Abstract
In the basin of Lake Biwa and Lake Kasumigaura, relationships between fractionation data of dissolved organic matter (DOM) and in inflowing river water and watershed characteristics were investigated by regression analysis and specific unit modeling. Most hydrophobic neutrals were found to originate from domestic sewage. Domestic wastewater treatment plant effluent was found to significantly contribute to the load of hydrophilic acids in river water. Specific unit modeling based on the load of DOM fraction and the ratio of land use contribution in watershed enabled source identification for each DOM fraction including refractory dissolved organic matter. In the north basin of Lake Biwa, forest outflow significantly contributed to the load of aquatic humic substances and refractory fractions. The loads of other DOM fractions were found to be dominated mainly by urban drainage.
