OPTICAL-ABSORPTION AND FLUORESCENCE PROPERTIES OF CHROMOPHORIC DISSOLVED ORGANIC-MATTER IN NATURAL-WATERS

Complete optical absorption and fluorescence spectra were collected fo r a diverse suite of 0.2-mu m-filtered marine, riverine, and estuarine waters, as well as for colored dissolved organic matter (CDOM) isolat ed from several of these waters by solid-phase C-18 extraction. Absorp tion and fluorescence parameters for these samples are reported. For s urface waters, variations in the fluorescence quantum yields obtained with 355- and 337-nm excitation fell within a narrow window (<2.5-fold variation about the mean values), demonstrating that fluorescence mea surements can be used to determine absorption coefficients of CDOM in the ultraviolet region with reasonably good accuracy. Methods for pred icting absorption coefficients and line shapes from the fluorescence d ata are introduced and tested. The absorption and fluorescence spectra of CDOM extracted from some seawaters differed significantly from tho se of the original waters, demonstrating that material isolated by hyd rophobic adsorption is not necessarily representative of the suite of colored organic matter present in aquatic systems. These results clear ly illustrate that great care must be taken when extracted material is used to infer the optical properties of natural waters.