Chromophoric dissolved organic matter (CDOM) is found ubiquitously in aquatic environments where its plays a central role, both through its impact on the aquatic light field and its photochemical reactions. Two researchers from the University of Maryland-College Park have proposed that optical absorption and emission properties of CDOM arise in part from intramolecular charge transfer interactions between hydroxy-aromatic donors and quinoid acceptors formed by the partial oxidation of soluble lignin precursors (i.e., charge transfer model). The scientists propose that the charge transfer model can largely explain the diverse suite of photochemical reactions attributed to this material and plan to test the hypothesis using a series of photochemical and photophysical measurements including the following: 1) the dependence of H2O2 quantum yields on O2 concentration and its associated wavelength dependence; 2) the dependence of the oxidation rates of selected (phenol) donors on both O2 concentration and donor concentration, as well as the associated wavelength dependencies; 3) the dependence of 1O2 yields on O2 concentrations; and 4) the wavelength dependence of emission quantum yields and lifetimes. The complete suite of measurements will be performed on one standard (Suwanee River fulvic acid) and three well-characterized aquatic humic substances (HS) collected on prior field work from oligotrophic, shelf and estuarine waters. The spectral dependence of the H2O2 yields on O2 concentration for 0.2 M-filtered, whole water samples will be compared to that of the HS samples to quantify the extent to which the properties of the HS samples reflect those of the original waters from which they were obtained. Further tests examining the impact of potentially key parameters such as pH, salinity, and metal ion content will also be conducted.

As regards broader impacts, one post doc and one graduate student will be supported and trained as part of this project. It is anticipated that undergraduate students will also participate in this study and learn about state of the art photochemical and photophysical methods.

Agency
National Science Foundation (NSF)
Institute
Division of Ocean Sciences (OCE)
Type
Standard Grant (Standard)
Application #
0648414
Program Officer
Donald L. Rice
Project Start
Project End
Budget Start
2007-03-01
Budget End
2011-02-28
Support Year
Fiscal Year
2006
Total Cost
$482,540
Indirect Cost
Name
University of Maryland College Park
Department
Type
DUNS #
City
College Park
State
MD
Country
United States
Zip Code
20742