[A-CG35_28PO1] 陸海相互作用－沿岸生態系に果たす水・物質循環の役割－

[ACG35-P05] 沿岸域海底下の地下水の水と溶存炭酸の安定同位体比

*山田 誠¹、杉本 亮²、大河内 允基²、本田 尚美²、小林 志保³、安部 豊¹、谷口 真人¹ (1.総合地球環境学研究所、2.福井県立大学、3.京都大学)

キーワード：海底湧水, 水の安定同位体, 溶存炭酸の炭素安定同位体

Groundwater often discharges from the seabed of the coastal zone. Such groundwater is called “submarine groundwater discharge (SGD)”. Mostly, SGD is the water which not fresh water but sea water and fresh water mixed. Although it is assumed that mixture has occurred under the seabed, there is almost no information about the behavior of water and dissolved component under the seabed such as the mixed process, zone of influence of sea water, and the behavior of the dissolved component from the land area. In order to clarify the behavior of water and dissolved component under the seabed of the coastal zone, we conducted the sampling of the water under the seabed of Obama Bay, Fukui prefecture. The stable carbon isotope ratio of dissolved inorganic carbon (DIC) was lower than that of sea water, and higher than that of groundwater which sampled from well near the seashore. The results show that not only mixture of water but mixture of DIC has occurred under the seabed. In the future, in order to comprehend the extent of the impact of sea water, it is necessary to research vertical distribution of the stable isotope composition under the seabed.