博士

出版者・発行元：Multidisciplinary Digital Publishing Institute  

出版者・発行元：なごや生物多様性センター  

出版者・発行元：MDPI  

Exploring how the hydrological and thermal conditions of a volcanic lake change in response to volcanic activity is important to identify the signs of a volcanic eruption. A water cycle system and a geothermal process in a crater lake, Okama, in the active Zao Volcano, Japan, were explored by estimating the hydrological and chemical budgets of the lake, and analyzing the time series of lake water temperature, respectively. In 2021, the lake level consistently increased by snowmelt plus rainfall in May–June, and then stayed nearly constant in the rainfall season of July–September. The hydrological budget estimated during the increasing lake level indicated that the net groundwater inflow is at any time positive. This suggests that the groundwater inflow to the lake is controlled by the water percolation into volcanic debris from the melting of snow that remained in the catchment. Solving the simultaneous equation from the hydrological and chemical budgets evaluated the groundwater inflow, Gin, at 0.012–0.040 m3/s, and the groundwater outflow, Gout, at 0.012–0.027 m3/s in May–September 2021. By adding the 2020 values of Gin and Gout evaluated at the relatively high lake level, it was found that Gin and Gout exhibit highly negative and positive correlations (R2 = 0.661 and 0.848; p < 0.01) with the lake level, respectively. In the completely ice-covered season of 15 December 2021–28 February 2022, the lake water temperature increased between the bottom and 15 m above the bottom at the deepest point, which reflects the geothermal heat input at the bottom. The heat storage change during the increasing water temperature was evaluated at a range of −0.4–5.5 W/m2 as the 10-day moving average heat flux. By accumulating the daily heat storage change for the calculated period, the water temperature averaged over the heated layer increased from 1.08 to 1.56 °C. The small temperature increase reflects a stagnant state of volcanic activity in the Zao Volcano. The present study could be useful to investigate how an active volcano responds to water percolation and geothermal heat.

出版者・発行元：MDPI  

Lake Tazawa, the deepest lake (423.4 m depth at maximum) in Japan underwent drastically changed water quality in 1940, because volcanic water from two active volcanos was then drawn into the lake for power generation and irrigation. Thereby, the pH of lake water decreased from 6.7 to 4.2, which exterminated a land-locked type of sockeye salmon, Oncorhynchus nerka kawamurae (locally called Kunimasu trout). Additionally, the mean residence time of lake water changed from 195 years to 8.9 years by rapidly increasing the outflow for power generation and irrigation. In this study, long-term chemical fluxes controlling lake water chemistry were obtained, and a groundwater water cycle system between the lake and the volcano was explored by estimating hydrological and chemical budgets of the lake. In the chemical budget estimate, two ionic species, SO42− and Cl−, in volcanic fluids were chosen and each mass conservation equation was yielded. The hydrological budget estimate gave us the net groundwater inflow at −1.36 m3/s on average over three periods in 2020–2021, and then the simultaneous equation coupled with the chemical budget equation allowed us to separate into groundwater inflow and outflow at 6.01 m3/s and 7.37 m3/s, averaged over the three periods, respectively. The evaluated groundwater inflow and outflow were compared with those of the other crater or caldera lakes. The linear relationship between the lake volume and the magnitude of groundwater inflow or outflow suggests that the groundwater cycle scale in such a lake increases with the magnitude of the volcanic eruption to have formed the lake.

出版者・発行元：東北地理学会  

宮古島南東の吉野海岸では，湧水の流路に沿って板状に固結した複数の砂層がみられる。湧水の水質が砂層の固結に関係している可能性が高いと推量し，因果関係を解明する基礎試料を得るため，湧水，固結砂層およびその下方の非固結砂層を採取して分析した。その結果，砂層の固結は石灰岩を溶解した湧水に含まれるCaCO3の析出による可能性が高いと考察した。

総ページ数：842 p.  

総ページ数：168  

日本陸水学会東海支部会(編)

総ページ数：240  

石川良文［編著］

この賞は、地域学の発展に著しく寄与し、その意義や貢献が多大である著作物に対して表彰されるものです。 受賞した著書は、新型コロナウイルス感染症の影響を社会、経済、環境の3側面から捉え、経済学、社会学、社会心理学、法学、政治学、環境科学など様々な学問分野の知見を基に分析しています。感染症の流行から2年間に及ぶ分析を早期にとりまとめ、パンデミックとなる感染症の影響と政策を地域の視点を入れつつ総合的に捉えた他に類のない著書として高く評価されました。