Assessing the optical changes in dissolved organic matter in humic lakes by spectral slope distributions

Research Area: Uncategorized Year: 2011
Type of Publication: Article Keywords: Absorption spectral slope, Argentina, CDOM, Humic lakes, Photodegradation
Journal: Journal of Photochemistry and Photobiology B: Biology Volume: 102
Number: 2 Pages: 132-139
Month: February
ISSN: 1011-1344
The impact of photodegradation and mixing processes on the optical properties of dissolved organic matter (DOM) was examined using a distribution of absorption spectral slopes and fluorescence measurements in two Argentine lakes. By examining the variability of the absorption spectral slopes throughout the ultraviolet and visible wavelengths, it was possible to determine which wavelength intervals were most sensitive to dominant loss processes. For DOM photodegradation, results show that increases in the absorption spectral slope between 265 and 305 nm were highly sensitive to increased exposure to solar ultraviolet radiation. A slightly larger wavelength range (265–340 nm) was found to be influenced when both mixing and photodegradation processes were considered, in terms DOM residence time, DOM absorption and UV diffuse attenuation coefficients. This same interval of spectral slopes (265–340 nm) was found to highly correlate with changes in fluorescence emission/excitation in wavelengths that are typically associated with terrestrial humic-like DOM. The identification of specific wavelength intervals, rather than the use of standard wavelength intervals or ratios, improved our ability to identify the dominant dissolved organic matter (humic-like) and major loss mechanisms (photodegradation) in these lakes.
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