2020 Volume 62 Issue 1 Pages 59-73
Gasoline is a typical substance in the soil pollution with petroleum hydrocarbons. In this study, focusing on hydrocarbons of methane series (alkanes: n-pentane ~ n-dodecane) which are main constituents of gasoline, the acute toxicity tests were carried out. The difference in the acute toxic effect on luminous bacteria due to the variation in the carbon number of the alkanes was assessed.
In the tests on 100 vol％of the alkanes without methanol solvent, the acute toxicity of the alkanes could not be clearly assessed since the bacteria might not absorb the alkanes which were hydrophobic. On the other hand, in the tests on the alkanes dissolved in methanol solvent, significant results could be obtained. The higher the carbon number of alkane and also the higher the concentration, the longer it took for the relative luminescence intensity ratio to reach a constant value. Regardless of the species of alkane, overall, the relative luminescence intensity ratio became lower as the alkane concentration became higher. The effects of the alkane concentration on the relative luminescence intensity ratio tended to be strongly in the alkanes with lower carbon number than alkanes with higher carbon number. This was presumed that reaction rate for the acute toxicity effect on the luminous bacteria becomes lower as the carbon number of the alkanes becomes higher. Therefore, when performing the acute toxicity evaluation for the alkanes under the test conditions in this study, the data at a reaction times of 60 minutes will be desirable to use rather than those at 30 minutes. Also, this study indicated that the results of the acute toxicity evaluation for the substances, such as gasoline, consisting of mixed
