Water Supply Vol 2 No 5-6 pp 481–486 © IWA Publishing 2002
Excitation-emission fluorescence spectra and trihalomethane formation potential in the Tama River, Japan
F. Nakajima*, M. Hanabusa** and H. Furumai***
*Department of Urban Engineering, University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-8656, Japan
**Department of Urban Engineering, University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-8656, Japan
***Department of Urban Engineering, University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-8656, Japan
ABSTRACT
Three-dimensional fluorescence spectroscopy was applied to investigate the water quality in the Tama River, Japan, and the variation of the excitation-emission matrix (EEM) profiles of the river water was discussed with particular reference to trihalomethane formation potential (THMFP). The EEMs of the water downstream of a lake exhibited a small but strong peak at 225 nm (excitation)/295 nm (emission) and a weak one at 270 nm/295 nm, which seemed to be derived from algae. The EEMs of the water receiving treated sewage had a distinctive, large and broad peak at around 345 nm/430 nm and also a strong fluorescence at 240 nm/330-450 nm. From the comparison with EEMs of human urine, humic acid and a laundry detergent with fluorescent whitening agents, the peak at around 345 nm/430 nm on the EEM of treated sewage was also found on the EEM of the laundry detergent. The fluorescence intensity had a good correlation with T-THMFP for a wide range of excitation/emission wavelengths considered. The fluorescence intensity at 255-295 nm/345-385 nm correlated with T-THMFP better than E260, and the maximum value of the determination coefficient was R2 = 0.90 at 260 nm/355 nm, where no distinctive peak was found on the EEMs of the river water samples. The highest correlation coefficient between the fluorescent intensity and DOC was R2 = 0.77 at 280 nm/335 nm. Multiple regression analysis revealed that the fluorescence emission from a unit concentration of THM precursors was 1,000 times or more higher than that of the overall DOC, particularly in the wavelength range of 250-265 nm/325-480 nm, and that the THM precursors in the river water contributed to a much larger degree to the fluorescence than the other DOMs not forming THM.
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