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111.
Y. M. Jo J. M. Oh J.G. Yoo 《中国海洋大学学报(英文版)》2006,5(4):305-310
The present paper deals with the behavior of the Attached Microbial Community (AMC) for water self-purification at different riverbeds in a typical local river. The study quantitatively investigated the problem starting with in-situ sampling. It was found that more biomass of AMC was at riffles with wider distribution than in pools. High current velocity (HCV) plays a negative role at the initial stage of attachment on the riverbed, but HCV aids the community proliferation after stable attachment. External disturbances such as rainfalls and discharges from dams or reservoirs would detach the periphyton depending on the intensity of turbulence in water. However, it was discovered that the flock of periphyton could be restored very quickly because it was not completely removed. Thus, in order to enhance self-purification by periphyton, a suitable configuration of the riverbed must be constructed, and occasional appropriate repair along the channels would improve the decontamination of the river. 相似文献
112.
Jin‐Yong Lee Myeong‐Jae Yi Young‐Kwon Yoo Kyung‐Hwan Ahn Gyoo‐Bum Kim Jong‐Ho Won 《水文研究》2007,21(7):907-919
The drastic expansion of cities and the rapid economic growth in Korea have caused dramatic increases to demand from groundwater supplies for drinking, domestic, agricultural and industrial water usage. The Ministry of Construction and Transportation and the Korea Water Resources Corporation have constructed and operated the National Groundwater Monitoring Network (NGMN) throughout the country since 1995. The NGMN, an official project establishing a total of 320 groundwater monitoring stations, was completed in 2005. Each national groundwater monitoring station serves as a baseline and primary station to monitor long‐term general trends in water‐level fluctuations and in groundwater quality. The present NGMN and its monitoring capabilities were evaluated to enhance the efficiency of groundwater monitoring and to meet the new societal conditions. Based on reviews and evaluations, some suggestions and recommendations are made with regard to improvements of the national network, including the installation of rainfall gauges in groundwater monitoring stations, gathering groundwater data every hour instead of every 6 h as at present, involving major cations and anions in the regular and periodic chemical analyses, regular periodic analyses of collected groundwater data, and construction of 199 additional groundwater monitoring stations to supplement the existing groundwater monitoring network. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
113.
Sumit Sen Puneet Srivastava Kyung H. Yoo Jacob H. Dane Joey N. Shaw Moon S. Kang 《水文研究》2008,22(21):4222-4232
Excessive application of poultry litter to pastures in the Sand Mountain region of north Alabama has resulted in phosphorus (P) contamination of surface water bodies and buildup of P in soils of this region. Since surface runoff is recognized as the primary mechanism of P transport, understanding surface runoff generation mechanisms are crucial for alleviating water quality problems in this region. Identification of surface runoff generation mechanisms is also important for delineation of hydrologically active areas (HAAs). Therefore, the specific objective of this study was to identify surface runoff generation mechanisms (infiltration excess versus saturation excess) using distributed surface and subsurface sensors and rain gauge. Results from three rainfall events (2·13–3·43 cm) of differing characteristics, and sensor data at four locations with differing soil hydraulic properties along the hillslope showed that the main surface runoff generation mechanism in this region is infiltration excess. Because of this, rainfall intensity and soil hydraulic conductivity were found to play dominant roles in surface runoff generation in this region. Further, only short periods of a few rainfall events during which the rainfall intensity is high produce surface runoff. This study indicates that perhaps subsurface flows and transport of P in subsurface flows need to be quantified to reduce P contamination of surface water bodies in this region. Current studies at this location are identifying spatial and temporal distribution of HAAs, quantifying rainfall characteristics that generate runoff, and estimating runoff volume that results from connected HAAs. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
114.
AbstractIn this article, the results of an experimental study on the effect of drilling fluid on concrete-soil/rock interface shear strength in the seawater drilling environment are presented. The series of direct shear tests using a purpose-designed shear box with seawater were performed considering different types of drilling fluid and base material, various normal stress levels at the interface, and filtration times. The results indicated that bentonite drilling fluid significantly decreased the concrete-soil/rock interface shear strength while a negligibly small effect was observed for polymer drilling fluid, confirming the findings from the previous studies. It was also observed that the degree of interface shear strength reduction when using bentonite drilling fluid varied with the type of base material as well as the level of normal stress at the interface. The results also confirmed that the groundwater chemistry does not alter governing mechanism of the drilling fluids and the concrete-soil/rock interface interaction and that significant benefit can also be expected when using polymer-based drilling fluid over bentonite in terms of the side resistance of a drilled shaft in seawater drilling environment as well. 相似文献
115.
Hoang Q. H. Phan Kyung-Yup Hwang Jun-Young Ahn Tae Yoo Kim Cheolyong Kim Inseong Hwang 《Environmental Earth Sciences》2017,76(22):771
A MgO-based binder developed to simultaneously solidify/stabilize contaminated sediment and store CO2 has been described previously. The objectives of the study presented here were to investigate the kinetics of the carbonation reactions of the binder and the extent to which carbonation occurred and to identify the optimal conditions for using the binder. The carbonation reaction was clearly faster and the degree of carbonation higher at CO2 concentrations of 50 and 100% than in the ambient atmosphere (which contains 0.04% CO2). A modified unreactive core model adequately described the kinetics. The rate constants were 0.0217–0.319 h?1 and were proportional to the degree of carbonation. A high degree of carbonation, 93.8%, was achieved at a CO2 concentration of 100%. The water to sediment ratio strongly affected carbonation, the optimal ratio being around 0.7. The relative humidity did not strongly affect the carbonation performance. The carbonation products were magnesite (MgCO3) and nesquehonite (MgCO3·3H2O). X-ray diffraction analysis showed that brucite (Mg(OH)2) was not present, suggesting that brucite was very quickly transformed into magnesium carbonates, the presence of which was confirmed by thermal gravimetric analysis. The results indicated that, in 7 d, 1 kg of binder could sequester up to 0.507 kg of CO2 in a 100% CO2 atmosphere. The results indicate that the MgO-based binder has great potential to be used to sequester CO2 under accelerated carbonation conditions. 相似文献
116.
Examination of multi-model ensemble seasonal prediction methods using a simple climate system 总被引:2,自引:0,他引:2
A simple climate model was designed as a proxy for the real climate system, and a number of prediction models were generated
by slightly perturbing the physical parameters of the simple model. A set of long (240 years) historical hindcast predictions
were performed with various prediction models, which are used to examine various issues of multi-model ensemble seasonal prediction,
such as the best ways of blending multi-models and the selection of models. Based on these results, we suggest a feasible
way of maximizing the benefit of using multi models in seasonal prediction. In particular, three types of multi-model ensemble
prediction systems, i.e., the simple composite, superensemble, and the composite after statistically correcting individual
predictions (corrected composite), are examined and compared to each other. The superensemble has more of an overfitting problem
than the others, especially for the case of small training samples and/or weak external forcing, and the corrected composite
produces the best prediction skill among the multi-model systems. 相似文献
117.
Chulsang Yoo Eunho Ha 《Stochastic Environmental Research and Risk Assessment (SERRA)》2007,21(3):287-297
In this study, the effect of zero measurements on the spatial correlation function of rainfall is analyzed for the quantification
of a rainfall field. The use of a bivariate mixed distribution function made it possible to analyze and compare the spatial
correlation functions for these three different data sets: only the positive measurements at both gauge locations, positive
measurements at either one or both gauge locations, and all measurements including zero at both locations. As an example,
the spatial correlation functions are derived for the Geum River Basin, Korea and evaluated for the wet and dry seasons, respectively.
Results show that the effect of zero measurements on spatial correlation structures is significant during the wet season,
when the inter-station correlations were estimated significantly lower than those during the dry season. It was also found
that only the case considering positive measurements are valid for the quantification of rainfall field. Even during the wet
season, the inter-station correlation coefficients derived by considering the zero measurements show their high variability
along with many abnormally looking high estimates, which made the quantification of the spatial correlation function become
very ambiguous. 相似文献
118.
Observations in channel 1 (Ch. 1, 50.3 GHz) and channel 2 (Ch. 2, 53.74 GHz) of the Microwave Sounding Unit (MSU) over the convective areas of tropical oceans are analysed to reveal the nature of extinction (contamination) in these data. From this analysis we find Ch. 2 data are not free from the influence of clouds and rain. Extinction due to clouds and rain manifests primarily as emission in Ch. 1, and as absorption in Ch. 2. Scattering due to hydrometeors in these channels apparently is of secondary importance. Furthermore we show, in the convective areas of tropical oceans, contamination due to hydrometeors in MSU Ch. 2 data is significant and it is extensive in area. Based on this study we conclude Spencer, Christy, and Grody (this issue) underestimate this contamination. 相似文献
119.
120.
Keiko Yamada Joji Ishizaka Sinjae Yoo Hyun-cheol Kim Sanae Chiba 《Progress in Oceanography》2004,61(2-4):193
Seasonal and interannual variability of chlorophyll a concentration in the Japan/East Sea (JES) was detected spatially by ocean color satellite remote sensing. Start timing of the spring bloom was different spatially. The spring bloom started at the subpolar front and southward of it in March, northward of subpolar front, along the Primorye coast and off Hokkaido in April and in the middle of the Japan Basin in May. The start of the spring bloom showed interannual variability that corresponded with the wind speed in the area. The spring bloom in 1998 and 2002 appeared about four weeks earlier than in 1997, 1999 and 2001, and it corresponded with weak winds that can lead to an early development of the thermocline. The bloom was late in 1999 and 2001 in the Japan Basin and along the Primorye coast, and in the southern area in 2000. It corresponded with stronger wind stress that delayed seasonal thermocline formation. The bloom along the Primorye coast appeared later in 1999, and it corresponded with stronger wind stress, and at the same time, it seemed to be related with the delay of melting of sea ice in Mamiya Strait. The fall bloom appeared from early October to early December, and it did not have a clear temporal transition. The area where chlorophyll a concentration exceeded 0.8 μg l−1 was wider in the western area than in the eastern area every year. The magnitude of the fall bloom was different between years, but it did not show a correlation with average wind speed in fall. Those results indicated that the timing of the seasonal bloom in the JES is largely affected by the variability of global climate such as ENSO events. 相似文献