UV spectrometry for measuring particulate organic matter in natural water |
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| Authors: | Nozomi Ytow Motoo Utsumi Humitake Seki |
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| Institution: | (1) Institute of Biological Sciences, University of Tsukuba, 305 Tsukuba, Ibaraki, Japan |
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| Abstract: | Ultraviolet (UV) spectra were measured to characterize the dissolved and particulate organic matter in a bog and to investigate the seasonal fluctuation of this organic matter. The optical density spectra in the UV region of dissolved organic matter (DOM) were proportional to
–4, where is the wavelength of incident light. There was also small absorption on the
–4 spectra. The optical density at a wavelength of 280 nm was proportional to the concentration of dissolved organic carbon (DOC). The spectra and the dependency of optical density on DOC did not vary throughout the investigation period. The UV spectra of acid extractions of particulate organic matter (POM) showed two absorption peaks at the wavelengths of 220 nm and 335 nm. These peaks are well represented by the sum of two Lorentz functions. The ratio of the absorbances,A
280/A
335, was dependent on the nitrogen/carbon ratio of POM and the chlorophyll fraction in particulate organic carbon (POC), and not dependent on POC itself. The dependency of POC absorption at 280 nm varied with this ratio which fluctuated seasonally. |
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| Keywords: | POM POC UV-spectra nitrogen/carbon ratio organic carbon cycle |
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