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New light on a dark subject: On the use of fluorescence data to deduce redox states of natural organic matter (NOM)

Aquatic Sciences

By:
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DOI: 10.1007/s00027-009-9174-6

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Abstract

This paper reports the use of excitation-emission matrix fluorescence spectroscopy (EEMS), parallel factor statistical analysis (PARAFAC), and oxidation-reduction experiments to examine the effect of redox conditions on PARAFAC model results for aqueous samples rich in natural organic matter. Fifty-four aqueous samples from 11 different geographic locations and two plant extracts were analyzed untreated and after chemical treatments or irradiation were used in attempts to change the redox status of the natural organic matter. The EEMS spectra were generated and modeled using a PARAFAC package developed by Cory and McKnight (2005). The PARAFAC model output was examined for consistency with previously reported relations and with changes expected to occur upon experimental oxidation and reduction of aqueous samples. Results indicate the implied fraction of total sample fluorescence attributed to quinone-like moieties was consistent (0.64 to 0.78) and greater than that observed by Cory and McKnight (2005). The fraction of the quinone-like moieties that was reduced (the reducing index, RI) showed relatively little variation (0.46 to 0.71) despite attempts to alter the redox status of the natural organic matter. The RI changed little after reducing samples using zinc metal, oxidizing at high pH with air, or irradiating with a Xenon lamp. Our results, however, are consistent with the correlations between the fluorescence indices (FI) of samples and the ratio of PARAFAC fitting parameters suggested by Cory and McKnight (2005), though we used samples with a much narrower range of FI values.

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
New light on a dark subject: On the use of fluorescence data to deduce redox states of natural organic matter (NOM)
Series title:
Aquatic Sciences
DOI:
10.1007/s00027-009-9174-6
Volume
71
Issue:
2
Year Published:
2009
Language:
English
Publisher:
Springer
Publisher location:
Amsterdam, Netherlands
Contributing office(s):
Colorado Water Science Center
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
Larger Work Title:
Aquatic Sciences
First page:
135
Last page:
143
Number of Pages:
9