Nitrate reduction zone in groundwater at a slope-wetland plot in Tsukuba upland, Ibaraki Prefecture

Abstract

More than 50 piezometers and observation wells were installed in about 210 m² slope-wetland plot in the Tsukuba upland, Japan to clarify whether NO3^- reduction zone in groundwater locates in the marginal slope of wetland or not. The result showed that NO₃^- reduction zone was located locally in the Younger Loam Formation near the interface between the sand and gravel layer and the Younger Loam Formation, where water table gradient dramatically deceased. As shown in Figure 7, the NO₃^- reduction zone (3) in the observed vertical cross-section ranged within about 20 cm in vertical and about 100cm in horizontal direction. Additionally, groundwater geochemistry in the NO₃^- reduction zone demonstrated that SO₄^2- concentration decreased and Mn concentration increased in the zone.