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  • 1
    Online Resource
    Online Resource
    Groundwater Dynamics near the Saltwater–Freshwater Interface in an Island of Seto Inland Sea
    MDPI AG ; 2023
    In:  Water Vol. 15, No. 7 ( 2023-04-05), p. 1416-
    Details
    In: Water, MDPI AG, Vol. 15, No. 7 ( 2023-04-05), p. 1416-
    Abstract: Groundwater dynamics near the saltwater–freshwater interface were investigated in an island of the Seto Inland Sea, using multiple tracers (δD, δ18O, Cl−, SF6, and 14C) at two coastal groundwater monitoring wells at depths of 10–40 m. The groundwater recharge area and age were also estimated using these tracers. Additionally, bedrock groundwater at a depth of 40 m at the 2.7 m altitude was brackish and considered to be near the saltwater–freshwater interface, and a mixture of seawater (2–3.5%) and fresh groundwater (97–98%) was estimated by the Cl− concentration. Based on the δ18O of fresh groundwater estimated from the seawater mixing ratio, the recharge area was estimated to range from near to above the summit; however, this region is unlikely to be the actual recharge area, as the groundwater may be old freshwater that was recharged during a previously colder period. Groundwater dating using SF6 and 14C suggests that the fresh groundwater originated during the last glacial period (assumed 20,000 years ago) and that the 40 m deep bedrock groundwater is a mixture of old water (0–28%), 30 m deep groundwater (76–100%), and stagnant seawater (1–3%).
    Type of Medium: Online Resource
    ISSN: 2073-4441
    URL: Article
    DOI: 10.3390/w15071416
    Language: English
    Publisher: MDPI AG
    Publication Date: 2023
    detail.hit.zdb_id: 2521238-2
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  • 2
    Online Resource
    Online Resource
    Potential Sources of Ammonium-Nitrogen in the Coastal Groundwater Determined from a Combined Analysis of Nitrogen Isotope, Biological and Geological Parameters, and Land Use
    MDPI AG ; 2020
    In:  Water Vol. 13, No. 1 ( 2020-12-25), p. 25-
    Details
    In: Water, MDPI AG, Vol. 13, No. 1 ( 2020-12-25), p. 25-
    Abstract: The origin of ammonium-nitrogen in Indonesian coastal groundwater has not been intensively examined, meanwhile the elevated concentration remains a concern. This research aims at tracing the potential sources of ammonium-nitrogen in the groundwater of Indramayu, Indonesia where groundwater is vital for livelihood. From results, a combined examination of nitrogen isotope, coliform bacteria, land-use, and geology confirmed the natural and anthropogenic origins of ammonium-nitrogen in the groundwater. In the brackish-water aquaculture region, groundwater has δ15NNH4 values from +1.8 to +4.8‰ signifying that ammonium-nitrogen is derived from mineralization of organic nitrogen to ammonium. Furthermore, ammonium has a significantly positive relationship with sodium indicating the exchangeable ammonium is mobilized to groundwater via cation exchange. Meanwhile ammonium-nitrogen from anthropogenic waste was detected in agricultural and residential region. The groundwater has more varied δ15NNH4 values, from −2.9 to +16.1‰, which implies attenuation of ammonium-nitrogen from several sources namely manure, mineral fertilizer, sewage, and pit latrines. Also, the presence of E. coli confirms the indication of human and animal waste contamination. However, since ammonium has no relationship with sodium, cation exchange is not feasible and ammonium-nitrogen flows into the groundwater from anthropogenic sources along with liquid wastes.
    Type of Medium: Online Resource
    ISSN: 2073-4441
    URL: Article
    DOI: 10.3390/w13010025
    Language: English
    Publisher: MDPI AG
    Publication Date: 2020
    detail.hit.zdb_id: 2521238-2
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  • 3
    Online Resource
    Online Resource
    Nitrate Contamination in Groundwater: Evaluating the Effects of Demographic Aging and Depopulation in an Island with Intensive Citrus Cultivation
    MDPI AG ; 2022
    In:  Water Vol. 14, No. 14 ( 2022-07-21), p. 2277-
    Details
    In: Water, MDPI AG, Vol. 14, No. 14 ( 2022-07-21), p. 2277-
    Abstract: Despite rapid population aging and depopulation in Japan, groundwater nitrate contamination still poses serious environmental problems. One of the main factors contributing to elevated nitrate levels in Japanese groundwater sources is agricultural intensification, frequently because of increased fertilizer use. We investigated the impact of population aging and depopulation on groundwater nitrate contamination on a western Japanese island that has extensive citrus farming. In comparison to Ocho village, where the average age of farmers is 73 years, Kubi village’s farmers are slightly older on average, at 76 years, and agricultural land has decreased by 46% over the past ten years, from 2005 to 2015. Ocho had 830 residents, which was twice as many as Kubi. In comparison to Ocho (4.8 mg/L), Kubi village had higher average NO3−−N concentrations (6.6 mg/L). NO3−−N contamination sources in Kubi and Ocho were determined using stable nitrogen isotopes and a Bayesian isotope mixing model. These source distributions were more strongly associated with social and land use factors. It was believed that the older farmers in Kubi employed a significant quantity of chemical fertilizers, which caused inefficient nitrogen uptake by plants, leading to increased leaching and more groundwater contamination than in Ocho.
    Type of Medium: Online Resource
    ISSN: 2073-4441
    URL: Article
    DOI: 10.3390/w14142277
    Language: English
    Publisher: MDPI AG
    Publication Date: 2022
    detail.hit.zdb_id: 2521238-2
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