Fluorescence spectrometric analysis, on which attention is increasingly focused as a method to measure dissolved organic matter in river water, was conducted using corrected fluorescence excitation and emission spectra.
The authors found that fluorescence from a fluorescence whitening agents (FWA) contained in household detergents is overlaps with fluorescence emitted by fulvic-like organic matter, which is the most characteristic fluorescent organic matter in river water, by decreasing the fluorescence intensity due to sunlight irradiation and comparison with the excitation spectrum. Excitation spectra at emission wavelength (λ_em) of 430nm were analyzed with the fluorescence intensity at excitation wavelengths (λ_ex) of 320nm, 345nm and 360nm of [DSBP], which was used as the reference material, to determine fluorescence emitted by the fulvic-like organic matter and FWA, respectively. As a result, a strong positive correlation was shown between the fluorescence derived from fulvic-like organic matter (λ_ex : 320nm, λ_em : 430nm) and [DOC]. Fluorescence excitation spectrometric analysis was useful to evaluating that fulvic-like organic matter is discharged from anthropogenic sources.

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It is clarified that acid species have been transported from the Asian Continent to Yakushima Island, and the major species in the acid depositions is sulfuric acid on this Island. The concentration rations of SO₄^2- to the sum of NO₃^- and SO₄^2- in rime-ice and rainwater were over 90%, as well as the river waters. The forest can be related to the cause of high ion concentration of G1 mountain stream, because it was clarified that Cl^- in mountain stream water only of the atmospheric origin was concentrated on the canopy in the cause of water circulation from the rainfall to the river water. Therefore, SO₄^2- of the atmospheric origin may have been concentrated similarly according to this process and then become in high concentration in the mountain stream water. It was examined whether these acid species influenced the water quality formation of the mountain streams in the western part of Yakushima Island, and found that the contribution of the H⁺ in the acid deposition resulted in the unexpected relation between the HCO₃^- and SiO₂ concentrations.

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In order to estimate the biological activities of sludge with a very low substrate degradability, to which batch experimental data usually cannot be applied, we developed a new analytical method combined with a mathematical model. During batch tests requiring a long time due to low activity levels, bacteria in the sludge must exponentially grow. The analytical method presented in this study, taking the bacterial growth into account, was applied to seven types of anaerobic digestion sludge to estimate the validity of the proposed method. The specific growth rates of methanogenic bacteria in the sludge, which were obtained by the mathematical model and the methane production data of batch tests, lie in the general range. The measurement results for methane production were significantly consistent with the theoretical simulation results based on the mathematical model with the appropriately calculated specific growth rates. These results indicate that the analytical method proposed here would be useful for determining the very low specific biological activities of sludge.

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Lysis and degradation of algal bloom mainly composed of cyanobacteria collected from Tsukui Lake were investigated. Excitation emission matrix spectroscopy (EEMS) and polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) were applied to elucidate the relationship between production of dissolved organic matter and bacterial community change during the lysis of algal bloom followed by their degradation in a batch incubation test. The lysis of algal bloom was indicated by rapid increases of dissolved organic carbon and UV absorbance at 260 nm within five days. In accordance with the lysis, several fluorescence peaks derived from humic- and protein-like substances appeared in the EEM. A significant shift of bacterial community was also demonstrated by the marked change in the DGGE profile. Phylogenetic analysis of the major DGGE bands showed that bacteria closely related to γ-Proteobacteria, CFB group and α-Proteobacteria probably played important roles in the lysis and degradation of algal bloom. When the fluorescence intensity of humic-like substances decreased significantly after 10 days incubation, one of the dominant DGGE bands had a very similar DNA sequence to that of the species reported to be able to degrade humic substances.

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