Development of laser fluorometer system for CDOM measurements

The colored fraction of dissolved organic matter, CDOM, directly influences water optical properties and spectral quality, playing an important role in aquatic ecosystems, optical remote sensing and carbon circulation in the sea. Measuring in situ CDOM absorption coefficient, however, is difficult because it requires prefiltration of water samples. An analytical laboratory and field instrument for fast diagnosis of chromophoric dissolved organic matter(CDOM) in water was developed. The laser fluorometer was integrated with spectral fluorescent signature(SFS) analysis of the laser stimulated emission excited at 405 nm and hyper spectra for surveillance of CDOM. CDOM and water Raman scattering components were derived from the laser stimulated emission spectra measured in the laboratory and field conditions with SFS technology, which added to analytical Lidar sensing the capability of detecting and identifying trace substances in a variety of targets in the presence of other background matters responding to optical excitation with overlapping signals. The influence of temperature change on CDOM fluorescence data in water was investigated in laboratory, and a temperature calibration method was employed for calibrating fluorometer data. Laboratory and in-situ studies with the laser fluorometer in the East China Sea (ECS) in April 2013 were carried out. Significant and positive correlation in the ECS was observed between CDOM absorption measurements and CDOM fluorescence (R2=0.83). The result demonstrated the possibilities of CDOM monitoring in real time based upon the laser fluorometer.