LASER-INDUCED FLUORESCENCE SPECTROSCOPY OF PHYTOPLANKTON AND CHEMICALS WITH REGARD TO AN IN-SITU DETECTION IN WATERS

In order to be able to detect chemicals in waters the suitability of l aser-induced fluorescence spectroscopy was evaluated as a tool for the in situ detection of water contaminants and possible interactions wit h phytoplankton and yellow-substances. A frequency doubled dye laser w as used as an excitation light-source. The substances were dissolved i n water and excited in the range from 265 nm to 400 nm. The fluorescen ce signal was recorded in the range from 310 nm to 750 nm. The absorpt ion-, fluorescence- and excitation-spectra of each contaminant were me asured in distilled water, artificial seawater and natural seawater. C omputer-simulations were applied to analyse the spectra of pollutant m ixtures. Firstly we investigated as to whether there are fluorescence- spectroscopically recognizable intermediate stages of phytoplankton an d their breakdown-products (yellow-substances). Modifications of the f luorescence spectra during the ageing and dying of phytoplankton could be shown. Phytoplankton which is subject to sudden death display spec tra differing from those of slowly dying organisms, e.g. the shift of the chlorophyl maximum to shorter wavelengths was measured. The spectr a of mixtures containing phytoplankton and chemicals show differences which depend on the characteristics of the chemicals concerned. PAHs a nd lead-acetate were used.