• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.12
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• pp.737-746
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• 2019

Most landslides in the country are shallow failures triggered by intense rainfall. Many researchers have revealed the possibility of predicting shallow failure through the volumetric water content (VWC). This study examined how to determine shallow failure using the gradient characteristics of the volumetric water content. For this, flume experiments were conducted using weathered granite soil. To confirm the saturation state of the surface layer under a rainfall intensity of 30 and 50mm/hr, VWC sensors were installed at depths of 10 and 20 cm on the upper, middle and lower slope. The test results showed that a shallow failure determination using VWC could be applied limitedly according to the slope degree. In addition, the effective cumulative rainfall due to the rainfall infiltration velocity is considered the main factor for the failure time. The failure prediction using the gradient of the VWC depends on the installation location and depth of the sensor. According to the experimental data, the measured value at 20 cm below the slope was most effective. Therefore, an analysis method of VWC and the method of selecting the installation location confirmed through this study can provide important data for presenting the measurement criteria using VWC in the future.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.41 no.3
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• pp.274-285
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• 1996

These experiments were conducted to evaluate the effects of seed coating with ten environmentally acceptable polymers, on germination percentage, water uptake, respiration, emergence and seedling growth characteristics. The water absorption of polymer-coated seeds in saturation condition was highest in klucel and lowest in polyvinyl pyrrolidone(PVP), and that in water was highest in klucel and lowest in maltrin. Respiration rates of polymer-coated seeds in Hwayoungbyeo and Ilpumbyeo were lower than those of none-coated seeds, and those in Daecheongbyeo and Jinmibyeo were higher than that of none-coated seeds, and those of sepiret coated seeds were higher than PVP coated seeds. The germination polimer-coated seed was reduced by one percentage by coating with seed coating machine. Germination percentage was not affected by any of polymer coating in high quality seed, but there were significant effects in low quality seed coating with waterlock, surelease 46 and sepiret significantly reduced germination some cultivars. Germination percentage after accelated ageing treatment were slightly higher most of polymer-coated seeds than in none-coated seeds, but those of sepiret-and klucel-coated seeds were lower significantly. Germination percentage of seeds coated with daran 8600, rnaltrin, sacrust and opadry were enhanced slightly under cold test other polimers reduced germination. The seedling height of polymer-coated seeds were longer than those of none-coated seeds, but those of waterlock, PVP and maltrin coating seeds were shorter, seedling hight was shortened by polimer coating under cold test. Polymer-coated seeds showed higher emergence percentage, shorter emergence time in field condition. The highest emergence percentage and the shortest emergence time was shown at 90% soil moisture content.

• Journal of the Korean Geosynthetics Society
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• v.13 no.3
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• pp.1-10
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• 2014

Several types of methods such as resistivity survey, ground penetration radar, etc are used for detection of levee leakage and according to the river design guidelines detection of levee leakage is performed by measuring the hydraulic conductivity of levee soil. But, the former can not verify the leakage point and degree of saturation, the latter is an after treatment method. Movable sensor, which is a high-tech TDR system developed since 2000, can obtain directly the dielectric constant profile covering the whole depth of levee. In this study, laboratory and field model experiments were carried out using movable TDR sensor in order to evaluate the applicability as detection system of levee leakage, As the result, movable TDR system has proven to be 3 times more sensitive to water contents than dry unit weight, and the results conclude that the dielectric constant, water contents and density of the ground proved to have a correlation among them, and the dielectric constant is expected to be a basic data on detection of levee leakage.

• Journal of Microbiology and Biotechnology
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• v.26 no.11
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• pp.1951-1964
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• 2016

1,4-Dioxane-degrading bacterial consortia were enriched from forest soil (FS) and activated sludge (AS) using a defined medium containing 1,4-dioxane as the sole carbon source. These two enrichments cultures appeared to have inducible tetrahydrofuran/dioxane and propane degradation enzymes. According to qPCR results on the 16S rRNA and soluble di-iron monooxygenase genes, the relative abundances of 1,4-dioxane-degrading bacteria to total bacteria in FS and AS were 29.4% and 57.8%, respectively. For FS, the cell growth yields (Y), maximum specific degradation rate ($V_{max}$), and half-saturation concentration ($K_m$) were 0.58 mg-protein/mg-dioxane, $0.037mg-dioxane/mg-protein{\cdot}h$, and 93.9 mg/l, respectively. For AS, Y, $V_{max}$, and $K_m$ were 0.34 mg-protein/mg-dioxane, $0.078mg-dioxane/mg-protein{\cdot}h$, and 181.3 mg/l, respectively. These kinetics data of FS and AS were similar to previously reported values. Based on bacterial community analysis on 16S rRNA gene sequences of the two enrichment cultures, the FS consortium was identified to contain 38.3% of Mycobacterium and 10.6% of Afipia, similar to previously reported literature. Meanwhile, 49.5% of the AS consortium belonged to the candidate division TM7, which has never been reported to be involved in 1,4-dioxane biodegradation. However, recent studies suggested that TM7 bacteria were associated with degradation of non-biodegradable and hazardous materials. Therefore, our results showed that previously unknown 1,4-dioxane-degrading bacteria might play an important role in enriched AS. Although the metabolic capability and ecophysiological significance of the predominant TM7 bacteria in AS enrichment culture remain unclear, our data reveal hidden characteristics of the TM7 phylum and provide a perspective for studying this previously uncultured phylotype.

• Journal of the Korean Association of Geographic Information Studies
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• v.15 no.1
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• pp.64-75
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• 2012

To predict the future distribution of forest vegetation, the present forest stand distributions of South Korea were represented by multinomial logit model with the following environmental variables: summer average precipitation, the coldest month average temperature, elevation, degree of base saturation, and soil organic matter. The future forest community was predicted by applying the MIROC3.2 hires A1B scenario. The future climate data were downscaled by statistically method. The coldest month average temperature increased $4.4^{\circ}C$, $6.0^{\circ}C$, and $9.4^{\circ}C$, and 3 months average precipitation changed -1.2%, 5.7%, and 5.3% for 2020s, 2050s, and 2080s respectively. For the projected summer precipitation and the coldest temperature, the future deciduous and mixed forests in the study area increased 56.9% and 8.3% and the coniferous forest decreased 11.2% in 2080s based on present.

• Journal of the Korean Geotechnical Society
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• v.29 no.5
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• pp.39-52
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• 2013

The shear stress characteristics of landslide materials can be affected by various factors. We examined the shear stress characteristics of two different soils using ring-shear apparatus, in which saturation-consolidation-shearing speed can be easily controlled. This paper presents (i) shear stress-time characteristics, (ii) shear stress depending on normal stress and shear speed and (iii) shear stress as a function of shearing speed. Materials used in this paper were the Nakdong River sand and muds taken from Jinhae coastal area in Korea. Samples were prepared in three types: Sand (upper)-Sand (lower), Clay (upper)-Clay (lower) and Sand (upper)-Clay (lower). The upper and lower indicate the samples placed in upper and lower ring shear boxes, respectively. For given normal stresses (50 and 100 kPa) and shearing speed (0.1 mm/sec), we performed ring shear tests. Then the failure lines were determined in the second test. Last, we determined the shear stress characteristics depending on different shearing speeds, such as 0.01, 0.1, 1, 10, 100 mm/sec. As a result, we found that shear stress characteristics are strongly dependent on above three factors. The shear stress of Sand (upper)-Clay (lower) is smaller than that of Sand (upper)-Sand (lower), but slightly larger than that of Clay (upper)-Clay (lower). The shear stress is also characterized by grain crushing and wetting process at slip surface.

• Journal of Korea Water Resources Association
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• v.52 no.4
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• pp.245-253
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• 2019

The objectives of this study are to estimate the return period of flash flood and evaluate its appropriateness based on the actual observation events for small mountainous watersheds in the Han River basin. For these goals, Flash Flood Guidance (FFG) was estimated from 1-hr duration Threshold Runoff (TR) and Saturation Deficit (SD) of soil moisture which was derived from Sejong University Rainfall Runoff (SURR) model. Then, the return period of flash flood was calculated by comparing the rainfall quantile to the 1-hr duration rainfall that exceeded the FFG during the past period (2002-2010). Moreover, the appropriateness of the estimated return period of flash flood was evaluated by using the observation events from 2011 to 2016. The results of the return period of flash flood ranged from 1.1 to 19.9 years with a mean and a standard deviation of 1.6 and 1.1 years, respectively. Also, the result of the appropriateness indicated that 83% of the return periods derived from observation events were within the return period of flash flood range. Therefore, the estimated return period of flash flood could be considered as highly appropriate.

• Journal of Korean Society of Environmental Engineers
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• v.29 no.7
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• pp.820-825
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• 2007

Earthworm casting was the natural fertilizer that contained high concentrations of nutrients such as nitrogen, phosphate and potassium and of over $10^8$ CFU/ml of microorganisms. Greater than 80% of feed was excreted through the fermentation by the intestinal enzyme, after worm had eaten feeds such as fallen leaves and rotten roots under the ground. Also, the soil structure of casting was known to be very efficient in the aspects of the porosity, the water permeability, and deodorizing activities. In this research, the biofilter packed with a biomedia made of casting and waste polyurethane foam, a binder, which helped to improve the durability and perpetuity of casting, was investigated to degrade malodorous hydrogen sulfide gas. The biomedia had no need of extra supply of nutrients and of microbial inoculations. On the beginning of the operations, it showed 100% removal of hydrogen sulfide gas without lag phase. At SV of 50 $h^{-1}$, hydrogen sulfide gas from the outlet of the biofilter was not detected, when inlet concentration increased to 450 ppmv. After that, removal efficiency decreased as increasing inlet hydrogen sulfide concentration. Hydrogen sulfide removal was maintained at almost 93% until inlet concentration was increased up to 950 ppmv, at which the elimination capacity of $H_2S$ was 61.2 g $S{\cdot}m^{-3}{\cdot}h^{-1}$. Maximum elimination capacity guaranteing 90% removal was 61.2, 65.9, 84.7, 89.4 g $S{\cdot}m^{-3}{\cdot}h^{-1}$ at SV ranging from 50 $h^{-1}$ to 300 $h^{-1}$, but was 59.3 g $S{\cdot}m^{-3}{\cdot}h^{-1}$ at SV of 400 $h^{-1}$. The results calculated from Michaelis-Menten equation revealed that $V_m$ increased from 66.04, 88.96, 117.35, 224.15, to 227.54 g $S{\cdot}m^{-3}{\cdot}h^{-1}$ with increasing space velocity in the range of 50 $h^{-1}$ to 400 $h^{-1}$. However, saturation constant$(K_s)$ decreased from 79.97 ppmv to 64.95 and 65.37 ppmv, and then increased to 127.72 and 157.43 ppmv.

• Journal of Soil and Groundwater Environment
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• v.7 no.3
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• pp.115-132
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• 2002

To distinguish the anthropogenic inputs from the chemical weathering with water-rock interaction on the chemical compositons of groundwater in Kwangju city, four different water groups were established based on the landuse type, lithology and topology. The sample from greenbelt area belongs to Group Ⅰ, whereas those from green buffer zone, urban area and industrial area belong to Group II, Group Ⅲ and Group Ⅳ, respectively. The geology of this city mainly consists of biotite granite and granitic gneiss. The concentration of main cations is subject to the behavior of feldspars, micas and carbonate minerals. Cl$\^$-/ and NO$_3$$\^$-/ are supplied by anthropogenic inputs such as domestic sewage whose concentration of these anions is highest in the Group Ⅲ samples. With the Piper diagram, the groundwaters of Group Ⅲ are mainly plotted in CaSO$_4$-CaCl$_2$ type, whereas those of other groups are plotted in Ca(HCO$_3$)$_2$ type, The calculation for the activities of ions and saturation indices of some minerals shows that most of the minerals are undersaturated and plotted in the area of equlibrium with kaolinite. Three factors were extracted from the factor analysis for chemical data. Factor 1 controlled by HCO$_3$$\^$-/, Ca$\^$2-/, SO$_4$$\^$2-/, Mg$\^$2+/ and Na$\^$+/, explains the dissolution of carbonate minerals. mica and plagioclase. Factor 2, controlled by Cl$\^$-/ and NO$_3$$\^$-/, explains the influence of artificial pollution. Factor 3, controlled by Mn, Fe and Zn is subject to the industrial waste water, but the evidence is not clear. Factor 1 is dominant in the Group I and II, indicating that those samples are subjected to natural chemical weathering, The higher scores of factor 2 in the Group Ⅲ samples indicate the potential artificial pollution.

• Journal of Soil and Groundwater Environment
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• v.11 no.6
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• pp.35-42
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• 2006

Experimental study was conducted to identify the active agent for reductive dechlorination of TCE in cement/Fe(II) systems. Several potential materials-hematite (${\alpha}-Fe_2O_3$), lepidocrocite (${\gamma}$-FeOOH), akaganeite (${\beta}$-FeOOH), ettringite ($Ca_6Al_2(SO_4)_3(OH)_{12}$)-that are cement components or parts of cement hydrates were tested if they could act as reducing agents by conducting TCE degradation experiments. From the initial degradation experiments, hematite was selected as a potential active agent. The pseudo-first-order degradation rate constant ($k\;=\;0.637\;day^{-1}$) for the system containing 200 mM Fe(II), hematite and CaO was close to that ($k\;=\;0.645\;day^{-1}$) obtained from the system containing cement and 200 mM Fe(II). CaO, which was originally added to simulate pH of the cement/Fe(II) system, was found to play an important role in degradation reactions. The reactivity of the hematite/CaO/Fe(II) system initially increased with increase of CaO dosage. However, the tendency declined in the higher CaO dosage region, implying a saturation type of behavior. The SEM analysis revealed that the hexagonal plane-shaped crystals were formed during the reaction with increasing degradation efficiency, which was brought about by increasing the CaO dosage. It was suspected that the crystals could be portlandite or green rust ($SO_4$) or Friedel's salt. The XRD analysis of the same sample identified the peaks of hematite, magnetite/maghemite, green rust ($SO_4$). Either instrumental analysis predicted the presence of the green rust ($SO_4$). Therefore, the green rust ($SO_4$) would potentially be a reactive agent for reductive dechlorination in cement/Fe(II) systems.