Dynamics and Biogeochemistry of River Corridors and Wetlands (Proceedings of symposium S4 held during the Seventh IAHS Scientific Assembly at Foz do Iguaçu, Brazil, April 2005). IAHS Publ. 294, 2005, 86-92

Abstract The transport of nitrate and the role of valley corridors and wetlands in the attenuation of groundwater pollution were evaluated in a small rural catchment in Japan. The site is located at the boundary between uplands and lowlands and is divided into a shallow and a deep aquifer. Shallow waters are rich in nutrients, but concentrations decrease dramatically with depth and towards a wetland. Simultaneous decreases in redox potential and oxygen, and increases in HCO₃^– and pH, suggest denitrification is taking place. Nitrate removal typically peaks within the first few metres of the valleys lowlands and therefore there is a significant potential for NO₃^– reduction within the rest of the lowland buffer strip, and also with depth beneath the uplands. The present study provides a new contribution for understanding the fate of NO₃^– in agricultural areas, and constitutes one of the first works of this type carried out in the region.

Key words agricultural pollution; denitrification; nitrate; wetland