Estimation of Groundwater and Spring Water Residence Times near the Coast of Fukushima, Japan.

The massive Tohoku earthquake, colloquially known as "The 2011 Great East Japan Earthquake," occurred off the Pacific coast of Japan on March 11, 2011. The coastal area of the Tohoku region was severely affected by the tsunami, and the tsunami also caused severe damage to the Fukushima Daiichi Nuclear Power Plant (FDNPP) releasing a large amount of radioactive material into the atmosphere and environment. Determining the residence time of groundwater is important for evaluating how long radioactive materials are present after nuclear accidents such as FDNPP and multiple methods are needed to account for mixing between old/young water that can occur.

Denitrification during vertical upwelling at an alluvium-diluvium interface below the upland perimeter of a riparian paddy.

Denitrification hotspots in riparian aquifers often develop in a relatively narrow zone at the upland-riparian interface, where nitrate-rich ground water of upland origin interacts with available soil organic carbon. In riparian paddy fields, denitrification in the aquifer has received less attention than that in the surface water and soil. This study aimed to determine the in situ activity of the denitrification hotspot formed at the vertical interface between the organic alluvial and the nitrate-rich diluvial aquifers around the depth of 2.