5:15 PM - 6:45 PM
[AHW25-P04] Microplastics found in shallow groundwater in the coastal lowlands of Shinagawa Ward, downtown Tokyo
Keywords:Tokyo Bay coastal lowlands, Urban area, Shallow groundwater, Microplastics, Sewage leakage
We are currently conducting a study on shallow groundwater in the Kita-Shinagawa area of Shinagawa Ward in the Tokyo Bay coastal lowlands to elucidate the origin and water quality evolution process of urban groundwater. In this presentation, we report on microplastics (MPs) detected in shallow groundwater in the area concerned.
In August 2021 (wet summer period), field surveys and water sampling were conducted at seven wells (depths: <12 m) in the Kita-Shinagawa area, and the role (contribution rate) of precipitation, water leakage and sewage leakage, which are considered to be sources of urban shallow groundwater recharge, was calculated using three-component mixing analysis based on the oxygen isotopic ratio and chloride ion concentration. In August 2022, shallow groundwater was sampled and analyzed again at wells N2 and N4, where the contribution of sewage leakage to groundwater recharge was the largest (48%) and smallest (4%) in August 2021, respectively, to confirm the presence of MPs in groundwater. As a result, 29 fibrous residues (112 fibers/L) were detected in 260 mL of groundwater at well N2, and 7 fibrous residues (9 fibers/L) in 780 mL of groundwater at well N4. Five representative fibrous residues were selected and identified by FT-IR (Fourier transform infrared spectrophotometer), and all were found to be MPs such as polyacrylonitrile and polyester. The density of fibrous residues (112 fibers/L at well N2 and 9 fibers/L at well N4) is consistent with the contribution rate of sewage leakage in August 2021, that is 48% at well N2 and 4% at well N4. Furthermore, since anthropogenic substances such as E. coli, anionic surfactants, and pharmaceuticals have been detected in shallow groundwater in the Kita-shinagawa area (Ito et al., 2022), it can be concluded the MPs detected in this study were derived from the sewage leakage.
In order to further investigate the relationship between the concentration of MPs in shallow groundwater and the contribution of sewage leakage to groundwater recharge, groundwater samples from seven wells were collected in January 2024 and are currently being analyzed. The results of this analysis will also be presented at the presentation. These MPs in shallow groundwater in the Tokyo Bay coastal lowlands are expected to eventually discharge to Tokyo Bay as groundwater flows. The results of this study strongly suggest that the MPs load to the ocean via groundwater should be paid much more attention in the future, although only the load via river water has been considered so far.
In August 2021 (wet summer period), field surveys and water sampling were conducted at seven wells (depths: <12 m) in the Kita-Shinagawa area, and the role (contribution rate) of precipitation, water leakage and sewage leakage, which are considered to be sources of urban shallow groundwater recharge, was calculated using three-component mixing analysis based on the oxygen isotopic ratio and chloride ion concentration. In August 2022, shallow groundwater was sampled and analyzed again at wells N2 and N4, where the contribution of sewage leakage to groundwater recharge was the largest (48%) and smallest (4%) in August 2021, respectively, to confirm the presence of MPs in groundwater. As a result, 29 fibrous residues (112 fibers/L) were detected in 260 mL of groundwater at well N2, and 7 fibrous residues (9 fibers/L) in 780 mL of groundwater at well N4. Five representative fibrous residues were selected and identified by FT-IR (Fourier transform infrared spectrophotometer), and all were found to be MPs such as polyacrylonitrile and polyester. The density of fibrous residues (112 fibers/L at well N2 and 9 fibers/L at well N4) is consistent with the contribution rate of sewage leakage in August 2021, that is 48% at well N2 and 4% at well N4. Furthermore, since anthropogenic substances such as E. coli, anionic surfactants, and pharmaceuticals have been detected in shallow groundwater in the Kita-shinagawa area (Ito et al., 2022), it can be concluded the MPs detected in this study were derived from the sewage leakage.
In order to further investigate the relationship between the concentration of MPs in shallow groundwater and the contribution of sewage leakage to groundwater recharge, groundwater samples from seven wells were collected in January 2024 and are currently being analyzed. The results of this analysis will also be presented at the presentation. These MPs in shallow groundwater in the Tokyo Bay coastal lowlands are expected to eventually discharge to Tokyo Bay as groundwater flows. The results of this study strongly suggest that the MPs load to the ocean via groundwater should be paid much more attention in the future, although only the load via river water has been considered so far.