• Journal of Environmental Science International
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• v.21 no.11
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• pp.1307-1320
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• 2012

The purpose of this paper is to provide information on planting construction for healthy plant growth. To achieve this purpose, this study analyzed the planting type, planting density, withering rate, soil characteristics, and cambium electrical resistance (CER) of withered trees in an apartment complex with a high withering rate. The major plant groups examined consisted of native broad-leaved tree species (39.3%), native narrow-leaved tree species (24.2%), and native broad-leaved - exotic narrow-leaved tree species (16.4%). The planting density of the green area, where trees were planted from 0.0 to 0.3 trees per unit area, was measured as 98.4%. Withered trees were found in 19 of the 20 planted species, and the withering rate was 41.8% (610 withered/1,461 planted). Withering rates for tree species were measured as follows: Sophora japonica and Salix babylonica (100.0%), Magmolia denudata (84.3%), Lindera obtusiloba (74.7%), cornus kousa (69.3%), acer triflorum (69.2%), diospyros kaki (66.7%), Prunus yedoensis (62.8%), Acer palmatum (52.6%), Prunus armeniaca (51.1%), Chaenomeles sinensis (43.7%), Ginkgo biloba (40.9%), Zelkova serrata (31.0%), Cornus officinalis (28.6%), Taxus cuspidata (25.6%), Pinus densiflora (21.4%), Pinus parviflora (15.2%), Pinus strobus (14.6%), and Abies holophylla (10.3%). Soil chemical analyses for 18 samples revealed that as the withering rate increased, the following occurred: (a) the ratio of silt and clay in soil increased; (b) the soil pH, organic matter rate, nitrogen, available phosphorus, and cation exchange capacity (CEC) in samples were graded as "inadequate," based on the plant grading evaluation; and (c) the NaCl and cation exchange capacity were evaluated as "somewhat satisfactory." The measurement of CER for withering rate shows electrical resistance for higher withering rate are higher, which could predict that a tree will not grow well.

• Journal of Biosystems Engineering
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• v.36 no.1
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• pp.33-39
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• 2011

An optical sensing approach based on diffuse reflectance has shown potential for rapid and reliable on-site estimation of soil properties. Important sensing ranges and the resulting regression models useful for soil property estimation have been reported. In this study, a similar approach was applied to investigate the potential of reflectance sensing in estimating soil properties for Korean paddy fields. Soil cores up to a 65-cm depth were collected from 42 paddy fields representing 14 distinct soil series that account for 74% of the total Korean paddy field area. These were analyzed in the laboratory for several important physical and chemical properties. Using air-dried, sieved soil samples, reflectance data were obtained from 350 to 2500 nm on a 3 nm sampling interval with a laboratory spectrometer. Calibrations were developed using partial least squares (PLS) regression, and wavelength bands important for estimating the measured soil properties were identified. PLS regression provided good estimations of Mg ($R^2$ = 0.80), Ca ($R^2$ = 0.77), and total C ($R^2$ = 0.92); fair estimations of pH, EC, $P_2O_5$, K, Na, sand, silt, and clay ($R^2$ = 0.59 to 0.72); and poor estimation of total N. Many wavelengths selected for estimation of the soil properties were identical or similar for multiple soil properties. More important wavelengths were selected in the visible-short NIR range (350-1000 nm) and the long NIR range (1800-2500 nm) than in the intermediate NIR range (1000-1800 nm). These results will be useful for design and application of in-situ close range sensors for paddy field soil properties.

• Journal of the Mineralogical Society of Korea
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• v.26 no.2
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• pp.65-80
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• 2013

Sediment transport mechanism and distribution of organic sediments are elucidated by the study of particle size, mineralogy, organic matters and microfossils of the surface samples collected from seafloor adjacent Dokdo island. Shallow marine sediments are dominated by coarse- grained sediments including gravel and sand, and their sedimentation has mainly been controlled by traction. While the samples collected from oceanic zone are characterized by high contents of fine- grained sediments such as silt and mud in bulk sediments, and the changes of mineral compositions including clay minerals and feldspar, and the fine sediments have been deposited mainly by suspension. The change of organic sedimentary communities is detected between neritic and oceanic zone. Although marine organic matter is predominant in neritic zone, terrestrial organic matter is monopolized according to increasing water depth. This trend is associated with grain size of sediments. The results also suggest that high pollen concentrations in whole organic matters may played an important role in excessive organic carbon in sediment.

• Journal of The Geomorphological Association of Korea
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• v.25 no.1
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• pp.31-45
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• 2018

This study investigated the characteristics of sedimentary environment changes across a tidal flat in Gagyeongju of Anmyeondo Island. We performed a spatio-temporal analysis on the grain sizes composition of sediments and micro-landform changes during the winter from 2013 to 2016. The results showed that erosion was a dominant processthroughout the study flat, reducing the surface elevation even by 1 m around the upper sand flat. As a consequence, headlands have formed in the entire region of Gagyeongju village. In addition, erosion quickly progressed along the low-lying subtidal zone and tide way and, in contrast, sedimentation progressed in the mid-elevation tidal flat. We posit that a jetty, which had been constructed as a pier facility on the eastern part of the study area, interfered with the flow of tidal current, thereby enhancing these erosional processes. This is because such interference can block the supply of fine-textured sediments from the nearby Cheonsu Bay and therefore reduce surface elevation. According to the surface sediment analysis, the sediments were categorized into 7 sedimentary facies, and generally displayed a high ratio of silt and clay. The result of time-series analysis (2012-2013) showed that the sediments on the tidal flat became fine-grained, and that sorting became worse. However, the sediments on the subtidal zone, embayment and along inside of the jetty tended to be coarse-grained. In conclusion, the tidal flat microlandform change in the study area was caused by a disruption in the seawater circulation due to the jittery construction within the tidal flat, which had a direct effect on erosional and sedimentary environment processes.

• Journal of the Korean GEO-environmental Society
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• v.4 no.4
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• pp.61-71
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• 2003

On the soft soil consisted of silty clay, the compulsion replacement method is useful for revetment and its safety is very much affected by compulsion replacement depth. Usual method calculating the compulsion replacement depth on silty clay is considered the bearing capacity of soft soil with undrained shear strength increase from ground surface and weight of revetment. But according to soil deposit, there are some cases of soft soil with inter sand layer or clayed silt, which affect the compulsion replacement depth. In this paper, the compulsion replacement depth on soft soil with inter sand layer is analyzed by layered weighted average bearing capacity considering influence effect of Perloff et al.(1967) and compared with numerical method(FLAC). In the result, the calculated depth from numerical method is nearest to layered weighted average bearing capacity in case that contact width under revetment is $0.2B_o$(soft soil with inter sand layer), $0.5B_o$(only soft soil) and the effect of contact width under revetment is less than undrained shear strength, thickness and location of inter sand layer. Also the compulsion replacement depth is as much as the inter sand thickness($d_2/B_o$) is thinner, the inter sand layer location($d_1/B_o$) is farther, and undrained shear strength is less.

• Journal of Wetlands Research
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• v.22 no.4
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• pp.295-301
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• 2020

This research analyzed the relationship between environmental factors and the density of Sycios angulatus in the Miho Stream, Geum River water system in order to secure basic data for the control of the ecosystem-distrubing plant Sycios angulatus. As a result of the soil particle size analysis of Sycios angulatus habitat, it was found that the density of Sycios angulatus decreased as the silty and clay contents increased. Most of the Sycios angulatus habitats had high sandy and silt content, and low clay content of less than 2%. The increased flow rate reduced the density of Sicyos angulatus. This is because when the flow rate is increased, the Sicyos angulatus cannot grow due to the change in soil characteristics. Water quality plays a role in supplying nutrients when Sicyos angulatus are submerged. However, due to the change in soil characteristics during flooding, the density of Sicyos angulatus tended to decrease due to impaired growth. The Sicyos angulatus can be managed through artificial and natural techniques. The appropriate natural control technique is the creation of a natural waterway in the habitats to change the water contents.

• Journal of the Korean Institute of Landscape Architecture
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• v.30 no.1
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• pp.87-95
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• 2002

This study was carried out to investigate the load of soil layers affected by soil depth in artificial soil alone or in blends with Loam with various ratio. The artificial soils were perlite large grain, perlite small grain, and perlite small grains blended with Loam (sand 46%, silt 40%, clay 14%) at a ratio of 8:2, 6:4, 5:5 (v/v). The soil layers were divided into a planting layer and a well-drained layer, then the weight of each layer in the air-dried state and in the field capacity were determined. The data were subjected to correlation analysis, regression analysis, and paired samples t-test. The summarized results are as follows; 1) In the air-dried state, the regression equations of the well-drained layer weight(kg/m2) in perlite large grain, planting layer weight in perlite small grain, planting layer weight in perlite small grain biended with loam(8:2, v/v), perlite small grain blended with loam(6:4, v/v), and perlite small grain blended with loam(5:5, v/v) were; 1.65824*X+0.026, 1.52292*X-0.052, 3.21468*X+0.515, 6.17549*X+ 0.083, and 6.02100*X + 33.133, respectively, where X is soil depth measured in Centimeters. 2) In the field capacity, the regression equations of the well-drained layer weight(kg/m2) in perlite large grain, planting layer weight in perlite small grain, planting layer weight in perlite small grain blended with loam(8:2, v/v), perlite small grain blended with loam(6:4, v/v), and perlite small grain blended with loam(5:5, v/v) were 5.055*X - 2.006, 7.073*X + 100.008, 8.092*X + 116.676, 10.766*X + 100.112, and 10.974*X + 124.423, respectively, where X is the soil depth measured in Centimeters. 3) All of the equations mentioned above were statistically reliable and therefore easily applicable in practical business affairs.

• Proceedings of the Korean Geotechical Society Conference
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• 2010.09a
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• pp.553-558
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• 2010

The behavior of composite piles composed of steel pipe pile in the upper part and concrete pile in the lower part by a mechanical splicing joint was examined by field lateral load tests and bending tests. A total of 7 piles including two instrumented piles for bending test were installed. The soil profile consists of soft clay with weak silt with shallow groundwater level. Laboratory tests were carried out to determine the basic soil characteristics and the strength parameters. This paper presents the composite pile behavior with various portions of the upper steel pile: 0, 20, 30, and 45% of the pile embedded pile length. Three-point bending tests were performed to investigate the stress-strain relation at the mechanical joint. Based on these test results, the behavior of composite piles with various upper steel pile length are evaluated and the stability of mechanical joints are examined. Through comparisons with results of field load tests, it was found that lateral load carrying capacity of the composite piles increased and deflections of the composite piles decreased with increasing the upper steel piles. The mechanical joint was proved to retain its structural stability against the tested load conditions. Economical benefits of composite pile of this kind can be gained by setting adequately the length of the upper steel pipe piles.

• Journal of the Korean Institute of Landscape Architecture
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• v.31 no.5
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• pp.1-10
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• 2003

The purpose of this study was to verify the shore margin protection effect of a root system developed from direct sticking of Salix gracilistyla Miq., focusing on the reinforcement of soil shear strength. The materials were 20cm long sticks whose average diameter and weight were 7.52mm and 14.58g respectively, and sandy loam(Sand 60.36%, Silt 28%, Clay 11.64%), whose maximum dry weight(${\gamma}$$_{dmax}$) was 1.59gf/㎤ at the water ratio( $W_{opt}$) 13.8%. The direct shearing test(KS F 2343) was applied to cylindric columms(diameter 132mm) of pure soil and two years old root reinforced soil. At each condition of vertical stress, 10N/$ extrm{cm}^2$, 14.41N/$\textrm{cm}^2$ and 18.82 N/$\textrm{cm}^2$, five soil+root columns were sheared. After shear tests, the root area ratio and soil moisture on the shear plane were measured. The results of this research were as follows: 1. The average of root area ratio was 1.86% and the soil moisture 14.67%. 2. Two years old root system was found to increase the soil shear strength of pure soil in terms of Cohesion(C) and Inner friction Angle($\phi$) as follows. 3. The relationship between root area ratio and the increased shear strength can be presented with the following equation, $\Delta$S ≒ 0.33ㆍ TrㆍAs/A $\Delta$S : Increased Shear Strength Tr : Average Tension Strength of Root, Ar/A : Root Area Ratioioage Tension Strength of Root, Ar/A : Root Area Ratio

• Korean Chemical Engineering Research
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• v.51 no.6
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• pp.733-738
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• 2013

Sediment contains a high fraction of organic matter, high buffering capacity, and a large portion of fine grained particles such as silt and clay, which are major barriers to remove heavy metals from sediments. In this study, a lab-scale electrokinetic (EK) technique was applied to remove heavy metals effectively from marine sediment at a constant voltage gradient of 2 V/cm. A concentration of 0.1 M of ethylenediaminetetraacetic acid (EDTA), citric acid (CA), $HNO_3$, and HCl were circulated in the cathode, and tap water was circulated in the anode. CA extracted 92.4% of Ni, 96.1% of Cu, 97.1% of Zn, and 88.1% of Pb from marine sediment. A higher voltage gradient enhanced the transport of citrate and EDTA into the sediment and, therefore, increased metal extraction from the marine sediment through a complexation reaction between metals and the chelates. Based on these results, the electrokinetic process using a high voltage gradient with EDTA and CA might be useful to extract heavy metals from marine sediment.