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

Takeshi Saito; Lorenzo Spadini; Hirotaka Saito; Jean M F Martins; Laurent Oxarango; Takato Takemura; Shoichiro Hamamoto; Per Moldrup; Ken Kawamoto; Toshiko Komatsu

doi:10.1016/j.scitotenv.2020.137783

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

Sci Total Environ. 2020 Jun 20:722:137783. doi: 10.1016/j.scitotenv.2020.137783. Epub 2020 Mar 6.

Authors

Affiliations

¹ Graduate School of Science and Engineering, Saitama University, Japan 255 Shimo-Okubo, Sakura-ku, Saitama 338-8570, Japan. Electronic address: saitou@mail.saitama-u.ac.jp.
² Univ Grenoble Alpes, Inst. Geosci Environ. IGE HyDRIMZ, CNRS, Grenoble-INP, IRD, UGA. CS 40 700, Grenoble, France.
³ Institute of Agriculture, Tokyo University of Agriculture and Technology, Japan 3-5-8 Saiwai-cho, Fuchu-shi, Tokyo 183-8509, Japan.
⁴ Department of Earth and Environmental Sciences, Nihon University, Japan 3-25-40 Sakurajosui, Setagaya-Ku, Tokyo 156-8550, Japan.
⁵ Graduate School of Agricultural and Life Sciences, The University of Tokyo, Japan 1-1-1, Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan.
⁶ Department of Civil Engineering, Aalborg University, Denmark Thomas Manns Vej 23, 1-256, 9220 Aalborg Ø, Denmark.
⁷ Graduate School of Science and Engineering, Saitama University, Japan 255 Shimo-Okubo, Sakura-ku, Saitama 338-8570, Japan.

PMID: 32208245
DOI: 10.1016/j.scitotenv.2020.137783

Abstract

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.

Keywords: Groundwater quality; Groundwater redox conditions; Hydrogeochemical processes; Long-term monitoring; Tokyo Metropolitan area of Japan.