Reconstraction of Limestone Solution Model in Japan

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Solution rate of the limestone tablets during the last 10 years were observed at the six stations (Asahikawa, Abukuma, Akiyoshidai, Shikoku, Ryugado and Minamidaito Island) in Japan. The 10 years total solution, rates were higher in B_2 horizon of soil than in the air 1.5 m above the ground at all stations. Especially, the total solution rates in B_2 horizon are extremely high at Akiyoshidai and Minamidaito: about 12 %. These values are roughly 4 times higher than these in the air.Inter-annual fluctuation of solution rates was also very large. When water deficits are high, the solution rates are clearly low. In a dry year, the solution rate in B_2 horizon is only 2 times higher than in the air.The CO_2 contents in soil were also examined at the all stations in 10 years. When water deficit is high, CO_2 content in soils becomes very small. However, after rainfall of 20 mm in a day, CO_2 content becomes extremely high. It is, therefore indicated that inter-annual fluctuation of solution rate is reflected by inter-annual fluctuation of water balance in soils.In Minamidaito, where is uplifted atoll, palaeo karst terrain can be used for calculation of ages, since the time when the island changed to uplift. That is, using solution rate, the formation model of karst terrain can be obtained, making use of relationship between time and palaeo water balance.