• Advances in environmental research
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• v.9 no.4
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• pp.251-273
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• 2020

Soil degradation has become a major worldwide environmental problem, particularly in arid and semi-arid climate zones due to irregular rainfall and the intensity of storms that frequently generate heavy flooding. The main objective of this study is the use of geographic information system and remote sensing techniques to quantify and to map the soil losses in the Wadi Saida watershed (624 ㎢) through the revised universal soil loss equation model and a proposed model based on the surface erosive runoff. The results Analysis revealed that the Wadi Saida watershed showed moderate to moderately high soil loss, between 0 and 1000 t/㎢/year. In the northern part of the basin in the region of Sidi Boubkeur and the mountains of Daia; which are characterized by steep slopes, values can reach up to 3000 t/㎢/year. The two models in comparison showed a good correlation with R = 0.95 and RMSE = 0.43; the use of the erosive surface runoff parameter is effective to estimate the rate of soil loss in the watersheds. The problem of soil erosion requires serious interventions, particularly in basins with disturbances and aggressive climatic parameters. Good agricultural practices and forest preservation areas play an important role in soil conservation.

• Proceedings of the Korea Water Resources Association Conference
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• 2021.06a
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• pp.205-205
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• 2021

Surface soil moisture, which governs the partitioning of precipitation into infiltration and runoff, plays an important role in the hydrological cycle. The assimilation of satellite soil moisture retrievals into a land surface model or hydrological model has been shown to improve the predictive skill of hydrological variables. This study aims to improve streamflow prediction with Weather Research and Forecasting model-Hydrological modeling system (WRF-Hydro) by assimilating Soil Moisture Active and Passive (SMAP) data at 3 km and analyze its impacts on hydrological components. We applied Cumulative Distribution Function (CDF) technique to remove the bias of SMAP data and assimilate SMAP data (April to July 2015-2019) into WRF-Hydro by using an Ensemble Kalman Filter (EnKF) with a total 12 ensembles. Daily inflow and soil moisture estimates of major dams (Soyanggang, Chungju, Sumjin dam) of South Korea were evaluated. We investigated how hydrologic variables such as runoff, evaporation and soil moisture were better simulated with the data assimilation than without the data assimilation. The result shows that the correlation coefficient of topsoil moisture can be improved, however a change of dam inflow was not outstanding. It may attribute to the fact that soil moisture memory and the respective memory of runoff play on different time scales. These findings demonstrate that the assimilation of satellite soil moisture retrievals can improve the predictive skill of hydrological variables for a better understanding of the water cycle.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.03a
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• pp.1095-1099
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• 2008

Critical state theory involves two state boundary surface. One is Roscoe surface and the other is Hvorslev surface. The shape of these boundary surface was changed because of several parameters : Critical state constant(M), spacing ratio (r) and critical state pore pressure coefficient($\wedge$). As these constants make difference to each model and the way of solution, they may affect the shape of state boundary surface. Specially, spacing ratio (r) is important. On this study, triaxial compression test was performed using remolded weathered mudstone soil and investigated variation of state boundary surface because of spacing ratio. In the results of prediction, critical state point was located highly and the shape of boundary surface was changed more tightly curve as decreasing spacing ratio.

• Environmental Engineering Research
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• v.12 no.2
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• pp.64-71
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• 2007

The necessity of disinfecting playground soil is an important issue, because pathogenic protozoa, bacteria, and parasite eggs remain viable for several months and can infect children. UV irradiation has been used to decontaminate water but its effectiveness on soil is unclear. We determined the efficacy of UV radiation for inactivation of an indicator bacteria, E. coli (strain ATCC 8739), on playground soil. While 99% inactivation of E. coli in the soil was readily achieved by UV radiation within 55 min at $0.4\;mW\;cm^{-2}$, complete inactivation was not achieved, even after prolonged treatment at $4\;mW\;cm^{-2}$. This was attributed to the irregular surface of the soil. A small number of E. coli escaped the UV radiation because they were situated in indentations or under small particles on the soil surface. Atomic force microscopy (AFM) and scanning electron microscopy (SEM) confirmed that the surface characteristics of the soil is the major limiting factor in the inactivation of E. coli by UV radiation. Thus UV treatment may not be adequate for disinfecting some soils and should be carefully evaluated before being used on playground soils.

• Korean Journal of Soil Science and Fertilizer
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• v.48 no.6
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• pp.671-676
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• 2015

Control of surface runoff from upland soil is essential to reduce nonpoint source pollution. The use of non-woven fabric as a soil cover can be helpful to control surface runoff. The field experiment was conducted to evaluate the furrow cover effects of black non-woven fabric on the nutrient discharge from upland soil used for red pepper cultivation. The experimental plots consisted of chemical fertilizer (CF), cow manure compost (CMC), and pig manure compost (PMC) treatment. Each nutrient material treatment plot has control (no furrow cover (NFC)) and black non-woven fabric cover treatment, respectively. The amount of nutrient application was chemical fertilizer of $190-112-149(N-P_2O_5-K_2O)kgha^{-1}$, cow manure compost of $29.5tonha^{-1}$, and pig manure compost of $7.9tonha^{-1}$ as recommended amount after soil test for red pepper cultivation. Compared to control (NFC), furrow cover treatment with black non-woven fabric reduced the amount of T-N discharge by 50% at CF treatment, 36.9% at CMC treatment, and 44.8% at PMC treatment. Furrow cover treatment with black non-woven fabric reduced the amount of T-P discharge by 37.1% at CF treatment, 49.9% at CMC treatment, and 63.4% at PMC treatment compared to control (NFC). The production of red pepper did not show significant difference. There was no weed occurring in furrow cover treatment plots with black non-woven fabric. Results from this study showed that the furrow cover with black non-woven fabric could play a significant role in reduce nutrient discharge from upland soil used for red pepper cultivation.

• Journal of Soil and Groundwater Environment
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• v.26 no.1
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• pp.1-7
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• 2021

Air-water interfacial area is of great importance for the analysis of contaminant mass transfer processes occurring in the soil systems. Capillary bundle model has been proposed to estimate the specific air-water interfacial areas in unsaturated soils. In this study, the measured air-water interfacial areas of a soil (loam) using the gaseous interfacial tracer technique were compared to those from capillary bundle model. The measured values converged to the specific solid surface area (7.6×104 ㎠/㎤) of the soil. However, the simulated air-water interfacial areas based on the capillary bundle model deviated significantly from those measured. The simulated values were substantially over-estimated at low end of the water content range, whereas the model under-estimated the air-water interfacial area for the most of the water content range. This under-estimation is considered to be caused by the nature of the capillary bundle model that replaces the soil pores with a bundle of glass capillaries and thus no surface roughness at the inner surface of the capillaries is taken into account for the estimation of the air-water interfacial area with the capillary bundle model. Subsequently, appropriate correction is necessary for the capillary bundle model to estimate the air-water interfacial area in soils. Since the soil-moisture release curve data is the basis of the capillary bundle model, the model can be of use due to its simplicity, while the gaseous tracer technique requires complicated experimental equipment followed by moment analysis of the breakthrough curves. The size distribution profile of the pores filled with gas estimated by the water retention curve was found to be similar to that of particle size at different size range. The shifted distribution of gas-filled pores toward smaller size side compared to the particle size distribution was also found.

• Journal of Korea Water Resources Association
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• v.48 no.7
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• pp.595-604
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• 2015

Interrill erosion by the rainfall is divided into a detachment of soil particles by raindrop splash when raindrops having kinetic energy strike on the surface soil and a sediment transport by sheet flow of surface runoff. Rainfall kinetic energy is widely used as an indicator expressing the potential ability to separate the soil particles from soil mass. In this study, the soil erosion experiments of rainfall simulation were operated to evaluate the effects of rainfall kinetic energy on interrill erosion as using the strip cover to control raindrop impact. The kinetic energy from rainfall simulator was 0.58 times to that of natural rainfall. Surface runoff and subsurface runoff increased and decreased respectively with increase of rainfall intensity. Surface runoff discharge from plots of non-cover was 1.82 times more than that from plots with cover. The rainfall kinetic energy influenced on the starting time of surface and subsurface runoff. Soil erosion quantity greatly varied according to existence of the surface cover that can intercept rainfall energy. Sediment yields by the interaction between raindrop splash and sheet flow increased 3.6~5.9 times and the increase rates of those decreased with rainfall intensity. As a results from analysis of relationship between stream power and sediment yields, rainfall kinetic energy increased the transport capacity according to increase of surface runoff as well as the detachment of soil particles by raindrop splash.

• Journal of Korea Water Resources Association
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• v.53 no.3
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• pp.181-191
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• 2020

In order to produce accurate initial condition of soil moisture for global Numerical Weather Prediction (NWP), spin-up experiment is carried out using Noah Land Surface Model (LSM). The model is run repeatedly through 10 years, under the atmospheric forcing condition of 2008-2017 until climatological land surface state is achieved. Spin-up time for the equilibrium condition of soil moisture exhibited large variability across Koppen-Geiger climate classification zone and soil layer. Top soil layer took the longgest time to equilibrate in polar region. From the second layer to the fourth layer, arid region equilibrated slower (7 years) than other regions. This result means that LSM reached to equilibrium condition within 10 year loop. Also, spin-up time indicated inverse correlation with near surface temperature and precipitation amount. Initialized from the equilibrium state, LSM was spun up to obtain land surface state in 2018. After 6 months from restarted run, LSM simulates soil moisture, skin temperature and evaportranspiration being similar land surface state in 2018. Based on the results, proposed LSM spin-up system could be used to produce proper initial soil moisture condition despite updates of physics or ancillaries for LSM coupled with NWP.

• Economic and Environmental Geology
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• v.32 no.6
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• pp.611-631
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• 1999

Enviromental geochemisty and heary metal contamination at the Kongjueil mine creek were underaken on the basis of physicohemical properties and mineralogy for various kinds of water (surface, mine and ground water),soil, precipitate and sediment collected of April and December in 1998. Hydrgeochemical composition of the water samples are characterized by relatively significant enricant of Ca+Na, alkiali ions $NO_3$ and Cl inground and surfore water, wheras the mine waters are relatively eneripheral water of the mining creek have the characteristics of the (Ca+Mg)-$(HCO_3+SO_4)$type. The pH of the mine water is high acidity (3.24)and high EC (613$\mu$S/cm)compared with those of surface and ground water. The range of $\delta$D and $\delta^{18}O$ values (relative to SMOW) in the waters are shpwn in -50.2 to -61.6% and -7.0 to -8.6$\textperthousand$(d value=5.8 to 8.7). Using computer program, saturation index of albite, calcite, dolomite in mine water are nearly saturated. The gibbiste, kaolinite and smectite are superaturated in the surface and ground water, respectively. Calculated water-mineral reaction and stabilities suggest that weathing of silicate minerals may be stable kaolinite owing to the continuous water-rock reaction. Geochemical modeling showed that mostly toxic heavy metals may exist larfely in the from of metal-sulfate $(MSO_4\;^2)$and free metal $(M^{2+})$ in nmine water. These metals in the ground and surface water could be formed of $CO_3$ and OH complex ions. The average enrichment indices of water samples are 2.72 of the groundwater, 2.26 of the surface water and 14.15 of the acid mine water, normalizing by surface water composition at the non-mining creek, repectively. Characteristics of some major, minor and rate earth elements (Al/Na, K/Na, V/Ni, Cr/V, Ni/Co, La/Ce, Th/Yb, $La_N/Yb_N$, Co/Th, La/Sc and Sc/Th) in soil and sediment are revealed a narrow range and homogeneous compositions may be explained by acidic to intermediate igneous rocks. And these suggested that sediment source of host granitic gneiss colud be due to rocks of high grade metamorphism originated by sedimentary rocks. Maximum concentrations of environmentally toxic elements in sediment and soil are Fe=53.80 wt.% As=660, Cd=4, Cr=175, Cu=158, Mn=1010, Pb=2933, Sb=4 and Zn=3740 ppm, and extremely high concentrations are found are found in the subsurface soil near the ore dump and precipitates. Normalizing by composition of host granitic gneiss, the average enerichment indices are 3.72 of the sediments, 3.48 of the soils, 10.40 of the precipitates of acid mine drainage and 6.25 of the soils near the main adit. The level of enerichment was very severe in mining drainage sediments, while it was not so great in the soils. mineral composition of soil and sediment near the mining area were partly variable being composed of quartz, mica, feldspar, chlorite, vermiculite, bethierin and clay minerals. reddish variable being composed of quartz, mica, feldspar, chlorite, vermiculite, bethierin and clay minerals. Reddish brown precipitation mineral in the acid mine drainage identifies by schwertmanite. From the separated mineralgy, soil and sediment are composed of some pyrite, arsenopyite, chalcopyrite, sphalerite, galena, malachite, goethite and various kinds of hydroxied minerals.

• Journal of Korean Tunnelling and Underground Space Association
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• v.16 no.6
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• pp.507-520
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• 2014

In this study, the surface displacement was investigated according to the various depth of cover when the tunnel excavation equipment was used in a clay soil. For this the laboratory scaled model test was carried out using the soil sample similar to the in-situ conditions. We carried out four tests according to tunnel depth(1.5D, 2.0D, 2.5D, 3.0D). The distribution of impact due to tunnelling was quantitatively analyzed in the three-dimension by measuring the surface displacement. In addition, the pattern of surface displacements was figured out.