and marine environments. Finally, a comparison will
be provided of the relative importance of studying FDOM versus CDOM absorb-
ance, as well as how fluorophores in FDOM differ from chromophores in CDOM.
2 Principle of Fluorescence (Excitation-Emission Matrix)
Spectroscopy
Fluorescence (excitation-emission matrix, EEM) spectroscopy (EEMS) gives
a three-dimensional image of an aqueous solution that is measured for the flu-
orescence intensity of the fluorophores as a function of the excitation and emis-
sion wavelengths. EEM spectra are a combination of multiple emission spectra
at a range of excitations. EEMS finds wide applications due to its precise, quick
and relatively simple characterization of DOM fractions in natural waters. The
