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Studies on Environment in Small Islans

小岛屿环境研究

基本信息

批准号：
04650464
负责人：
KAKINUMA Tadao
金额：
$ 1.28万
依托单位：
EHIME UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1992
资助国家：
日本
起止时间：
1992 至 1993
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-04650464/
关键词：
island groundwater seawater intrusion fertilizer dissolution stable isotope seto inland sea coral atoll fresh-water lens

项目摘要

Various water qualities, especially stable isotope ratios, of groundwater in shallow wells were measured, together with groundwater levels, in Gogo Island, Ehime Prefecture. In a coastal region of the Yura district, chloride ion concentration far greater than 200mg/l(the stadard value of city water) was always found and the delta D versus delta^<18>O diagram suggests that the groundwater in this region is a mixture of seawater and upstream groundwater. Non-dimensional values of deltaD, delta^<18>O and Cl^- of groundwater near the bottom of a well in a coastal region of the Yura district indicate almost the same value, and it was estimated that groundwater contained approximately 20% seawater. The vertical distribution of non-dimensional Cl^- is different from those of deltaD or delta^<18>O.The former indicates higher concentration in the upper part of the well. The higher concentration may be caused by the Cl source except seawater, e.g.fertilizer.The behavior of coastal and insular groundwaters was investigated by use of a sand tank. In the case of seawater intrusion into confined coastal aquifers, both the fresh-water/salt-water interfaces simulated by using an analytical solution adopting Dupuit's assumptions and by a boudary element method (BEM) have a relatively good agreement with the experimental ones, though further inland saltwater situation in lower hydraulic gradients. In the hydrodynamic dispersion model, isopleths of concentration in the case of velocity-dependent dispersion coefficient agree well with experimental ones than in the case of constant dispersion coefficient, and the Cauchy's boundary condition is rather realistic. In the case of freshwater lenses, both the fresh-water/salt-water interfaces simulated by using the analytical solution and by the hydrodynamic dispersion model exist slightly above the experimental visual interfaces.

在爱媛县后后岛测量了浅威尔斯井中地下水的各种水质，特别是稳定同位素比率，以及地下水位。在Yura地区的沿海地区，氯离子浓度一直远大于200 mg/l（城市水的标准值），Δ D-Δ ^<18>O图表明该地区的地下水是海水和上游地下水的混合物。尤拉<18>地区沿海地区一口井底部附近地下水的δ D、δ ^ O和Cl^-的无量纲值表明几乎相同的值，据估计，地下水含有约20%的海水。无因次Cl^-的垂向分布与δ D或δ ^ O的垂向分布不同<18>，前者表明井上部浓度较高。高浓度的氯可能是由除海水以外的氯源引起的，如化肥。在海水侵入封闭沿海含水层的情况下，淡水/盐水界面模拟使用的解析解，采用Dupuit的假设和bouquet元素法（BEM）有一个相对较好的协议与实验的，虽然进一步内陆盐水的情况下，在较低的水力梯度。在水动力弥散模型中，弥散系数随速度变化时的浓度等值线与实验值吻合较好，而弥散系数为常数时的浓度等值线与实验值吻合较好，柯西边界条件更符合实际。在淡水透镜体的情况下，淡水/盐水界面模拟使用的解析解和水动力弥散模型存在略高于实验的视觉界面。