Hisashi Sumitomo

Use of chlorophyll fluorescence of Closterium ehrenbergii and Lemna gibba for toxic effect evaluation of sewage treatment plant effluent and its hydrophobic components

In this study fluorometric methods using an alga, Closterium ehrenbergii, and a higher plant, Lemna gibba, were employed to evaluate the toxicity of sewage treatment plant (STP) effluent and its hydrophobic components. Fluorescence parameters such as the operational photosystem II quantum yield at steady state of electron transport, the nonphotochemical quenching, and the complementary area were modified in the presence of hydrophobic components, particularly with C. ehrenbergii. It was found that C. ehrenbergii was a suitable species to be used in a hydrophobic components bioassay, since this alga was 400 times more sensitive than L. gibba to hydrophobic components. Results indicate that hydrophobic STP effluent components are less toxic as a constituent of the STP effluent than when they are extracted from the effluent. We also demonstrated here that in addition to the growth inhibition test, fluorometric methods can be usefully employed in bioassays for the toxic effect evaluation of pollutants present in municipal wastewater treatment plant effluents.

Changes of activity inducing chromosomal aberrations and transformations of chlorinated humic acid.

The change of the toxicity of chlorinated water after chlorine injection was examined. For the measurement of toxicity, chromosomal aberration test and transforming test were carried out as indexes to initiating activity and to promoting activity in the carcinogenesis process, respectively. Activity inducing chromosomal aberrations of chlorinated humic acid gradually decreased with time after chlorination. In contrast, activity inducing transformations measured by the two-stage assay gradually increased. Thus, the toxicity that decreases or increases is present in chlorinated water. Furthermore, activity inducing transformations measured by the non-two-stage assay gradually decreased. This direction of change was reverse to that of activity inducing transformations by the two-stage assay and consistent with that of activity inducing chromosomal aberrations. It is speculated that the main reason of decreasing activity inducing transformations by the non-two-stage assay is because initiating activity detected as activity inducing chromosomal aberrations in chlorinated water decreases drastically. Directions of changes of total organic halogen and carbonyl group were qualitatively consistent with that of activity inducing chromosomal aberrations. Directions of changes of chloroform and dichloroacetic acid were qualitatively consistent with that of activity inducing transformations by the two-stage assay. Findings of this study suggest that further research is necessary to compare carcinogenicity of tap water near water purification plant and distant tap water.

An Estimation of Pollution Sources with Monitoring of River Water Quality

Abstract This paper deals with the method of the identification of pollution sources along a river with water quality measurements at a monitoring site. Especially, the central purpose of this paper is to present the applicability of mathematical estimation methods to actual field monitoring data. Some examples of the identification of pollution sources are shown, to both of tests in an experimental flume, and observations in an urban river. The equation of water quality transport in rivers is described by one-dimensional dispersive equation. The problem is formulated to find the optimal pollution sources, which minimize the differences between the observed water quality concentrations and the expected water quality concentrations. According to the nonuniformity and unsteadiness of river conditions, the methods of minimization must be divided in two.In this paper, the impulse response function is introduced analytically, and the problems are solved by several notable mathematical programming methods with some constraints, when the river conditions are nearly uniform and steady. However, almost all the rivers are not uniform, either steady. Under these conditions, the objective function is minimized iteratively by the direct method using the gradient of the objective function. Mathematically, these problems essentially belong to ill-posed problems. To stabilize and to increase the confidence of the identified solution, the objective function is slightly changed to find the minimum norm solution. Alternatively, to control the sampling interval, we can make the problem more feasible, and well posed one, and some concerns are paid to this point.