Field study on a role of particulate matter in transportation of micropollutants in aquatic environments

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1. Seasonal changes in conventional water qualities, agrochemicals concentration and mutagenicity (the Ames test) of reservoir, influent river and conveyance channel water were made clear through year-round surveys. In the soluble phase samples direct and indirect mutagenicity were sometimes positive or quasi-positive for the river water from May to August but mostly negative for the channel and reservoir water all year round. In the particulate phase samples direct and indirect mutagenicity were mostly negative for the channel water, whereas indirect mutagenicity was sometimes quasi-positive for the river and reservoir water. Some kinds of agrochemicals were detected mainly during the rice-planting season. Few kinds of agrochemicals adsorbed on particulate matter were detected. The relation between mutagenicity and agrochemicals was not clear.2. Surveys were carried out for the river water during rainy or snowy days as well as the runoff water from forest. In some of the particulate phase samples mutagenicity was quasi-positive when the water flow increased, but the temporal variation was large. Although pretilachlor, one of herbicides, was detected in the soluble phase samples of the river water in March, mutagenicity was negative.3. A year-round survey was performed for rainfall and snowfall. In the soluble phase samples mutagenicity was mostly positive from November to February but negative or weak from May to September. Mutagenicity showed a tendency to become weak by the metabolic activation. In the particulate phase samples mutagenicity was mostly negative but sometimes positive in winter. It is considered that substances which caused positive mutagenicity might be PAHs and nitroPAHs.4. These results suggest that soluble direct mutagens in the precipitation were decomposed or changed and soluble indirect mutagens were adsorbed onto the soil during the runoff process, and then, the adsorbed mutagens flowed out and down with the eroded soil.