Characterization and comparison of groundwater quality and redox conditions in the Arakawa Lowland and Musashino Upland, southern Kanto Plain of the Tokyo Metropolitan area, Japan

• Published in: The Science of the total environment Vol. 722; p. 137783
• Main Authors: Saito, Takeshi, Spadini, Lorenzo, Saito, Hirotaka, Martins, Jean M.F., Oxarango, Laurent, Takemura, Takato, Hamamoto, Shoichiro, Moldrup, Per, Kawamoto, Ken, Komatsu, Toshiko
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 20.06.2020; Elsevier
• Subjects: Environmental Sciences; Groundwater quality; Groundwater redox conditions; Hydrogeochemical processes; Long-term monitoring; Sciences of the Universe; Tokyo Metropolitan area of Japan; Long-term monitoring; Tokyo Metropolitan area of Japan; Groundwater quality; Groundwater redox conditions; Hydrogeochemical processes
• ISSN: 0048-9697; 1879-1026
• DOI: 10.1016/j.scitotenv.2020.137783

Groundwater is essential for the Earth biosphere but is often contaminated by harmful chemical compounds due to both anthropogenic and natural causes. A key factor controlling the fate of harmful chemicals in groundwater is the reduction/oxidation (redox) conditions. The formation factors for the groundwater redox conditions are insufficiently understood. In this study, long-term groundwater quality beneath one of the world megacities was monitored and evaluated. We measured and compared hydrogeochemical conditions including groundwater quality (35 chemical parameters) and redox conditions of five aquifers in the Arakawa Lowland and Musashino Upland, southern Kanto Plain of the Tokyo Metropolitan area, Japan. Monitoring results suggested the following: The main origin of groundwater is precipitation in both the Lowland and Upland areas. The three aquifers in the Arakawa Lowland are likely fully separated, with one unconfined and two confined aquifers under iron reducing and methanogenic conditions, respectively. Oppositely, in the Musashino Upland, the water masses in the two aquifers are likely partly connected, under aerobic conditions, and undergoing the same groundwater recharge and flow processes under similar hydrogeological conditions. The different groundwater redox conditions observed are likely caused by the very different groundwater residence times for the Arakawa Lowland and Musashino Upland. [Display omitted] •Long-term groundwater quality including 35 chemical parameters was monitored.•Five aquifers in the Arakawa Lowland and Musashino Upland of Japan were targeted.•Completely different groundwater redox conditions were observed for both study areas.•Three aquifers in the Lowland were under iron reducing to methanogenic conditions.•Two aquifers in the Upland were under aerobic conditions.