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Determination of the role of entrapped air in water flow in a closed soil pipe using a laboratory experiment 
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下载免费PDF全文 Soil pipes, continuous macropores parallel to the soil surface, are an important factor in hillslope hydrological processes. However, the water flow dynamics in soil pipes, especially closed soil pipes, are not well understood. In this study, the water and air dynamics within closed soil pipes have been investigated in a bench‐scale laboratory experiment by using a soil box with an artificial acrylic soil pipe. In order to grasp the state of water and air within the soil pipe, we directly measured the existing soil pipe flow and air pressure in the soil pipe. The laboratory experiment showed that air in the soil pipe had an important role in the water flow in the closed soil pipe. When air entrapment occurred in the soil pipe before the soil matrix around the soil pipe was saturated with water, water intrusion in the soil pipe was prevented by air entrapped in the pipe, which inhibited the soil pipe flow. This air entrapment in the soil pipe was controlled by the soil water and air flow. Moreover, after the soil pipe flow started, the soil pipe was not filled completely with water even when the soil pipe was completely submerged under the groundwater table. The entrapped air in the soil pipe prevented further water intrusion in the soil pipe. 相似文献
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Yoshihisa Iio Takeshi SagiyaYoji Kobayashi Ichiro Shiozaki 《Earth and Planetary Science Letters》2002,203(1):245-253
The nature and origin of the concentrated deformation zone along the Japan Sea coast (NKTZ: Niigata-Kobe tectonic zone) was investigated by carefully analyzing the GPS data and qualitatively modeling the lower crust in NKTZ. It was concluded that this deformation zone is not a plate boundary between the Amurian plate (AMU) and the North America plate but is rather an internal deformation zone near the eastern margin of AMU. The data previously obtained on the conductivity anomalies in the lower crust and the 3He/4He ratios suggest that the concentrated deformation in NKTZ results from the lower crust in NKTZ being weakened by a high water content. The high water content is thought to result from the dehydration of subducting slabs. NKTZ has a higher water content in the lower crust than other regions do because there is no Philippine Sea plate (PHS) seismic slab beneath NKTZ. In other regions, it is estimated that the mantle wedge above the seismic Philippine Sea slab prevents the water dehydrated from the slab from rising to the lower crust, and that the lithosphere within PHS itself prevents the water dehydrated from the Pacific plate from rising up through it. 相似文献
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To elucidate the ecological importance of mixotrophic nanoflagellates in the open ocean and the environmental factors that regulate their abundance, we surveyed latitudinal distributions of autotrophic, mixotrophic and heterotrophic nanoflagellates in the central North Pacific Ocean along a transect at 170°W. Mixotrophic nanoflagellates significantly contributed (26–64 %) to total bacterivory, as measured by the fluorescently-labeled bacteria method, from the equatorial through the subarctic regions, which reinforces the importance of mixotrophic nanoflagellates as a trophic link in the open ocean. The proportion of mixotrophic to total plastidic nanoflagellates was significantly higher in the nutrient-depleted subtropical gyre than in other regions, sometimes exceeding 10 %. Additionally, the proportion was negatively correlated with soluble reactive phosphorus concentration within the tropical and subtropical waters, suggesting that low nutrient availability could facilitate phagotrophy of plastidic nanoflagellates, which may explain the survival of nano-sized eukaryotic phytoplankton in the ultraoligotrophic water. In the subarctic regions, the proportion exhibited no obvious relationship with any environmental parameter. Conversely, the numerical proportion of mixotrophic nanoflagellates in total phagotrophic nanoflagellates (sum of mixotrophic and heterotrophic nanoflagellates) was positively correlated with nutrient concentrations. In contrast to macronutrient availability, the physical stability of the water column did not appear to affect the contribution of mixotrophic nanoflagellates. 相似文献
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In the present study, we used catalyzed reporter deposition-fluorescence in situ hybridization to quantify the abundance of five bacterial (Alphaproteobacteria, SAR11, Gammaproteobacteria, SAR86, and Bacteroidetes) and two archaeal (Crenarchaeota and Euryarchaeota) phylotypes in the epipelagic layer (0–200 m) of the Central South Pacific Ocean along 170°W from 0° to 40°S. We found that the distribution patterns of these phylotypes differed from each other. All phylotypes except Gammaproteobacteria were particularly abundant at the surface water of the equatorial region, whereas Gammaproteobacteria was relatively abundant in the area from the southern part of the South Pacific Ocean. SAR11, affiliated with Alphaproteobacteria was the dominant phylotype at all depths, throughout the study area. The abundance of SAR11 significantly increased with chlorophyll a concentration, suggesting that phytoplankton could affect their distribution pattern. There was a positive correlation between Bacteroidetes abundance and water temperature, suggesting that the temperature gradient could be a critical factor determining their distribution in the South Pacific Ocean. Crenarchaeota and Euryarchaeota were more abundant at the equatorial region than in other study areas. Euryarchaeota abundance significantly decreased with depth, and increased with chlorophyll a concentration. This suggests that there was ecological interaction between Euryarchaeota and phytoplankton in the equatorial surface. Our data indicate that distinct hydrographic properties such as seawater temperature, salinity, and the concentrations of chlorophyll a and nutrients can principally control the basin-scale distribution of different prokaryotic phylotypes in the epipelagic layer of the Central South Pacific Ocean. 相似文献
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Soil pipes (continuous macropores expanding laterally in the soil subsurface) are a key factor controlling hillslope water cycles and sediment transport. Soil pipes usually enhance slope stability under rainfall events through their high water drainage ability, and pipe clogging by sediments is regarded as a risk for slope failure. In this study, we conducted a bench-scale pipe clogging experiment to clarify the effect of air mobility in soil pipes on water flow and water pressure build-up in the slope at the clogged point. Before pipe clogging, the soil pipe drained rainwater effectively and lowered the groundwater table. After the pipe clogging event, the mobility of air in the soil pipe before the clogging determined the water flow in the slope. When the air in the soil pipe connected to the atmosphere and moved freely, the water level in the soil pipe increased at the pipe clogging, and water pressure build-up was limited near the pipe outlet. On the other hand, when air in the soil pipe was entrapped by the clogging, water pressure suddenly increased, and the groundwater table of the whole slope rose correspondingly. This study clearly demonstrated the importance of pipe morphology with respect to air connectivity between the pipe and atmosphere to elucidate the water flow and slope stability during the pipe clogging event. © 2019 John Wiley & Sons, Ltd. 相似文献
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