Influences of topography on nitrate export from forested watersheds on Yakushima Island, a Natural World Heritage site.

In East Asia, high levels of atmospheric nitrogen are deposited onto land. This could elevate the nitrate levels in coastal waters river runoff, even from areas where anthropogenic sources are minimal. It is important to identify NO sources in river water and the mechanisms involved in NO runoff.

Runoff characteristics of pesticides from paddy fields and reduction of risk to the aquatic environment.

Simultaneous rice-transplanting and subsequent application of pesticides to the paddy fields in the catchment of a rural river on weekends from late May to mid June caused high concentrations and high loadings of pesticides in the river. Imperfections in irrigation water management and the overflow discharge from paddy fields during heavy storm events increased the risk of drinking water contamination and threatened the aquatic ecosystems. Several pesticides were detected at nearly ten ppb in the biofilms on the river bed.

Runoff characteristics of particulate pesticides in a river from paddy fields.

Runoff characteristics of particulate pesticides from paddy fields have been intensively observed in the Koise River in Japan. The 8 pesticides that are applied to paddy fields were analyzed in both particulate and dissolved forms. The concentrations and the detection frequencies of particulate pesticides were lower than those of dissolved pesticides.

Runoff of acidic substances that originated from atmospheric deposition on Yakushima Island, a world natural heritage site.

In this paper we present monitoring data of stream waters that may reflect acidic impacts on the island as well as the rainwater qualities. The pH ranges of the river water in the Kawara streams in the western part of the island and the Yodogo stream in the central part of the island were 5.71-6.