MUNSELL Color Systemによる養魚池等の水色表示について

抄録

We had hitherto no suitable method to measure or notate the color grades of inland waters, especially of the extremely eutrophic ones like the piscicultureponds. The FOREL-ULE'S color standards do not agree with the actual water-colors, and the method by the platinum-cobalt standard, which can express exactly the brownish waters, is ineffective to other colors.
In the recent time, YAMAZAKI and WATANABE reported a new colorimetric method which can indicate the three values of the C. I. E. color language, in combination with the principle of “MAXWELL's disc”. While this method has a merit in its exactness, it seems to involve a complicated treatment. In general, it seems to be more convenient in measuring and denoting the color grades by direct comparison with the standard papers.
Now, the MUNSELL Book of Color provides an orderly arrangement of standard papers which serve as guide for the measurement and notation of all colors, and, in addition, it has the characteristics in that these standards represent equally spaced divisions of the three attributes of color, known in the MUNSELL System of Color Notation as Hue, Value and Chroma.
By using the MUNSELL Book of Color, we can easily and quickly specify and notate the color of a substance by simple numerals, instead of obscure, nonrelated, customary name of color, and can also let it know internationally. Strictly speaking, the MUNSELL Color System is a method for the notation of the surface color of substances, but is impossible to use for either the color of a liquid or the source of light. This method can, however, be employed in the case under consideration, because the water-color of pisciculture-ponds is the characteristic “Vegetätionsfarbung”, which is caused chiefly by the thriving of phytoplankton, etc., and can be considered as a sort of surface color.
In 1955, the author has measured and recorded the water-color of eel-cultureponds in the Tokai region by using the MUNSELL Book of Color. By these records, he has investigated the seasonal variation of water-color, the comparison of water-colors of fish-ponds in different districts, the relationship between the water-color and the salinity of the pond-water, and also the relationship between the composition of phytoplankton and the water-color respectively. The results obtained are as follows :
(1) Seasonal variation of the water-colors of the ponds in the Izumi district is shown in Table 1, in which the maximum value of Hue, 35.0 (5.0 BG), in August, is recorded.
(2) The Hue value was usually very high in the ponds in both the Kawajiri and Hamana districts (both in Shizuoka Pref.), considerably high in those in various districts of Aichi Pref., and the lowest (30.0 in average) in the ponds in Mié Pref.
(3) As shown in Fig. 2, there was a clear tendency that the higher the salinity of pond-water, the lower the Hue value of the water-color.
(4) While the blue-green algae, such as Microcystis, Oscillatoria, etc., are the source of the higher Hue value, as 37.5-40.0 (distinct bluish green coloration), the green algae (Scenedesmus and others) show the tendency to manifest a little lower Hue value, as 30.0-35.0 (green or yellowish green coloration). There is also a tendency that the predominance of green algae and in particular the planktonic diatoms reduces not only the Hue but also the Value and Chroma.