Aquatic Sciences Meeting, Albuquerque 2001
| SS02 Photochemical Reactions In Surface Waters: A Major Issue in the 21st Century? (Environmental Connections) |
| Date: Thursday, February 15, 2001, Time: 10:30:00 AM |
| Location: San Miguel |
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| Mopper, K, , Washington State University, Department of Chemsitry, Pullman, WA, USA, mopper@wsu.edu |
| Hofsetz, B, D, Washington State University, Department of Chemistry, Pullman, WA, USA, hofsetz@mail.wsu.edu |
| Kieber, D, J, University of New York, College of Environmental Science and Forestry, Syracuse, NY, USA, djkieber@syr.edu |
| Medovich, T, M, University of New York, College of Environmental Science and Forestry, Syracuse, NY, USA, tmmedovi@syr.edu |
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| ABSORBANCE CHARACTERISTICS OF ANTARCTIC AND OPEN OCEANIC WATER |
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| DOM is the dominant UV absorbing component in seawater. However, in optically clear waters and upwelling regions, other components can affect absorbance. Antarctic surface waters contain DOM chromophores mainly of microbial origin, and are not significantly impacted by soil run-off and rivers like lower latitude coastal waters. Consequently, Antarctic waters are remarkably transparent at wavelengths >310nm, which necessitates using two spectral slopes to fit log-linearized absorbance plots, instead of one normally used for terrestrially impacted waters. Furthermore, changes in spectral slope with depth were observed, probably due to DOM photobleaching at the surface and chromophore production at depth. Specific chromophores (protein, nitrate and nitrite) were found to impact the spectra. For surface waters, 7-45% of the 200 and 400nm absorbance was due to nitrate. Relative to surface water, deep water displays a pronounced absorbance at 218nm, which may be protein-related. In contrast, surface waters (<500m) are enriched in 250-270nm absorbing chromophores. DOM absorbance:fluorescence ratios are impacted by these different chromophores. The Antarctic results differ from those obtained at a mid-latitude, open oceanic site. |
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