The system of grondwater percolation and the growth mechanism of stalgmaites under different covers based on in situ observation within limestone caves

2016 Fiscal Year Final Research Report

• Project/Area Number: 26550011
• Research Category: Grant-in-Aid for Challenging Exploratory Research
• Allocation Type: Multi-year Fund
• Research Field: Environmental dynamic analysis
• Research Institution: Kumamoto University
• Principal Investigator: MATSUDA HIROKI 熊本大学, 大学院先端科学研究部(理), 教授 (80274687)
• Project Period (FY): 2014-04-01 – 2017-03-31
• Keywords: 鍾乳石 / 炭素・酸素同位体比 / 地下水涵養 / 植生変遷 / 炭酸塩続成作用 / 南大東島

Outline of Final Research Achievements

To clarify the groundwater (GW) percolation system and the growth mechanism of stalagmites under different vegetation covers, the measurements of the soil and cave environments and water chemistry of the drip waters (DW) were carried out in Minami-Daito Island.
Saturation index for calcite (SIc) in DW are positive and are higher in dry season and under sugarcane field than under forests. The amounts of DW are relatively constant under forests, while those change responding to rainfall under sugarcane field. From the results, the growth mechanism of stalagmites is as follows; At first, GW has high CO2 due to percolating through soil with high CO2, and dissolves underlying carbonate rocks. With GW flowing downward, degassing of the dissolved CO2 with evaporation leads to increase in the SIc. Especially, the SIc become higher by intense evaporation in dry season, which is more active in sugarcane field. Consequently, the growth rate of stalagmite under sugarcane field is higher.

Free Research Field

炭酸塩堆積学