Sunlight-Induced Electron Ejection in Natural Waters

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ABSTRACTOCE-0099027Although geochemists know that sunlight-induced photochemical reactions involving dissolved colored organic matter (CDOM) are ubiquitous in natural waters everywhere, observational difficulties have dictated that the detailed study of the underlying reaction mechanisms has been largely confined to the laboratory. The two principal laboratory techniques -- laser flash photolysis (LFP) and steady-state probes (SS-P) used to trigger photolysis imply reactions such asCDOM + hn @ CDOM+ + eaq-where hn represents a photon impinging upon a reactive site in the CDOM molecular structure, and eaq- is a hydrated electron ejected into solution as a consequence. However, investigators have been puzzled that LFP is significantly more efficient that SS-P in hydrated electron production. LFP is an important tool for photochemical research, so it is important to understand the discrepancy.In this project, researchers at the Woods Hole Oceanographic Institution, Brandeis University, and the University of Maryland combine efforts to re-evaluate the key reaction (above) by comparing LFP and SS-P data for samples from fresh and estuarine waters. The comparative studies would be calibrated using compounds with well-characterized photochemical properties, The focus would then shift to detailed comparative studies of estuarine and terrestrial CDOM fractions. If possible, unprocessed water samples would also be examined.