Continuous Determination of Water Quality by Light Scattering Spectrophotometry

Light scattering and fluorescence spectrophotometry with radiation of Xe lamp has been investigated to determine continuous water quality. The items of water quality of the determination are Suspended Solids (SS), Nitrate and Nitrite (NOx-N), Chlorophyll a (Chl. a), Total Organic Carbon (TOC) and Dissolved Organic Carbon (DOC). Continuous and simultaneous determination of these items were conducted by the change of wavelengths for excitation and detection. Water quality of Lake Biwa was almost constant during monitoring. Averages of errors on monitoring were 0.5mgN·l-1 in SS, 0.13mgN·l-1 in NOx-N, 0.2μg·l-1 in Chl.a, 0.2mgC·l-1 in TOC and 0.4mgC·l-1 in DOC. It was shown that this method responded rapidly to the water quality change by addition of tracers. We could calculate the instant specific growth rates of Microcystis aeruginosa from the continuous change of the Chl.a concentration of the culture. The result showed that M. aeruginosa were increased rapidly in daytime. This method can determine rapidly water quality because it is not necessary that the samples are pre-treated with such as filtration and addition of reagent.