HR: 0800h
AN: A51B-03    [Abstracts]
TI: Effects of Solar Radiation on the Optical Quality of Dissolved Organic Material in a Tidal Marsh Estuarine Ecosystem
AU: * Tzortziou, M
EM: martz@snarktoo.gsfc.nasa.gov
AF: University of Maryland, ESSIC, Computer and Space Science Building, UMCP, College Park, MD 20742-2425, United States
AU: Neale, P J
EM: nealep@si.edu
AF: Smithsonian Environmental Research Center, P.O. Box 28, 647 Contees Wharf Road, Edgewater, MD 21037-0028, United States
AU: Osburn, C L
EM: christopher.osburn@nrl.navy.mil
AF: US Naval Research Laboratory, Code 6114, Room 308A 4555 Overlook Ave SW, Washington DC, DC 20375, United States
AU: Herman, J R
EM: jay.r.herman@nasa.gov
AF: NASA/Goddard Space Flight Center, GSFC, Code 613.3, Greenbelt, MD 20771, United States
AB: Photochemical alteration of colored dissolved organic matter (CDOM) during exposure to solar UV and Visible radiation generates a variety of photoproducts, including reactive oxygen species, atmospherically important trace gases, and microbially labile carbonyl compounds. Sunlight-induced changes in CDOM chemical structure are reflected in changes of its optical properties that provide a first order measure of the photoreactivity of CDOM in a water body of interest. Here, we examined the effects of solar exposure on the photochemical degradation of CDOM derived from different sources in a tidal marsh-estuarine ecosystem. Consistent with changes in fluorescence emission, absorption loss upon exposure to different portions of the solar spectrum (i.e. different long-pass cut-off filters) occurred across the entire spectrum but the wavelength of maximum photobleaching decreased as the cut-off wavelength of the filter decreased. Our results illustrate that solar exposure can cause either an increase or a decrease in the CDOM absorption spectral slope depending on the spectral quality of irradiation and, thus, on the parameters (e.g. aerosol and ozone amounts) that affect the spectral characteristics of the light to which CDOM is exposed. Quantitative description of this response, as needed to model optical quality in coastal waters, is hampered by the lack of models that predict both absorbance and spectral changes. We have developed a simple spectral model for describing the effects of solar radiation on CDOM optical quality. The model accurately, and consistently, predicted the observed dependence of CDOM photobleaching on the amount and spectral quality of solar exposure.
DE: 0300 ATMOSPHERIC COMPOSITION AND STRUCTURE
DE: 0315 Biosphere/atmosphere interactions (0426, 1610)
DE: 0360 Radiation: transmission and scattering
DE: 0365 Troposphere: composition and chemistry
DE: 0414 Biogeochemical cycles, processes, and modeling (0412, 0793, 1615, 4805, 4912)
SC: Atmospheric Sciences [A]
MN: 2007 Joint Assembly