J.of Soc of Agri Struc, Japan.
Vol.31,No.1 June 2000, 11-21
Original:
Language: English

    Intensity and type of offensive odors from two hypertrophied lake waters (L. Kasumigaura and L. Tsukushi) incubation process were examined and evaluated using human sensory test method and handy odor sensors.
    By measuring the types and intensities of offensive odors and standard odor agents with sensory test method, it was found that the odor types from the incubation process of L. Kasumigaura water were methyl mercaptan, isopropyl mercaptan and di-methyl mercaptan. Besides, the relationship between the indicator of the odor sensor of hydrogen sulfide type and chlorophyll a concentrations of both lakes was fairly high.
    As for the kinds of algae during summer of the study, 85% of algal population in the L. Kasumigaura were M.aeruginosa, followed by P.Tenue, the producer of MIB. For the L. Tsukushi, M.aeruginosa comprised about 38% of the total population of algae.
    With the sensory test, the type of odor from L. Kasumigaura was earthy. The odor intensity of the L. Tsukushi was about 1/2 of that of the L. Kasumigaura. Using 10 standard odor agents, it was that detectable limits for human were 0.00038 ppm for isopropyl mercaptan, and 0.00085 ppm for methyl mercaptan, 8.75 ppm for ammonia and 9.40 ppm for hydrogen sulfide. Using four odor sensors for evaluating the odor intensity (as odor index), the intensities of isobutyl mercaptan, isopropyl mercaptan, methyl mercaptan and hydrogen sulfide were favorably correlated with those with the human sensory test method.

Keywords: offensive odor, Microcystis, sensory test, odor sensor

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