Journal of Geography (Chigaku Zasshi)
Online ISSN : 1884-0884
Print ISSN : 0022-135X
ISSN-L : 0022-135X
Volume 132, Issue 2
Displaying 1-11 of 11 articles from this issue
Cover
  • 2023 Volume 132 Issue 2 Pages Cover02_01-Cover02_02
    Published: April 25, 2023
    Released on J-STAGE: May 15, 2023
    JOURNAL FREE ACCESS

     This well is located in an alluvial lowland area in the western coastal part of Tokyo Bay. In Shinagawa area, there still remain a number of wells with hand pumps, which were used as domestic water sources in the past. This well is 9.1 m deep and its screen width is unknown. The hand pump on this well is covered with an orangecloth because it is currently out of order.

     Although the public sewerage coverage ratio of Tokyo's Shinagawa area is 99.5% (Bureau of Sewerage Tokyo Metropolitan Government1)), the results of an end member mixing analysis (EMMA) based on the δ15N-NO3 and nitrogen concentration suggest sewage is seeping into the groundwater sampled from this well. And its Cl concentration is higher than that of groundwater sampled in nearby areas. Meanwhile, other water quality results indicate a lower NO3 concentration (n.d. −5 mg/L), a higher HCO3 concentration (120-200 mg/L), and a lower ORPSHE (50-200 mV), despite seasonal variations, which are signs of denitrification under an anaerobic environment (Itoh et al., 2023).

    (Photograph: Yuki ITOH; Explanation: Seongwon LEE)

    Note

    1) 東京都下水道局下水道100%普及達成年次表

     https://www.gesui.metro.tokyo.lg.jp/living/a2/spread/tasseinennzi/index.html [Cited 2023/1/28].

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Special Issue: Groundwater Pollution by Nitrate: Past, Present, and Future Perspectives
Review Articles
  • Kentaro HAYASHI
    2023 Volume 132 Issue 2 Pages 75-91
    Published: April 25, 2023
    Released on J-STAGE: May 15, 2023
    JOURNAL FREE ACCESS

     Nitrogen (N) provides great benefits as a fertilizer for food production and as a material for industrial production. However, its use simultaneously induces N pollution, which threatens the health of human beings and ecosystems due to low N use efficiency in the anthroposphere. This is the N issue—a tradeoff between large benefits and threats. It is our responsibility to have future generations inherit sustainable N use by resolving the N issue. Groundwater nitrate pollution is a form of N pollution that should be addressed to prevent harm to human and animal health through drinking water and aquatic ecosystems through excess eutrophication. Links between groundwater nitrate pollution in N cycling and the N issue are reviewed to provide information for international and domestic actors to address the N issue, and to indicate groundwater nitrate pollution research needed to comprehensively address the N issue. Concretely, global and local N cycling and links with groundwater N processes are overviewed. The status of the N issue is summarized and a comprehensive framework to grasp the entire issue is introduced, i.e., the driver–pressure–state–impact–response (DPSIR) framework. Programs and projects tackling the N issue in Japan and around the world are summarized. Research required on groundwater nitrate pollution that contributes to resolving the N issue is discussed, and future expectations are indicated.

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  • Tatemasa HIRATA
    2023 Volume 132 Issue 2 Pages 93-105
    Published: April 25, 2023
    Released on J-STAGE: May 15, 2023
    JOURNAL FREE ACCESS

     Among all substances, nitrate nitrogen exceeds groundwater environment standards the most. The average excess rate of 87,000 samples collected across the nation so far is 4.5%. Efforts implemented by the Ministry of Environment to address such groundwater pollution caused by nitrate nitrogen are described. The Ministry of Environment has established guidelines for comprehensive regional measures to improve nitrate groundwater pollution. The guidelines include methods for investigating nitrate groundwater pollution, measures for reducing nitrogen loads, and methods for simulating groundwater numerical analyses to confirm the effects.

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  • Kiyonori HAGA
    2023 Volume 132 Issue 2 Pages 107-125
    Published: April 25, 2023
    Released on J-STAGE: May 15, 2023
    JOURNAL FREE ACCESS

     The rapid growth in livestock farming since the late 1960s has resulted in problems managing excess waste excreted from livestock. A study on the water quality of groundwater, river water, and soil solution clarified that groundwater pollution by nitrate nitrogen was caused by nitrogenous compounds permeating livestock wastes under inappropriate waste management, including dumping and/or digging in. The appropriate treatment of livestock waste as compost and liquid fertilizer improved nitrate nitrogen pollution. The full-scale enforcement of “The Law Concerning the Appropriate Treatment and Promotion of Utilization of Livestock Manure” in 2004 reduced inappropriate waste management practices such as dumping and/or digging in. In 2019, all livestock farms installed comprehensive waste management facilities for composting, wastewater treatment, and other measures. However some issues remain to be resolved relating to the inappropriate operation of facilities and the existence of facilities aged over 20 years, which may cause pollution problems. In addition, elution of nitrate nitrogen from place of use digging in requires care even now. In 2021, an investigation report on livestock waste management was published by the Ministry of Agriculture, Forestry and Fisheries. Most solid livestock waste matter is converted into compost, which can be widely distributed on croplands of agricultural farms. Broiler litter is used for combustion energy. Liquid dairy cattle waste is applied on croplands. Wastewater from pig farms is purified with an activated sludge process to obtain clear water that complies with effluent standards and then is discharged into rivers and public waters. An appropriate application rate of compost on croplands is recommended to promote the recycling of organic and nitrogen resources and to control nitrate nitrogen in groundwater.

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  • Masaru YAMANAKA
    2023 Volume 132 Issue 2 Pages 127-139
    Published: April 25, 2023
    Released on J-STAGE: May 15, 2023
    JOURNAL FREE ACCESS

     Nitrate nitrogen pollution in groundwater can be understood from three viewpoints: generation sources, mobility, and elimination effects (natural purification effects). Alluvial fans are often utilized for farmland where nitrate fertilizer (pollutant source) may be used. Nitrate pollutants readily spread in groundwater at alluvial fans where two controlling factors for pollutant mobility are high: permeability and hydraulic gradient of groundwater. Moreover, the denitrification process, which is one of the most important natural purification effects, is not expected to occur readily in alluvial fan groundwater, which is seldom under anoxic conditions and contains little organic matter. In numerous previous studies, groundwater at alluvial fans has been researched using four main methods: water quality monitoring, calculations based on pollutant load per unit activity of source, stable isotopic tracers, and computed simulation models. As a result, processes and reactions of nitrate nitrogen in groundwater can now be evaluated quantitatively and visualized. Of these, because an oxidation reaction of ammonium sulfate, which is one of the main sources of nitrate nitrogen, multiplies the effects on groundwater chemistry, it is noted that NO3 : SO42− molar ratios and δ13CDIC values are secondary indicators for identifying this process in terms of groundwater pollution.

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Original Article
  • Yuki ITOH, Masaya YASUHARA, Seongwon LEE, Takashi NAKAMURA, Akihiko IN ...
    2023 Volume 132 Issue 2 Pages 141-160
    Published: April 25, 2023
    Released on J-STAGE: May 15, 2023
    JOURNAL FREE ACCESS

     Shallow groundwater in the densely populated Shinagawa area (Kita-Shinagawa and Minami-Shinagawa), central Tokyo, was sampled from 10 shallow wells (less than 12 m deep) in February (cold dry season) and July (hot wet season) 2019. The concentrations in seven groundwater samples from Kita-Shinagawa in February and July were 1.6-34.1 mg/L and not detected −34.8 mg/L for NO3, and 17.4-31.9 mg/L and 15.7-42.3 mg/L for Cl. The measured isotopic ratios were 11.9-23.8‰ and 12.3-21.8‰ for δ15N-NO3, and 5.1-11.8‰ and 0.8-19.9‰ for δ18O-NO3, respectively. Shallow groundwater with elevated NO3 and Cl concentrations was probably contaminated by sewage leaking from damaged sewers. Although the wells are near each other in a small area of about 100 m (E–W) and about 60 m (N–S), shallow groundwater in Kita-Shinagawa showed a wide range of chemical concentrations and stable isotopic ratios, indicating sewage leakage as a source of groundwater contamination. Among groundwater samples collected once every two months in Kita-Shinagawa from January 2019 to February 2020, δ15N-NO3 and δ18O-NO3 values generally plot along the trendline with a slope of 0.5. This indicates that the study area had suitable conditions for denitrification to occur, although the degree of denitrification depended on the season and relative location of each well in the study area. The observed NO3 concentration and seasonal variability in the shallow groundwater were attributed to the mixing of three groundwater sources: 1) rainfall infiltration (natural recharge), 2) water-supply leakage, and 3) sewage leakage, with subsequent denitrification.

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Short Articles
  • Tsutomu NAGATA, Michiko OTSUZUKI, Takayuki SATO
    2023 Volume 132 Issue 2 Pages 161-167
    Published: April 25, 2023
    Released on J-STAGE: May 15, 2023
    JOURNAL FREE ACCESS

     Kumamoto City has been known as the “Water City” since ancient times, and it has also earned the title “Japan's Number 1 Groundwater City” because 100% of the water used by all 740,000 residents is supplied entirely by groundwater. Previously, the city implemented various measures to protect water quality by monitoring wastewater from industries and purifying groundwater polluted by organochlorides. However, in recent years, there has been an increasing trend of nitrate nitrogen in groundwater in the eastern and central parts of the city, and creating countermeasures for this problem has become an urgent issue. In order to preserve the quality of groundwater for future generations, the city began to implement countermeasures against nitrate nitrogen pollution by establishing the Kumamoto City Tobu Compost Center in order to properly treat domesticated animal manure, which is the main cause of nitrate nitrogen pollution in the eastern part of the city. Countermeasures will continue to be developed against nitrate nitrogen pollution through cooperation among citizens, private cattle farmers, and municipal governments.

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  • Seongwon LEE, Norio TASE
    2023 Volume 132 Issue 2 Pages 169-181
    Published: April 25, 2023
    Released on J-STAGE: May 15, 2023
    JOURNAL FREE ACCESS

     Numerous groundwater problems involving nitrate contamination, mainly derived from fertilizer and livestock waste, are reported worldwide. In Japan, although livestock wastes thrown in unlined pits has been banned by a law established in 1999, unlined pits still remain, causing high nitrogen discharges into groundwater. At the Tsukuba Plateau Ibaraki Pref., groundwater with more than 100 mgNO3/L is observed just below an old unlined pit with 4.1 kgN/year of nitrogen estimated to be released from the pit. In addition, a large part of the released nitrogen is denitrified in a percolation process through a clay layer beneath the pit.

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Original Article
  • Takashi NAKAMURA, Ken'ichi OSAKA, Saroj Kumar CHAPAGAIN, Kei NISHIDA
    2023 Volume 132 Issue 2 Pages 183-196
    Published: April 25, 2023
    Released on J-STAGE: May 15, 2023
    JOURNAL FREE ACCESS

     The high contaminated shallow groundwater by nitrate (NO3) and ammonium (NH4+) in the Kathmandu Valley, Nepal were investigated along with their nitrogen sources and distribution mechanisms. Thirty-six shallow groundwater samples were collected from the tube- and dug- wells during the monsoon season (August) of 2009 and 2010. High levels of NO3 (maximum: 63.9 mg/L) and NH4+ (maximum: 36.7 mg/L) concentrations were detected in shallow groundwater. NO3 represented a significant contribution to the total dissolved inorganic nitrogen in most the dug wells; these wells were characterized by unprotected inner walls, indicating the possible influx of nitrified NO3 from the unsaturated zone to the insides of the wells. The dual isotopic (δ15N and δ18O) NO3 approach suggested that sewer leakage is a major source of nitrogen contamination in shallow aquifers. In addition, the exponential increase in NO315N accompanied by NO3 reduction with the distinct δ18O/δ15N slopes of NO3 (∼0.5) indicated denitrification. Finally, we established a negative nonlinear relationship between NO3 and the dissolved organic carbon, suggesting that organic carbon strongly affects denitrification reactions in shallow groundwater.

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