抄録
In order to grasp the nationwide river pollution by synthetic detergents and surfactants, monitoring data of MBAS (Methylene Blue Active Substances), an indicator of anionic type sharing a major part of surfactant production, were analyzed statistically at 957 river monitoring stations of nine prefectures in Japan.
Average MBAS concentrations during 1985-89 indicated the log-normal distribution with 35% of low level below 0.1mg·l-1, 49% of middle level between 0.1 and 1mg·l-1 and 15% of high level above 1mg·l-1.
The testings for the variation of MBAS concentration during 1980's at each monitoring station showed that the variations for about half of the stations were statistically significant in each of three prefectures, Saitama, Tokyo and Hyogo, where trends of variations were relatively similar at each concentration level.
From the analysis of MBAS data in rivers of Kinki Region in 1989, the percentage of monitoring station with high concentration appearing for three months or more was estimated to be 20% and 60% in case of MBAS exceeding 1mg·l-1 and 0.1mg·l-1, respectively. In the estimation by average BOD, these percetages grew high as the level or average BOD increased.
