A characteristic peak of fluorescent whitening agents (FWAs) was detected by fluorescence excitation spectrum (FES) measurement of river water samples. The main causative chemical was 4,4'-bis(2-sulfostyryl)-biphenyl (DSBP), which is commonly added to household detergents in Japan. As the fluorescence of DSBP overlaps with that of fulvic-like organic matter in the spectral fluorescent signatures, DSBP concentration was determined by the newly proposed calculation method, which uses fluorescence intensity at three excitation wavelengths of 320, 345 and 360 nm at emission wavelength of 430 nm for baseline correction. The concentration of DSBP calculated using this method showed strong correlation (correlation coefficient: r = 0.992) with that obtained by high-performance liquid chromatography analysis. The concentrations of DSBP detected in river water samples were 0.28 to 1.84 μg l −1 , with high concentrations observed at the stations with relatively high flow rates of upstream sources of treated domestic wastewater and untreated gray water (domestic wastewater excluding flush toilet wastewater).It was proved that the concentration of DSBP in river water is useful for giving rough estimation of the magnitude of domestic wastewater contamination in river water.

A non-intrusive measurement technique based on spontaneous Raman imaging was proposed for investigating microscale flow structures. It has the advantage that it does not require tracer particles or fluorescent dye to measure fluid velocity and scalar quantities. Raman scattering from ions in solution is substance specific and is observed as Raman spectra that contain peaks due to molecular species. The spontaneous Raman intensity from an electrolyte solution strongly depends on the electrolyte concentration. Thus, a bandpass filter attached to an EM-CCD camera detects only the strong Raman scattering at the selected Raman shift. The spontaneous Raman image obtained was converted to an electrolyte concentration distribution by using a calibration curve that expressed the relationship between the Raman intensity and the concentration. The flow velocity in a millichannel was calculated from the peak-value displacement of the time-series concentration distribution.

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