AN EXPERIMENTAL-MODEL OF THE SOLAR-STIMULATED FLUORESCENCE OF CHROMOPHORIC DISSOLVED ORGANIC-MATTER

We present an experimental model of CDOM solar-stimulated fluorescence . Three-dimensional fluorescence spectra of natural waters were used t o determine the solar-stimulated emission as a function of depth in th e water column. Inclusion of the wavelength-dependent fluorescence qua ntum yield provides emission values in absolute units of photons s-1 c m-2 5 nm-1. Attenuation of light in the water column was also modeled, allowing determination of total upwelled emission. The upwelled fluor escence is compared to irradiance reflectance calculated from a semian alytical model. The fluorescence contribution to reflectance in the bl ue-green to green region can be as high as 70% for blackwater but is r apidly reduced by the introduction of scattering particles. Except for blackwaters, CDOM fluorescence does not significantly affect irradian ce reflectance ratios commonly used in remote-sensing applications. In water with moderate amounts of CDOM (absorption coefficient at 355 nm greater-than-or-equal-to 0.5 m-1), fluorescence will dominate water R aman scattering as a secondary influence on the light field in the gre en spectral region.