Fate and Toxicity Evaluation of Toxic Chemicals in An Aquatic Environment

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The main themes and their results we have obtained are as follows;(1) New Technical Development in Chemical Analysis of Micro Heavy Metals in An Aquatic EnvironmentA simple and accurate method was developed for the determination of trace metals in water by graphite furnace atomic absorption spectrometry(GFAAS) after two preconcentration techniques, (1) flow system utilizing silica-immobilized 8-hydroxyquinoline column and (2)tetrahydroborate reductive precipitation. A rapid method was developed for the determination of trace metals in sediment and biological tissue samples by GFAAS using microwave acid digestion system.(2) Fate of Chemicals in An Aquatic EnvironmentOne of principal factors affecting the fate of chemicals in an aquatic environment is a biotranslocation of chemicals by aquatic organisms, especially through a food chain. Chlorella ellipsoidea and Daphnia magna were used as a model prey - predator system, respectively. Cadmium and Chromium were use as toxichnts. The uptake … More of both metals by Daphinia magna was stimulated by feeding. The uptake of active surface agents by Water hyacinth was investigated. The chemicals inhibited the growth of the plant according to the concentration in the plant.(3) Toxicity Evaluation of Micro Heavy Metals toward Micro-organisms.Many kinds of organisms from bacteria to higher organisms have been properly used for toxicity testing of chemicals according to the objectives. This study aims the toxicity evaluation of chemicals in an aquatic ecosystem and new development of environmental mutaginicty testing using mutants of yeast. The effect of bioaccumulation of heavy metals through a food chain were investigated for the evaluation of eco-toxicity in the aquatic environment. Chrorella ellipsoidea and Daphnia nagna were used for a prey-predator system. The toxicity of Cd for Chlorella and Daphnia was stimulated by the Cr uptake. Both metals interacted synergistically each other. Mortality of Daphnia increased with time and it was stimulated by feeding of Chlorella contaminated with metals.Possibility of Yeast, Saccharomyces cerevisiae as a new testing materials for toxicity testing was studied. Yeast is easier in handling the life cycle is -shorter than phytoplankton, therefore it is pertinent as a test organism. It could also be used for environmental mutaginic testing of chemicals using mutants which are deficient in DNA repair capability. Yeast has three kind of independent DNA repair systems. Mutants which are deficient in one, two or all repair systems were used and compared with each other in toxicity sensitivity to chemical. The order of a repair capability of the DNA damaged by 4NQO in different strains of yeast was as follows:Wild type > Excision repair deficient mutant > Mutation repair deficient mutant > Recombination repair deficient mutant > Mutant having recombination repair system > Mutant having mutation repair system > Mutant having excision repair system > All repair deficient mutant. Less