تخمین حجم تخلیه آب زیرزمینی به دریا با استفاده از تلفیق داده‌های مکانی و سری زمانی رادیوایزوتوپ رادون 222، مطالعه موردی در جنوب ژاپن

نوع مقاله : علمی -پژوهشی

نویسندگان

1 دانشکده علوم زمین، دانشگاه شهید بهشتی

2 Department of Earth Sciences, GSST, Kumamoto University, Japan

3 Priority Organization for Innovation and Excellence, Kumamoto University, Japan

4 National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Japan

5 Center for Marine Environment Studies, Kumamoto University, Kumamoto, Japan

چکیده

تخلیه آب‌های زیرزمینی به دریا (SGD)[1] به­عنوان بخشی از چرخه هیدرولوژی که در اثر آن مواد محلول و سایر آلاینده‌ها از محیط‌های خشکی وارد اقیانوس می‌شوند، مورد توجه قرار گرفته است. روش‌های متنوعی به منظور ارزیابی SGD ارائه شده است. روش رادیوایزوتوپ رادون 222 (222Rn) به­عنوان یک ردیاب ژئوشیمیایی طبیعی با هدف انجام مطالعات غیرمستقیم ناحیه‌ای SGD توسعه یافته است. در این تحقیق تلاش شده است تا حجم تخلیه آب زیرزمینی به دریا در نوار شمالی دریای یاتسوشیرو[2] واقع در جنوب کشور ژاپن با روش 222Rn ارزیابی گردد. بدین منظور، با بهره‌گیری از نتایج تحقیقات منتشر شده گذشته توسط نویسندگان بالا، محدوده با پتانسیل بالای SGD معین گردید. سپس، سری زمانی غلظت گاز 222Rn در آب دریا به منظور تحلیل اثر جذر و مد بر تغییرات زمانی تخلیه آب زیرزمینی به دریا ثبت گردید. هم­چنین، تصحیحات لازم بر روی داده‌های سری زمانی اعمال شد تا اثر رودخانه‌های موجود در منطقه حذف گردد و امکان تخمین جریان SGD فراهم شود. در نهایت، نتایج حاصل از بررسی تغییرات مکانی غلظت گاز 222Rn در نوار ساحلی مورد مطالعه با داده‌های سری‌های زمانی 222Rn در منطقه مذکور تلفیق گردید. نتایج به دست آمده نشان داد که حجم SGD در محدوده مورد مطالعه حدود 65/10 متر مکعب در ثانیه می‌باشد.[1]-Submarine Groundwater Discharge[2]-Yatsushiro Sea

کلیدواژه‌ها


عنوان مقاله [English]

Evaluation of submarine groundwater discharge (SGD) volume using 222Rn spatial and temporal variations, case study, south Japan

چکیده [English]

Submarine groundwater discharge (SGD) has addressed recently as part of the hydrologic cycle by which solutes and other pollutants travel from terrestrial areas toward the coastal waters. 222Rn as a naturally occurring geochemical radioisotope tracer can be applied for indirect regional SGD studies. This study aims to estimate the net SGD volume toward the northern coastline of the Yatsushiro Sea, south Japan, using the 222Rn method. For this, areas with high SGD potential calculated. Then, seawater 222Rn concentration time series recorded in selected points to evaluate the SGD temporal fluctuations and it`s correlation with tidal cycles. Also, corrections conducted over the 222Rn time series to remove the 222Rn noise originated from the rivers discharging into the bay. The results applied to simulate the seawater 222Rn concentration and to estimate the SGD rate in the study area. Finally, the spatial and temporal 222Rn analysis results combined to estimate the SGD net volume. The results show that the SGD volume in the study area is about 0.92×106 m3 day-1.

کلیدواژه‌ها [English]

  • submarine groundwater discharge-SGD-222Rn-Japan
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