Synchronous-scan fluorescence of algal cells for toxicity assessment of heavy metals and herbicides

Synchronous-scan spectrofluorometry was applied to Chlorella vulgaris cells to assess the toxicity of heavy metals and herbicides in water. Simultaneous scan of both the excitation and emission spectra was done at a constant wavelength difference Δλ (20–140 nm) between the emission and excitation wavelengths in the range of 420–700 nm emission, where a peak of fluorescence was observed. Its position depends on Δλ. Fluorescence measurements were conducted with algal cells in suspension in water and immobilized in a translucent silica matrix. The influence of toxic chemicals was tested with cadmium as a heavy metal and with atrazine, diuron, DNOC and paraquat as herbicides. The toxic effect of those chemicals mainly results in a quenching of algal cells fluorescence by reducing their photosynthetic activity.