Luminescence quenching of dissolved organic matter in seawater

• Published in: Marine chemistry 1989, Vol.27 (3), p.147-164
• Main Authors: Milne, Peter J, Zika, Rod G
• Format: Article
• Language: English
• Subjects: Earth sciences; Earth, ocean, space; Exact sciences and technology; Isotope geochemistry; Isotope geochemistry. Geochronology; Marine
• ISSN: 0304-4203; 1872-7581
• DOI: 10.1016/0304-4203(89)90045-5

To characterize more fully the nature of the fluorophores present in the dissolved organic matter found in seawater, steady state and time-resolved measurements of the luminescence quenching of a number of samples of marine dissolved organic matter with known quenchers, such as iodide, acrylamide and methyl viologen (MV) (1,1′-dimethyl-4,4′-bipyridinium), were compared. Quenching characteristics of these systems were analyzed using Stern-Volmer plots for both intensity and lifetime measurements. The bimolecular quenching constants, κ q, for these quenchers were found to decrease in the order MV 2+ (κ q ∼ 10 10M −1s −1) > I − ( κ q ∼ 2 × 10 9 M −1 s −1) >CH 2CHCONH 2 ( κ q ∼ 2 × 10 8 M −1 s −1) for the samples measured. The results also show that different samples are quenched to differing extents by the quenchers studied, that ionic strength alters the quenching constants, and that both static and diffusional quenching mechanisms may operate. Such studies are appropriate to the quantification of the reactivity of the singlet states of the chromophores found within marine dissolved organic matter. Although excess energy of the singlet state may be readily transferred to another chemical species, the combination of competing physical deactivation paths and the low concentrations of efficient quenches in the oceans serves to lessen the direct chemical impact of this process.