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The remediation effects of a permeable reactive barrier (PRB) using sulfur-limestone are investigated. The results show that highly concentrated NO 3 -(133180 mg/L) in shallow groundwater decreased below the detection limit within the PRB. This phenomenon was maintained for approximately 300 days; therefore, the remediation effects within the PRB and its durability are demonstrated. It is suggested that the remediation effects due to the PRB are not solely restricted to the area within the barrier, because the decrease in NO 3 extended 4.0 m downstream.Furthermore, the results of ORP SHE , δ 15 N, and isotopic fractionation factor (ε) indicate that a reductive condition forms within the PRB, where sulfur-oxidizing denitrifying bacterium preferentially exists. Before installing the PRB, three-dimensional (3-D) groundwater flow systems around the study site and detailed hydrogeological setting should be investigated first.

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Akaike is a small, temporary pond located about 1 km east of Lake Shoji at the northern foot of Mt. Fuji, which appears following heavy rainfall events. It is widely accepted that the pond is connected to Lake Shoji by groundwater. However, this connection has not yet been evaluated because of a lack of scientific data including water quality and environmental isotopes from both Akaike Pond and Lake Shoji. Major dissolved ion and trace element contents, hydrogen (δD) and oxygen (δ 18 O) stable isotope ratios of water, and nitrogen (δ 15 N-NO 3 ) and oxygen (δ 18 O-NO 3 ) stable isotope ratios of nitrate ions were measured in water samples from Akaike Pond, which appeared between July 9th and August 20th in 2020. These data are compared with surface water and rainfall samples collected from the surrounding area to reveal the origin of Akaike Pond. It is found that the δD and δ 18 O values of Akaike Pond significantly increased after the late July (21st28th) rainfall events. Mass balance analysis based on the δD and δ 18 O before and after the rainfall indicates that water flowing into Akaike Pond during this period was mainly derived from the immediately preceding rainfall. Major dissolved ion compositions in Akaike Pond show lower Ca 2+ and HCO 3 concentrations than water samples around the pond. This suggests that water in Akaike Pond appeared in a relatively short period (within a few days) after the heavy rainfall events, without deep underground percolation, which is further supported by δ 18 O-NO 3 and trace element composition.