UV SPECTROMETRY FOR MEASURING PARTICULATE ORGANIC-MATTER IN NATURAL-WATER

Ultraviolet (UV) spectra were measured to characterize the dissolved a nd particulate organic matter in a bog and to investigate the seasonal fluctuation of this organic matter. The optical density spectra in th e UV region of dissolved organic matter (DOM) were proportional to lam bda(-4) where lambda is the wavelength of incident light. There was al so small absorption on the lambda(-4) spectra. The optical density at a wavelength of 280 nm was proportional to the concentration of dissol ved organic carbon (DOG). The spectra and the dependency of optical de nsity 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 p eaks are well represented by the sum of two Lorentz functions. The rat io of the absorbances, A(280)/A(335), was dependent on the nitrogen/ca rbon ratio of POM and the chlorophyll fraction in particulate organic carbon (POC), and not dependent on POC itself. The dependency of POC a bsorption at 280 nm varied with this ratio which fluctuated seasonally .