Natural Organic Matter and Humic Substances Interactions

4. Conclusions
15th IHSS Meeting- Vol. 3
This study examined the differential absorbance spectra of metal complexation with
Suwannee River fulvic acid. While absorbance spectra show a very subtle change in intensity
with increasing metal concentrations, they retain their characteristic featureless shape
throughout the titrations. Differential absorbance spectra, on the other hand, show a number
of features that are not present in the traditionally interpreted absorbance spectra. These
features can be analyzed to reveal information about the nature of complexation-active
chromophores in NOM. The differential absorbance spectra of SRFA can be successfully
correlated to bound metal concentrations calculated based on the NICA-Donnan model
theory. This study demonstrates that differential absorbance spectroscopy is a useful method
to examine in situ the complexation behaviour of NOM. DAS can potentially provide detailed
information about the emergence and contribution of different complexation-active functional
groups and has the potential to elucidate the presence of functionalities which may not be
detectable in traditional potentiometric experiments. In principle, this technique could allow
the obtainment of detailed in situ information about NOM chemistry and reactivity caused by
a wide variety of environmental and water treatment processes.
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