Tracking the direct impact of rainfall on groundwater at Mt. Fuji by multiple analyses including microbial DNA

A total of 2 to 3 million tons of spring water flushes out from the foot of Mt. Fuji, the largest volcanic mountain in Japan. Based on the concept of piston flow transport, residence time of stored groundwater at Mt. Fuji was estimated at  ∼ 15–30 years by the 36Cl∕Cl ratio (Tosaki et al., 2011). This range, however, represents the average residence time of groundwater that was mixed before it flushed out. To elucidate the route of groundwater in a given system, we determined signatures of direct impacts of rainfall on groundwater, using microbial, stable isotopic (δ18O), and chemical analyses (concentration of silica). Chemical analysis of the groundwater gave an average value of the water, which was already mixed with waters from various sources and routes in the subsurface environment. The microbial analysis suggested locations of water origin and paths.In situ observation during four rainfall events revealed that the stable oxygen isotopic signature obtained from spring water (at 726ma.s.l., site SP-0m) and shallow groundwater (at 150ma.s.l., site GW-42m), where the average recharge height from rainfall was 1700–1800m, became greater than values observed prior to a torrential rain producing more than 300mm of precipitation. The concentration of silica decreased after this event. In addition, the abundance of Bacteria in spring water increased, suggesting the influence of heavy rain. Such changes did not appear when rainfall was less than 100mm per event. The above findings indicate a rapid flow of rain through the shallow part of the aquifer, which appeared within a few weeks of torrential rain extracting abundant microbes from soil in the studied geologic setting. Interestingly, we found that after the torrential rain, the abundance of Archaea increased in the deep groundwater at site GW-550m,  ∼ 12km downstream of SP-0m. However, chemical parameters did not show any change after the event. This suggests that strengthened piston flow caused by the heavy rain transported archaeal particles from the geologic layer along the groundwater route. This finding was supported by changes in constituents of Archaea, dominated by Halobacteriales and Methanobacteriales, which were not seen from other observations. Those two groups of Archaea are believed to be relatively tightly embedded in the geologic layer and were extracted from the environment to the examined groundwater through enforced piston flow. Microbial DNA can thus give information about the groundwater route, which may not be shown by analysis of chemical materials dissolved in the groundwater

Groundwater flow system under a rapidly urbanizing coastal city as determined by hydrogeochemistry

In the Jakarta area (Indonesia), excessive groundwater pumping due to the rapidly increasing population has caused groundwater-related problems such as brackish water contamination in coastal areas and land subsidence. In this study, we adopted multiple hydrogeochemical techniques to demonstrate the groundwater flow system in the Jakarta area. Although almost all groundwater existing in the Jakarta basin is recharged at similar elevations, the water quality and residence time demonstrates a clear difference between the shallow and deep aquifers. Due to the rapid decrease in the groundwater potential in urban areas, we found that the seawater intrusion and the shallow and deep groundwaters are mixing, a conclusion confirmed by major ions, Br−:Cl− ratios, and chlorofluorocarbon (CFC)-12 analysis. Spring water and groundwater samples collected from the southern mountainside area show younger age characteristics with high concentrations of 14C and Ca–HCO3 type water chemistry. We estimated the residence times of these groundwaters within 45 years under piston flow conditions by tritium analysis. Also, these groundwater ages can be limited to 20–30 years with piston flow evaluated by CFCs. Moreover, due to the magnitude of the CFC-12 concentration, we can use a pseudo age indicator in this field study, because we found a positive correlation between the major type of water chemistry and the CFC-12 concentration

Stable isotopic and geochemical characteristics of groundwater in Kherlen River basin, a semi-arid region in eastern Mongolia

Inorganic solute ion concentrations and stable isotopes of oxygen and hydrogen ingroundwater, river water and precipitation were investigated to gain insight into thegroundwater recharge process in the Kherlen River basin, a semi-arid region in easternMongolia. The solute constituents in the river water (main stream) were of Ca-HCO3 type,spatially invariant and low in concentration. Groundwater in the upstream region was alsocharacterized by a Ca-HCO3 type, though all ion concentrations were higher than in the riverwater. On the other hand, the chemical composition of the groundwater in the midstreamregion (southern and eastern) was spatially variable and the Na+, Mg2+, Cl- and HCO3-concentrations were considerably higher than in the river water and upstream groundwater.The stable isotopic compositions showed an evaporation effect on the groundwater and river water, as well as an altitude effect in the precipitation and river water. Preferential rechargeby relatively large rainfall events is thought to have caused the depleted isotopic ratio in thegroundwater in the dry regions. The stable isotope, chemical and hydrological data suggestthat the main stream water of the Kherlen River is recharged by precipitation that falls in aheadwater region at an altitude of more than 1650 m, and that the interaction between thegroundwater and river water is not dominant in the midstream and downstream regions ofthe river basin

東日本大震災後のエコ行動とエコ意識 -実践女子大学生を対象としたアンケート調査-

A survey to investigate environmental behavior difference between the period of programmedblackout (March of 2011)and one month after the finish of the blackout (May of 2011)hasbeen performed. Three respondent groups and three behavior groups are obtained by clusteranalysis of the questionnaire data of environmental behaviors. The positive people forenvironmental behaviors do almost of all listed behaviors, the moderate people do two thirds ofthe behaviors, and the negative people do one third of the behaviors. It has a tendency that thenegative people think public offices have responsibility for environmental conservation, andhave less knowledge of ecorogical information

Legal and other institutional aspects of groundwater governance

This chapter defines the linked concepts of groundwater governance and groundwater management, explaining how they differ from each other. Then, it describes the prevailing legal instruments for, and the institutional aspects of, groundwater management and governance

〈研究ノート〉筑波大学陸域環境研究センター構内における地下水と土壌水の酸素・水素安定同位体比の特徴について

It is necessary to make clear the formation process of the stable isotopic compositions of oxygen and hydrogen in soil water for consideration of the soil water movement. We have taken soil samples in the Terrestrial Environment Research Center (TERC) at eleven times from April 28 to November 15, 2001 and analyzed stable isotopic compositions of oxygen and hydrogen in soil water.There are cyclic variations of the δ18Ο and δD profiles in soil water. Isotopic compositions of soil water near soil surface become isotopically heavy because of the evaporation in particular summer season, thus the isotopic heavy peak is formed near the soil surface. In fall season, there is strongly rainfall by a number of typhoons and autumn rain fronts, so relatively large amount of precipitation are supplied to the soil. At that time, the cyclic variations of the isotopes in soil water move downward wholly, but when rainfall is relatively small amount, the cyclic variations do not move clearly. This result indicate that the recharge occurs only after intense rainfall events of typhoons or autumn rain front. And as a result of the stable isotopic compositions of soil water and groundwater, the piston flow is dominantly in the soil water movement in TERC. Consequently, cyclic variations of δ18Ο and δD in soil water are caused by the evaporation in summer season and transmitted downward by the storm events