Aquatic Sciences Meeting, Albuquerque 2001

PC15 Photochemistry

Date: Thursday, February 15, 2001

Location: Southwest Hall

Osburn, C, L, NRC-Naval Research Laboratory, Washington, DC, USA, cosburn@ccs.nrl.navy.mil

Pohlman, J, P, Geocenters, Inc.-Naval Research Laboratory, Washington, DC, USA, johnp@ccs.nrl.navy.mil

Boyd, T, J, EQS-Naval Research Laboratory, Washington, DC, USA, tboyd@ccf.nrl.navy.mil

Morris, D, P, Lehigh University, Bethlehem, PA, USA, dpm2@lehigh.edu

Coffin, R, B, EQS-Naval Research Laboratory, Washington, DC, USA, rcoffin@ccf.nrl.navy.mil

MOLECULAR AND OPTICAL CHANGES IN DISSOLVED ORGANIC MATTER FROM EXPOSURE TO ULTRAVIOLET RADIATION

A previous study of solar photochemical oxidation of humic freshwater dissolved organic matter (DOM) from a Sphagnum bog showed a 47% loss of aromatic C, a 15% loss of dissolved organic C (DOC) concentration, and a 1‰ increase in d13C. However, a 30% loss of dissolved UV absorbance (a_d) was observed, suggesting that molecular changes in DOM chemistry may not directly correlate with optical changes in its chromophoric (CDOM) component after exposure to ultraviolet radiation (UVR). Our current study investigates changes in DOC concentration, dissolved inorganic carbon (DIC) concentration, a_d, and stable isotopes using both sunlight and lamp exposures that will provide new insight into the relationship between CDOM photobleaching and DOC photooxidation. Samples of DOM isolated from river, estuarine, and marine locations in the Chesapeake Bay watershed combined with freshwater bog and lake DOM data will provide a comprehensive analysis of DOM chemical and optical photoreactivity. A laboratory exposure system is described that allows for the simultaneous collection of discrete samples for both DOC and DIC concentration and stable carbon isotope analysis, in addition to a_d.

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Aquatic Sciences Meeting, Albuquerque 2001

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